Abstract:
A service level management (SLM) system where the system learns the structure of a web application, monitors the operation of the application, and controls the processing of incoming requests to achieve optimal performance as defined in a service level agreement (SLA). The system is operative for example in enterprise web applications and in enterprise data centers that deploy web applications and optimally is capable of controlling and maintaining a level of service of web applications.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from a U.S. provisional application 60/779,706 filed on Mar. 6, 2006 which is hereby incorporated for all that it contains. 

   TECHNICAL FIELD 
   The present invention relates generally to controlling and managing the performance of web applications. 
   BACKGROUND OF THE INVENTION 
   Enterprises and organizations expose their business information and functionality on the web through software applications, usually referred to as “web applications.” Web applications provide great opportunities for an organization. Web applications use the Internet technologies and infrastructures. These applications are generally event-driven software programs which react to hyper text transfer protocol (HTTP) requests from the client. The applications are generally executed on application servers, constructed according to N-tier architecture, in which presentation, business logic, and data access layers are kept separate. Recently, web applications have evolved into large-scale applications that demand more sophisticated computing services. 
     FIG. 1  shows an exemplary network system  100  that is utilized for executing web applications. System  100  includes clients  110 - 1  through  110 -N, web servers  120 - 1  through  120 -M, application servers  130 - 1  through  130 -Q, back-end systems  150 , a load balancer  160 , and a network  170 . Clients  110  submit requests (e.g., HTTP requests) to web servers  120  through network  170 . Load balancer  160  distributes the requests among the servers  120  to balance the load between servers  120  and  130 . Each of web servers  120  dynamically generates presentation, for example, using servlets, or extensible markup language (XML), extensible style-sheet language (XSL), and the likes. Application servers  130  are often responsible for deploying and running the business logic layer and for interacting with and integrating various enterprise-wide resources, such as web servers  120 , and back-end systems  150 . The back-end system  150  may include, for example, a database and a legacy system. 
   Workload may be distributed across a cluster of application servers  130  in different ways. For example, application code may be replicated across multiple application servers in the cluster, enabling a given request to be processed by any of these multiple application servers  130 . Also, application code may be logically partitioned over multiple application servers  130 , e.g., so that a particular server  130  is responsible for performing particular types of operations. This type of application partitioning may improve the application performance. For example, data-intensive application logic may be configured to run on an application server that is closest to a data source, in order to reduce the latencies associated with accessing remotely located data. 
   As the web and application servers  120  and  130  become busier with handling more and more requests, the quality and level of service sharply decrease. With existing load balancing capabilities, once the servers are saturated, the quality of service drops drastically for all clients accessing a web site. Currently, a standard tool that automatically monitors, manages, and controls the operation and load of applications and servers is not found in the related art. The management and control of web applications mostly relies on technical personnel. This results with many drawbacks including unpredictable level of service and uncontrolled user experience as well as costly maintenance of applications. Additionally, the application management is static, i.e., the ability to detect problems and solve them in real-time is not feasible. Another major drawback is the inability to deliver services according to predefined service level agreements (SLAs), as the ability to provide committed services increasingly becomes a competitive requirement. Yet another major drawback is the inability to balance the load differently per application in servers that are installed with multiple applications. 
   It would be therefore advantageous to provide a network solution for automatically managing and controlling web applications that overcome the drawbacks mentioned in the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention includes a service level management (SLM) system in a network with a plurality of clients and a plurality of web servers. The SLM system includes a traffic processor for processing data traffic sent from a the plurality of clients and from a the plurality of web servers; an application learner for identifying transactions sent from the plurality of clients; a monitor for monitoring and generating statistics respective of the operation of the web servers and their respective web applications; and a controller for performing corrective actions according to a plurality of predefined policies. 
   The present invention also includes a method for controlling and maintaining a level of service of web applications. The method includes generating a context for each request sent from a client to a web server and for each reply sent from a web server to a client; determining whether the context belongs to an identified web application; gathering statistics respective of the identified web application; determining whether at least one policy predefined for the identified application is violated; and performing a plurality of corrective actions if at least one policy is determined to be violated. 
   The present invention also includes a computer program product including a computer-readable medium comprising software instructions operable to enable a computer to perform a method for controlling and maintaining a level of service of web applications The program product causes a computer to execute the processes of generating a context for each request sent from a client to a web server and for each reply sent from a web server to a client; determining whether the context belongs to an identified web application; gathering statistics respective of the identified web application; determining whether at least one policy predefined for the identified application is violated; and performing a plurality of corrective actions if at least one policy is determined to be violated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 —is a non-limiting network system utilized for executing web applications (prior art); 
     FIG.  2 —is a diagram of a network system constructed in accordance with an exemplary embodiment of the present invention; 
     FIG.  3 —is a block diagram of the SLM system disclosed in accordance with an embodiment of the present invention; 
     FIG.  4 —is a flowchart describing the operation of the SLM system in accordance with an embodiment of the present invention; and 
     FIG.  5 —is an exemplary diagram of a site tree. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  shows a non-limiting and exemplary diagram of a network system  200  constructed in accordance with one embodiment of the present invention. System  200  includes clients  210 - 1  through  210 -N, web servers  220 - 1  through  220 -M, application servers  230 - 1  through  230 -Q connected to backend systems  250 , a load balancer  260 , and a network  270 . System  200  further includes a service level management (SLM) system  280  that allows the maintaining of a consistent level of service of web applications. Web servers  220  process requests sent from clients and responds with the processing result. Application servers  230  execute the business logic of the web applications and communicate with back-end systems  250 , which implement the data layer of the applications. In some configurations, a web server and a web application may act as a single entity, e.g., web application  230 -Q. Load balancer  260  mainly distributes incoming requests to servers  220  and  230  that run the applications to which the requests are targeted. 
   SLM system  280  controls and manages applications executed by servers  220  and  230  in real-time, and thus ensures a committed level of service. The level of service may be defined by a service level agreement (SLA) and be different for each application. With this aim, SLM system  280  learns the structure of a web-application, monitors the operation of the application, and controls the processing of incoming requests to achieve optimal performance and level of service. In an exemplary embodiment shown in  FIG. 2  SLM system  280  is configured to operate in the line of traffic, i.e., traffic passing directly through system  280  to web servers  220 . 
     FIG. 3  shows a non-limiting block diagram of SLM system  280  disclosed in accordance with an embodiment of the present invention. SLM system  280  comprises a traffic processor  310 , an application learner  320 , a monitor  330 , and a controller  340  connected to a common bus  350 . SLM system  280  further includes databases  360  and  370  coupled to application learner  320  and a database  380  coupled to monitor  330  and controller  340 . In other embodiments, SLM system  280  includes a single database commonly coupled to application learner  320 , monitor  330 , and controller  340 . 
   Traffic processor  310  receives HTTP requests submitted by clients  210  as well as replies sent from servers  220  and  230  (see also  FIG. 2 ). Specifically, once a session is established with a client  210  a client connection handler (not shown) is allocated. The client connection handler waits for data, i.e., a HTTP request submitted by a client  210 , and once received, the data is sent to a parser (not shown). Both the parser and the client connection handler are part of the traffic processor  310 . While processing the request, the parser returns a context of the request. A context is a joined HTTP request-reply entity. The context fields include, but are not limited to, a site name, a HTTP method, a URL, request parameters, HTTP cookies, a HTTP status code, a HTTP server, a HTTP content type, a HTTP content length, a HTML title field, and the like. The context is sent to application learner  320 , monitor  330 , and controller  340 . The incoming request is forwarded to one of web servers  220 . 
   When load-balance or SLM schemes are utilized by controller  340 , requests may be stalled or dropped. When a reply, i.e., HTTP response is sent from a web server  230 , a web server (WS) connection handler (not shown), in the traffic processor, is allocated. The WS connection handler waits until the header of the response arrives, and then forwards the header to the parser, which sends the context to application learner  320 , monitor  330 , and controller  340 . In addition, the incoming response is sent to a client  210  through the respective client connection handler, i.e., the response is sent to the client that initiated the request. 
   Application learner  320  identifies web applications their transactions and modules and registers the learnt information in a classify data structure (CDS). The CDS includes a list of identified sites, for each site a list of its applications, and for each application a list transactions and modules that construct the application. A module is a group of transactions. Application learner  320  further generates for display purposes a site tree, which includes all discovered applications that belong to a designated site. The CDS is used in real-time to classify incoming requests to applications. The site tree and the CDS are saved in database  370 . 
     FIG. 5  provides an example for a site tree. A web site  500  has two applications: a healthcare  510  and finance  520 . Healthcare application  510  is composed of two applications, a patient  511  and a physician  512 . Patient application  511  includes the transactions Login  511 - 1 , Logout  511 - 2 , View Medical Record  511 - 3 , and Edit Profile  511 - 4 . Physician application  512 - 1  includes the transactions: Login  512 - 1 , Logout  512 - 2 , and Edit Medical Record  512 - 3 . Finance application  520  includes only the transactions GetQuote  520 - 1  and ListStocks  520 - 1 . 
   Application learner  320  performs at least three tasks that include classifying, learning, and collecting. The classification includes determining, on-the-fly, for each context (i.e., parsed request) whether the incoming request belongs to a previously discovered application, and if so an application identification (ID) number is assigned to the context. Unidentified context messages may be further processed for the purpose of learning new applications and their transactions and modules. The collection task is invoked upon a reply message and it decides if the context should be collected. A context to be collected is saved, in a chronologic order, in database  360 . The learning task is invoked every predefined period of time or whenever the number of collected contexts is above a predefined threshold. The learning task processes data stored in database  360  and attempts to discover a new application using a plurality of application definers and correlation processes. The application definers include conditions that are checked against context data in database  360 . An example for application definers are a path of a cookie, the name of the parameter name, and so on. If one of the application definers is satisfied, then a new application is found and inserted to the CDS in an entry of the relevant site. That is, a new entry is created and the application ID together with the URL are added to the entry. In one embodiment of the present invention, the learning of applications can also be performed by correlating a plurality of saved contexts that share a common property, such URL and parameter. 
   Monitor  330  executes all activities related to the generation of statistics respective of the operation of the web servers and their respective applications. The statistics include, but are not limited to, measuring throughput, response time, number of errors, and so on. The statistics are kept in database  380  on a per server basis, on a per application basis, and on a per application/server combination basis. In accordance with an embodiment of the disclosed invention, a plurality of reports are produced based on the gathered statistics. These reports can be presented by means of a graphical user interface (GUI) and/or sent to a system administrator by email. 
   Controller  340  executes tasks that optimize the performance of each web application executed by the web and application servers. These tasks include, but are not limited to, scheduling requests to reduce response time, shaping traffic to balance the load, recovery actions when one of the servers fails, redirecting of requests, and so on. The controller&#39;s  340  tasks are performed according to a set of policies predetermined for each server, application, transaction, and module in an application. Generally, a policy defines an allowed value range for each status parameter and the actions to be taken if a status parameter is not within its range. Each policy is assigned with a priority and the time periods that the policy should be activated and the users it is relevant for. For example, a policy may define a maximum allowable latency value that is for an application and a threshold from which corrective actions should be taken. The corrective action may be, but is not limited to, the transfer of requests to a less busy server. As another example, a policy may define the minimum allowable throughput for an application and the corrective action may be stalling traffic directed to the server that executes the application. It should be noted that if a policy includes two or more corrective actions, then each of the actions may be assigned with a different priority. 
     FIG. 4  shows a non-limiting and exemplary flowchart  400  describing the operation of SLM system  280 , in accordance with one embodiment of the present invention. At S 410 , an HTTP request sent from a client  210  is received at the SLM system  280 . At S 420 , the HTTP request is parsed to generate a context of the request. At S 430 , the request is classified to determine whether the request belongs to a known or unknown application. This is performed by matching the context against the CDS and a plurality of classification filters and if the filtering result with an application ID, the incoming request belongs to a known (learnt) application. At S 440 , a check takes place to determine if an application ID was detected, and if so execution continues with S 460 ; otherwise, executions proceeds to S 445  where the context is saved in database  360 . Subsequently, the context is sent to a web server  220 . At S 450 , application learner  320  discovers the applications and preferably applications&#39; transactions and modules related to the context. The learnt information is kept, at S 455 , in a CDS format in database  370 . 
   At S 460 , statistics respective of the application are gathered. That is, at least the status parameters: throughput, response time, hits per second, latency and number of returned errors are measured and saved in database  380 . At S 470 , it is checked if at least one of the policies defined for the application is violated. Namely, it is determined if the measured status parameters are within the allowed range, and if so execution proceeds to S 490  where the request is sent to a web server  220 ; otherwise, execution continues with S 480  where one or more corrective actions, as defined in the violated policy, are taken. Examples for such actions are discussed in greater detail above. The method described herein can be further utilized for processing HTTP replies sent from web servers or application servers. 
   The SLM system  280  and method described herein further implement a feedback mechanism. Specifically, after a corrective action is taken, SLM system  280  monitors the result of the action, i.e., whether the monitored parameters values improved due to the corrective action or actions. Accordingly, SLM system  280  updates controller  340  with the next corrective actions to activate. For example, if an action has not made a difference, this action would be less likely to be activated when subsequent request is received. 
   In accordance with an embodiment of the present invention, SLM system  280  tracks transactions and actual users that access the web applications in servers  220  and  230 . Tracking users is performed by: a) adding a token (e.g., a cookie) to the HTTP traffic; b) identifying existing cookies that are used by existing user-management mechanisms; c) tracking SSL sessions; or d) any combination thereof. The ability to track user activity allows for identifying transactions. Specifically, SLM system  280  detects navigation routes of users, i.e., how users move between applications&#39; transactions; compares between the detected routes; and deduces from the collected information which parts of the routes comprise independent transactions. It should be noted that not all navigation routes are considered as transactions or identified as such. 
   It should be noted that various modifications, combinations, sub-combinations and alterations of the above-described embodiments may occur, as required, insofar as they are within the scope of the appended claims or the equivalents thereof. 
   The principles of the present invention may be implemented as a combination of hardware and software. The software may be implemented as an application program tangibly embodied on a program storage unit or computer readable medium. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture, for example a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU, whether or not such computer or processor is explicitly shown. 
   It is to be further understood that, because some of the constituent system components and methods depicted in the accompanying drawings are preferably implemented in software, the actual connections between the system components or the process function blocks may differ depending upon the manner in which the present invention is programmed. Given the teachings herein, one of ordinary skill in the pertinent art will be able to contemplate these and similar implementations or configurations of the present invention. All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. 
   All statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. It is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context. 
   In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements that performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicants thus regards any means that can provide those functionalities as equivalent to those shown herein.