Patent Publication Number: US-9886365-B2

Title: Transactional boundaries for software system debugging

Description:
BACKGROUND 
     The present disclosure relates in general to the field of computer software development tools, and more specifically, to facilitating a shared software development environment. 
     Software development can involve a variety of tools to support a development life cycle of an application or system. The development cycle can include activities such as system design, development, integration and testing, deployment, maintenance, and evaluation. As software systems become more complex, such as in service-oriented architectures linking multiple traditional systems (from potentially multiple different software vendors) other development cycles and strategies are emerging, including waterfall, spiral, Agile development, rapid prototyping, incremental, and synchronize and stabilize. In the case of Agile methodologies, the focus can be on lightweight processes which allow for rapid and iterative changes within the development cycle. Further complicating the tasks and management of development activities within modern software development is the reality that multiple developers often collaborate to build and perform development tasks involving a single system. Traditional development tools, such as debuggers, profilers, loggers, etc. can be ill-equipped to handle the evolving landscape of software development, particularly within shared development environments. 
     BRIEF SUMMARY 
     According to one aspect of the present disclosure, transaction data is received from a particular agent instrumented on a first one of a plurality of software components in a system, the transaction data identifying characteristics observed by the particular agent during monitoring of the first software component during a transaction involving the first software component and a second one of the plurality of software components. A second thread running on the second software component can be identified that is at least partially dependent on a first thread run on the first software component during the transaction, the second thread corresponds to code of the second software component with a conditional breakpoint, and the conditional breakpoint is to be triggered based on when the second thread falls within a defined transaction boundary for the system. From the transaction data, it can be determined that the second thread falls within the transaction boundary. The conditional breakpoint can be triggered during debugging of the system to interrupt the second thread based on determining that the second thread falls within the transaction boundary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic diagram of an example computing system including an example development system in accordance with at least one embodiment; 
         FIG. 2  is a simplified block diagram of an example computing system including an example shared development platform in accordance with at least one embodiment; 
         FIG. 3  is a simplified block diagram of an example system in accordance with at least one embodiment; 
         FIGS. 4A-4F  are simplified block diagrams illustrating transaction flow paths involving the example system of  FIG. 3  in accordance with at least one embodiment; 
         FIG. 5  is a simplified block diagram illustrating selective deployment of a debugger; 
         FIGS. 6A-6B  are simplified block diagrams illustrating transaction data generated by example agents deployed on software component within a system; 
         FIG. 7  is a simplified block diagram illustrating a collection of execution threads running in connection with operation of an example software system; 
         FIG. 8  is a simplified flowchart illustrating example techniques in connection with selective debugging of a software system in accordance with at least one embodiment. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     As will be appreciated by one skilled in the art, aspects of the present disclosure may be illustrated and described herein in any of a number of patentable classes or context including any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof. Accordingly, aspects of the present disclosure may be implemented entirely hardware, entirely software (including firmware, resident software, micro-code, etc.) or combining software and hardware implementation that may all generally be referred to herein as a “circuit,” “module,” “component,” or “system.” Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable media having computer readable program code embodied thereon. 
     Any combination of one or more computer readable media may be utilized. The computer readable media may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an appropriate optical fiber with a repeater, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. 
     A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing. 
     Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, CII, VB.NET, Python or the like, conventional procedural programming languages, such as the “C” programming language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages such as Python, Ruby and Groovy, or other programming languages. The program code may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider) or in a cloud computing environment or offered as a service such as a Software as a Service (SaaS). 
     Aspects of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatuses (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable instruction execution apparatus, create a mechanism for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     These computer program instructions may also be stored in a computer readable medium that when executed can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions when stored in the computer readable medium produce an article of manufacture including instructions which when executed, cause a computer to implement the function/act specified in the flowchart and/or block diagram block or blocks. The computer program instructions may also be loaded onto a computer, other programmable instruction execution apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatuses or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     Referring now to  FIG. 1 , a simplified block diagram is shown illustrating an example computing system  100  including a shared software development system  105  and a transaction analysis system  110 , among other hardware and software computing systems. In some implementations, functionality of the development system  105 , transaction analysis service system  110 , and other systems and tools can be combined or even further divided and implemented among multiple different systems. The shared software development system  105  can be provided with tools for use in the development cycle of a software program, such as a program, or application, hosted on one or more software systems (e.g.,  115 ,  120 ,  125 ). Development tools can be provided or supported by the development system  105  such as a profiler tool, a logging tool, a debugger, a source control tool for managing proposed software patches and updates, a software virtualization system, among other examples. 
     The transaction analysis system  110  can include functionality for enhancing use of the development tools provided by development system  105 . For instance, the transaction analysis system  110  can detect conditions or transaction boundaries involving software transactions that may span multiple different systems in a tiered software system. For instance, satisfaction of a condition can be detected upstream from a particular component of the software system, but can be used to selectively trigger performance of a development activity on the particular component, even when the condition would otherwise be impossible to detect from monitoring only the particular component, among other examples. More generally, where certain development activities might traditionally affect multiple portions of a software system (and multiple different developers working on the same software system), the transaction analysis system can enable more precise application of the development tools of development system  105 . The transaction analysis system  110  can detect transaction or session boundaries in which a particular development activity is to be performed based on transaction data collected from software-based agents deployed throughout a multi-component software system. This transaction data can be further utilized to observe how software transactions proceed, or flow, through the system. 
     At least some of software systems (e.g.,  115 ,  120 ) can host software that is the subject of development activities performed using tools of development system  105 . This software can be an application, program, or portion (collectively referred to herein as “component”) of a larger, multi-tiered software system. Software components can utilize, consume data and services of, provide data or services to, or otherwise be at least partially dependent on or function in association with one or more other software components hosted on the same (e.g.,  115 ) or a different software server system (e.g.,  120 ,  125 ). Software components in the system can be hosted on systems (e.g.,  115 ,  120 ) of a single entity or may be distributed on systems (e.g.,  125 ) controlled by one or more third parties, among other examples. Further, software components in some software systems can interact with and consume data from and/or contribute data to one or more data services or data stores, such as database  130 , among other examples. Development activities can potentially be utilized during the development cycles of any one of the various software components in a broader software system and may target only specific functionality or transaction capabilities of the components and the system as a whole. 
     One or more computing systems and services can be hosted on machines communicatively coupled by one or more networks (e.g.,  140 ), including local networks, public networks, wide area networks, broadband cellular networks, the Internet, and the like. Systems with which a system under development (e.g.,  115 ) can interact can include data stores (e.g.,  130 ), other software systems (e.g.,  120 ,  125 ), and constituent software components accessible over the one or more networks  140 . Further, systems and services (e.g.,  105 ,  110 , etc.) provided to support development of the one or more of systems (e.g., hosted on  115 ,  120 ,  125 ,  130 , etc.) can also be provided local to or remote from (e.g., over network  140 ) the target systems (e.g.,  115 ,  120 ,  125 ,  130 ), among other examples. Additionally, computing environment  100  can include one or more user devices (e.g.,  145 ,  150 ) that can allow users to interact with one or more of the servers, services, data structures, and services (e.g.,  105 ,  110 ,  115 ,  120 ,  125 ,  130 , etc.) provided in the environment. Such user interactions can take place locally at the host systems of such software components or remotely over network  140 , using user devices (e.g.,  145 ,  150 ). 
     In general, “servers,” “clients,” “computing devices,” “network elements,” “hosts,” “system-type system entities,” “user devices,” and “systems” (e.g.,  105 ,  110 ,  115 ,  120 ,  125 ,  130 ,  145 ,  150 , etc.) in example computing environment  100 , can include electronic computing devices operable to receive, transmit, process, store, or manage data and information associated with the computing environment  100 . As used in this document, the term “computer,” “processor,” “processor device,” or “processing device” is intended to encompass any suitable processing device. For example, elements shown as single devices within the computing environment  100  may be implemented using a plurality of computing devices and processors, such as server pools including multiple server computers. Further, any, all, or some of the computing devices may be adapted to execute any operating system, including Linux, UNIX, Microsoft Windows, Apple OS, Apple iOS, Google Android, Windows Server, etc., as well as virtual machines adapted to virtualize execution of a particular operating system, including customized and proprietary operating systems. 
     Further, servers, clients, network elements, systems, and computing devices (e.g.,  105 ,  110 ,  115 ,  120 ,  125 ,  130 ,  145 ,  150 , etc.) can each include one or more processors, computer-readable memory, and one or more interfaces, among other features and hardware. Servers can include any suitable software component or module, or computing device(s) capable of hosting and/or serving software applications and services, including distributed, enterprise, or cloud-based software applications, data, and services. For instance, in some implementations, a shared development system  105 , transaction analysis system  110 , server system (e.g.,  115 ) or other sub-system of computing environment  100  can be at least partially (or wholly) cloud-implemented, web-based, or distributed to remotely host, serve, or otherwise manage data, software services and applications interfacing, coordinating with, dependent on, or used by other services and devices in environment  100 . In some instances, a server, system, subsystem, or computing device can be implemented as some combination of devices that can be hosted on a common computing system, server, server pool, or cloud computing environment and share computing resources, including shared memory, processors, and interfaces. 
     While  FIG. 1  is described as containing or being associated with a plurality of elements, not all elements illustrated within computing environment  100  of  FIG. 1  may be utilized in each alternative implementation of the present disclosure. Additionally, one or more of the elements described in connection with the examples of  FIG. 1  may be located external to computing environment  100 , while in other instances, certain elements may be included within or as a portion of one or more of the other described elements, as well as other elements not described in the illustrated implementation. Further, certain elements illustrated in  FIG. 1  may be combined with other components, as well as used for alternative or additional purposes in addition to those purposes described herein. 
     Modern software development can involve the participation of multiple development team members working substantially concurrently to build, test, deploy, and assess the system. Development activities within a shared software system can be complicated by the multiple developers attempting to access and utilize the same portions of the system to perform development tasks falling under each developer&#39;s responsibilities within the team. Further, traditional development tools used to analyze and test systems during development may lack the precision to selectively perform development activities on only a portion of the system (and its transactions) without interfering with the activities of other users (or even customers, in the case of a production system). 
     As an example, debuggers can be utilized to test and debug one or more software components in the system. Breakpoints can be defined throughout the code of software components of the system for use by various developers in a development team to test the portions of the system they are responsible for managing and developing. Some of these breakpoints can likewise be “owned” by individual developer users by virtue of the developer being the author of the breakpoint or the breakpoint having particular debugging value within an area of the system&#39;s development that most closely pertains to a given developer-user&#39;s responsibilities. In some cases, different breakpoints owned by, or otherwise associated with, different users can be included in the same software component. Further, in some cases, debugging of a software component shared by two or more developers can cause an interruption (e.g., due to the triggering of a corresponding breakpoint) that interferes with the ability of other developer-users to utilize the debugged software component and perform other software development activities contemporaneously. In still additional examples, an instruction set simulator (ISS)-based debuggers can be utilized. For instance, an ISS-based debugger can be loaded with a target software component based on a determination that it falls within a particular transaction boundary, among other example implementations. 
     At least some of the systems described in the present disclosure, such as the systems of  FIGS. 1 and 2 , can include functionality that at least partially remedy or otherwise address at least some of the above-discussed examples deficiencies and issues, among others. For instance, a shared development platform can be provided that leverages intelligence garnered by a transaction analysis system that can be used to detect boundaries between the various transactions, processes, and threads running contemporaneously in a multi-component software system. A variety of different boundaries can be defined by users, each boundary indicating a respective set of one or more conditions that are to apply if a given transaction, transaction fragment, and/or thread is to “fall” within the boundaries. One or more development activities can be triggered to be performed selectively on the specific transactions, processes, and threads that are determined to fall within a corresponding boundary (or “transaction boundary”). This can allow a single user (e.g., developer) to define logical boundaries in which a given development activity is to apply (e.g., debugging), without interfering with the development activities of other users who may be accessing or using the same software component(s) in connection with their own development activities. Thus, the shared development platform can enable logical, dedicated “sandboxes” in which an individual user (or subset of users) in a development team can perform various development activities, among other examples and potential benefits. 
     Turning to the example of  FIG. 2 , a simplified block diagram  200  is shown illustrating an example environment  200  including a shared development platform  205 , a virtualization system  210 , and one or more services, database management systems, programs, or applications (referred to in this example collectively as “applications” (e.g.,  215 ,  220 ,  225 ). The systems  205 ,  210 ,  215 ,  220 ,  225 , etc. can interact, for instance, over one or more networks  140 . In one example implementation, a development platform  205  can include one or more processor devices (e.g.,  226 ) and one or more memory elements (e.g.,  228 ) for use in executing one or more components, tools, or modules, or engines, such as a transaction path engine  230 , boundary detection engine  232 , agent manager  234 , and one or more development tools. For instance, in the example of  FIG. 2 , the development platform  205  can provide a suite of development tools including examples such as a debugger  235 , profiler  236 , logger  238 , patch manager  240 , and virtualization  242 , among other potential tools and components including combinations or further compartmentalization of the foregoing. In some implementations, development platform  205  can be implemented as multiple different distinct systems including, for example, varying combinations of the foregoing components and tools (e.g.,  230 ,  232 ,  234 ,  235 ,  236 ,  238 , etc.) and accompanying data (e.g.,  244 ,  245 ,  246 ,  248 ). 
     In one example, test system  205  can include a transaction path engine  230  configured to inspect a particular application (e.g.,  215 ,  220 ,  225 ) or combination of co-functioning applications (e.g.,  215  and  220 ) to identify one or more transactions involving the application(s) as well as the respective software components (e.g.,  262 ,  268 ,  272 ) of the applications (e.g.,  215 ,  220 ,  225 ) invoked and utilized within a broader software system and software transactions. Information gathered from monitoring or inspection of the transaction can be stored in transaction data  244 . Further, the flow path of the transactions can additionally be identified and flow path data  245  can be generated describing the flow between software components (e.g.,  262 ,  268 ,  272 ) and the respective contributions, operations, processes, or transaction fragments of the applications within the flow. 
     In some implementations, transaction path engine  230  can operate cooperatively with an agent manager  234  interfacing with or otherwise managing one or more instrumentation agents (or “agents”) (e.g.,  258 ,  264 ) deployed on one or more applications (e.g.,  215 ,  220 ) for use in aiding the monitoring of performance of various components (e.g.,  256 ,  264 ) of the applications. In some cases, a single agent (e.g.,  258 ) can monitor operation of and transactions involving more than one software component and in other cases each software component (e.g.,  268 ) can be instrumented with a respective agents (e.g.,  264 ). Agents (e.g.,  258 ,  264 ), in either implementation, can be software-implemented agents that are configured to provide visibility into the internal operations of each instrumented component (e.g.,  256 ,  264 , etc.) as well as the data being communicated into and out of each component. Each agent can be configured, for example, to detect requests and responses being sent to and from the component or application in which that agent is embedded. Each agent (e.g.,  258 ,  264 ) can be configured to generate information about the detected requests and/or responses and to report that information to other services and tools, such as agent manager  236 , virtualization system  210 , transaction path engine  230 , and one or more development tools (e.g.,  235 ,  236 ,  268 ,  240 ,  242 , etc.). Additionally, each agent can be configured to detect and report on activity that occurs internal to the component in which the instrumentation agent is embedded. Collectively, such information can be embodied as transaction data generated by the agents (e.g.,  258 ,  264 ) to report characteristics of the components&#39; operation and transaction observed by the respective agent. Transaction data from an agent can be marked to identify the agent from which it originates. 
     In response to detecting a request, response, and/or other activity of a transaction to be monitored, each agent (e.g.,  258 ,  264 ) can be configured to detect one or more characteristics associated with that activity and/or the monitoring of that activity by the agent. The characteristics can include a frame identifier, which identifies a message, with respect to the agent, sent by the agent to a managing service, such as agent manager  236 , embodying at least a portion of the transaction data sent from the agent to report the characteristics observed by the agent. For instance, frames can include a parent identifier, which identifies the requester software component that generated the request sent to the component or sub-component monitored by the instrumentation agent; a transaction identifier, identifying the transaction, with respect to the component or sub-component being monitored, such as transactions between components carried out through communications and calls made over one or more network connections; a session identifier (or token) to propagate session information detected in one portion of the transaction throughout the transaction; and an agent identifier that identifies the agent, with respect to the other instrumentation agents in the testing system, that is generating the characteristics, among other characteristics. Such characteristics can include other information such as a system clock value, current processor and/or memory usage, contents of the request, contents of the response to the request, identity of the requester that generated the request, identity of the responder generating the response to the request, Java virtual machine (JVM) statistics, standard query language (SQL) queries (SQLs), number of database rows returned in a response, logging information (e.g., messages logged in response to a request and/or response), error messages, simple object access protocol (SOAP) requests, values generated by the component that includes the instrumentation agent but that are not returned in the response to the request, web service invocations, method invocations (such as Enterprise Java Beans (EJB) method invocations), entity lifecycle events (such as EJB entity lifecycle events), heap sizing, identification of network connections involved in transactions, identification of messages and data exchanged between components, including the amount of such data, and the like. Characteristics can also include the thread name of a thread processing the request to generate the response and other data describing threads involved in a transaction, the class name of the class of an object invoked to process the request to generate the response, a Web Service signature used to contain the request and/or response, arguments provided as part of the request and/or response, an ordinal (e.g., relating to an order within a transaction), the duration of time spent processing the request and/or generating the response, state information, a local Internet Protocol (IP) address, a local port, a remote IP address, a remote port, and the like, among other examples. 
     As the above examples indicate, characteristic information can include information generated by the agent itself and information generated and/or processed by the component or sub-component monitored (and collected) by the agent (such as data sent or received by the component that intercepted by one or more agents). The agent can then cause information identifying those characteristics to be provided to one or more other services or tools (e.g., development tools  235 ,  236 ,  238 ,  240 ,  242 , etc.) communicatively coupled to the agent or agent manager. In some embodiments, each instrumentation agent collects information to form a message, also referred to herein as a frame, which describes characteristics associated with either or both a detected request and a detected response to the request in a transaction. In some instances, an agent can return transaction data in a frame to describe both the request and its corresponding response as observed at a software component monitored by the agent. In such cases, the respective agent can wait for the response corresponding to the request to be generated and sent before sending the frame to another tool or engine (e.g.,  234 ,  235 ,  236 ,  240 ,  242 , etc.) making use of the information in the frame. 
     Additionally, agents can monitor and report characteristics independently for each transaction in which its respective monitored component(s) (e.g.,  262 ,  268 , etc.) participates. In some cases, an agent can send transaction data for each fragment of a transaction observed by the agent. For instance, separate frames can be sent for the request and corresponding response. An agent manager  234  can receive frames containing the transaction data and determine which requests and responses belong to which transaction fragments and transactions. Further, the transaction path engine  230  can utilize these relationships to stitch transaction fragment information collected from potentially multiple frames from multiple agents, to develop a chain of transaction fragments that map to the actual flow of the transaction as it traverses multiple software components of the system (and potentially multiple agent domains). 
     In some embodiments, all or some of agents (e.g.,  258 ,  264 ) can be configured to perform interception and/or inspection (e.g., using the Java™ Virtual Machine Tool Interface, or JVM TI). Such an instrumentation agent can register with the appropriate application programming agent (API) associated with the component or process being monitored in order to be notified when entry and/or exit points occur. This allows the agent to detect requests and responses, as well as the characteristics of those requests and responses. In particular, this functionality can allow an agent to detect when a component begins reading and/or writing from and/or to a socket, to track how much data is accessed (e.g., read or written), obtain a copy of the data so read or written, and generate timing information (as well as information describing any other desired characteristics such as inbound/read or outbound/write identifiers) describing the time or order at which the data was read or written, among other information describing the data accessed, processed, or generated by the component. 
     In some instances, agents (e.g.,  258 ,  264 ) can be configured to monitor individual threads by monitoring the storage used by each thread (i.e., the thread local storage for that thread), variable values utilized in the thread, functions called in the thread, among other information. Such agents can detect when the monitored thread begins reading or writing to a thread local variable in the thread local storage. In response to detecting this access to the thread local variable, the agent can track the amount (e.g., in bytes, as tracked by incrementing a counter) of data that has been accessed, as well as the starting offset within the thread local storage to which the access takes place. In response to detecting that the thread&#39;s access to the thread local variable has ended, the instrumentation agent can use the information about the access to identify characteristics such as the time of the access, the variable being accessed, the value being accessed, network calls being made, and the like. 
     As noted above, in some implementations, one of the characteristics that can be collected by agents (e.g.,  258 ,  264 ) can include timing information, such as a timestamp, that indicates when a particular request was received or when a particular response was generated. Such timing information can be included in transaction data  244  and be used, for instance, by transaction path engine  230 , to identify that frames, including frames received from different agents, are related to the same transaction. In some implementations, timers used by agents (e.g.,  258 ,  264 ) can be synchronized to assist in correlating timing information collected between multiple agents. Additionally or alternatively, flow, organization, hierarchy, or timing of a particular transaction can be identified through the generation of transaction identifiers that include characteristics collected by agents (e.g.,  258 ,  264 ) for use in identifying fragments of the transaction. Such transaction identifiers, or transaction fragment identifiers, can include data collected by instrumentation agents in connection with, for example, the exchange of data, messaging, and other communications between components in the transaction, from thread jumps identified within software processes involved in the transaction, and other features of the transaction or fragments of the transaction. 
     In some implementations, agents (e.g.,  258 ,  264 ) can be implemented by inserting a few lines of code into the software component (or the application server associated with that software component) being instrumented. Such code can be inserted into a servlet filter, SOAP filter, a web service handler, an EJB3 method call, a call to a Java Database Connectivity (JDBC) handler, and the like. For example, an agent configured to monitor an EJB can be configured as an EJB3 entity listener (e.g., to monitor entity beans) or interceptor (e.g., to monitor session beans, etc.). Some components (or their corresponding application servers) may not provide users with the ability to modify their code, and thus some instrumentation agents can be implemented externally to the component being monitored in a manner that can cause all requests and responses being sent to and/or from that component to be handled by the corresponding agent(s). For example, for an existing database, an agent can be implemented as a driver. Calling components can be configured (e.g., by manipulating a driver manager) to call the instrumentation driver instead of the database&#39;s driver. The instrumentation driver can in turn call the database&#39;s driver and cause the database&#39;s driver to return responses to the instrumentation driver. For example, in one embodiment, the identity of the “real” driver for the database can be embedded in the uniform resource locator (URL) that is passed to the instrumentation driver. In this way, the instrumentation driver can intercept all calls to the database, detect characteristics of those calls, pass the calls to the appropriate database, detect characteristics of the corresponding responses, and then return the characteristics of those calls and responses within corresponding transaction data  240 , among other examples. 
     In implementations utilizing one or more agent managers (e.g.,  234 ), multiple agents (e.g.,  258 ,  264 ) can communicate with single agent manager  234  via a messaging system. In some cases, agents monitoring components hosted on distinct, or remote, devices can communicate over one or more networks with one or more centralized, or semi-centralized, agent managers  234 . In one example implementation, agents (e.g.,  258 ,  264 ) can communicate with an agent manager  234  using a messaging system such as Java™ Message Service (JMS), among other examples. For instance, agent manager  234  can create a messaging system topic for each transaction (referred to herein as a transaction frame (TF) topic) and subscribe to that TF topic. The instrumentation agents, upon startup, can broadcast their existence to each other and/or to agent manager  234 . The agents (e.g.,  258 ,  264 ) can then get the TF topic from agent manager  234  and begin publishing messages onto a message bus on that TF topic. Agent manager  234  can monitor the published messages and determine whether those messages relate to the current TF topic. As needed, agent manager  236  creates new TF topics for new transactions. In other examples, agents (e.g.,  258 ,  264 ) can alternatively communicate with agent manager  234  using techniques other than those involving messaging systems. For example, agents can write information to shared data repository (e.g., a database associated with the test system) using database commands, and an agent manager  234  can monitor those database commands to detect new information, among other examples. 
     As requests and responses progress through one or more systems (e.g.,  215 ,  220 ,  225 ), additional characteristic information can be captured, for instance, as transaction data  244 . For example, the operation of one or more software systems (e.g.,  215 ,  220 ,  225 ) engaged in one or more transactions can be monitored, for instance, by one or more agents (e.g.,  258 ,  264 ) and the agents can capture characteristic information associated with requests in the transaction (e.g., the time at which the request was received, the sender of that request, the time at which corresponding requests were sent to a database and/or other service, etc., how much data was exchanged, the identity of the communication channel used in the request or response, and the like) and the corresponding response, and generate transaction data  244  (e.g., frames) embodying the information. Agents, in some instances, can report transaction data to an agent manager  234  and additionally (or alternatively) store at least a portion of the transaction data at the agent. 
     As noted above, a transaction path engine  230  can determine and track the specific path, or flow, taken by a given transaction based on transaction data  244  captured and reported by agents observing the transaction at the participating software components. The path can be determined as the transaction progresses in substantially real time, with some transaction data being returned as some transaction fragments complete (but before others finish or begin). The transaction path engine  230  can access and utilize transaction information in transaction data  244  to identify fragments of a transaction and organize transaction fragments and accompanying information describing characteristics of the fragment of a particular transaction into groups corresponding to a common transaction. For instance, transaction fragment characteristics can be correlated to group corresponding frames into groups of frames that describe a complete transaction or session (that includes multiple transactions). 
     In some embodiments, in order to group frames, or otherwise identify relationships between frames or transaction fragments, transaction path engine  230  (or another tool) can sort the frames based upon particular characteristics, such as timing information associated with and/or included within those frames, the presence of a common session token included in the reported transaction data frames, parent and child component identifiers, the size of requests sent/received, among other information. After being sorted, the frames can be arranged in ascending or descending order, with respect to the timing or parent-child information, etc. For example, the frames can be sorted according to a timestamp indicating when each frame was generated, when one or more requests identified in each frame were generated or received, and/or when one or more responses identified in each frame were generated or received. In some embodiments, the frames can be sorted based upon multiple pieces of timing information. 
     In other examples, frames can be sorted, for example, based on an amount of data exchanged, the identity of a particular communication channel or network connection used, addresses of the receiving and sending components, the identification of the particular agents that provided the frames, etc. For instance, frames and accompanying transaction fragments can be correlated according to the amount and type of data that was received and/or generated, as detected by the agent, as well as information identifying the components or sub-components involved in the monitored activity. For example, such identity information can include information identifying the network ports (e.g., of the requester and responder), IP addresses, network information, or other features describing the communication of a request and corresponding response between a requester and responder. This information can be used to correlate or otherwise identify relationships between two different frames that have similar timing information and data amounts, for example. Identified network connections can be mapped to a particular portion, or fragment, of a transaction, and such fragments can be grouped (e.g., using the collected network connection description data) to identify particular transactions involving multiple different software components (and network connections), among other examples. 
     Within a group of frames or identified transaction fragments associated with the same transaction, transaction path engine  230  can order, or stitch, the frames to define a chain or order of transaction fragments within a given transaction or set of instances of a similar transaction. The stitching of the frames can be based on determined correlations between grouped frames (e.g., to identify parent-child relationships between given frames and their corresponding transaction fragments). The stitched frames can then define a transaction flow to allow the path, or flow, of the transaction to be followed from the start of the transaction to the end of the transaction and across a chain of potentially many different software components. Each frame can include a field that identifies that frame (e.g., a frame ID), as well as a field that identifies a parent frame (e.g., a parent frame ID). The value of each frame&#39;s parent frame ID can equal another frame&#39;s frame ID. These frame identifiers can be generated by the agents. In one embodiment, the frame identifiers can be generated from information identifying the IP address (or other addressing information) and port number used by the monitored component or sub-component, the amount of data sent or received by the monitored component during the monitored activity, and/or the instrumentation agent itself, among other information. Relationships can thereby be identified between parent frames, transaction fragments, and software components and corresponding child frames, transaction fragments, and components, to stitch these frames together, among other examples. 
     In addition to being able to use relationships or correlations to predict or determine a stitching or flow path of transaction fragments, transaction path engine  230 , in some instances can use the lack of correlative data reported by an agent to determine that a given frame corresponds to a transaction fragment that represents a root or leaf (e.g., beginning or end) of a particular transaction or branch of a transaction. For instance, it can be identified that no related connections (or other transaction fragments) involving a particular software component (or just a single correlation) have been identified or reported and conclude, predictively, that the lack of further connections or other reporting data relating to the component or a flow including the component indicate that the transaction terminated at the component, among other examples. Similarly, root nodes can be predictively determined based on the absence of frames documenting an inbound connection at a particular component from which other transaction fragments (and related connections) originate, among other examples. Root nodes can be considered to represent the furthest “upstream” component in a flow, while leaf nodes represent the further “downstream” components in the flow. 
     A transaction path engine  230  can utilize and correlate transaction data  244  generated in part by one or more agents (e.g.,  258 ,  264 ) to determine one or more transaction flow paths. The transaction path engine  230  can generate and maintain path data  245  describing the determined flow paths involving one or more software components (e.g.,  256 ,  264 ,  266 ) or one or more software systems or applications (e.g.,  215 ,  220 ,  225 ). Other tools, as well as other systems, can consume path data  245  to perform additional activities and services in support of tests and development of software systems (e.g.,  215 ,  220 ,  225 ) described in the paths. For instance, graphical representations of the transaction paths can be generated from the path data to illustrate the involvement of a set of software components and how the transaction progressed through the set of software components. Additionally, the graphical representation can present representations of characteristics defined in the transaction information (e.g., characteristics of requests and responses in individual transaction fragments, characteristics of individual software components, etc.). 
     Transaction data (e.g.,  244 ) can also be used to determine that one or more boundary conditions (e.g.,  246 ) have been satisfied triggering targeted application of one or more development tools on transactions, fragments, and/or threads falling within the transaction boundary defined by the conditions (e.g.,  246 ). As noted above, agents (e.g.,  258 ,  264 ) can report at least some transaction data  244  in real time as it collected to identify that a transaction, transaction fragment, thread, or set of transactions or threads (including downstream threads and transaction fragments that have yet to begin and/or complete) fall within a transaction boundary. Boundary detection logic  232  can receive or otherwise access transaction data as it is reported by one or more agents (e.g.,  258 ,  264 ) and can identify characteristics reported in the transactions that are included as conditions in one or more transaction boundary definitions (e.g., embodied in condition definition data  246 ). Boundary definitions (e.g.,  246 ) can further identify one or more development tools (e.g.,  235 ,  236 ,  238 ,  240 ,  242 ) that are to triggered when transactions (or portions of transactions) are determined to fall into one of the defined transaction boundaries. The boundary detection engine  232  can then interface with or otherwise control the invocation of these corresponding detection tools in response to detecting that transactions fall within one of the defined transaction boundaries. 
     A variety of different transaction boundaries can be defined for a single system. The system may include a number of different sub-systems, or tiers, and some of the boundaries may target development tasks to be performed on particular sub-systems or software components in the overall multi-tier software system. Some of the conditions may only be determinable based on the intensive view of the overall transaction(s) provided through a collection of agents instrumented throughout the software system. In some cases, determining that a condition applies to a particular transaction, transaction fragment, or thread may be dependent on another agent on another software component and/or server detecting the condition and the transaction path engine (or boundary detection) logic determining that an earlier (e.g., upstream) detected transaction characteristic triggers inclusion of various downstream transactions or transaction fragments within the transaction boundary. Indeed, in some cases, without the information provided by certain upstream agents, it may not be possible to determine that other downstream software transactions or threads are to fall within a transaction boundary and have corresponding development activities performed upon them. 
     As an example, a particular user may interface with a frontend system to send a request to the frontend system. The frontend system, in turn, may participate in transactions with various backend systems in connection with generating a response to the request. The backend systems, too, may transact with additional backend systems further downstream from the original request. In this example, a transaction boundary may be defined that triggers a corresponding set of debugging breakpoints (e.g., using debugger  236 ) in software components involved in those transactions, transaction fragments, or threads within a user session associated with a particular user (e.g., a particular developer-user). However, the frontend system may be the only system that receives data interpretable to identify that the transaction involves a session of the particular user. Further, conditional breakpoints to be triggered by identification of the session may be backend software component code where the session is unidentifiable, among other issues. An agent at the frontend system can capture session-identifying information and cause a session token or identifier to be appended to data in downstream transactions in the session or to transaction data generated by agents monitoring the downstream software components. Accordingly, the transaction data received from the agents monitoring software components involved in transactions of the session can be used to identify downstream (or child) transactions and corresponding threads that are also included in the session, triggering the selective activation of a set of breakpoints defined within the code that are to be activated when the code is executed in connection with the particular user session. Activation is selective in that other contemporaneous transactions and threads, involving, in some cases, the execution of the very same code, are allowed to progress without triggering the same breakpoints and corresponding debugging activities, among other examples. 
     Transaction boundaries can be defined for a variety of different development tools (e.g.,  235 ,  236 ,  238 ,  240 ,  242 ) with differing conditions (e.g.,  246 ) defined for triggering selective deployment of the tools on the various different software components in the system. Indeed, users can define transaction boundaries to enable the user to “carve out” that portion of the shared software system (under development) managed by the developer user, such that the user&#39;s development activities do not interfere with other development activities of other users of the system (or even, in some cases, the production operation of the system). 
     In one example, development tools for which transaction boundaries can be defined may include a debugger  235 , profiler  234 , logger  238 , patch manager  240 , and virtualization manager  242 , among potentially other development tools. A debugger can be used to debug code of the various software components included within the software system. For instance, a debugger  236  may run based on breakpoints defined in the code. In one example, transaction boundaries can be defined as conditions for conditional invocation of specific breakpoints to be used in debugging of the system. A profiler  236  can perform software profiling on a software component, for instance, to identify the usage of particular instructions, the frequency and duration of various function calls, etc. during operation of the software components. In the case of profilers, example transaction boundaries can be defined to filter which threads of a software component or system are to be profiled during a profile session. Additionally, or alternatively, transaction boundaries may also be defined to cause a collection of diverse software components or transactions/transaction fragments to be selectively profiled during a profiling session, for instance, to generate profile results that describe operation of a chain of transactions in a session, a collection of instances of a particular type of transactions, etc. Similarly, a logger  238  can be utilized to log events that occur during execution of a software system and transaction boundaries can be similarly defined to selectively log only a particular portion of the transactions within a system of interest to an author of the transaction boundary, among other examples. 
     Continuing with the above example, development tools can assist developers in testing or observing the hypothetical implementation of certain changes to the code and/or functionality of various software component within the broader system. Applying such changes can be particular disruptive within a shared development project. A patch manager  240  can be used to selectively apply a patch (or code modification) to one or more software components in the system under development. A transaction boundary can be defined such that a patch to a particular software component is only applied selectively when the software component is involved in a transaction falling within the transaction boundary, among other examples. In other implementations, rather than selectively applying patches to a particular software component to test a hypothetical change to the particular software component, a virtualized instance of the particular software component can be provided that simulates the operation of the particular software component were it to have the change. Thus, the virtualized instance can be selectively invoked (e.g., in connection with a corresponding transaction boundary) to replace the actual software component in transactions within the transaction boundary to simulate the change, among other examples. 
     In development platforms (e.g.,  205 ) including a virtualization development tool (e.g.,  242 ), a supporting virtualization system (e.g.,  210 ) may be provided separate from (or, alternatively, integrated with) the development platform  205 . The virtualization system  210 , in example, may include one or more processor devices  250 , memory devices  252 , and other hardware and software components including, for instance, a virtual service generator  254 , virtual environment  255  for provisioning and executing virtual services, among other examples. A virtualization system  210  can be used to generate and manage virtual services (e.g.,  256 ) that model software components and systems. Such virtual services  256  can be used as stand-ins (e.g., for particular software components) in tests and other development tasks involving the real-world systems modeled by the virtual service. Virtual services  256  can be generated by virtualization system  210  (e.g., using virtual service generator  248 ) based on detected requests and responses exchanged between two or more software components or systems. Such request and response information can be captured, for instance, by the same agents (e.g.,  258 ,  264 ) in transaction data  244  and can be used to generate virtual services  256 . Virtual services can capture and simulate the behavior, data and performance characteristics of complete composite application environments, making them available for development and testing at the request of a user or system and throughout the software lifecycle, among other advantages. 
     A virtualization system  210  can include functionality for the creation of complete software-based environments that simulate observed behaviors, stateful transactions and performance scenarios implemented by one or more software components or applications. Such virtual services provide functionality beyond traditional piecemeal responders or stubs, through logic permitting the recognition of input/requests and generation of outputs/responses that are stateful, aware of time, date, and latency characteristics, support such transaction features as sessions, SSL, authentication, and support string-based and dynamic request/response pairs, among other features. Service virtualization and other virtual models can be leveraged, for instance, when live systems are not available due to project scheduling or access concerns. In cases where components have not been built yet, environments can employ virtual services to rapidly model and simulate at least some of the software components to be tested within an environment. Virtual services can be invoked and executed in a virtual environment  255  implemented, for instance, within on-premise computing environments, in private and public cloud-based lab, using virtual machines, traditional operating systems, and other environments, among other examples. In some implementations, virtualization system  210  and virtual services  256  can utilize or adopt principled described, for example, in U.S. patent application Ser. No. 13/341,650 entitled “Service Modeling and Virtualization,” incorporated herein by reference in its entirety as if completely and fully set forth herein. 
     As noted above, software systems and their constituent software components can include functionality for transacting with one or more other systems and components in a multi-tiered system. In some cases, software components can transact with other components over one or more networks (e.g.,  140 ) (using corresponding network ports, sockets, etc.), APIs, or other interfaces (e.g.,  260 ,  265 ,  270 ), among other examples. Some applications can include front-end, user-facing services and applications that further include user interfaces (e.g.,  266 ) for presenting at least some of the outputs and results of a transaction to a user. Such user interfaces can further accept one or more inputs or request values provided by a user, among other examples. Applications, software systems, and software components can perform any variety of tasks or services and be implemented using potentially any suitable programming language, architecture, and format. 
     Turning to  FIG. 3 , a simplified block diagram is shown representing, for purposes of illustrating certain principles of this disclosure, an example software system and composite software components capable of engaging in one or more transactions. It should be appreciated that this particular system (and the transactions in this example) represents but a single example, and that a potentially unlimited variety of alternative systems, transactions, and architectures may make be monitored, analyzed, have defined transaction boundaries, and otherwise utilize the general features and principles outlined herein. 
     In the particular example of  FIG. 3 , a servlet component  305  is provided as a front end for an example Login transaction  315  and New Account transaction  320  accessible to users of user computer devices (e.g.,  310 ). The Login transaction can involve calling a web service of a web application  325  and use of a Login software component (e.g., implemented in this particular example as JavaBean software components) and Lightweight Directory Access Protocol (LDAP) system to facilitate the logging-in of a user into an account of the web application  325 . The web application  325  can potentially interact with multiple different users in multiple different concurrent session. Accordingly, the web application  325  can also maintain session identifiers, cookies, or other data to track sessions with the users. Other components of the system (e.g., backend service  330 ), however, may not maintain session or maintain different session data that abstracts the identity of the original requester (e.g., user), among other examples. 
       FIG. 4A  illustrates the flow path of an example Login transaction  315  as well as example request values  405  of the Login transaction together with example response values  410  returned in the transaction in response to the request values  405 . For instance, Login transaction can include a user-provided username and password pair (provided through servlet  305 ) resulting in a Login Okay response value when the provided username-password pair matches the username-password pair of an existing account managed by the LDAP system of web application  325 . Further, the identity of the username can also be returned, for instance, in a welcome message identifying the username. 
     Returning to  FIG. 3 , additional transactions can be provided and identified. For instance, the New Account transaction  325  can support the creation and storage of a new account, such as an account for an ecommerce, banking, media subscription, or other application or service. For instance, as shown in the example of  FIG. 4B , a more complex flow path can be identified for the New Account transaction  325  including multiple branches in the flow path. For example, upon creation of a new account (using New Account transaction  325 ) corresponding account information can be entered into a database  335  maintained outside of web application  325  and account service  330 . The account information can be generated by one or more software components, such as by software components of account service  330 , database  345 , third party service  340 , or other services and entities. New Account transaction can accept inputs or request values  415 , such as username, first name, last name, account type, and account balance (e.g., for a loan, bank, e-payment, or other financial account). These request values  415 , when processed in the transaction, can cause the retrieval, generation, and return of response values  420  including response values (such as values corresponding to user ID, first name, last name, account type, and balance) that are at least partially dependent or predictable based on values of the request values  415 , as well as additional response values (such as values of an account number, account open date, account ID, credit score, etc.) that are not derived from or based on any of the request values  415 . Such response values (e.g., account number, account open date, account ID, credit score) that are at least partially independent of request values  415  of the transaction can be considered dynamic values that are not easily derivable or predicted from the request values  415 . 
     The flow paths of each respective transaction involving a particular software component or system can be represented in transaction path data generated, for instance, using a transaction path engine. Transaction path data can be generated by grouping and correlating transaction fragment information included in transaction data and/or agent data captured and generated by one or more agents  355 ,  360  deployed on the software components and/or systems involved in the transactions, as illustrated in the example of  FIG. 3 . Some software components, such as third party service  340 , may be unmanaged in that they are not instrumented with agents under the control of or otherwise accessible to a transaction path engine, test engine, or other tool or entity monitoring the transaction. The involvement and functionality of such unmanaged software components may remain unknown to the tools utilized in the development of transaction paths and tests of a particular transaction, and can be effectively regarded as a black box within the transaction that accepts certain monitored requests and returns corresponding responses captured, in some instances, by the agent (e.g.,  360 ) of a neighboring monitored software component (e.g., SOAP client  370 ) receiving the response value from the unmonitored component (e.g., third party service  340 ), among other examples. 
     In some implementations, a single transaction can include the generation, communication, and use of multiple different response values. The generation and processing of various data within a transaction can involve the transmission of request values and response values to multiple different software components along multiple different sub-paths, or branches, of the transaction flow path. For example,  FIG. 4C  shows an example of a first branch of a transaction flow path shown bolded in  FIG. 4B . The flow path branch of  FIG. 4C  shows a path for generating and storing a response value in database  335 . For example, a response value can be generated or communicated by a New Customer software component for a new customer record utilizing other account information generated in the transaction. Response values such as UID, First_name, and Last_name may be provided from or generated by a New Customer software component or from a database call of database  335 , among other examples. The actual values of UID, First_name, and Last_name, in some examples, can be obtained from request values provided by a user, such as the request values User, First_name, and Last_name. In some examples, proper operation of the New Customer software component may be evidenced by the generation of response values UID, First_name, and Last_name that echo request values User, First_name, and Last_name, among other examples. 
       FIG. 4D  illustrates another branch of an example New Account transaction, such as the New Account transaction introduced in the example of  FIG. 4B . An account open date (e.g., Open_date) can be one of the response values returned in connection with the New Account transaction. In one example, an Open Date software component can include the logic for generating an account open date to be associated with a record to be provided to database  335  corresponding to the opening of the new account in connection with the New Account transaction. The account Open_date value can be generated by the Open Date component in response to a call from a New Account component of account service  330 . The New Account component can additionally manage the generation of additional account data, such as by the Account Info component. The New Account component can be called through a web service call (such as a SOAP call) from web application  325  to account service  330  triggered by a New Account component at web application  325 . Accordingly, as shown in the example of  FIG. 4D , the invocation of an Open Date software component object can be triggered through a series of calls originating at servlet  305  and the response value Open_date can be generated and passed back from the Open Date component as a response over the same transaction flow path branch to be returned to servlet  305 . The value of Open_date can be passed and reappear at each of the components upstream (i.e., in the direction of the flow path toward the software component originating the transaction request (e.g., servlet  305 )). The Open Date software component can be identified as the source of the Open_date response value based on an identification of the Open Date component as a leaf in the transaction flow path branch corresponding to the Open_date response value. The Open Date software component can be identified as the leaf of the transaction flow path branch based on, for example, transaction data illustrating that the Open Date software component has no children components but is, instead, only a child component of other components with respect to the Open_date response value and the corresponding transaction path branch, among other examples. 
     The example of  FIG. 4E  illustrates another example transaction flow path branch, in this case, relating to the chain of requests resulting in the generation of response values Account_no (e.g., providing the new account number generated for the account) and Account_id (e.g., corresponding to a database record for the new account), generated, for instance, by an unmonitored software component, such as database  345  or other data store, external to monitored software systems  325 ,  330 , among other examples. The values of Account_no and Account_id, as with Open_date, may be independent of the request values provided in the transaction and involve calls by software components across application boundaries and networks connecting two disparate applications (e.g.,  325 ,  330 ). For instance, the New Account software component of web application  325  may call the New Account software object of account service  330  using a web service call. An Account Info software component of account service  330  may in turn be called to generate values for the new account. For example, a database component  345  may include logic for auto-incrementing account number values (e.g., Account_no) for each new record that is added to the database  345 . It can be identified that a database call was made to database  345  and that such a database call is a leaf of the transaction path branch. Further, it can be identified that the database  345  is the source of a particular value, such as in the example of  FIG. 4E . Although the database  345  is not monitored by an agent, in some implementations, a transaction path engine or other tool can recognize certain types of calls to external components, such as SQL database calls, inverted list database calls, virtual storage access method (VSAM) calls, indexed sequential access method (ISAM) calls, flat file queries, and cache database calls, among other examples. Through such types of calls, the transaction path engine can make certain assumptions about the nature and operation of the external component. For instance, in the example of  FIG. 4E , in instances of a SQL call to component  345 , the SQL call can be identified, by an agent  350 , and interpreted to conclude that component  345  is a database and the source of the value returned in response to the SQL call, among other examples. For instance, other types of calls can be used to implicitly identify the general character of a software component generating or returning a particular value in a transaction. 
       FIG. 4F  illustrates another example transaction path branch involving a call to an unmonitored third party service  340 . Transaction data collected or generated by agents  355 ,  360  can be processed to create transaction path data that can be analyzed to identify that a CredScoreBase value is returned from a third party service  340  and that the CredScoreBase value is utilized by a Score Calc software component to generate a CredScoreFinal value. Accordingly, an analysis of the corresponding transaction path data can result in the identification of the third party service  340  as the source of the CredScoreBase value and the Score Calc component of the account service  330  as the source of the CredScoreFinal value. As the third party service  340 , in this example, is unmanaged, agents  355 ,  360  used to monitor the transaction are left without intelligence regarding how the CredScoreBase value is generated within the third party service  340 , whether other external services are called in connection with the generation of the CredScoreBase value by the third party service  340 , and so on. On the other hand, the agent  360  monitoring Score Calc component can identify with precision that the CredScoreFinal value was generated by the Score Calc component based on a CredScoreBase value returned from the unknown third party service  340 . Further, agent  360  can capture the value returned by third party service  340  through monitoring of web service client  370 , Score Calc component, etc. 
     In one example implementation, through transaction flow data (e.g.,  245 ) generated by the transaction path engine  230 , the nature of a particular response value and its dependency on one or more request values can be identified. For instance, transaction data can be correlated from consecutive transaction fragments and identify, for instance, from clock or timing data, or through a comparison of data included in requests and responses, that a particular response value corresponds to a particular request value. Additionally, characteristics detected at one component in a set of software components involved in a transaction flow (or a particular thread in the transaction flow) can be attributed to other components (and/or threads running on the components) based on determining that the components and/or threads are included in the same transaction flow. For instance, a session identifier detected by an agent (e.g.,  355 ) during a session involving a request of web application  325  by a particular user can identify that the session pertains to the particular user. Using transaction data, downstream threads (e.g., from agents  355 ,  360 ), such as running on account service  330 , can be determined to be within the same transaction or session causing these downstream threads to also be associated with the particular user (e.g., even when the downstream software component (e.g.,  330 )) is unaware of the particular user&#39;s involvement in the session. In the example of  FIGS. 3-4F , the particular user may be a user different from the “user” identified in [Username], [FIRST], [LAST], etc. For instance, the user may correspond to a developer who performs an instance of the Login or New Account transactions in connection with testing or development of the software system illustrated in  FIG. 3  (e.g., using test values for [Username], [FIRST], [LAST], etc., among other examples 
     Linking together a set of distinct (and potentially disparate) transactions, transaction fragments, threads, software components, etc. on the basis of user session using agent-generated transaction data and determined transaction flows can be a powerful tool to support filtering development activities. For instance, development activities on a shared software system or component can be filtered on the basis of individual developer users (or particular groups of developer users). For example, a developer-user can initiate a session in connection with a particular development activity. The user session may not explicitly identify the developer-user, but because the user session originates from the developer-user, the session can be identified as associated with the developer-user. In one example, at least one of the software components utilized in the session may be session-aware and an agent instrumented on this software component can identify that the transaction, or session, is a session to be associated with the particular developer-user. The agent and/or agent manager can tag transaction data describing transaction fragments in this session (as observed at this software component) with a token or other identifier to indicate that the transaction fragment is to be associated with the particular developer-user. Subsequent transactions in the session, as observed at this software component can be likewise identified. Further, through stitching (e.g., the determination that one transaction fragment is related to an immediately subsequent or previous transaction fragment in a transaction flow, can cause subsequent and/or previous transaction fragments to be likewise tagged as included in the user session and associated with the particular developer-user. This can be useful, for instance, when at least some portions of the software system are shared and potentially multiple different users (and user sessions) are on-going during the particular developer-user&#39;s session and use of the shared software system. 
     Turning to  FIG. 5 , a simplified block diagram is shown illustrating selective deployment of a debugger based on detecting that a subset of transactions during operation of a software component fall within a defined transaction boundary. In this example, the software system can be a multi-tier system including multiple server devices (e.g.,  505 ,  510 ,  515 ) each hosting a portion of the composite software components (e.g.,  535 ,  540 ,  545 ,  550 ) of the system. Agents (e.g.,  555 ,  560 ,  565 ,  570 ) can be instrumented on each of the server devices (e.g.,  505 ,  510 ,  515 ) and/or software components (e.g.,  535 ,  540 ,  545 ,  550 ) to monitor operation of and transactions involving the software components (e.g.,  535 ,  540 ,  545 ,  550 ). Multiple users (e.g.,  520 ,  525 ,  530 ) may make use of the system. Such users can be multiple developer-users working together to perform development tasks on the system. In some cases, some of the users (e.g.,  520 ,  525 ,  530 ) can be users interacting with a live production system. In either case, the users  520 ,  525 ,  530  can each be engaged in initiating and performing transactions on the system. In other instances, the transactions can be initiated by other systems or processes, such as a background process or test system, among other examples. 
     In the particular example of  FIG. 5 , each of the users  520 ,  525 ,  530  can each attempt, within a same window of time, to initiate transactions that utilize at least some of the same software components. For instance, two users (e.g.,  520 ,  525 ) can initiate different types of transactions, but each type of transaction may utilize at least one of the same software components (e.g.,  545 ) within the same window of time. Indeed, in some cases, the two transactions can involve two threads of the same software component (e.g.,  545 ) that run at least partially concurrently. In some cases, the different transactions of the multiple users  520 ,  525 ,  530  may be different instances of the same transaction type and two or more threads at two or more of the software components (e.g.,  535 ,  540 ,  545 ,  550 ) can at least partially overlap, among other examples. 
     Continuing with the above example, as the transactions take place, agents  555 ,  530 ,  565 ,  570  (e.g., similar to the agents discussed above) may monitor their respective software components and transactions (or transaction fragments) in which their software component participates and report transaction data to an agent manager  234  (or another component of a shared development platform). The transaction data may identify characteristics of the software components and/or threads involved in the transaction(s) as well as characteristics of messages (and their content) as sent during the transaction(s). Such characteristics can then serve as the basis of a transaction boundary used to trigger targeted development tasks, such as targeted debugging and activation  580  of conditional debugging breakpoints (conditioned on the transaction boundary) using a debugger (e.g.,  235 ). For instance, a transaction boundary can be used to define the selective application of the debugger  235  and/or certain defined breakpoints, such that debugging of a particular transaction or participating software component only takes place when the transaction falls within one or more corresponding transaction boundaries defined for the breakpoints or debugging activity. Other transactions, including contemporaneous transactions involving execution of the same code that is to be debugged for transactions within the transaction boundary, may be allowed to run, uninterrupted while the debugging of the transactions within the transaction boundary occurs. 
     In one example, a debugger can interface with other components of a development system such as boundary detection logic (e.g.,  232 ) such that the debugger  235  queries (or otherwise obtains information from) the boundary detection logic each time a breakpoint is encountered in the code by the debugger, to determine whether a transaction boundary applies to the breakpoint thereby causing the debugger to apply the breakpoint or not. Any threads within the corresponding transaction boundary can be paused (e.g., while allowing other contemporaneous threads falling outside the transaction boundary to continuing running). In some cases, multiple debugger clients can be utilized and when a breakpoint is reached for a particular transaction boundary, a debugger manager in the development system can broadcast a “breakpoint reached” event to allow the collection of debugger clients to also perform related debugging activities, among other examples. 
     As illustrated in  FIG. 5 , transaction data can be sent to an agent manager (or another component of a shared development platform) capable of using the transaction data to determine relationships between parent and child transaction fragments and/or determine that distinct transactions belong to the same session. Determining such relationships between transactions can serve as the basis for determining commonality between the transaction data of related transactions across the multiple tiers (e.g., different servers and components) of the system. Accordingly, characteristics observable at one tier, software component, transaction, or transaction fragment in a transaction or session can be mapped to other components, transaction, or transaction fragments by association. This can allow portions of a transaction to be determined as falling within a transaction boundary (based on an identified characteristic) even when the characteristics was effectively invisible or unobservable at that portion of the transaction (e.g., a corresponding software component or transaction fragment downstream from the agent observing the characteristic). 
     Turning to  FIGS. 6A-6B , simplified block diagrams are shown representing agent-generated transaction data collected during different windows of time. In the example of  FIG. 6A , transaction data has been collected from the agents (e.g.,  555 ,  560 ,  565 ,  570 ) instrumented on software components (e.g.,  535 ,  540 ,  545 ,  550 ) involved in three instances of a particular transaction (e.g., “Transaction 1,” “Transaction 2”, and “Transaction 3”) supported by a software system. Accordingly, transaction data can be received by the agents (e.g.,  555 ,  560 ,  565 ,  570 ) during the monitoring of each of these three instances and an agent manager (and/or transaction path engine) can identify relationships between individual transaction data frames (e.g.,  610   a ,  615   a ,  620   a ,  625   a ) received from different agents (e.g.,  555 ,  560 ,  565 ,  570 ) relating to different transaction fragments and determine (e.g., using the principles described herein) that the transaction fragments and corresponding transaction data should be grouped together (e.g., at  605 ). Likewise transaction data  610   b ,  615   b ,  620   b ,  625   b  and transaction data  610   c ,  615   c ,  620   c ,  625   c  can be determined to “belong” to their respective transaction instances (e.g., Transaction B and Transaction C respectively) and can be similarly grouped (e.g., at  630 ,  635 ). In the example of  FIG. 6A , a particular transaction boundary can be defined to indicate that all transaction fragments in an instance of the transaction having a particular characteristic (e.g.,  640 ) should cause a set of breakpoints corresponding to the particular transaction boundary to be activated (where software components having the breakpoints in their code are utilized during the transactions falling within the transaction boundary). In some instances, the breakpoints may only be activated when a debugging session involving the corresponding software component is active and the particular transaction boundary is satisfied. For instance, a user can launch a debugging session and identify one or more transaction boundaries that are to apply during the debugging session. Accordingly, instances of the transaction that occur during the debugging session and that fall within the defined transaction boundaries will result in the activation of corresponding conditional breakpoints. For instance, in the example of  FIG. 2 , the presence of characteristic  640  in a portion (e.g.,  615   b ) of the transaction data reported during a debugging session by a particular agent during Transaction 2 can cause a determination (e.g., by boundary detection logic  232 ) that Transaction 2 falls within the transaction boundary causing at least a portion of Transaction 2 to be debugged. Other transactions (including contemporaneous transactions) taking place during the debugging session and falling outside the transaction boundary, such as Transaction 1 and Transaction 3, may run without being debugged in the session. 
     Turning to  FIG. 6B , additional examples of transaction data are illustrated, in this case for transactions “Transaction 4,” “Transaction 5”, and “Transaction 6”. AS noted above, transaction data can also be used to group transactions (and their transaction data) according to session, such as a session initiated or involving a particular user or client system. For instance, a transaction boundary can be defined that causes all transactions falling within a session of a particular user (e.g., a particular one of a team of developer-users) to be considered as falling within a transaction boundary to filter the application of a particular development tool (e.g., a debugger) on the system. For instance, in the example of  FIG. 6B , transaction data (e.g.,  610   d ,  610   e ,  610   f ,  615   d ,  615   f ,  620   d ,  620   e ,  620   f ,  625   d ,  625   f ) is collected from instances of at least two different types of transactions. A characteristic  660   a ,  660   b  can be identified in transaction data  645 ,  650  of two different transactions, Transactions 4 and 5, that identifies that each transaction was included in particular user session (e.g., of the particular developer-user). Accordingly, Transactions 4 and 5 can be determined to fall within the corresponding transaction boundary and corresponding debug breakpoints reached during these transactions can be selectively activated (while Transaction 6 is not). This can allow, for instance, user-specific breakpoints to be selectively activated only when transactions are determined (from corresponding transaction data) to be within user sessions corresponding to the particular user (while other users&#39; breakpoints are left deactivated and other users&#39; sessions run unaffected). 
     Turning now to  FIG. 7 , a simplified diagram  700  is shown illustrating a collection of execution threads  705 ,  710 ,  715  running in connection with operation of a particular software system. At least some of the threads may run (at least partially) concurrently and involve the same portion(s) of software component code  720 . A number of breakpoints (e.g.,  725 ,  730 ) can be defined in the software code  720 . At least some of the breakpoints can be associated with transaction boundaries defined within the system. Indeed, in the present example, breakpoints  725 ,  730  can each be associated with a respective transaction boundary. For instance, breakpoint  725  can associated with a transaction boundary defined to encompass all transaction fragments and corresponding threads that run within user sessions associated with a first user. Breakpoint  730  can be associated with another similar transaction boundary that is defined to encompass all transaction fragments and corresponding threads that run within user sessions associated with a different second user. Indeed, breakpoint  725  can be associated and/or set by the first user and breakpoint  730  can be associated and/or set by the second user, with the corresponding transaction boundaries allowing each breakpoint to be automatically enabled in only those sessions associated with or controlled by the owner of the breakpoint. 
     For example, as shown in  FIG. 7 , transaction data  735  may be collected by software-based agents  740  instrumented within the system and monitoring operation of the system while one or more debugging sessions are active. The transaction data can be accessed by the development system  205  and used to determine which threads relate to corresponding transactions in various user sessions involving the system. In this example, a transaction boundary can be defined such that certain corresponding debug breakpoints (e.g.,  725 ) encountered in threads (of transactions) in a user session “Session A” are to be selectively enabled during the debugging session(s). Similarly, another transaction boundary can cause another set of breakpoints (e.g.,  725 ) encountered in threads (of transactions) in a user session “Session C” to be selectively enabled during the debugging sessions. Accordingly, a shared development platform  205  can identify (from previously or contemporaneously generated transaction data) the sessions (and/or transactions) to which each thread corresponds. 
     In this example, Thread 1 ( 705 ), run using code  720 , can be determined to run within an instance of Session A, causing breakpoint  725  to be enabled and thread  705  to be interrupted accordingly (at  740 ). When Thread 1 ( 705 ) resumes running following the breakpoint (not shown), in may skip breakpoint  730  and proceed through the execution of code  720 . The transaction fragment incorporating Thread 1 ( 705 ) may be but one of many transaction fragments and transactions that a given user may desire to test within a debugging session. Indeed, other breakpoints, defined in the same or different code (including code of software components hosted on other remote server devices) may also have breakpoints that are enabled during the debugging session by virtue of these additional transactions also falling within Session A and the corresponding transaction boundary. 
     Continuing with the example of  FIG. 7 , Thread 2 ( 710 ) also runs using code  720 . However, Thread 2 ( 710 ) is determined (from corresponding transaction data  735 ) to be associated with another user session, “Session B,” that falls outside of the transaction boundaries defined to enable either breakpoint  725  or  730 . Accordingly, Thread 2 ( 710 ) progresses through code  720  without interruption. For instance, Thread 2 may be a thread of a transaction not involved in any of the active debugging sessions of the system. Finally, Thread 3 ( 715 ), also run using code  720 , may be determined, through transaction data  735 , to be within Session C and therefore within a transaction boundary that causes breakpoint  730  to be enabled (but not breakpoint  725 ). Accordingly, Thread C ( 715 ) may be interrupted at breakpoint  730  within a corresponding debug session (that utilizes the corresponding transaction boundary), as shown in  FIG. 7  (at  745 ). 
     While  FIG. 7  illustrates selective enablement of debug breakpoints based on the transaction boundaries defined to coincide with detected user sessions, other debug breakpoints can be enabled by other transaction boundaries, such as transaction boundaries based on the detection of characteristics such as a particular system (e.g., client) invoking or otherwise contributing to at least a portion of a transaction or set of transactions, when content of messages passed in one or more transaction fragments includes certain defined values or possesses other attributes, among other examples. Additionally, a single breakpoint can be linked, in some cases, to multiple different transaction boundaries and can be enabled for transactions falling within any one of these transaction boundaries. In some cases, a determination that a chain of transaction fragments is within a defined transaction boundary can cause each of the transaction fragments to be debugged (including, in some instances, code that has already been executed in connection with an already performed fragment in the chain of transaction fragments. Further, a single breakpoint can prompt debugging by multiple debugger clients (including instances where the multiple debugger clients focus debugging on threads or processes determined to fall within the corresponding transaction boundary). Further, transaction boundaries can be paired with conventional conditions such that the breakpoint is enabled when one or more of a defined combination of conditions are met, among other example implementations and features. 
       FIG. 8  is a flowchart of an example technique for performing targeted debugging of a software system. For instance, transaction data can be received  805  from a variety of agents monitoring a plurality of software components in the system. The transaction data can identify characteristics of various fragments of a plurality of transactions observed by the agents. Further, such transaction monitoring can occur during a debugging session and the resulting transaction data can be used to identify what portions of the system to debug. For instance, at least a particular one of the transactions can be determined  810  to fall within a defined transaction boundary. In some cases, the particular transaction can be one of several transactions (e.g., in one or more sessions) determined (from the transaction data) to fall within the transaction boundary. Determining that the particular transaction falls within the transaction boundary can be based on detecting a characteristic of the particular transaction (e.g., by an agent monitoring the transaction). Further, other transactions, transaction fragments, processes, and/or threads can be determined to be related to the particular transaction, for instance, as a transaction in the same or a related chain of transactions or session. The characteristic determined from the monitoring of the particular transaction can be attributed to other transactions determined to be associated with the particular transaction. For instance, due to the characteristic and a determination that a second transaction is related to the particular transaction, the second transaction (and related processes and/or threads) can be determined  815  to also fall within the transaction boundary. The transaction boundary can be further associated with one or more debug breakpoints inserted in the code of the software components involved in transaction fragments within the transaction boundary. The breakpoints can be conditionally enabled  820  for those transaction instances determined to fall within the transaction boundary, causing some threads and/or processes within the transaction boundary to be interrupted in accordance with the enabled breakpoints. The corresponding software components and/or transactions can be debugged  825  utilizing the enabled breakpoints and a debugger. In some instance, debug results can be generated from debugging performed in connection with a set of one or more enabled breakpoints related to the transaction boundary. Such debug results can be presented in a graphical representation of the transaction, such as one shown and described, for example, in U.S. patent application Ser. No. 14/990,173 entitled “Transactional Boundaries for Software System Profiling,” filed Jan. 7, 2016 and incorporated herein by reference in its entirety as if completely and fully set forth herein. 
     The flowcharts and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various aspects of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions. 
     The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of any means or step plus function elements in the claims below are intended to include any disclosed structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The aspects of the disclosure herein were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure with various modifications as are suited to the particular use contemplated.