Abstract:
A cache manager application provides a data caching policy in a multiple tenant enterprise resource planning (ERP) system. The cache manager application manages multiple tenant caches in a single process. The application applies the caching policy. The caching policy optimizes system performance compared to local cache optimization. As a result, tenants with high cache consumption receive a larger portion of caching resources.

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 61/883,812 filed on Sep. 27, 2013. The provisional application is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     One of the primary functions of an Enterprise Resource Planning (ERP) middle-tier server is reading and writing data from a relational database, which stores business data. Typically, read operations are performed much more frequently than write operations, and often the same data may be read repeatedly. Reading data from a database is frequently a performance bottleneck as data needs to be retrieved from another tier and the query may take some time to be processed by the database. 
     Substantial performance improvements are realized when caching data in memory of an ERP server after the data has been read from the database. Subsequent reads of the same data are retrievable from the memory rather than accessing the data from the database. 
     The challenges in implementing or using a cache include how to limit the cache size while maintaining its effectiveness and how to remove or update cached items when the items no longer accurately reflect the data in the database as a result of updates of other changes applied to the data. 
     A multiple tenant ERP middle-tier server processes data for multiple tenants, which include multiple organizations. The ERP system is capable of achieving greater economy of scale as a hosting entity by sharing computing resources across many tenants. Tenants or security policies may demand that data separation between the tenants be maintained. Furthermore, hardware resources are to be used and allocated with efficiency and fairness in mind so that a responsive system is maintained for all tenants at all times. 
     SUMMARY 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to exclusively identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. 
     Embodiments are directed to providing data caching policy in a multiple tenant enterprise resource planning (ERP) system. In some example embodiments, a cache manager application may manage multiple tenant caches in a single process. The cache manager application may apply a caching policy. The caching policy may optimize system performance compared to local cache optimization. As a result, tenants with high cache consumption may receive a larger portion of caching resources. 
     These and other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory and do not restrict aspects as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a conceptual diagram illustrating an example enterprise resource planning (ERP) system, where a caching policy may be provided in an ERP server according to embodiments; 
         FIG. 2  illustrates an example set of caches, which are independent and unaware of each other; 
         FIG. 3  illustrates an example caching mechanism, where a least recently used (LRU) policy is applied to items across shared caches according to embodiments; 
         FIG. 4  is a simplified networked environment, where a system according to embodiments may be implemented; 
         FIG. 5  is a block diagram of an example computing operating environment, where embodiments may be implemented; and 
         FIG. 6  illustrates a logic flow diagram for a process to provide a data caching policy in a multiple tenant ERP system according to embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     As briefly described above, a data caching policy may be provided in a multiple tenant enterprise resource planning (ERP) system. A cache manager application may manage multiple tenant caches in a single process. The cache manager application may apply a caching policy. The caching policy may optimize system performance compared to local cache optimization (optimization on individual independent caches). 
     In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustrations specific embodiments or examples. These aspects may be combined, other aspects may be utilized, and structural changes may be made without departing from the spirit or scope of the present disclosure. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents. 
     While the embodiments will be described in the general context of program modules that execute in conjunction with an application program that runs on an operating system on a computing device, those skilled in the art will recognize that aspects may also be implemented in combination with other program modules. 
     Generally, program modules include routines, programs, components, data structures, and other types of structures that perform particular tasks or implement particular abstract data types. Moreover, those skilled in the art will appreciate that embodiments may be practiced with other computer system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, and comparable computing devices. Embodiments may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. 
     Embodiments may be implemented as a computer-implemented process (method), a computing system, or as an article of manufacture, such as a computer program product or computer readable media. The computer program product may be a computer storage medium readable by a computer system and encoding a computer program that comprises instructions for causing a computer or computing system to perform example process(es). The computer-readable storage medium is a computer-readable memory device. The computer-readable storage medium can for example be implemented via one or more of a volatile computer memory, a non-volatile memory, a hard drive, and a flash drive. 
     Throughout this specification, the term “platform” may be a combination of software and hardware components to provide a data caching policy in a multiple tenant ERP system. Examples of platforms include, but are not limited to, a hosted service executed over a plurality of servers, an application executed on a single computing device, and comparable systems. The term “server” generally refers to a computing device executing one or more software programs typically in a networked environment. However, a server may also be implemented as a virtual server (software programs) executed on one or more computing devices viewed as a server on the network. More detail on these technologies and example embodiments may be found in the following description. 
       FIG. 1  is a conceptual diagram illustrating an example ERP system, where a caching policy may be provided in an ERP server according to embodiments. 
     As shown in diagram  100 , an ERP system  102  may host services provided to tenants  110 . The ERP system  102  may provide services to the tenants  110  through physical servers  104  and virtual machines executed in those servers. The ERP system  102  may execute one or more applications  106  on the servers  104  to provide services to the tenants  110 . The application  106  may store and retrieve data to and from data store  108 . The tenants (there may be one or more tenants)  110  may each have an associated data store  114 . Each of the tenants may have its own users who may access the provided services through client applications executed on computing devices  116 - 118 . The client applications may be thick client applications or thin clients such as browsers. The users&#39; access may be managed in sessions  112 . The sessions  112  may include handshake protocols, a secure pipeline established through encrypted communications, and similar connection attributes. 
     The ERP system  102  may host a set of caches for the tenants  110 . The set of caches may be managed by a cache manager application providing a data caching policy for managing access to the set of caches for the tenants  110 . As the types and sizes of the tenants varies, their needs for system-hosted cache may also vary. For example, some tenants may be small businesses, while others hosted by the same ERP system may be large businesses with relatively larger cache needs. 
     As mentioned above, functionality of the services provided by the ERP system  102  may be provided by distinct or integrated applications and accessed through client applications on user computers. The client applications may render the functionality of the services of the ERP system  102  while hiding the applications executing on the system servers such as application  106 . 
     While the example system in  FIG. 1  has been described with specific components including an ERP system  102  providing services executing a cache manager application providing a data caching policy in the multiple tenant ERP system, embodiments are not limited to these components or system configurations and can be implemented with other system configuration employing fewer or additional components. 
       FIG. 2  illustrates an example set of caches, which are independent and unaware of each other, according to embodiments. 
     In diagram  200 , an example scheme is provided to manage server cache for multiple tenants by maintaining separate caches. In an example scenario, a first tenant may have access to a cache A  202  and a second tenant may have access to a cache B  204 . The cache A  202  and the cache B  204  may be unaware of each other as such may not share hardware resources such as available memory. The cache A  202  may include an item A 1   206  and an item A 2   208  accessed by the first tenant. The cache B  204  may include an item B 1   210  an item B 2   212  accessed by the second tenant. The second tenant may be unable to access a memory assigned to the cache A  202  in order to store additional items within a scenario such as unavailable space in the cache B  204 . Similarly, the first tenant may be unable to access a memory assigned the cache B  204  in order to store additional items within a scenario such as unavailable space in the cache A  202 . 
     Maintenance of separate caches in tenants may also adversely affect determination of maximum size for each cache. In an example scenario, 1 GB of memory may be set aside by the ERP system as data cache for tenants. A predetermined number of tenants (e.g., 1000) may be determined to have access to the data cache. As such, the data cache may be partitioned to 1 MB parts for each tenant. In variety of use scenarios, the determined maximum size of 1 MB for each tenant may be insufficient. Additionally, large sections of the data cache may be underutilized because of offline or idling tenants while active tenants are limited with the 1 MB cache size limitation. A dynamic scheme to determine a maximum size of the cache allocated to tenants may better serve tenants accessing the cache in an uneven process. 
     In another example scenario, server cache management in multiple tenant environments may include maintenance of a single cache containing data from all tenants. In a single cache scenario, cache operations for each tenant may be expensive. Clearing a cache of data from one tenant may involve enumerating the cache or maintaining additional indices. Moreover, data from different tenants may be stored in the same container, which may increase the risk that a programming error may return data from the wrong tenant. 
     Embodiments are directed to maintaining multiple isolated data caches. A data cache may be maintained for each tenant. The data caches may be managed by a caching policy. A cache manager application may ensure that the total amount of data stored in all the caches does not exceed a predefined limit. When the amount of data does exceed the limit, the cache manager application may make an intelligent choice for which data to remove from which cache. In an example scenario, data that is least likely to be accessed in a near future by the tenants may be removed from one or more of the caches managed by the cache manager application within the ERP system. 
       FIG. 3  illustrates an example caching mechanism, where a least recently used (LRU) policy is applied to items across shared caches according to embodiments. 
     As shown in diagram  300 , a cache manager application  314  managing data cache for tenants at an ERP system may recycle old items in the cache through item removal mechanism  316  to allow better utilization of the memory, while maintaining complete separation between the caches. For example, the cache manager application  314  may apply a caching policy such as a least recently used (LRU) policy across the shared data cache. In an example scenario, a cache manager application  314  may determine the caching policy to be a LRU caching policy. A cache  302  and a cache B  304  may be maintained by the cache manager application  314  based on the LRU caching policy. The cache manager application  314  may order items (data) stored in the cache A  302  and the cache B  304  according to a recentness of use by one of the tenants. For example, the item with a timestamp closest to a current time may be ranked a most recently used (MRU) item. In diagram  300 , the cache manager application may rank an item B 2   312  as the MRU item. An item A 2   308  and an item B 1   310  may be ranked as near the MRU item by the cache manager application according to their timestamp associated with access to the items. An item A 1   306  may be ranked an LRU item by the cache manager application  314  based on its timestamp of access by the tenant associated with cache A  302 . The items A 1   306  and A 2   308  is associated with the cache A  302 . The items B 1   310  and B 2   312  is associated with the cache B  304 . A scavenging process may be activated by the cache manager application  314  in response to determining a request for cache resources utilized by the cache A  302  and cache B  304 . The cache manager application may remove the LRU item which is the item A 1   306  to make available resources dedicated to cache A  302  to other tenants requesting the resources (e.g.: memory utilized by the cache A  302 ). Additional items may be removed subsequent to removal of item A 1   306  based on evaluation of the LRU item, which may be the item B 1   310  followed by item A 2   308 , and so on. 
     The example implementation of diagram  300  for illustration purposes and is not intended to limit embodiments. Other data caching policies such as Least Frequently Used (LFU) or weighted combinations of different policies may be employed as well. In an LFU caching policy scenario, one or more of the cached items may be determined to be an LFU cached item subsequent to ranking the cached items based on a frequency of access. The LFU cached item may be removed by the cache manager application in response to detecting a total consumed cache memory exceeding a predefined limit. Furthermore, a caching policy may be applied to the cache items from different tenant in a weighted manner. 
     According to some embodiments, each item in each cache may be registered in the cache manager application. The cache manager application keeps track of the number of cached items and the total amount of memory consumed by the cached items. With this information, the cache manager application may also enforce the caching policy, which is to keep the total memory consumed by the cache below a defined limit, by removing items when necessary. 
     Items may be ranked from the shared cache based on a variety of data caching policies evaluating attributes including, but not limited to, frequency of access, a last time of an access associated with an item, an expense to re-compute the item, an association with one of the cache, attributes of an associated tenant (e.g., service level agreement), and comparable ones. One or more of the cached items may be removed from a bottom of the ranked cached items. 
     In some embodiments, a single attribute may be employed for item removal. In other embodiments, a weighted combination of attributes may be employed. The removal may be based on a static or dynamic algorithm, or a heuristic. For example, a machine learning algorithm may adjust the removal strategy to changes over time such as frequency of access by different tenants changing over time. Diagram  300  shows a simple configuration employing LRU strategy for removal of items. 
     The cache manager application  314  may expose a number of application programming interfaces (APIs) to enable interaction with the shared caches by the applications hosted by the tenants. Example APIs may include, but are not limited to, a RegisterItem operation, which may be parameterized by a cache item that has been added to a cache. A DeregisterItem operation may be parameterized by a cache item that has been removed from one of the caches (e.g., when the cached item has been invalidated). A NotifyItemAccessed operation may be parameterized by a cache item that has just been accessed in a cache through a successful lookup operation (otherwise known as a cache hit). 
     In response to calls to the RegisterItem operation, the cache policy may be enforced if the total size of cached items exceeds the predetermined limit. Next, one or more items may be selected for removal by the cache manager application  314 . The selected item(s) may be deregistered by the cache manager application. Alternatively, the selected item(s) may be removed from the associated cache(s). 
     The example scenarios and schemas in  FIGS. 2 and 3  are shown with specific components, data types, and configurations. Embodiments are not limited to systems according to these example configurations. Providing a data caching policy in a multiple tenant ERP system may be implemented in configurations employing fewer or additional components in applications and user interfaces. Furthermore, the example schema and components shown in  FIGS. 2 and 3  and their subcomponents may be implemented in a similar manner with other values using the principles described herein. 
       FIG. 4  is an example networked environment, where embodiments may be implemented. A cache manager application for providing a data caching policy in a multiple tenant ERP system may be implemented via software executed over one or more servers  414  such as a hosted service. The platform may communicate with client applications on individual computing devices such as a smart phone  413 , a laptop computer  412 , or desktop computer  411  (“client devices”) through network(s)  410 . 
     Client applications executed on any of the client devices  411 - 413  may facilitate communications via application(s) executed by servers  414 , or on individual server  416 . A multiple tenant ERP system may store a portion of data retrieved from database(s) on server memory for fast access. A cache manager application may provide a data caching policy across tenant data in the server memory. The ERP system may store data associated with provided services such as data caching policies in data store(s)  419  directly or through database server  418 . 
     Network(s)  410  may comprise any topology of servers, clients, Internet service providers, and communication media. A system according to embodiments may have a static or dynamic topology. Network(s)  410  may include secure networks such as an enterprise network, an unsecure network such as a wireless open network, or the Internet. Network(s)  410  may also coordinate communication over other networks such as Public Switched Telephone Network (PSTN) or cellular networks. Furthermore, network(s)  410  may include short range wireless networks such as Bluetooth or similar ones. Network(s)  410  provide communication between the nodes described herein. By way of example, and not limitation, network(s)  410  may include wireless media such as acoustic, RF, infrared and other wireless media. 
     Many other configurations of computing devices, applications, data sources, and data distribution systems may be employed to provide a data caching policy in a multiple tenant ERP system. Furthermore, the networked environments discussed in  FIG. 4  are for illustration purposes only. Embodiments are not limited to the example applications, modules, or processes. 
       FIG. 5  and the associated discussion are intended to provide a brief, general description of a suitable computing environment in which embodiments may be implemented. With reference to  FIG. 5 , a block diagram of an example computing operating environment for an application according to embodiments is illustrated, such as computing device  500 . In a basic configuration, computing device  500  may be any computing device executing one or more applications associated with a hosted ERP system according to embodiments and include at least one processing unit  502  and system memory  504 . 
     Computing device  500  may also include a plurality of processing units that cooperate in executing programs. Depending on the exact configuration and type of computing device, the system memory  504  may be volatile (such as RAM), non-volatile (such as ROM, flash memory, etc.) or some combination of the two. System memory  504  typically includes an operating system  505  suitable for controlling the operation of the platform, such as the WINDOWS® operating systems from MICROSOFT CORPORATION of Redmond, Wash. The system memory  504  may also include one or more software applications such as program modules  506 , ERP service  522 , and a cache manager application  524 . 
     The ERP service  522  may cache a portion of data retrieved from one or more databases for the tenants at server memory for fast access. The cache manager application  524  may provide a data caching policy in one or more servers of an ERP system. This basic configuration is illustrated in  FIG. 5  by those components within dashed line  508 . 
     Computing device  500  may have additional features or functionality. For example, the computing device  500  may also include additional data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. Such additional storage is illustrated in  FIG. 5  by removable storage  509  and non-removable storage  510 . Computer readable storage media may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. System memory  504 , removable storage  509  and non-removable storage  510  are all examples of computer readable storage media. Computer readable storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing device  500 . Any such computer readable storage media may be part of computing device  500 . Computing device  500  may also have input device(s)  512  such as keyboard, mouse, pen, voice input device, touch input device, an optical capture device for detecting gestures, and comparable input devices. Output device(s)  514  such as a display, speakers, printer, and other types of output devices may also be included. These devices are well known in the art and need not be discussed at length here. 
     Computing device  500  may also contain communication connections  516  that allow the device to communicate with other devices  518 , such as over a wired or wireless network in a distributed computing environment, a satellite link, a cellular link, a short range network, and comparable mechanisms. Other devices  518  may include computer device(s) that execute communication applications, web servers, and comparable devices. Communication connection(s)  516  is one example of communication media. Communication media can include therein computer readable instructions, data structures, program modules, or other data. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. 
     Example embodiments also include methods. These methods can be implemented in any number of ways, including the structures described in this document. One such way is by machine operations, of devices of the type described in this document. 
     Another optional way is for one or more of the individual operations of the methods to be performed in conjunction with one or more human operators performing some. These human operators need not be collocated with each other, but each can be only with a machine that performs a portion of the program. 
       FIG. 6  illustrates a logic flow diagram for a process to provide a data caching policy in a multiple tenant ERP system according to embodiments. Process  600  may be implemented on a hosted ERP system. 
     Process  600  begins with operation  610 , where a cache policy may be received by a cache manager application from a management server, an application database server, or an administrator. The cache manager application may also periodically retrieve the cache policy to ensure updates to the policy are implemented. At operation  620 , the cache manager may monitor cached items and the total consumed memory to determine whether any cached items need to be removed in order to maintain the total consumed memory below its predefined (physical or otherwise defined) limit. At operation  630 , cached items may be removed from the cache upon determination of the limit being approached or exceeded based on the cache policy. The cache policy may be based on a single attribute or a combination of attributes. 
     The operations included in process  600  are for illustration purposes. An ERP system according to embodiments may be implemented by similar processes with fewer or additional steps, as well as in different order of operations using the principles described herein. 
     The above specification, examples and data provide a complete description of the manufacture and use of the composition of the embodiments. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims and embodiments.