Patent Publication Number: US-2022232089-A1

Title: Transaction tracking for high availability architecture

Description:
BACKGROUND 
     The present invention generally relates to computer systems, and more specifically, to transaction tracking for a high availability architecture. 
     A high availability architecture can include a group of computers that support server applications that can be reliably utilized with relatively low downtime. Software in a high availability architecture can harness redundant computers in groups or clusters that provide continued service when system components fail. In a highly available architecture, if there is an error (e.g., a server running a particular application crashes), the highly available architecture can detect and hardware and/or software faults associated with the error and restart the application on another system without requiring administrative intervention, a process known as failover. Highly available architectures can be used for many types of services, such as critical databases, file sharing on a network, business applications, and customer services such as electronic commerce websites. 
     SUMMARY 
     Embodiments of the present invention are directed to transaction tracking for a high availability architecture. A non-limiting example computer-implemented method includes receiving a first request from a client, the first request corresponding to a start of a transaction having transaction affinity. The method also includes, based on receiving the first request from the client, generating a transaction tracking token. The method also includes sending the first request with the transaction tracking token to a gateway. The method also includes receiving a first response corresponding to the first request from the gateway, the first response including middleware instance information corresponding to a middleware instance, wherein a plurality of subsequent requests from the client corresponding to the transaction are processed by the middleware instance corresponding to the middleware instance information. 
     Other embodiments of the present invention implement features of the above-described method in computer systems and computer program products. 
     Additional technical features and benefits are realized through the techniques of the present invention. Embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed subject matter. For a better understanding, refer to the detailed description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The specifics of the exclusive rights described herein are particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the embodiments of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a block diagram of components of a system for transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention; 
         FIG. 2  is a block diagram of components of a system for transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention; 
         FIG. 3  is a flow diagram of a process for application server transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention; 
         FIG. 4  is a flow diagram of a process for gateway transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention; 
         FIG. 5  is a flow diagram of a process for transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention; and 
         FIG. 6  is a block diagram of an example computer system for use in conjunction with one or more embodiments of transaction tracking for a high availability architecture. 
     
    
    
     DETAILED DESCRIPTION 
     One or more embodiments of the present invention provide transaction tracking for a high availability architecture. A high availability architecture can be an online transaction processing (OLTP) topology that includes multiple tiers (i.e., an N-tier architecture) for processing of client requests. The tiers in an N-tier architecture can include, but are not limited to, load balancers, application servers, gateways, middleware (e.g., customer information control system, or CICS regions), and one or more databases. Clients can access the data in the database of a highly available architecture via the plurality of tiers. Client requests can be grouped into transactions that each include a set of requests. It may be necessary for the requests corresponding to a particular transaction to be processed by the same middleware instance. Embodiments of the invention include transaction tracking tokens that are implemented in the application servers and gateways of a highly available architecture in order to ensure that requests belonging to the same transaction can be processed by the same middleware instance. 
     In some embodiments of the invention, custom fields in a transaction tracking token can be used to enforce end-to-end transaction affinity for requests in a high availability architecture. The application server and the gateway can each include a respective transaction tracking module. The application server transaction tracking module can generate a unique transaction tracking token for every transaction instance. A transaction tracking token can contain transaction information fields, such as a transaction correlator (e.g., identifier) and system information fields, that are populated by the application server, and a middleware instance information field that is populated by the gateway transaction tracking module. The gateway transaction tracking module can ensure that any requests belonging to the same transaction are routed to the same middleware instance based on the transaction tracking token information that is associated with each request in order to ensure transaction affinity in the high availability architecture. 
     A unique transaction correlator can be generated for every transaction that is initiated by the client. When the request reaches the gateway, the gateway can select the appropriate middleware instance in the next tier based on the workload balancer logic. The gateway can append the selected middleware instance information to the transaction tracking token as additional metadata. Because the transaction correlator may not change within a transaction, the metadata, including the previous selected middleware instance information, can be used by the gateway to route any requests associated with a single transaction to the same middleware instance, maintaining end-to-end transaction affinity. In some embodiments of the invention, particular middleware instances can include specific functionalities that may be needed for particular transaction types. Therefore, requests associated with a single transaction can be routed by the gateway to a particular middleware instance having a specific functionality that is required by the single transaction. 
     Turning now to  FIG. 1 , a system  100  that includes transaction tracking for a high availability architecture is generally shown in accordance with one or more embodiments of the present invention. System  100  can be implemented in conjunction with any appropriate computer system, including but not limited to computer system  600  of  FIG. 6 . System  100  includes a number of clients  101 A-C that are in communication with a session affinity load balancer  102 . The session affinity load balancer  102  passes requests from clients  101 A-C to application servers  103 A-C. The application servers  103 A-C host one or more applications that process requests from clients  101 A-C using data from database  106  that is retrieved via gateways  104 A-B and middleware instances  105 A-C. In some embodiments of the invention, middleware instances  105 A-C can each include a CICS region. 
     In some embodiments of the invention, individual middleware instances of middleware instances  105 A-C can be configured to have different functionalities (e.g., may be configured to execute priority workloads or user-specific workloads). Therefore, any requests belonging to a transaction that requires specific middleware functionality can be routed to a same middleware instance of middleware instances  105 A-C by the gateways  104 A-B based on transaction tracking tokens that are implemented in application servers  103 A-C and gateways  104 A-B. A transaction tracking token can be generated by an application server of application servers  103 A-C based on the start of a transaction that is initiated by a client of clients  101 A-C. The transaction tracking token that is generated by an application server such as application server  103 A can include a transaction correlator and any other appropriate system information associated with a transaction. The transaction tracking token can also include one or more additional fields that are populated by a gateway of gateways  104 A-B with information corresponding to a particular middleware instance of middleware instances  105 A-C that is selected for processing the requests associated with the transaction. Implementation of transaction tracking tokens in system  100  of  FIG. 1  is discussed in further detail below with respect to  FIG. 2 . 
     It is to be understood that the block diagram of  FIG. 1  is not intended to indicate that the system  100  is to include all of the components shown in  FIG. 1 . Rather, the system  100  can include any appropriate fewer or additional components not illustrated in  FIG. 1  (e.g., additional memory components, embedded controllers, functional blocks, connections between functional blocks, modules, inputs, outputs, clients, load balancers, application servers, gateways, middleware instances, databases, tiers, etc.). Further, the embodiments described herein with respect to system  100  may be implemented with any appropriate logic, wherein the logic, as referred to herein, can include any suitable hardware (e.g., a processor, an embedded controller, or an application specific integrated circuit, among others), software (e.g., an application, among others), firmware, or any suitable combination of hardware, software, and firmware, in various embodiments. 
     Turning now to  FIG. 2 , a system  200  that includes transaction tracking for a high availability architecture is generally shown in accordance with one or more embodiments of the present invention. System  200  can be implemented in conjunction with system  100  of  FIG. 1 . Application server  201  can correspond to any of application servers  103 A-C of system  100  of  FIG. 1 ; gateway  203  can correspond to any of gateways  104 A-B of system  100  of  FIG. 1 ; and middleware instance  205  can correspond to any of middleware instances  105 A-C of system  100  of  FIG. 1 . Application server  201  includes an application server transaction tracking module  202 ; application server transaction tracking module  202  can implement embodiments of method  300  of  FIG. 3 , which is discussed below. Gateway  203  includes a gateway transaction tracking module  204 ; gateway transaction tracking module  204  can implement embodiments of method  400  of  FIG. 4 , which is discussed below. Each of application servers  103 A-C that are illustrated in system  100  of  FIG. 1  can include a respective application server transaction tracking module  202 , and each of gateways  104 A-B that are illustrated in system  100  of  FIG. 1  can include a respective gateway transaction tracking module  204 . 
     The gateway transaction tracking module  204  in the gateway  203  receives a transaction tracking token from the application server transaction tracking module  202  in application server  201  for every request associated with a transaction instance. The gateway  203  routes the request to a selected middleware instance  205  of the available middleware instances  105 A-C. The middleware instance  205  retrieves data corresponding to the request from the database  106  and sends the response including the retrieved data to the gateway  203 . The gateway transaction tracking module  204  can append the middleware instance information corresponding to middleware instance  205  to the transaction tracking token and send the response and the transaction tracking token to application server  201 . The application server  201  and gateways  203  can use the middleware instance information from the transaction tracking token for subsequent requests that belong to the same transaction. Based on the middleware instance information corresponding to a request, the gateway  203  can send the requests corresponding to a single transaction to a particular middleware instance  205  corresponding to the transaction. 
     It is to be understood that the block diagram of  FIG. 2  is not intended to indicate that the system  200  is to include all of the components shown in  FIG. 2 . Rather, the system  200  can include any appropriate fewer or additional components not illustrated in  FIG. 2  (e.g., additional memory components, embedded controllers, functional blocks, connections between functional blocks, modules, inputs, outputs, application servers, gateways, middleware instances, etc.). Further, the embodiments described herein with respect to system  200  may be implemented with any appropriate logic, wherein the logic, as referred to herein, can include any suitable hardware (e.g., a processor, an embedded controller, or an application specific integrated circuit, among others), software (e.g., an application, among others), firmware, or any suitable combination of hardware, software, and firmware, in various embodiments. 
       FIG. 3  shows a process flow diagram of a method  300  for application server transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention. Method  300  of  FIG. 3  can be implemented in an application server transaction tracking module such as application server transaction tracking module  202  in application server  201  of system  200  of  FIG. 2 . In block  301  of method  300 , the application server transaction tracking module  202  in an application server  103 A/ 201  in system  100  starts a new transaction instance based on a request received from a client  101 A in system  100 . In block  302 , it is determined whether a transaction affinity extension is required for the new transaction; the determination of block  302  can be made based on information contained in the client request. If it is determined in block  302  that a transaction affinity extension is required, flow proceeds to block  303 , in which the application server transaction tracking module  202  generates a transaction tracking token corresponding to the transaction associated with the request, and the application server  103 A/ 201  sends the request with the transaction tracking token to a gateway  104 A/ 203  in the system  100 . The transaction tracking token that is generated in block  303  can include a transaction correlator and any other appropriate system information, and can include one or more blank fields that are reserved to be populated by the gateway  104 A/ 203 . Flow then proceeds from block  303  to block  305 . If it is determined in block  302  that a transaction affinity extension is not required, flow proceeds to block  304 , and the request is sent from the application server  103 A/ 201  to the gateway  104 A/ 203  without a transaction tracking token. Flow then proceeds from block  304  to block  305 . 
     In block  305 , a response corresponding to the request that was forwarded in either block  303  or  304  is received at the application server  103 A/ 201  from the gateway  104 A/ 203 . The response that is received in block  305  can include data that was retrieved by a middleware instance of middleware instances  105 A-C from database  106 , and application server  103 A/ 201  can process the request based on the data in the response from the gateway  104 A/ 201 . In block  306 , it is determined whether the response from the gateway  104 A/ 201  includes a transaction tracking token including middleware instance information. If it is determined in block  306  that the response includes a transaction tracking token including middleware instance information, flow proceeds from block  306  to block  307 . In block  307 , the middleware instance information is extracted from the transaction tracking token associated with the response by application server transaction tracking module  202  for use with any subsequent client requests corresponding to the same transaction. The middleware instance information can be stored in application server transaction tracking module  202  with the transaction correlator corresponding to the request, and used for routing subsequent requests corresponding to the same transaction correlator. The application server  103 A/ 201  then sends a response to the client  101 A based on the response received from the gateway  104 A/ 201 . If it is determined in block  306  that there is no middleware instance information in the response, flow proceeds to block  308 , and a response is sent from the application server  103 A/ 201  to the client  101 A without any middleware instance information. 
     The process flow diagram of  FIG. 3  is not intended to indicate that the operations of the method  300  are to be executed in any particular order, or that all of the operations of the method  300  are to be included in every case. Additionally, the method  300  can include any suitable number of additional operations. 
       FIG. 4  shows a process flow diagram of a method  400  for gateway transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention. Method  400  of  FIG. 4  can be implemented in a gateway transaction tracking module such as gateway transaction tracking module  204  in gateway  203  of system  200  of  FIG. 2 . In block  401  of method  400 , a client request (e.g., a request that was forwarded in one of blocks  303  and  304  of method  300  of  FIG. 3 ) is received by a gateway  104 A/ 203  in system  100  from an application server  103 A/ 201 . In block  402 , it is determined whether the request that was received in block  401  includes a transaction tracking token. If it is determined in block  402  that the request includes a transaction tracking token, flow proceeds from block  402  to block  403 , and the transaction information from the transaction tracking token is stored in gateway transaction tracking module  204 . Flow then proceeds from block  403  to block  404 . If it is determined in block  402  that the request does not include a transaction tracking token, flow proceeds from block  402  to block  404 . 
     In block  404 , the request is forwarded to a middleware instance  205 / 105 A of middleware instances  105 A-C. In some embodiments of block  404 , the request can be forwarded to a particular middleware instance  105 A that is selected by the gateway  104 A/ 203  based on specific capabilities of the middleware instance that are required by the request (e.g., the selected middleware instance may be configured to execute priority workloads or user-specific workloads). In block  405 , a response is received from the middleware instance  105 A. The response that is received in block  405  can include data that was retrieved by the middleware instance  105 A from database  106  in order to fulfill the request. In block  406 , it is determined whether the received response is part of a transaction that requires transaction affinity. The determination of block  406  can be made based on the transaction information that was stored in gateway transaction tracking module  204  in block  403 . If it is determined in block  406  that the response is part of a transaction that requires transaction affinity, flow proceeds from block  406  to block  407 , in which an identifier of the middleware instance that processed the response is appended to the transaction tracking token, and the response is forwarded to the application server  103 A/ 201  with the transaction tracking token including the middleware instance information (e.g., as described with respect to blocks  305 ,  306 , and  307  of method  300  of  FIG. 3 ). The middleware instance information can be inserted into a blank field in the transaction tracking token by gateway  104 A/ 203  in block  407 . If it is determined in block  406  that the response is not part of a transaction that requires transaction affinity, flow proceeds to block  408 , and the response is sent to the application server  103 A/ 201  without any middleware instance information (e.g., as described above with respect to blocks  305 ,  306 , and  308  of method  300  of  FIG. 3 . 
     The process flow diagram of  FIG. 4  is not intended to indicate that the operations of the method  400  are to be executed in any particular order, or that all of the operations of the method  400  are to be included in every case. Additionally, the method  400  can include any suitable number of additional operations. 
       FIG. 5  shows a process flow diagram of a method  500  for transaction tracking for a high availability architecture in accordance with one or more embodiments of the present invention. Method  500  of  FIG. 5  can be implemented in conjunction with embodiments of system  100  of  FIG. 1 , and system  200  of  FIG. 2  based on transaction tracking tokens as are discussed above with respect to method  300  of  FIG. 3  and method  400  of  FIG. 4 . In block  501 , application server  103 A/ 201  receives a request from client  101 A that is part of an existing transaction. The request can include a transaction correlator corresponding to the existing transaction in some embodiments of the invention. In block  502 , the application server  103 A/ 201  sends the request to gateway  104 A/ 203  with a transaction tracking token including middleware instance information corresponding to the existing transaction that was stored in application server transaction tracking module  202 . In block  503 , the gateway  104 A/ 203  receives the request, and sends the request to the middleware instance  105 A/ 205  corresponding to the middleware instance information in the transaction tracking token, which is processed by gateway transaction tracking module  204 . In block  504 , the gateway  104 A/ 203  receives a response from the middleware instance  105 A/ 205 . The response can include information that was retrieved from database  106  corresponding to the request. In block  505 , the response is forwarded to the application server  103 A/ 201 , and the application server  103 A/ 201  processes the request based on the data in the response, and provides a response to the client  101 A. Method  500  can be repeated for any number of requests from client  101 A corresponding to the existing transaction; any requests corresponding to the existing transaction can be routed to a same application server  103 A/ 201  by session affinity load balancer  102  in some embodiments of the invention. 
     The process flow diagram of  FIG. 5  is not intended to indicate that the operations of the method  500  are to be executed in any particular order, or that all of the operations of the method  500  are to be included in every case. Additionally, the method  500  can include any suitable number of additional operations. 
     Turning now to  FIG. 6 , a computer system  600  is generally shown in accordance with an embodiment. The computer system  600  can be an electronic, computer framework comprising and/or employing any number and combination of computing devices and networks utilizing various communication technologies, as described herein. The computer system  600  can be easily scalable, extensible, and modular, with the ability to change to different services or reconfigure some features independently of others. The computer system  600  may be, for example, a server, desktop computer, laptop computer, tablet computer, or smartphone. In some examples, computer system  600  may be a cloud computing node. Computer system  600  may be described in the general context of computer system executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, and so on that perform particular tasks or implement particular abstract data types. Computer system  600  may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices. 
     As shown in  FIG. 6 , the computer system  600  has one or more central processing units (CPU(s))  601   a ,  601   b ,  601   c , etc. (collectively or generically referred to as processor(s)  601 ). The processors  601  can be a single-core processor, multi-core processor, computing cluster, or any number of other configurations. The processors  601 , also referred to as processing circuits, are coupled via a system bus  602  to a system memory  603  and various other components. The system memory  603  can include a read only memory (ROM)  604  and a random access memory (RAM)  605 . The ROM  604  is coupled to the system bus  602  and may include a basic input/output system (BIOS), which controls certain basic functions of the computer system  600 . The RAM is read-write memory coupled to the system bus  602  for use by the processors  601 . The system memory  603  provides temporary memory space for operations of said instructions during operation. The system memory  603  can include random access memory (RAM), read only memory, flash memory, or any other suitable memory systems. 
     The computer system  600  comprises an input/output (I/O) adapter  606  and a communications adapter  607  coupled to the system bus  602 . The I/O adapter  606  may be a small computer system interface (SCSI) adapter that communicates with a hard disk  608  and/or any other similar component. The I/O adapter  606  and the hard disk  608  are collectively referred to herein as a mass storage  610 . 
     Software  611  for execution on the computer system  600  may be stored in the mass storage  610 . The mass storage  610  is an example of a tangible storage medium readable by the processors  601 , where the software  611  is stored as instructions for execution by the processors  601  to cause the computer system  600  to operate, such as is described herein with respect to the various Figures. Examples of computer program product and the execution of such instruction is discussed herein in more detail. The communications adapter  607  interconnects the system bus  602  with a network  612 , which may be an outside network, enabling the computer system  600  to communicate with other such systems. In one embodiment, a portion of the system memory  603  and the mass storage  610  collectively store an operating system, which may be any appropriate operating system, such as the z/OS or AIX operating system from IBM Corporation, to coordinate the functions of the various components shown in  FIG. 6 . 
     Additional input/output devices are shown as connected to the system bus  602  via a display adapter  615  and an interface adapter  616  and. In one embodiment, the adapters  606 ,  607 ,  615 , and  616  may be connected to one or more I/O buses that are connected to the system bus  602  via an intermediate bus bridge (not shown). A display  619  (e.g., a screen or a display monitor) is connected to the system bus  602  by a display adapter  615 , which may include a graphics controller to improve the performance of graphics intensive applications and a video controller. A keyboard  621 , a mouse  622 , a speaker  623 , etc. can be interconnected to the system bus  602  via the interface adapter  616 , which may include, for example, a Super I/O chip integrating multiple device adapters into a single integrated circuit. Suitable I/O buses for connecting peripheral devices such as hard disk controllers, network adapters, and graphics adapters typically include common protocols, such as the Peripheral Component Interconnect (PCI). Thus, as configured in  FIG. 6 , the computer system  600  includes processing capability in the form of the processors  601 , and, storage capability including the system memory  603  and the mass storage  610 , input means such as the keyboard  621  and the mouse  622 , and output capability including the speaker  623  and the display  619 . 
     In some embodiments, the communications adapter  607  can transmit data using any suitable interface or protocol, such as the internet small computer system interface, among others. The network  612  may be a cellular network, a radio network, a wide area network (WAN), a local area network (LAN), or the Internet, among others. An external computing device may connect to the computer system  600  through the network  612 . In some examples, an external computing device may be an external webserver or a cloud computing node. 
     It is to be understood that the block diagram of  FIG. 6  is not intended to indicate that the computer system  600  is to include all of the components shown in  FIG. 6 . Rather, the computer system  600  can include any appropriate fewer or additional components not illustrated in  FIG. 6  (e.g., additional memory components, embedded controllers, modules, additional network interfaces, etc.). Further, the embodiments described herein with respect to computer system  600  may be implemented with any appropriate logic, wherein the logic, as referred to herein, can include any suitable hardware (e.g., a processor, an embedded controller, or an application specific integrated circuit, among others), software (e.g., an application, among others), firmware, or any suitable combination of hardware, software, and firmware, in various embodiments. 
     Various embodiments of the invention are described herein with reference to the related drawings. Alternative embodiments of the invention can be devised without departing from the scope of this invention. Various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. Moreover, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. 
     One or more of the methods described herein can be implemented with any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc. 
     For the sake of brevity, conventional techniques related to making and using aspects of the invention may or may not be described in detail herein. In particular, various aspects of computing systems and specific computer programs to implement the various technical features described herein are well known. Accordingly, in the interest of brevity, many conventional implementation details are only mentioned briefly herein or are omitted entirely without providing the well-known system and/or process details. 
     In some embodiments, various functions or acts can take place at a given location and/or in connection with the operation of one or more apparatuses or systems. In some embodiments, a portion of a given function or act can be performed at a first device or location, and the remainder of the function or act can be performed at one or more additional devices or locations. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. 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, element components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to 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 embodiments 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 for various embodiments with various modifications as are suited to the particular use contemplated. 
     The diagrams depicted herein are illustrative. There can be many variations to the diagram or the steps (or operations) described therein without departing from the spirit of the disclosure. For instance, the actions can be performed in a differing order or actions can be added, deleted, or modified. Also, the term “coupled” describes having a signal path between two elements and does not imply a direct connection between the elements with no intervening elements/connections therebetween. All of these variations are considered a part of the present disclosure. 
     The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus. 
     Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include both an indirect “connection” and a direct “connection.” 
     The terms “about,” “substantially,” “approximately,” and variations thereof, are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes 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), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
     Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions 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). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instruction by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. 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 readable program instructions. 
     These computer readable 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 data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart 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 embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks 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 carry out combinations of special purpose hardware and computer instructions. 
     The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments 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 described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments described herein.