Patent Publication Number: US-2022231926-A1

Title: Standardized format for containerized applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior application Ser. No. 16/216,570, filed on Dec. 11, 2018, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter disclosed herein generally relates to containerized applications. Specifically, the present disclosure addresses systems and methods to implement a standardized format for containerized applications based on Kubernetes. 
     BACKGROUND 
     Kubernetes is a system for automating deployment, scaling, and management of containerized applications. Application containerization is a virtualization method used by operating systems to deploy and run distributed applications without launching an entire virtual machine for each application. Applications are deployed in Kubernetes by invoking a command-line tool to execute a customized deployment script. Kubernetes does not provide middleware, data-processing frameworks, databases, caches, or cluster storage systems as built-in services. 
     Containerized applications have advantages over standard applications. When a standard application is installed on a server, libraries required by the application are also installed. Thus, if multiple applications are installed, the libraries on the server are an amalgamation of the libraries required by each of the multiple applications. If one application installs a different version of a library used by another application, the first installed version is overwritten. As a result, an application may use a version of a library that was not tested with the application, which may further result in unexpected behavior. 
     One solution to this problem is to run each application in a virtual machine that only has the operating system and the application installed. This ensures that different applications will not cause problems for each other. However, virtual machines have substantial overhead associated with them. As a result, to achieve the same performance as with a standard, non-virtual, deployment, additional or higher-performing computing hardware will be required, increasing costs. 
     Kubernetes provides another solution in the form of containerized applications. Each container comprises an application and its libraries, but the containers are installed and managed with much less overhead than virtual machines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings. 
         FIG. 1  is a network diagram illustrating a network environment suitable for making use of a standardized format for containerized applications, according to some example embodiments. 
         FIG. 2  is a block diagram of an application server, according to some example embodiments, suitable for deploying containerized applications by making used of a standardized format for the containerized applications. 
         FIG. 3  is an example of a file in a standardized format for a containerized application. 
         FIGS. 4-6  are an example of a file in a standardized format for a containerized application. 
         FIG. 7  is a flowchart illustrating operations of a method suitable for deploying a containerized application based on a file in a standardized format, according to some example embodiments. 
         FIG. 8  is a user interface diagram of a user interface suitable for selecting a containerized application, according to some example embodiments. 
         FIG. 9  is a block diagram illustrating components of a machine, according to some example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Example methods and systems are directed to standardized formats for containerized applications. A file is created in a standardized format that defines a type of a containerized application and includes information for deployment of the containerized application. A single parser of the standardized format is thus enabled to deploy different types of containerized applications. 
     The standardized file format includes an application name, an application version, an application programming interface (API) version, an application type, an application definition, or any suitable combination thereof. The application definition includes a service, a port list, a container list, a volume mount list, an access mode list, a resource usage list, or any suitable combination thereof. 
     A client device presents a user interface that allows a user to select a containerized application to execute. An application server parses an application template file for the selected containerized application and, based on the information in the application template file, causes one or more servers (e.g., one or more Kubernetes cluster nodes) to execute the containerized application. 
     By comparison with existing methods of deploying containerized applications that use non-standardized file formats, requiring a different parser for each type of containerized application, the methods and systems herein reduce efforts involved with supporting multiple types of containerized applications. When these effects are considered in aggregate, one or more of the methodologies described herein may obviate a need for certain efforts or resources that otherwise would be involved in supporting multiple types of containerized applications. Computing resources used by one or more machines, databases, or networks may similarly be reduced. Examples of such computing resources include processor cycles, network traffic, memory usage, data storage capacity, power consumption, and cooling capacity. 
       FIG. 1  is a network diagram illustrating a network environment  100  suitable for making use of a standardized format for containerized applications, according to some example embodiments. The network environment  100  includes a network-based application  105 , client devices  140 A and  140 B, and a network  155 . The network-based application  105  is provided by an application server  110  in communication with a Kubernetes cluster  120 . The application server  110  accesses application template files  115  to configure and deploy an application to the Kubernetes cluster  120  via a Kubernetes API server  125  interacting with a set of cluster nodes  130 A,  130 B. The containerized application is provided to the client devices  140 A and  140 B via a web interface  145  or an application interface  150 , respectively. The application server  110 , the Kubernetes API server  125 , the cluster nodes  130 A and  130 B, and the client devices  140 A and  140 B may each be implemented in a computer system, in whole or in part, as described below with respect to  FIG. 9 . The cluster nodes  130 A and  130 B may be referred to collectively as the cluster nodes  130  or generically as a cluster node  130 . The client devices  140 A and  140 B may be referred to collectively as client devices  140  or generically as a client device  140 . 
     The application server  110  provides a user interface for selecting an application to the client devices  140 . The Kubernetes API server provides an interface to the Kubernetes cluster  120  and deploys applications to the cluster nodes  130 . Any of the machines, databases, or devices shown in  FIG. 1  may be implemented in a general-purpose computer modified (e.g., configured or programmed) by software to be a special-purpose computer to perform the functions described herein for that machine, database, or device. For example, a computer system able to implement any one or more of the methodologies described herein is discussed below with respect to  FIG. 9 . As used herein, a “database” is a data storage resource and may store data structured as a text file, a table, a spreadsheet, a relational database (e.g., an object-relational database), a triple store, a hierarchical data store, a document-oriented NoSQL database, a file store, or any suitable combination thereof. The database may be an in-memory database. Moreover, any two or more of the machines, databases, or devices illustrated in  FIG. 1  may be combined into a single machine, database, or device, and the functions described herein for any single machine, database, or device may be subdivided among multiple machines, databases, or devices. 
     The application server  110 , the Kubernetes API server  125 , the cluster nodes  130 A- 130 B, and the client devices  140 A- 140 B may be connected by the network  155 . The network  155  may be any network that enables communication between or among machines, databases, and devices. Accordingly, the network  155  may be a wired network, a wireless network (e.g., a mobile or cellular network), or any suitable combination thereof. The network  155  may include one or more portions that constitute a private network, a public network (e.g., the Internet), or any suitable combination thereof. 
       FIG. 2  is a block diagram  200  illustrating components of the application server  120 , according to some example embodiments. The application server  120  is shown as including a communication module  210 , a user interface module  220 , a Kubernetes module  230 , a deployment module  240 , a database module  250 , and a storage module  260 , all configured to communicate with each other (e.g., via a bus, shared memory, or a switch). Any one or more of the modules described herein may be implemented using hardware (e.g., a processor of a machine). For example, any module described herein may be implemented by a processor configured to perform the operations described herein for that module. Moreover, any two or more of these modules may be combined into a single module, and the functions described herein for a single module may be subdivided among multiple modules. Furthermore, according to various example embodiments, modules described herein as being implemented within a single machine, database, or device may be distributed across multiple machines, databases, or devices. 
     The communication module  210  receives data sent to the application server  120  and transmits data from the application server  120 . For example, the communication module  210  may receive, from the client device  140 A, data for a selected containerized application. The communication module  210  provides the data to the Kubernetes module  230 . The Kubernetes module  230  parses a file for the selected containerized application, the file being in a standardized format. Based on data from the file, the deployment module  240  communicates with the Kubernetes API server  125  to cause one or more of the cluster nodes  130  to execute the containerized application. The cluster nodes  130  executing the containerized application communicate with the client device  140 A via the network  155  to provide the selected application. In some example embodiments, data from the file is stored in a database via the database module  250  and the storage module  260 . After being stored, the data may be accessed from the database. The communication module  210  may transmit a user interface from the user interface module  220  to the client device  140 A that includes data for available containerized applications. The list of available applications may be generated by accessing a manifest file that identifies the available applications; by accessing a directory that contains the files, in the standardized format, for the available applications; by accessing a table in a database that contains entries for the available applications; or any suitable combination thereof. Communications sent and received by the communication module  210  may be intermediated by the network  155 . 
     The user interface module  220  causes presentation of a user interface for the application server  120  on a display associated with the client device  140 A or  140 B. The user interface allows a user to select an application from a list of applications, to upload an application template file, to delete an application template file, to modify an application template file, or any suitable combination thereof. 
       FIG. 3  is an example of a file  300  in a standardized format for a containerized application. The file  300  is a JavaScript object notation (JSON) file and includes a header  310  and a body  320 . The body  320  includes a header  330 , a service section  340 , and a deployment section  350 . 
     The header  310  includes a name of the containerized application, a version of the containerized application, an API version of the containerized application, and a type of the containerized application. The name of the containerized application may be used to identify the application (e.g., in a user interface). The version of the containerized application may be used to distinguish between multiple versions of the containerized application (e.g., by the Kubernetes cluster  120  to ensure that the version being requested is the version available on the Kubernetes cluster  120  or to select between multiple available versions). The API version identifies the version of the application server API to which the file  300  conforms. The application server API may select which parser to use based on the API version. 
     The header  330  of the body  320  includes an identifier that corresponds to the type in the header  310  and an API version of the body  320 . Parsing of the body  320  may be performed based on the API version of the body  320 . For example, additional fields may be expected for one API version than for another. 
     The service section  340  includes a specification section that specifies a list of ports to be used by the containerized application. In the example of  FIG. 3 , the ports list declares that port  80  is to be used with the transmission control protocol (TCP). Thus, in this example, the port  80  for the application “Example Application” is exposed to users and may be used by users to access the application. 
     The deployment section  350  includes a specification section that contains a template section with a further specification subsection. In some example embodiments, the structure of the deployment section  350  follows the definition of a Kubernetes deployment manifest file. Additional fields or structures may be present in the deployment/specification section. For example, another Kubernetes object could be defined at this level or a number of replicas could be defined (e.g., by adding “replicas:3” to instruct the server to provide three replicas). The specification subsection includes a list of containers. The inner specification element (e.g., deployment/specification/template/specification) defines a pod. The pod definition may include one or more containers, mount volumes, mount secrets, environment variable definitions, or any suitable combination thereof. The list of containers identifies the name of each container, an image of each container, and a list of ports to be used by the containers. Optionally, the name of the image of a container is followed by a separator character (e.g., “:”) and a version number for the image. Thus, in the example of  FIG. 3 , the version 1.15.4 of the image nginx is to be used. 
       FIGS. 4-6  are an example of a file  400  in another standardized format for a containerized application. The file  400  is a yet another markup language (YAML) file and comprises a header  410  and a body  420 . The body  420  comprises a header  430 , a service section  440 , a deployment section  450 , and a persistent volume claim (PVC) section  460 . 
     The header  410  includes a name of the containerized application, a version of the containerized application, an API version of the containerized application, and a type of the containerized application. The name of the containerized application may be used to identify the application (e.g., in a user interface). The version of the containerized application may be used to distinguish between multiple versions of the containerized application (e.g., by the Kubernetes cluster  120  to ensure that the version being requested is the version available on the Kubernetes cluster  120  or to select between multiple available versions). The API version identifies the version of the Kubernetes API to use in communication between the application server  110  and the Kubernetes API server  125  when deploying the containerized application. 
     The header  430  of the body  420  includes an identifier that corresponds to the type in the header  410  and an API version that corresponds to the API version in the header  410 . Detection of a mismatch of these values may result in an error condition. 
     The service section  440  includes a specification section that specifies a list of ports to be used by the containerized application. In the example of the standardized format file  400 , the ports list declares that port  137  is to be used with the user datagram protocol (UDP). Thus, in this example, the port  137  for the application “Sample Application” is exposed to users and may be used by users to access the application. 
     The deployment section  450  includes a specification section that contains a template section with a further specification subsection. The specification subsection includes a list of containers. The list of containers identifies the name of each container, an image of each container, a list of ports to be used by the containers, and a list of volume mounts for mounting the containers. Optionally, the name of the image of a container is followed by a separator character (e.g., “:”) and a version number for the image. Thus, in the example of the standardized format file  400 , the version 1.15.4 of the image nginx is to be used. 
     The list of volume mounts identifies one or more volumes that are made accessible to the containerized application. Thus, in this example, the system path of /usr/share/nginx/html will be made available to the application under the name “volume.” 
     The PVC section  460  includes a specification section with a list of access modes and resources. In this example, the containerized application is permitted to read data and to write data, but not to modify data once written. The containerized application also requests 1 gibibyte (1,073,741,824 bytes) of storage. 
     The volume mounts of the deployment section  450  and the PVC section  460  work together to define the storage requested by the containerized application and to define the name by which the containerized application will access the storage. In some example embodiments, multiple volumes are mounted using a list in the PVC section  460  and a corresponding list in the deployment section  450 . 
       FIG. 7  is a flowchart illustrating operations of a method  700  suitable for deploying a containerized application based on a file in a standardized format, according to some example embodiments. The method  700  includes operations  710 ,  720 , and  730 . By way of example and not limitation, the method  700  is described as being performed by the devices and modules of  FIGS. 1-2  and the files of  FIGS. 3-6 . 
     In operation  710 , the deployment module  240  of the application server  110  accesses a file that comprises an indication of a type of an application. For example, the file  300  may be accessed, wherein the type “web” is indicated in the header  310 . As another example, the file  400  may be accessed, wherein the type “stateful-web” is indicated in the header  410 . 
     In operation  720 , the deployment module  240 , based on the type of the application, parses a portion of the file to identify deployment information for the application. For example, the body  320  may be determined to contain deployment information for the application based on the type “web” of the header  330  matching the type of the application referenced with respect to operation  710 . Accordingly, the deployment section  350  may be parsed in operation  720  to identify deployment information for the application such as the containers to be deployed and the ports to be allocated to them. With reference to the file  400 , the deployment section  450  further identifies volume mounts for the application. 
     In operation  730 , the deployment module  240 , based on the deployment information, deploys the application to a server. For example, the Kubernetes module  230  may communicate with the Kubernetes API server  125  through a representational state transfer (REST) API to indicate the containers to be deployed and resources to be allocated to the containers. The Kubernetes API server  125 , in response, deploys the containerized application to one or more of the cluster nodes  130 . 
     The method  700  may be repeated for any number of files. For example, a second file comprising a second indication of a second type of a second application may be accessed in a repeated operation  710  for the second file. To illustrate, the method  700  may be performed for the file  300 , with a type of “web” and repeated for the file  400 , with a type of “stateful-web.” 
       FIG. 8  is a user interface diagram of a user interface  800  suitable for plausibility-based validation of product costing structures, according to some example embodiments. The user interface  800  includes the title  810  and buttons  820  and  830 . The title  810  indicates that the user interface  800  is for application selection. The user interface  800  may be presented on a display of the client device  140 A or  140 B in response to data received from the application server  110  via the network  155 . 
     Each of the buttons  820  and  830  is operable to select a containerized application to be deployed on the Kubernetes cluster  120 . The labels of the buttons  820  and  830  may be derived from the name data stored in files in a standardized format for the containerized applications. For example, the label “Example Application” may have been extracted by the application server  110  from the file  300  and the label “Sample Application” may have been extracted by the application server  110  from the file  400 . Operation of a button causes an indication of the selected application to be sent to the application server  110 . In response to receiving the selection of the application name, the application server  110  accesses a file corresponding to the selected name and deploys the selected application (e.g., by performing the method  700 ). 
     Examples 
     Example 1. A method comprising: 
     causing a user interface to be presented, the user interface comprising a plurality of application names;
 
receiving, via the user interface, a selection of an application name of the plurality of application names;
 
in response to the receipt of the selection, accessing, by one or more processors, a file that corresponds to the selected application name and comprises an indication of a type of an application;
 
identifying a keyword based on the type of the application;
 
based on the keyword, parsing a portion of the file to identify deployment information for the application; and
 
based on the deployment information, deploying the application to a server.
 
     Example 2. The method of example 1, wherein the deploying of the application to the server comprises interacting with a Kubernetes cluster through a representational state transfer (REST) application programming interface (API). 
     Example 3. The method of example 1 or example 2, wherein the file is a JavaScript object notation (JSON) file. 
     Example 4. The method of any of examples 1 to 3, wherein the file is a yet another markup language (YAML) file. 
     Example 5. The method of any of examples 1 to 4, further comprising: 
     accessing a second file that comprises a second indication of a second type of a second application, the second type being different from the type;
 
based on the second type of the second application, parsing a second portion of the second file to identify second deployment information for the second application; and
 
based on the second deployment information, deploying the second application to the server; wherein
 
the parsing of the portion of the file comprises identifying a first keyword based on the type of the application; and
 
the parsing of the second portion of the second file comprises identifying a second keyword based on the second type of the second application, the second keyword being different from the first keyword.
 
     Example 6. The method of any of examples 1 to 5, wherein: 
     the deployment information comprises a version of the application; and
 
the deploying of the application to the server is based on the version of the application.
 
     Example 7. The method of any of examples 1 to 6, wherein the file comprises an identification of a port for the application that is exposed to users. 
     Example 8. The method of any of examples 1 to 7, wherein the application is a containerized application. 
     Example 9. A system comprising: 
     a memory that stores instructions; and
 
one or more processors configured by the instructions to perform operations comprising:
 
causing a user interface to be presented, the user interface comprising a plurality of application names;
 
receiving, via the user interface, a selection of an application name of the plurality of application names;
 
in response to the receipt of the selection, accessing a file that corresponds to the selected application name and comprises an indication of a type of an application;
 
identifying a keyword based on the type of the application;
 
based on the keyword, parsing a portion of the file to identify deployment information for the application; and
 
based on the deployment information, deploying the application to a server.
 
     Example 10. The system of example 9, wherein the deploying of the application to the server comprises interacting with a Kubernetes cluster through a representational state transfer (REST) application programming interface (API). 
     Example 11. The system of example 9 or example 10, wherein the file is a JavaScript object notation (JSON) file. 
     Example 12. The system of any of examples 9 to 11, wherein the file is a yet another markup language (YAML) file. 
     Example 13. The system of any of examples 9 to 12, wherein the operations further comprise: 
     accessing a second file that comprises a second indication of a second type of a second application, the second type being different from the type;
 
based on the second type of the second application, parsing a second portion of the second file to identify second deployment information for the second application; and
 
based on the second deployment information, deploying the second application to the server; wherein
 
the parsing of the second portion of the second file comprises identifying a second keyword based on the second type of the second application, the second keyword being different from the keyword.
 
     Example 14. The system of any of examples 9 to 13, wherein: 
     the deployment information comprises a version of the application; and
 
the deploying of the application to the server is based on the version of the application.
 
     Example 15. The system of any of examples 9 to 15, wherein the file comprises an identification of a port for the application that is exposed to users. 
     Example 16. A non-transitory computer-readable medium that stores instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising: 
     causing a user interface to be presented, the user interface comprising a plurality of application names;
 
receiving, via the user interface, a selection of an application name of the plurality of application names;
 
in response to the receipt of the selection, accessing a file that corresponds to the selected application name and comprises an indication of a type of an application;
 
identifying a keyword based on the type of the application;
 
based on the keyword, parsing a portion of the file to identify deployment information for the application; and
 
based on the deployment information, deploying the application to a server.
 
     Example 17. The computer-readable medium of example 16, wherein the deploying of the application to the server comprises interacting with a Kubernetes cluster through a representational state transfer (REST) application programming interface (API). 
     Example 18. The computer-readable medium of example 16 or example 17, wherein the file is a JavaScript object notation (JSON) file. 
     Example 19. The computer-readable medium of any of examples 16 to 18, wherein the file is a yet another markup language (YAML) file. 
     Example 20. The computer-readable medium of any of examples 916 to 19, wherein the operations further comprise: 
     accessing a second file that comprises a second indication of a second type of a second application, the second type being different from the type;
 
based on the second type of the second application, parsing a second portion of the second file to identify second deployment information for the second application; and
 
based on the second deployment information, deploying the second application to the server; wherein
 
the parsing of the second portion of the second file comprises identifying a second keyword based on the second type of the second application, the second keyword being different from the keyword.
 
       FIG. 9  is a block diagram illustrating components of a machine  900 , according to some example embodiments, able to read instructions from a machine-readable medium (e.g., a machine-readable storage medium, a computer-readable storage medium, or any suitable combination thereof) and perform any one or more of the methodologies discussed herein, in whole or in part. Specifically,  FIG. 9  shows a diagrammatic representation of the machine  900  in the example form of a computer system within which instructions  924  (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine  900  to perform any one or more of the methodologies discussed herein may be executed, in whole or in part. In alternative embodiments, the machine  900  operates as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, the machine  900  may operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a distributed (e.g., peer-to-peer) network environment. The machine  900  may be a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a personal digital assistant (PDA), a cellular telephone, a smartphone, a web appliance, a network router, a network switch, a network bridge, or any machine capable of executing the instructions  924 , sequentially or otherwise, that specify actions to be taken by that machine. Further, while only a single machine is illustrated, the term “machine” shall also be taken to include a collection of machines that individually or jointly execute the instructions  924  to perform all or part of any one or more of the methodologies discussed herein. 
     The machine  900  includes a processor  902  (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a radio-frequency integrated circuit (RFIC), or any suitable combination thereof), a main memory  904 , and a static memory  906 , which are configured to communicate with each other via a bus  908 . The machine  900  may further include a graphics display  910  (e.g., a plasma display panel (PDP), a light-emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)). The machine  900  may also include an alphanumeric input device  912  (e.g., a keyboard), a cursor control device  914  (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or another pointing instrument), a storage unit  916 , a signal generation device  918  (e.g., a speaker), and a network interface device  920 . 
     The storage unit  916  includes a machine-readable medium  922  on which are stored the instructions  924  embodying any one or more of the methodologies or functions described herein. The instructions  924  may also reside, completely or at least partially, within the main memory  904 , within the processor  902  (e.g., within the processor&#39;s cache memory), or both, during execution thereof by the machine  900 . Accordingly, the main memory  904  and the processor  902  may be considered as machine-readable media. The instructions  924  may be transmitted or received over a network  926  via the network interface device  920 . 
     As used herein, the term “memory” refers to a machine-readable medium able to store data temporarily or permanently and may be taken to include, but not be limited to, random-access memory (RAM), read-only memory (ROM), buffer memory, flash memory, and cache memory. While the machine-readable medium  922  is shown, in an example embodiment, to be a single medium, the term “machine-readable medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store instructions. The term “machine-readable medium” shall also be taken to include any medium, or combination of multiple media, that is capable of storing instructions for execution by a machine (e.g., the machine  900 ), such that the instructions, when executed by one or more processors of the machine (e.g., the processor  902 ), cause the machine to perform any one or more of the methodologies described herein. Accordingly, a “machine-readable medium” refers to a single storage apparatus or device, as well as “cloud-based” storage systems or storage networks that include multiple storage apparatus or devices. The term “machine-readable medium” shall accordingly be taken to include, but not be limited to, one or more data repositories in the form of a solid-state memory, an optical medium, a magnetic medium, or any suitable combination thereof. 
     Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein. 
     Certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium or in a transmission signal) or hardware modules. A “hardware module” is a tangible unit capable of performing certain operations and may be configured or arranged in a certain physical manner. In various example embodiments, one or more computer systems (e.g., a standalone computer system, a client computer system, or a server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein. 
     In some embodiments, a hardware module may be implemented mechanically, electronically, or any suitable combination thereof. For example, a hardware module may include dedicated circuitry or logic that is permanently configured to perform certain operations. For example, a hardware module may be a special-purpose processor, such as a field-programmable gate array (FPGA) or an ASIC. A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform certain operations. For example, a hardware module may include software encompassed within a general-purpose processor or other programmable processor. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations. 
     Accordingly, the phrase “hardware module” should be understood to encompass a tangible entity, be that an entity that is physically constructed, permanently configured (e.g., hardwired), or temporarily configured (e.g., programmed) to operate in a certain manner or to perform certain operations described herein. As used herein, “hardware-implemented module” refers to a hardware module. Considering embodiments in which hardware modules are temporarily configured (e.g., programmed), each of the hardware modules need not be configured or instantiated at any one instance in time. For example, where a hardware module comprises a general-purpose processor configured by software to become a special-purpose processor, the general-purpose processor may be configured as respectively different special-purpose processors (e.g., comprising different hardware modules) at different times. Software may accordingly configure a processor, for example, to constitute a particular hardware module at one instance of time and to constitute a different hardware module at a different instance of time. 
     Hardware modules can provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple hardware modules exist contemporaneously, communications may be achieved through signal transmission (e.g., over appropriate circuits and buses) between or among two or more of the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at different times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate communications with input or output devices, and can operate on a resource (e.g., a collection of information). 
     The various operations of example methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions described herein. As used herein, “processor-implemented module” refers to a hardware module implemented using one or more processors. 
     Similarly, the methods described herein may be at least partially processor-implemented, a processor being an example of hardware. For example, at least some of the operations of a method may be performed by one or more processors or processor-implemented modules. Moreover, the one or more processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), with these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., an API). 
     The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the one or more processors or processor-implemented modules may be located in a single geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the one or more processors or processor-implemented modules may be distributed across a number of geographic locations. 
     Some portions of the subject matter discussed herein may be presented in terms of algorithms or symbolic representations of operations on data stored as bits or binary digital signals within a machine memory (e.g., a computer memory). Such algorithms or symbolic representations are examples of techniques used by those of ordinary skill in the data processing arts to convey the substance of their work to others skilled in the art. As used herein, an “algorithm” is a self-consistent sequence of operations or similar processing leading to a desired result. In this context, algorithms and operations involve physical manipulation of physical quantities. Typically, but not necessarily, such quantities may take the form of electrical, magnetic, or optical signals capable of being stored, accessed, transferred, combined, compared, or otherwise manipulated by a machine. It is convenient at times, principally for reasons of common usage, to refer to such signals using words such as “data,” “content,” “bits,” “values,” “elements,” “symbols,” “characters,” “terms,” “numbers,” “numerals,” or the like. These words, however, are merely convenient labels and are to be associated with appropriate physical quantities. 
     Unless specifically stated otherwise, discussions herein using words such as “processing,” “computing,” “calculating,” “determining,” “presenting,” “displaying,” or the like may refer to actions or processes of a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or any suitable combination thereof), registers, or other machine components that receive, store, transmit, or display information. Furthermore, unless specifically stated otherwise, the terms “a” or “an” are herein used, as is common in patent documents, to include one or more than one instance. Finally, as used herein, the conjunction “or” refers to a non-exclusive “or,” unless specifically stated otherwise.