Patent Publication Number: US-2022237505-A1

Title: Using container information to select containers for executing models

Description:
COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     The subject matter discussed in the background section should not be assumed to be prior art merely because of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed inventions. 
     Operating-system-level virtualization, also known as containerization, refers to an operating system feature in which an operating system kernel enables the existence of multiple isolated user-space instances. Each of these instances, also referred to as software containers, partitions, or virtualization engines, can wrap an executing application in a complete environment containing everything that the application needs, such as memory, disk space, network access, and an operating system. Software containers are used by machine-learning serving infrastructures, which are becoming ubiquitous in the emerging machine-learning industry as well as in public cloud computing services. Existing machine-learning serving infrastructures typically provide machine-learning models&#39; services through a one-to-one relationship, by dedicating each individual serving container to hosting only one corresponding machine-learning model and all its required dependencies. 
     An application can be a computer program or piece of software designed and written to fulfill a particular purpose of a user. A serving container can be an isolated computer program execution environment that is enabled by a computer&#39;s operating system, and which executes the main functionality of a machine-learning model. A machine-learning model can be a computer system that scientifically studies algorithms and/or statistical models to perform a specific task effectively by relying on patterns and inference instead of using explicit instructions. A routing container can be an isolated computer program execution environment that is enabled by a computer&#39;s operating system, and which executes load-balancing code to direct requests for execution by machine-learning models. A request can be an instruction to a computer to provide information or perform another function. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following drawings like reference numbers are used to refer to like elements. Although the following figures depict various examples, the one or more implementations are not limited to the examples depicted in the figures. 
         FIG. 1  illustrates a block diagram of an example system for using container information to select containers for executing models, under an embodiment; 
         FIGS. 2A-B  illustrate diagrams of example hash rings for using container information to select containers for executing models, under an embodiment; 
         FIGS. 3  A-B depict an operational flow diagram illustrating an overview of a method for using container information to select containers for executing models, in an embodiment; 
         FIG. 4  illustrates a block diagram of an example of an environment wherein an on-demand database service might be used; and 
         FIG. 5  illustrates a block diagram of an embodiment of elements of  FIG. 4  and various possible interconnections between these elements. 
     
    
    
     DETAILED DESCRIPTION 
     General Overview 
     Automated machine-learning, feature engineering, and training enables a multi-tenancy approach to serving containers hosting machine-learning models, such that a single serving container can host hundreds of machine-learning models for multiple tenants. Within a multitenant architecture, an instance of a software application is designed to provide every tenant with a dedicated share of the instance—including its data, configuration, user management, and tenant individual properties and functionality. 
     A tenant can be a group of users who share a common access with specific privileges to a software architecture in which a single instance of software serves multiple such groups. A cluster can be a group of similar entities. A cluster of serving containers can be a group of duplicates of an isolated computer program execution environment that is enabled by a computer&#39;s operating system, and which executes the main functionality of a machine-learning model for all tenants. 
     Each routing container, or cluster of routing containers, can authenticate any requesting tenant, and then route any tenant&#39;s request for a service by machine-learning models to any serving container in a cluster of serving containers. A machine-learning serving infrastructure can include multiple clusters of serving containers, with each cluster serving a different version of any type of machine-learning model. For example, three clusters of serving containers serve versions 5.7, 5.8, and 5.9 of the type of machine-learning models that generate scores of business opportunities, and one cluster of serving containers serves a new version 1.0 of a different type of machine-learning models that generate recommendations of business opportunities. Each cluster of serving containers can use lazy caching to cache each of its machine-learning models onto all its serving containers. A version can be a form of an entity that differs in certain respects from an earlier form or other forms of the same type of entity. 
     A cluster of serving containers that can host all machine-learning models of the same version for all tenants is limited by the number of these machine-learning models that a single serving container can hold. Therefore, scaling to accommodate future additions of machine-learning models may become a problem when these machine-learning models exceed the capacity of any individual serving container in the cluster. Since each machine-learning model&#39;s size, ranging from hundreds of kilobytes (KB_ to hundreds of megabytes (MB), initialization time, and number of requests can vary widely based on each tenant&#39;s underlying database, some clusters of serving containers may be limited by a scarcity of supporting resources, while other clusters of serving containers may have a surplus of supporting resources. The failure or the addition of any container in a cluster of serving containers can create the need to rebalance the supporting resources in the clusters of serving containers. When a machine-learning serving infrastructure adds a new cluster of a serving containers for a new use case, each routing container may need to update software code to route requests to the new cluster of serving containers. 
     In accordance with embodiments described herein, there are provided methods and systems for using container information to select containers for executing models. A system receives a request from an application and identifies a version of a machine-learning model associated with the request. The system identifies a set of each serving container corresponding to the machine-learning model from a cluster of available serving containers associated with the version of the machine-learning model. The system selects a serving container from the set of each serving container corresponding to the machine-learning model. If a copy of the machine-learning model is not loaded in the serving container, the system loads the machine-learning model in the serving container. If a copy of the machine-learning model is loaded in the serving container, the system executes, in the serving container, the machine-learning model on behalf of the request. The system responds to the request based on executing the machine-learning model on behalf of the request. 
     For example, a machine-learning serving infrastructure receives a request for scoring a business opportunity from a Customer Relationship Management (CRM) application and identifies the request requires executing a version of an opportunity scoring machine-learning model. A routing container uses a consistent hashing function to identify the scoring serving containers A, D, and G that can load or have loaded a copy of the opportunity scoring machine-learning model from the cluster of available scoring serving containers A, B, C, D, E. F, and G that can load or have loaded a version of a scoring machine-learning model. The routing container uses a round-robin strategy to select the scoring serving container A from the scoring serving containers A, D, and G that can load or have loaded a copy of the specific opportunity scoring machine-learning model. If a copy of the specific opportunity scoring machine-learning model is not already loaded in the scoring serving container A, then the scoring serving container A loads the specific opportunity scoring machine-learning model. When a copy of the specific opportunity scoring machine-learning model is verified to be loaded in the scoring serving container A, the specific opportunity scoring machine-learning model executes the requested service in the scoring serving container A, and the machine-learning serving infrastructure responds to the CRM application&#39;s request. Since not every scoring serving container in the cluster of available scoring serving containers A-G will potentially host each machine-learning model, the cluster of available scoring serving containers can scale to host more machine-learning models than any individual scoring serving container can host. 
     Methods and systems are provided for using container information to select containers for executing models. First, systems and hash rings for using container information to select containers for executing models will be described with reference to example embodiments. Then methods for using container information to select containers for executing models will be described. 
     Any of the embodiments described herein may be used alone or together with one another in any combination. The one or more implementations encompassed within this specification may also include embodiments that are only partially mentioned or alluded to or are not mentioned or alluded to at all in this summary or in the abstract. Although various embodiments may have been motivated by various deficiencies with the prior art, which may be discussed or alluded to in one or more places in the specification, the embodiments do not necessarily address any of these deficiencies. In other words, different embodiments may address different deficiencies that may be discussed in the specification. Some embodiments may only partially address some deficiencies or just one deficiency that may be discussed in the specification, and some embodiments may not address any of these deficiencies. 
       FIG. 1  depicts an example of a system for using container information to select containers for executing models, in an embodiment. As shown in  FIG. 1 , a system  100  may illustrate a cloud computing environment in which data, applications, services, and other resources are stored and delivered through shared data centers and appear as a single point of access for the users. The system  100  may also represent any other type of distributed computer network environment in which servers control the storage and distribution of resources and services for different client users. 
     In an embodiment, the system  100  represents a cloud computing system that includes a first client  102 , a second client  104 , and a third client  106 ; and a machine-learning serving infrastructure  108 , that may be provided by a hosting company. Although  FIG. 1  depicts the first client  102  as a desktop computer  102 , the second client  104  as a laptop computer  104 , and the third client  106  as a mobile phone  106 , each of the clients  102 - 106  may be any type of computer. The clients  102 - 106  and the machine-learning serving infrastructure  108  communicate via a network  110 . 
     The machine-learning serving infrastructure  108  includes a gateway  112 , and clusters  114 - 120  of software containers. The cluster  114  of software containers includes software containers  122 - 126 , the cluster  116  of software containers includes software containers  128 - 132 , the cluster  118  of software containers includes software containers  134 - 138 , and the cluster  120  of software containers includes software containers  140 - 152 . The software container  140  includes the machine-learning models  154 - 160 . The machine-learning serving infrastructure  108  also includes a service discovery system  162 . 
       FIG. 1  depicts the system  100  with three clients  102 - 106 , one machine-learning serving infrastructure  108 , one network  110 , one gateway  112 , four clusters  114 - 120  of software containers, sixteen software containers  122 - 152 , four machine-learning models  154 - 160 , and one service discovery system  162 . However, the system  100  may include any number of clients  102 - 106 , any number of machine-learning serving infrastructures  108 , any number of networks  110 , any number of gateways  112 , any number of clusters  114 - 120  of software containers, any number of software containers  122 - 152 , any number of machine-learning models  154 - 160 , and any number of service discovery systems  162 . The systems depicted in  FIGS. 4 and 5  and described below may be substantially like the clients  102 - 106  and to the components  112 - 162  of the machine-learning serving infrastructure  108 . 
     The cluster  114  of software containers is a cluster  114  of routing containers  122 - 126 , the cluster  116  of software containers is a cluster  116  of ranking serving containers  128 - 132 , and the cluster  118  of software containers is a cluster  118  of recommending containers  134 - 138 . Since the cluster  120  of software containers is a cluster  120  of scoring serving containers  140 - 152 , the scoring serving container  140  includes the models  154 - 160  that are machine-learning models which learn to score. Each cluster  116 - 120  of serving containers may load a version of a type of machine-learning models. For example, the cluster  120  of scoring serving containers load a version of a type of machine-learning models  154 - 160  which share a library for scoring opportunities. In another example, the cluster  118  of recommending serving containers load a version of a type of machine-learning models which share a library for recommending opportunities to sales representatives. In yet another example, the cluster  116  of ranking serving containers load a version of a type of machine-learning models that share a library for ranking opportunities for each sales representative. Therefore, if a request from a tenant&#39;s application requires the services of these versions of machine-learning models, then any of the routing containers  122 - 126  can split the request into separate sub-requests, and then route the sub-requests to their corresponding clusters  116 - 120  of serving containers. Although these examples describe the clusters  116 - 120  of serving containers that serve one version of the scoring type of machine-learning models  140 - 152 , one version of the recommending type of machine-learning models  134 - 138 , and one version of the ranking type of machine-learning models  128 - 132 , any clusters of any serving containers may serve any number of versions of any number of any types of any machine-learning models. 
     Upon startup, each of the serving containers  128 - 152  registers with the service directory  162  by providing the serving container&#39;s registration information, such as the host and/or the port. When any of the serving containers  128 - 152  is no longer available, or becomes unavailable (intentionally or unintentionally), the service discovery system  162  deletes the unavailable serving container&#39;s registration information. An available serving container may be referred to as an actual serving container. An available serving container can be an isolated computer program execution environment that is enabled by a computer&#39;s operating system, and which is currently able to execute the main functionality of a machine-learning model. 
     The service discovery system  162  may be implemented by HashiCorp Consul, Apache Zookeeper, Cloud Native Computing Foundation etcd, Netflix eureka, or any similar tool that provides a service discovery and/or a service registration system. The service discovery system  162  may not be designed to store a large amount of data, such as each serving container&#39;s comprehensive registration information. The following is a hierarchy of virtual directories, files, or cnodes that can represent the serving container information for the serving containers A  128 , B  130 , . . . G  152 , which the machine-learning serving infrastructure  108  uses to determine what to do at any point of time. Container information can be data about an isolated computer program execution environment that is enabled by a computer&#39;s operating system, and that executes the main functionality of a machine-learning model. 
     /mlservices/cluster[i]/scoring/version 
     /container_state
         /containerA 140 //ephemeral node—if not there, the container is dead   . . .   /containerG 152 
 
/mlservices/cluster[i]/recommending/version
       

     /container_state
         /containerA 134 //ephemeral node—if not there, the container is dead   . . .   /containerC 138 
 
/mlservices/cluster[i]/ranking/version
   /container_state   /containerA 128 //ephemeral node—if not there, the container is dead   . . .   /containerC 132         

     For the following numerical examples, the size of the data that the service discovery system  162  keeps in memory is based on the following assumptions. Each cluster  116 - 120  of serving containers includes 100 serving containers, with 5 supported cluster versions per cluster type. For this example, the machine-learning serving infrastructure  108  is also going to serve 10 Bring Your Own serving Container (BYOC) use cases with 5 cluster versions per each cluster type. 
     /mlservices/cluster[i]/scoring/version/container_state/containerN (on a scoring container) stores 64 bytes (hostname+port) of container information per serving container
 
/mlservices/cluster[i]/scoring/version/container_state stores 64 B of container information per serving container for 100 containers per cluster version: 64 B*100=6.4 KB of container information per cluster version
 
/mlservices/cluster[i]/scoring/stores 6.4 KB of container information per cluster version for 5 cluster versions per cluster type: 6.4 KB*5=32 KB of container information per cluster type
 
/mlservices stores 32 KB of container information per cluster for 13 clusters types (scoring, recommending, ranking, and 10 BYOC): 32 KB*13=416 KB of container information for the service discovery system  162 .
 
     When the machine-learning serving infrastructure  108  adds any new cluster  116 - 120  of serving containers, any of the new serving containers  128 - 152  registers with the service discovery system  162  according to the data model (container_state), without any need to update the code in any of the routing containers  122 - 126 . When the machine-learning serving infrastructure  108  discontinues or terminates any old cluster  116 - 120  of serving containers, the metadata for any of the old cluster&#39;s serving containers  128 - 152  is removed from the service discovery system  162  according to the data model (container_state). 
     When the machine-learning serving infrastructure  108  adds any of the new serving containers  128 - 152  to any of the existing clusters  116 - 120  of serving containers, any of the new serving containers  128 - 152  updates the service discovery system  162  according to the data model (container_state). When any of the existing serving containers  128 - 152  in any of the existing clusters  116 - 120  of serving containers dies unexpectedly, or gracefully, the serving container&#39;s heartbeat to the service discovery system  162  fails. Then the machine-learning serving infrastructure  108  removes the ephemeral virtual directory, file, or cnode from the service discovery system  162 , which updates the container_state in the service discovery system  162 . 
     Each of the routing containers  122 - 126  has a watcher that watches the service discovery system  162  for changes in the available serving containers  128 - 152  in the clusters  116 - 120  of serving containers, and then provides notifications of any changes in the information about the serving containers  128 - 152  to its routing container  122 - 126  to update a map, or any similar data structure, of the available serving containers  128 - 152  asynchronously. The notified routing containers  122 - 126  will use their updated maps of the available serving containers  128 - 152  to route new requests, which are received via the gateway  112 , to the available serving containers  128 - 152 . Based on the previous numerical examples, each of the routing containers  122 - 126  requires 416 KB additional memory to store registration information for the available serving containers  128 - 152 . A data structure can be the organization, management, and storage format of information which enables efficient access and modification. 
     If a new version of a machine-learning model is available, and a request from a tenant&#39;s application identifies the new version of the machine-learning model, then any one of the routing containers  122 - 126  will identify any subset of the available serving containers  128 - 152  in the clusters  116 - 120  of serving containers that may have loaded a copy of the old version of the machine-learning model, which may be used for loading the new version of the machine-learning model. A copy can be an entity that is made to be similar or identical to another entity. If the old version of the machine-learning model is to be discontinued, the routing metadata will change to route requests to the new version of the machine-learning model, such that a copy of the old version of the machine-learning model expires in cache and is unloaded from memory. 
     When routing a request to any of the serving containers  128 - 152  in any of the clusters  116 - 120  of available serving containers, each of the routing containers  122 - 126  can use a function, such as a consistent hashing function, to determine which potential set of serving containers, which would be a subset of the available serving containers  128 - 152  in any of the clusters  116 - 120  of serving containers, are the potential destination serving containers for routing the request. A consistent hashing function can be an operation that can be used to repeatedly map specific data of arbitrary size to the same corresponding fixed-size values. A set can be a group or collection of entities that belong together or resemble one another or are usually found together. 
     In a general example of consistent hashing, a routing container uses a hash function to hash the identifiers of each of the serving containers in a cluster of available serving containers onto corresponding hashed value locations on a hash ring, which may be referred to as a unit circle. Upon receiving a request from a tenant which requires the service of a specific machine-learning model, the routing container uses the same hash function to hash the identifier of the specific machine-learning model to its corresponding hashed value location on the same hash ring. Then the routing container identifies the tenant&#39;s replication factor for the specific machine-learning model and equates the replication factor to the number of the serving containers that will be identified as the potential subset of the serving containers, from the cluster of available serving containers, for loading the specific machine-learning model. Beginning from the same hash ring&#39;s hashed value location for the specific machine-learning model, the routing container traverses the hash ring, identifying the hashed value locations on the hash ring to which the identifiers of the serving containers have been hashed, until the number of hashed value locations to which the identifiers of the serving containers have been hashed equals the tenant&#39;s replication factor for the specific machine-learning model. Then the routing container identifies the serving containers that correspond to these locations on the hash ring as the serving containers that will potentially load the specific machine-learning model. An identifier can be a sequence of characters used to refer to a computer program or an element, such as a variable or a set of data, within the program. 
       FIG. 2A  depicts an example hash ring  200  for copies of machine-learning models that need to be executed to respond to requests from applications. The routing container  122  applies the consistent hash function to the identifier of the new machine-learning model D  160  to determine its hash value, and then determines that the location of this hash value on the hash ring  200  is before the location of the hash value of the scoring serving container G  152  in the hash ring. In this case, since the replication factor for the new machine-learning model D  160  is two, the routing container  122  selects the next two locations of the next two hash values on the hash ring  200 , which correspond to the scoring serving container G  152  and the scoring serving container A  140  as the potential containers for loading a copy of the new machine-learning model D  160 . 
     Since multiple serving containers could potentially load a machine-learning model, a routing container can implement a round-robin strategy, rotating container strategy, or any other strategy that may be aligned with usual load balancing strategies. For example, each of the routing containers  122 - 126  can use a different seed value, so that not all of them implement the same round-robin strategy starting from the same serving container. In this example, the three routing containers  122 - 126  are responsible for routing requests to the three scoring serving containers A  140 , B  142 , and C  144 . Then the first routing container  122  may route requests to these scoring serving containers in the order of the scoring serving containers A  140 , B  142 , and C  144 ; the second routing container  124  may route requests to these scoring serving containers in the order of the scoring serving containers B  142 , C  144 , and A  140 ; and the third routing container  126  may route requests to the scoring serving containers in the order of the scoring serving containers C  144 , A  140 , and B  142 . Therefore, a routing container can select one serving container from the subset of serving containers and route the request to the selected scoring serving container. 
     If the selected serving container has already loaded a copy of the specific machine-learning model, and the selected serving container is not currently executing the specific machine-learning model for a previous request, the selected serving container executes a copy of the specific machine-learning model that has been pre-loaded in cache to provide a service for the new request. If a copy of the selected serving container has not already loaded the specific machine-learning model, the selected serving container loads the specific machine-learning model in cache, and then executes a copy of the specific machine-learning model that was just loaded in cache to provide a service for the new request. If the selected serving container is currently executing the specific machine-learning model for a previous request, then depending on the resource capacities of the selected serving container, the selected serving container can wait until finished executing the specific machine-learning model for a previous request before loading the specific machine-learning model in cache, can load an additional copy of the specific machine-learning model in cache, or can request that one of the other potential serving containers loads the specific machine-learning model in cache. Once verified to be loaded in cache, a copy of the specific machine-learning model is executed to provide a service for the new request. 
     If needed, a routing container combines any sub-responses to any sub-requests into one response for one request. A routing container routes any response(s) from any cluster(s) of available serving containers to the requesting tenant&#39;s application. 
     A routing container can perform load balancing if any serving container is added to and/or subtracted from a cluster of available serving containers. For a pre-load balancing example,  FIG. 2A  depicts the example hash ring  200  for a copy of the machine-learning model E  161  (which is not depicted in  FIG. 1 ) that was loaded to provide a service for a request from a tenant&#39;s application. The routing container  122  applied the consistent hash function to the identifier of a copy of the machine-learning model E  161  to determine its hash value, and then determined that the location of this hash value on the hash ring  200  is before the location of the hash value of the scoring serving container B  142  in the hash ring. In this case, since the replication factor for the machine-learning model E  161  is two, the routing container  122  selected the next two locations of the next two hash values on the hash ring, which corresponded to the scoring serving container B  142  and the scoring serving container E  148  as the potential scoring serving containers for loading a copy of the machine-learning model E  161 . 
     In another pre-load balancing example, as described above,  FIG. 2A  depicts the example hash ring  200  for a copy of the machine-learning model D  160  that was loaded to provide another service for another request from another tenant&#39;s application. The routing container  122  applied the consistent hash function to the identifier of a copy of the machine-learning model D  160  to determine its hash value, and then determined that the location of this hash value on the hash ring  200  is before the location of the hash value of the scoring serving container G  152  in the hash ring. In this case, since the replication factor for the machine-learning model D  160  is two, the routing container  122  selected the next two locations of the next two hash values on the hash ring  200 , which corresponded to the scoring serving container G  152  and the scoring serving container A  140  as the potential scoring serving containers for loading a copy of the machine-learning model D  160 . 
     The routing container  122  performs load balancing when the scoring serving container A  140  is subtracted from the cluster  116  of scoring serving containers and when the scoring serving container H  153  (which is not depicted in  FIG. 1 ) is added to the cluster  116  of scoring serving containers. For example,  FIG. 2B  depicts an example hash ring  202  for a copy of the machine-learning model D  160  that is requested by a tenant&#39;s application. The routing container  122  applies the consistent hash function to the identifier of a copy of the machine-learning model D  160  to determine its hash value, and then determines that the location of this hash value on the hash ring  202  is before the location of the hash value of the scoring serving container G  152  in the hash ring. 
     In this case, since the replication factor for the machine-learning model D  160  is two, the routing container  122  selects the next two locations of the next two hash values on the hash ring  202 . These two locations correspond to the scoring serving container G  152  as the first potential scoring serving container for loading a copy of the machine-learning model D  160  and would have corresponded to the scoring serving container A  140  as the second potential scoring serving container for loading a copy of the machine-learning model D  160 . However, since the scoring serving container A  140  is unavailable in this example, the routing container  122  selects the next location of the next hash value on the hash ring  202 , which corresponds to the scoring serving container D  146  as the second potential scoring serving container for loading a copy of the machine-learning model D  160 . In this example, the routing container  122  performs load balancing when the scoring serving container A  140  is subtracted from the cluster  116  of scoring serving containers by identifying the scoring serving container D  146 , instead of the currently unavailable scoring serving container A  140 , as the second potential container for loading a copy of the machine-learning model D  160 . 
     In another example,  FIG. 2B  depicts the example hash ring  202  for the machine-learning model E  161  that is requested by a tenant&#39;s application. The routing container  122  applies the consistent hash function to the identifier of a copy of the machine-learning model E  161  to determine its hash value, and then determines that the location of this hash value on the hash ring  202  is before the location of the hash value of the scoring serving container B  142  in the hash ring  202 . In this case, since the replication factor for a copy of the machine-learning model E  161  is two, the routing container  122  selects the next two locations for the next two hash values on the hash ring  202 , which correspond to the scoring serving container B  142  as the first potential scoring serving container for loading a copy of the machine-learning model E  161  and would have corresponded to the scoring serving container E  148  as the second potential scoring serving container for loading a copy of the machine-learning model E  161 . 
     However, the location of the hash value for the new scoring serving container H  153  is between the locations of the hash values for the scoring serving container B  142  and the scoring serving container E  148  on the hash ring  202 . Therefore, the routing container  122  selects the next location for the next hash value after the location for the hash value for the scoring serving container B  142  on the hash ring  202 , which corresponds to the new scoring serving container H  153  as the second potential scoring serving container for loading a copy of the machine-learning model E  161 . In this example, the routing container  122  performs load balancing when the new scoring serving container H  153  is added to the cluster  116  of scoring serving containers by identifying the new scoring serving container H  153 , instead of the scoring serving container E  148  as the second potential scoring serving container for loading a copy of the machine-learning model E  161 . 
       FIGS. 3  A-B depict an operational flow diagram illustrating a high-level overview of a method  300  for using container information to select containers for executing models. The method  300  may be implemented on either a centralized computing platform or in parallel on a distributed computing platform. 
     A data structure is optionally updated with container information associated with serving containers in any corresponding cluster of serving containers, box  302 . The system can update a map of available serving containers. In embodiments, this can include the service discovery system  162  receiving notifications of the available container information from each of the serving containers  128 - 152  in the clusters  116 - 120  of serving containers, and then updating the container_state map for the serving containers  128 - 152  in the clusters  116 - 120  of serving containers. 
     In addition to optionally updating a map of serving containers that are available to execute machine-learning models, a request is received from an application, box  304 . The system receives many requests that can require the execution of machine-learning models. For example, and without limitation, this can include the machine-learning serving infrastructure  108  receiving a request for scoring a list of purchasable contacts as Acme Corporation&#39;s business opportunities. The request is from a Customer Relationship Management (CRM) application executed by an Acme sales manager Ann on her laptop computer  104 . Ann&#39;s request also requires that the scored business opportunities be recommended to various Acme sales representatives, such as Bob. 
     After a request is received, a version is identified of a machine-learning model associated with the request, box  306 . The system identifies a version of a machine-learning model to be executed. By way of example and without limitation, this can include the machine-learning serving infrastructure  108  identifying that Ann&#39;s request requires executing a version of the opportunity scoring machine-learning model A  154  used by Acme&#39;s CRM application. 
     Following receipt of a request, another version is optionally identified of another machine-learning model associated with the request, box  308 . The system can identify multiple versions of machine-learning models to be executed. In embodiments, this can include the machine-learning serving infrastructure  108  identifying that Ann&#39;s request also requires executing a version of the opportunity recommending machine-learning model used by Acme&#39;s CRM application. Therefore, the machine-learning serving infrastructure  108  splits Ann&#39;s request into sub-requests due to identifying both a version of Acme&#39;s opportunity scoring machine-learning model A  154  and a version of Acme&#39;s opportunity recommending machine-learning model. 
     Having identified a version of a machine-learning model, a set is identified of each serving container corresponding to the machine-learning model from a cluster of available serving containers associated with the version of the machine-learning model, box  310 . The system identifies a cluster of available serving containers that serve a version of the identified machine-learning model and the specific serving containers in the cluster that might load the identified machine-learning model. For example, and without limitation, this can include the routing container  122  using a consistent hashing function to identify the scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 , from the cluster  120  of available scoring serving containers A  140 , B  142 , C  144 , D  146 , E  148 . F  150 , and G  152 , which can load or have loaded a copy of any scoring machine-learning model that shares the same library to generate the scores of business opportunities. 
     In addition to identifying another version of another machine-learning model, another set is optionally identified of each serving container corresponding to the other machine-learning model from a cluster of available serving containers associated with the other version of the other machine-learning model, box  312 . The system can identify another cluster of available serving containers that serve a version of another identified machine-learning model and the specific serving containers in the other cluster that might load the other identified machine-learning model. By way of example and without limitation, this can include the routing container  122  using the same consistent hashing function to identify the recommending serving containers B  136  and C  138 , which can load or have loaded a copy of Acme&#39;s opportunity recommending machine-learning model, from the cluster  118  of recommending serving containers A  134 , B  136 , and C  138 , which can load or have loaded a copy of any recommending machine-learning model that shares the same library to generate recommendations of business opportunities. 
     After identifying a set of each serving container corresponding to a machine-learning model, a serving container is selected from the set of each serving container corresponding to the machine-learning model, box  314 . The system selects one of the identified serving containers. In embodiments, this can include the routing container  122  using a round-robin strategy to select the scoring serving container A  140  from the scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . 
     Following identification of another set of each serving container corresponding to another machine-learning model, another serving container is optionally selected from the other set of each serving container corresponding to the other machine-learning model, box  316 . The system can select one of the other identified serving-containers. For example, and without limitation, this can include the routing container  122  using a round-robin strategy to select the recommending serving container C  138  from the recommending serving containers B  136  and C  138 , which can load or have loaded a copy of Acme&#39;s opportunity recommending machine-learning model. 
     Having selected a serving container, a determination is made whether a copy of the identified machine-learning model is loaded in the serving container, box  318 . The system determines whether a copy of the selected serving container needs to load the identified machine-learning model. By way of example and without limitation, this can include the scoring serving container A  140  determining whether the scoring serving container A  140  has loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . If a copy of the identified machine-learning model is not loaded in the selected serving container, the method  300  continues to block  320  to load the identified machine-learning model in the selected serving container. If a copy of the identified machine-learning model is loaded in the selected serving container, the method  300  proceeds to block  322  to execute a copy of the identified machine-learning model in the selected serving container. 
     If a copy of the identified machine-learning model is not loaded in the selected serving container, a copy of the identified machine-learning model is loaded in the selected serving container, box  320 . The system can load the identified machine-learning model in the selected serving container if needed. In embodiments, this can include the scoring serving container A  140  loading a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . 
     If a copy of the identified machine-learning model is loaded in the selected serving container, a copy of the identified machine-learning model is executed in the selected serving container on behalf of the request, box  322 . The system executes the identified machine-learning model in the selected serving container. For example, and without limitation, this can include a copy of Acme&#39;s opportunity scoring machine-learning model A  154  scoring the purchasable business contacts as Acme&#39;s business opportunities, after a copy of Acme&#39;s opportunity scoring machine-learning model A  154  is verified as loaded in the scoring serving container A  140 . 
     In addition to selecting another serving container, a determination is optionally made whether a copy of the other identified machine-learning model is loaded in the other selected serving container, box  324 . The system can determine whether the other selected serving container needs to load the other identified machine-learning model. By way of example and without limitation, this can include the recommending serving container C  138  determining whether a copy of the recommending serving container C  138  has loaded a copy of Acme&#39;s opportunity recommending machine-learning model. If a copy of the other identified machine-learning model is not loaded in the other selected serving container, the method  300  continues to block  326  to load a copy of the other identified machine-learning model in the other selected serving container. If a copy of the other identified machine-learning model is loaded in the other selected serving container, the method  300  proceeds to block  328  to execute a copy of the other identified machine-learning model in the other selected serving container. 
     If a copy of the other identified machine-learning model is not loaded in the other selected serving container, a copy of the other identified machine-learning model is optionally loaded in the other selected serving container, box  326 . The system can load a copy of the other identified machine-learning model in the other selected serving container. In embodiments, this can include the recommending serving container C  138  loading a copy of Acme&#39;s opportunity recommending machine-learning model. 
     If a copy of the other identified machine-learning model is loaded in the other selected serving container, a copy of the other identified machine-learning model is optionally executed in the other selected serving container on behalf of the request, box  328 . The system can execute the other identified machine-learning model in the other selected serving container. For example, and without limitation, this can include a copy of Acme&#39;s opportunity recommending machine-learning model recommending the purchasable business contacts as Acme&#39;s business opportunities to Acme&#39;s sales representatives, after a copy of Acme&#39;s opportunity recommending machine-learning model is verified as loaded in the recommending serving container C  138 . 
     After executing a copy of the identified machine-learning model in the selected serving container on behalf of a request, the request is responded to, based on executing a copy of the identified machine-learning model on behalf of the request, box  330 . The system responds to a request by executing a copy of the identified machine-learning model(s) in the selected serving container(s). By way of example and without limitation, this can include the machine-learning serving infrastructure  108  responding to Ann&#39;s request with the scored list of purchasable contacts as Acme Corporation&#39;s business opportunities, which are recommended to various Acme sales representatives, such as Bob. 
     In addition to receiving a request from an application, an additional request is optionally received from the same application, box  332 . The system can receive many requests that can require the execution of machine-learning models. In embodiments, this can include the machine-learning serving infrastructure  108  receiving an additional request, which requires scoring some of last week&#39;s list of purchased contacts as Acme&#39;s business opportunities. The additional request is from Acme&#39;s CRM application executed by an Acme sales representative Bob on his mobile phone  106 . Bob&#39;s request also requires that his scored business opportunities be ranked to determine his personal priorities for working on these business opportunities. 
     After an additional request is received, a version is optionally identified of a machine-learning model associated with the additional request, box  334 . The system can identify a version of a machine-learning model to be executed. For example, and without limitation, this can include the machine-learning serving infrastructure  108  identifying that Bob&#39;s request requires executing a version of the opportunity scoring machine-learning model A  154  used by Acme&#39;s CRM application. The machine-learning serving infrastructure  108  may also identify that Bob&#39;s request also requires executing a version of the opportunity ranking machine-learning model used by Acme&#39;s CRM application. Therefore, the machine-learning serving infrastructure  108  may split Bob&#39;s request into sub-requests due to identifying both a version of Acme&#39;s opportunity scoring machine-learning model A  154  and a version of Acme&#39;s opportunity ranking machine-learning model. 
     Following an identification of a version of a machine-learning model, a set is optionally selected of each serving container corresponding to the machine-learning model from a cluster of available serving containers associated with the version of the machine-learning model, box  336 . The system can identify the cluster of available serving containers that serve a version of the identified machine-learning model and the specific serving containers in the cluster that might load the identified machine-learning model. By way of example and without limitation, this can include the routing container  124  using the same consistent hashing function to identify the scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 , from the cluster  120  of available scoring serving containers A  140 , B  142 , C  144 , D  146 , E  148 . F  150 , and G  152 , which can load or have loaded a copy of any scoring machine-learning model that shares the same library to generate the scores of business opportunities. The routing container  124  may also use the same consistent hashing function to identify the ranking serving containers A  128  and C  132 , which can load or have loaded a copy of Acme&#39;s opportunity ranking machine-learning model, from the cluster  116  of ranking serving containers A  128 , B  130 , and C  132 , which can load or have loaded a copy of any ranking machine-learning model that shares the same library to generate the rankings of business opportunities. 
     Having identified a set of each serving container corresponding to an identified machine-learning model, an additional serving container is optionally selected from the set of each serving container corresponding to the identified machine-learning model, box  338 . The system can select one of the identified serving containers. In embodiments, this can include the routing container  124  using the same round-robin strategy with a different seed to select the scoring serving container G  152  from the scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . The routing container  124  may also use the same round-robin strategy with a different seed to select the ranking serving container C  132  from the ranking serving containers A  128  and C  132 , which can load or have loaded a copy of Acme&#39;s opportunity ranking machine-learning model. 
     The machine-learning serving infrastructure  108  may use the same consistent hashing function to route Ann&#39;s sub-request for opportunity scoring and Bob&#39;s sub-request for opportunity scoring to the same scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . However, the use of the same round-robin strategy with different seeds enables the routing containers  122  and  124  to select the different scoring serving containers A  140  and G  152  for Ann&#39;s sub-request and Bob&#39;s sub-request, respectively. These different scoring serving containers A  140  and G  152  can simultaneously execute their own copies of Acme&#39;s opportunity scoring machine-learning model A  154 . Even if the same scoring serving container loaded different copies of Acme&#39;s opportunity scoring machine-learning model A  154  for Ann&#39;s sub-request and Bob&#39;s sub-request, the same scoring serving container could simultaneously execute both copies of Acme&#39;s opportunity scoring machine-learning model A  154 . 
     In addition to selecting an additional serving container, a determination is optionally made whether a copy of the identified machine-learning model is loaded in the additional serving container, box  340 . The system can determine whether the selected additional serving container needs to load a copy of the identified machine-learning model. For example, and without limitation, this can include the scoring serving container G  152  determining whether the scoring serving container G  152  has loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . The routing container  124  may also determine whether the ranking serving container C  132  has loaded a copy of Acme&#39;s opportunity ranking machine-learning model. If a copy of the identified machine-learning model is not loaded in the additional selected serving container, the method  300  continues to block  342  to load a copy of the identified machine-learning model in the additional selected serving container. If a copy of the identified machine-learning model is loaded in the additional selected serving container, the method  300  proceeds to block  344  to execute the copy of the identified machine-learning model in the additional selected serving container. 
     If a copy of the identified machine-learning model is not loaded in the additional selected serving container, a copy of the identified machine-learning model is optionally loaded in the additional selected serving container, box  342 . The system can load a copy of the identified machine-learning model in the selected additional serving container. By way of example and without limitation, this can include the scoring serving container G  152  loading a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . Also, the ranking serving container C  132  may load a copy of Acme&#39;s opportunity ranking machine-learning model. 
     If a copy of the identified machine-learning model is loaded in the additional selected serving container, the copy of the identified machine-learning model is optionally executed in the additional selected serving container on behalf of the additional request, box  344 . The system can execute a copy of the identified machine-learning model in the additional selected serving container. In embodiments, this can include a copy of Acme&#39;s opportunity scoring machine-learning model A  154  scoring some of last week&#39;s purchased business contacts as Acme&#39;s business opportunities, after a copy of Acme&#39;s opportunity scoring machine-learning model A  154  is verified as loaded in the scoring serving container G  152 . Also, a copy of Acme&#39;s opportunity ranking machine-learning model may rank some of last week&#39;s purchased business contacts to determine Bob&#39;s personal priorities for working on these business opportunities, after a copy of Acme&#39;s opportunity ranking machine-learning model is verified as loaded in the ranking serving container C  132 . 
     After executing a copy of the identified machine-learning model for an additional request in an additional selected serving container, the additional request is optionally responded to, based on executing the copy of the identified machine-learning model on behalf of the additional request, box  346 . The system can respond to an additional request by executing a copy of any identified machine-learning model(s) in any selected serving container(s). For example, and without limitation, this can include the machine-learning serving infrastructure  108  responding to Bob&#39;s request with his priority-ranked list of some of last week&#39;s purchased contacts. 
     In addition to receiving a request from an application, an extra request is optionally received from an extra application, box  348  The system can receive many requests that can require the execution of machine-learning models. By way of example and without limitation, this can include the machine-learning serving infrastructure  108  receiving an extra request, which requires scoring a list of purchasable contacts as Mega Corporation&#39;s business opportunities. The extra request is from a CRM application executed by a MegaCorp sales manager Chris on the desktop computer  102 . Chris&#39; request also requires that the scored business opportunities be recommended to various MegaCorp sales representatives, and that these scored business opportunities be ranked to determine each MegaCorp sales representatives&#39; personal priorities for working on these business opportunities. 
     After an extra request is received, an extra version is optionally identified of an extra machine-learning model associated with the extra request, box  350 . The system can identify a version of a machine-learning model to be executed. In embodiments, this can include the machine-learning serving infrastructure  108  identifying that Chris&#39; request requires executing a version of the opportunity scoring machine-learning model E  161  used by MegaCorp&#39;s CRM application. The machine-learning serving infrastructure  108  may also identify that Chris&#39; request also requires executing a version of the opportunity recommending machine-learning model used by MegaCorp&#39;s CRM application and a version of the opportunity ranking machine-learning model used by MegaCorp&#39;s CRM application. Therefore, the machine-learning serving infrastructure  108  may split Chris&#39; request three ways into sub-requests due to identifying a version of MegaCorp&#39;s opportunity scoring machine-learning model E  161 , a version of MegaCorp&#39;s opportunity recommending machine-learning model, and a version of MegaCorp&#39;s opportunity ranking machine-learning model. 
     Following an identification of an extra version of an extra machine-learning model, an extra set is optionally selected of each serving container corresponding to the extra machine-learning model from a cluster of available serving containers associated with both the extra version of the extra machine-learning model and the identified version of the identified machine-learning model, box  352 . The system can identify the cluster of available serving containers that serve a version of the identified machine-learning model and the specific serving containers in the cluster that might load the identified machine-learning model. For example, and without limitation, this can include the routing container  126  using the same consistent hashing function to identify the scoring serving containers B  142  and E  148 , which can load or have loaded a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 , from the cluster  120  of available scoring serving containers A  140 , B  142 , C  144 , D  146 , E  148 . F  150 , and G  152 , which can load or have loaded a copy of any scoring machine-learning model that shares the same library to generate the scores of business opportunities. 
     The routing container  126  may also use the same consistent hashing function to identify the recommending serving containers A  134  and B  136 , which can load or have loaded a copy of MegaCorp&#39;s opportunity recommending machine-learning model, from the cluster  118  of recommending serving containers A  134 , B  136 , and C  138 , which can load or have loaded a copy of any recommending machine-learning model that shares the same library to generate the recommendations of business opportunities. The routing container  126  may further use the same consistent hashing function to identify the ranking serving containers B  130  and C  132 , which can load or have loaded a copy of MegaCorp&#39;s opportunity ranking machine-learning model, from the cluster  116  of ranking serving containers A  128 , B  130 , and C  132 , which can load or have loaded a copy of any ranking machine-learning model that shares the same library to generate the rankings of business opportunities. 
     Having identified an extra set of each serving container corresponding to an extra machine-learning model, an extra serving container is optionally selected from the extra set of each serving container corresponding to the extra machine-learning model, box  354 . The system can select one of the identified serving containers. By way of example and without limitation, this can include the routing container  126  using the same round-robin strategy with a different seed to select the scoring serving container E  148  from the scoring serving containers B  142  and E  148 , which can load or have loaded a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 . 
     The routing container  126  may also use the same round-robin strategy with a different seed to select the recommending serving container B  136  from the recommending serving containers A  134  and B  136 , which can load or have loaded a copy of MegaCorp&#39;s opportunity recommending machine-learning model. The routing container  126  may further use the same round-robin strategy with a different seed to select the ranking serving container B  130  from the ranking serving containers B  130  and C  132 , which can load or have loaded a copy of MegaCorp&#39;s opportunity ranking machine-learning model. 
     The routing container  126  may use a consistent hashing function to route MegaCorp&#39;s sub-request for opportunity scoring to the cluster  120 , which includes the scoring serving containers B  142  and E  148 , which can load or have loaded a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 . The routing containers  122  and  124  may also use the same consistent hashing function to route Acme&#39;s sub-requests for opportunity scoring to the same cluster  120 , which includes scoring serving containers A  140 , D  146 , and G  152 , which can load or have loaded a copy of Acme&#39;s opportunity scoring machine-learning model A  154 . Therefore, even though both MegaCorp&#39;s sub-request for opportunity scoring and Acme&#39;s sub-requests for opportunity scoring are routed to the same cluster  120  of scoring serving containers, these two tenants&#39; specific opportunity scoring machine-learning models E  161  and A  154 , respectively, are hosted by different scoring serving containers. 
     However, the same serving container may host both tenants&#39; machine-learning models E  161  and A  154 . In a multi-tenant system, the data for multiple tenants may be stored in the same physical database object, but the tenant data is arranged so that data of one tenant is kept logically separate from that of other tenants so that one tenant does not have access to another tenant&#39;s data, unless such data is expressly shared. No tenant or identifiable data is stored in the shared service discovery system  162 . The machine-learning serving infrastructure  108  provides security mechanisms to keep each tenant&#39;s data separate unless the data is shared. Each serving container  128 - 152  is configured to handle requests for any user associated with any organization that is a tenant. 
     The three scoring serving containers A  140 , D  146 , and G  152  in the cluster  120  potentially host a copy of Acme&#39;s opportunity scoring machine-learning model A  154 , the two scoring serving containers B  142  and E  152  in the cluster  120  potentially host a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 , and the two scoring serving containers C  144  and F  154  in the cluster  120  do not host either a copy of Acme&#39;s opportunity scoring machine-learning model A  154  or a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 . Consequently, the seven scoring serving containers  140 - 152  host an aggregated total of five copies of these tenants&#39; specific opportunity scoring machine-learning models. In contrast, each of the seven completely redundant scoring serving container in a typical cluster of seven completely redundant scoring serving containers would host copies of the two opportunity scoring machine-learning models for the tenants, which would result in an aggregated total of fourteen copies of these tenants&#39; specific opportunity scoring machine-learning models. Even when using numerical examples based on a small cluster of only seven scoring serving containers, the cluster  120  filling with five copies of models compared against the typical cluster filling with fourteen copies of models results in an estimate that each scoring serving container in a typical cluster would fill with models approximately 2.8 times (fourteen copies divided by five copies) faster than the cluster  120  would fill with models. 
     In addition to selecting an extra serving container, a determination is optionally made whether a copy of an extra identified machine-learning model is loaded in the extra selected serving container, box  356 . The system can determine whether the extra selected serving container needs to load a copy of the extra identified machine-learning model. In embodiments, this can include the scoring serving container E  148  determining whether the scoring serving container E  148  has loaded a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 . The routing container  126  may also determine whether the recommending serving container B  136  has loaded a copy of MegaCorp&#39;s opportunity recommending machine-learning model. The routing container  126  may further determine whether the ranking serving container B  130  has loaded a copy of MegaCorp&#39;s opportunity ranking machine-learning model. If a copy of the extra identified machine-learning model is not loaded in the extra selected serving container, the method  300  continues to block  358  to load the extra identified machine-learning model in the extra selected serving container. If a copy of the extra identified machine-learning model is loaded in the extra selected serving container, the method  300  proceeds to block  360  to execute the extra identified machine-learning model in the extra selected serving container. 
     If a copy of the extra identified machine-learning model is not loaded in the extra selected serving container, a copy of the extra identified machine-learning model is optionally loaded in the extra selected serving container, box  358 . The system can load a copy of the extra identified machine-learning model in the extra selected serving container. For example, and without limitation, this can include the scoring serving container E  148  loading a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161 . Also, the recommending serving container B  136  may load a copy of MegaCorp&#39;s opportunity recommending machine-learning model, and the ranking serving container B  130  may load a copy of MegaCorp&#39;s opportunity ranking machine-learning model. 
     If a copy of the extra identified machine-learning model is loaded in the extra selected serving container, the extra identified machine-learning model is optionally executed in the extra selected serving container on behalf of the extra request, box  360 . The system can execute a copy of the extra identified machine-learning model in the extra selected serving container. By way of example and without limitation, this can include a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161  scoring some purchasable business contacts as MegaCorp&#39;s business opportunities, after a copy of MegaCorp&#39;s opportunity scoring machine-learning model E  161  is verified as loaded in the scoring serving container E  148 . 
     Also, a copy of MegaCorp&#39;s opportunity recommending machine-learning model may recommend some of the purchasable business contacts as MegaCorp&#39;s business opportunities to MegaCorp&#39;s sales representatives, after a copy of MegaCorp&#39;s opportunity recommending machine-learning model is verified as loaded in the recommending serving container B  136 . Additionally, a copy of MegaCorp&#39;s opportunity ranking machine-learning model may rank the recommended business opportunities for each MegaCorp sales representative to determine their personal priorities for working on these business opportunities, after a copy of MegaCorp&#39;s opportunity ranking machine-learning model is verified as loaded in the ranking serving container B  130 . 
     After executing an extra identified machine-learning model in an extra selected serving container on behalf of an extra request, the extra request is optionally responded to, based on executing a copy of the extra identified machine-learning model on behalf of the extra request, box  362 . The system can respond to an extra request by executing a copy of any extra machine-learning model(s) in any extra serving container(s). In embodiments, this can include the machine-learning serving infrastructure  108  responding to Chris&#39; request with each MegaCorp sales representative&#39;s priority-ranked list of recommended business opportunities. 
     The method  300  may be repeated as desired. Although this disclosure describes the blocks  302 - 362  executing in a particular order, the blocks  302 - 362  may be executed in a different order. In other implementations, each of the blocks  302 - 362  may also be executed in combination with other blocks and/or some blocks may be divided into a different set of blocks. 
     System Overview 
       FIG. 4  illustrates a block diagram of an environment  410  wherein an on-demand database service might be used. The environment  410  may include user systems  412 , a network  414 , a system  416 , a processor system  417 , an application platform  418 , a network interface  420 , a tenant data storage  422 , a system data storage  424 , program code  426 , and a process space  428 . In other embodiments, the environment  410  may not have all the components listed and/or may have other elements instead of, or in addition to, those listed above. 
     The environment  410  is an environment in which an on-demand database service exists. A user system  412  may be any machine or system that is used by a user to access a database user system. For example, any of the user systems  412  may be a handheld computing device, a mobile phone, a laptop computer, a workstation, and/or a network of computing devices. As illustrated in  FIG. 4  (and in more detail in  FIG. 5 ) the user systems  412  might interact via the network  414  with an on-demand database service, which is the system  416 . 
     An on-demand database service, such as the system  416 , is a database system that is made available to outside users that do not need to necessarily be concerned with building and/or maintaining the database system, but instead may be available for their use when the users need the database system (e.g., on the demand of the users). Some on-demand database services may store information from one or more tenants stored into tables of a common database image to form a multi-tenant database system (MTS). Accordingly, the “on-demand database service  416 ” and the “system  416 ” will be used interchangeably herein. A database image may include one or more database objects. A relational database management system (RDMS) or the equivalent may execute storage and retrieval of information against the database object(s). The application platform  418  may be a framework that allows the applications of the system  416  to run, such as the hardware and/or software, e.g., the operating system. In an embodiment, the on-demand database service  416  may include the application platform  418  which enables creation, managing and executing one or more applications developed by the provider of the on-demand database service, users accessing the on-demand database service via user systems  412 , or third-party application developers accessing the on-demand database service via the user systems  412 . 
     The users of the user systems  412  may differ in their respective capacities, and the capacity of a particular user system  412  might be entirely determined by permissions (permission levels) for the current user. For example, where a salesperson is using a particular user system  412  to interact with the system  416 , that user system  412  has the capacities allotted to that salesperson. However, while an administrator is using that user system  412  to interact with the system  416 , that user system  412  has the capacities allotted to that administrator. In systems with a hierarchical role model, users at one permission level may have access to applications, data, and database information accessible by a lower permission level user, but may not have access to certain applications, database information, and data accessible by a user at a higher permission level. Thus, different users will have different capabilities with regard to accessing and modifying application and database information, depending on a user&#39;s security or permission level. 
     The network  414  is any network or combination of networks of devices that communicate with one another. For example, the network  414  may be any one or any combination of a LAN (local area network), WAN (wide area network), telephone network, wireless network, point-to-point network, star network, token ring network, hub network, or other appropriate configuration. As the most common type of computer network in current use is a TCP/IP (Transfer Control Protocol and Internet Protocol) network, such as the global internetwork of networks often referred to as the “Internet” with a capital “I,” that network will be used in many of the examples herein. However, the networks that the one or more implementations might use are not so limited, although TCP/IP is a frequently implemented protocol. 
     The user systems  412  might communicate with the system  416  using TCP/IP and, at a higher network level, use other common Internet protocols to communicate, such as HTTP, FTP, AFS, WAP, etc. In an example where HTTP is used, the user systems  412  might include an HTTP client commonly referred to as a “browser” for sending and receiving HTTP messages to and from an HTTP server at the system  416 . Such an HTTP server might be implemented as the sole network interface between the system  416  and the network  414 , but other techniques might be used as well or instead. In some implementations, the interface between the system  416  and the network  414  includes load sharing functionality, such as round-robin HTTP request distributors to balance loads and distribute incoming HTTP requests evenly over a plurality of servers. At least as for the users that are accessing that server, each of the plurality of servers has access to the MTS&#39; data; however, other alternative configurations may be used instead. 
     In one embodiment, the system  416 , shown in  FIG. 4 , implements a web-based customer relationship management (CRM) system. For example, in one embodiment, the system  416  includes application servers configured to implement and execute CRM software applications as well as provide related data, code, forms, webpages and other information to and from the user systems  412  and to store to, and retrieve from, a database system related data, objects, and Webpage content. With a multi-tenant system, data for multiple tenants may be stored in the same physical database object, however, tenant data typically is arranged so that data of one tenant is kept logically separate from that of other tenants so that one tenant does not have access to another tenant&#39;s data, unless such data is expressly shared. In certain embodiments, the system  416  implements applications other than, or in addition to, a CRM application. For example, the system  416  may provide tenant access to multiple hosted (standard and custom) applications, including a CRM application. User (or third-party developer) applications, which may or may not include CRM, may be supported by the application platform  418 , which manages creation, storage of the applications into one or more database objects and executing of the applications in a virtual machine in the process space of the system  416 . 
     One arrangement for elements of the system  416  is shown in  FIG. 4 , including the network interface  420 , the application platform  418 , the tenant data storage  422  for tenant data  423 , the system data storage  424  for system data  425  accessible to the system  416  and possibly multiple tenants, the program code  426  for implementing various functions of the system  416 , and the process space  428  for executing MTS system processes and tenant-specific processes, such as running applications as part of an application hosting service. Additional processes that may execute on the system  416  include database indexing processes. 
     Several elements in the system shown in  FIG. 4  include conventional, well-known elements that are explained only briefly here. For example, each of the user systems  412  could include a desktop personal computer, workstation, laptop, PDA, cell phone, or any wireless access protocol (WAP) enabled device or any other computing device capable of interfacing directly or indirectly to the Internet or other network connection. Each of the user systems  412  typically runs an HTTP client, e.g., a browsing program, such as Microsoft&#39;s Internet Explorer browser, Netscape&#39;s Navigator browser, Opera&#39;s browser, or a WAP-enabled browser in the case of a cell phone, PDA or other wireless device, or the like, allowing a user (e.g., subscriber of the multi-tenant database system) of the user systems  412  to access, process and view information, pages, and applications available to it from the system  416  over the network  414 . Each of the user systems  412  also typically includes one or more user interface devices, such as a keyboard, a mouse, trackball, touch pad, touch screen, pen, or the like, for interacting with a graphical user interface (GUI) provided by the browser on a display (e.g., a monitor screen, LCD display, etc.) in conjunction with pages, forms, applications, and other information provided by the system  416  or other systems or servers. For example, the user interface device may be used to access data and applications hosted by the system  416 , and to perform searches on stored data, and otherwise allow a user to interact with various GUI pages that may be presented to a user. As discussed above, embodiments are suitable for use with the Internet, which refers to a specific global internetwork of networks. However, other networks may be used instead of the Internet, such as an intranet, an extranet, a virtual private network (VPN), a non-TCP/IP based network, any LAN or WAN or the like. 
     According to one embodiment, each of the user systems  412  and all its components are operator configurable using applications, such as a browser, including computer code run using a central processing unit such as an Intel Pentium® processor or the like. Similarly, the system  416  (and additional instances of an MTS, where more than one is present) and all their components might be operator configurable using application(s) including computer code to run using a central processing unit such as the processor system  417 , which may include an Intel Pentium® processor or the like, and/or multiple processor units. A computer program product embodiment includes a machine-readable storage medium (media) having instructions stored thereon/in which may be used to program a computer to perform any of the processes of the embodiments described herein. Computer code for operating and configuring the system  416  to intercommunicate and to process webpages, applications and other data and media content as described herein are preferably downloaded and stored on a hard disk, but the entire program code, or portions thereof, may also be stored in any other volatile or non-volatile memory medium or device as is well known, such as a ROM or RAM, or provided on any media capable of storing program code, such as any type of rotating media including floppy disks, optical discs, digital versatile disk (DVD), compact disk (CD), micro-drive, and magneto-optical disks, and magnetic or optical cards, nano-systems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data. Additionally, the entire program code, or portions thereof, may be transmitted and downloaded from a software source over a transmission medium, e.g., over the Internet, or from another server, as is well known, or transmitted over any other conventional network connection as is well known (e.g., extranet, VPN, LAN, etc.) using any communication medium and protocols (e.g., TCP/IP, HTTP, HTTPS, Ethernet, etc.) as are well known. It will also be appreciated that computer code for implementing embodiments may be implemented in any programming language that may be executed on a client system and/or server or server system such as, for example, C, C++, HTML, any other markup language, Java™, JavaScript, ActiveX, any other scripting language, such as VBScript, and many other programming languages as are well known may be used. (Java™ is a trademark of Sun Microsystems, Inc.). 
     According to one embodiment, the system  416  is configured to provide webpages, forms, applications, data, and media content to the user (client) systems  412  to support the access by the user systems  412  as tenants of the system  416 . As such, the system  416  provides security mechanisms to keep each tenant&#39;s data separate unless the data is shared. If more than one MTS is used, they may be near one another (e.g., in a server farm located in a single building or campus), or they may be distributed at locations remote from one another (e.g., one or more servers located in city A and one or more servers located in city B). As used herein, each MTS could include one or more logically and/or physically connected servers distributed locally or across one or more geographic locations. Additionally, the term “server” is meant to include a computer system, including processing hardware and process space(s), and an associated storage system and database application (e.g., OODBMS or RDBMS) as is well known in the art. It should also be understood that “server system” and “server” are often used interchangeably herein. Similarly, the database object described herein may be implemented as single databases, a distributed database, a collection of distributed databases, a database with redundant online or offline backups or other redundancies, etc., and might include a distributed database or storage network and associated processing intelligence. 
       FIG. 5  also illustrates the environment  410 . However, in  FIG. 5  elements of the system  416  and various interconnections in an embodiment are further illustrated.  FIG. 5  shows that the each of the user systems  412  may include a processor system  412 A, a memory system  412 B, an input system  412 C, and an output system  412 D.  FIG. 5  shows the network  414  and the system  416 .  FIG. 5  also shows that the system  416  may include the tenant data storage  422 , the tenant data  423 , the system data storage  424 , the system data  425 , a User Interface (UI)  530 , an Application Program Interface (API)  532 , a PL/SOQL  534 , save routines  536 , an application setup mechanism  538 , applications servers  500   1 - 500   N , a system process space  502 , tenant process spaces  504 , a tenant management process space  510 , a tenant storage area  512 , a user storage  514 , and application metadata  516 . In other embodiments, the environment  410  may not have the same elements as those listed above and/or may have other elements instead of, or in addition to, those listed above. 
     The user systems  412 , the network  414 , the system  416 , the tenant data storage  422 , and the system data storage  424  were discussed above in  FIG. 4 . Regarding the user systems  412 , the processor system  412 A may be any combination of one or more processors. The memory system  412 B may be any combination of one or more memory devices, short-term, and/or long-term memory. The input system  412 C may be any combination of input devices, such as one or more keyboards, mice, trackballs, scanners, cameras, and/or interfaces to networks. The output system  412 D may be any combination of output devices, such as one or more monitors, printers, and/or interfaces to networks. As shown by  FIG. 5 , the system  416  may include the network interface  420  (of  FIG. 4 ) implemented as a set of HTTP application servers  500 , the application platform  418 , the tenant data storage  422 , and the system data storage  424 . Also shown is the system process space  502 , including individual tenant process spaces  504  and the tenant management process space  510 . Each application server  500  may be configured to access tenant data storage  422  and the tenant data  423  therein, and the system data storage  424  and the system data  425  therein to serve requests of the user systems  412 . The tenant data  423  might be divided into individual tenant storage areas  512 , which may be either a physical arrangement and/or a logical arrangement of data. Within each tenant storage area  512 , the user storage  514  and the application metadata  516  might be similarly allocated for each user. For example, a copy of a user&#39;s most recently used (MRU) items might be stored to the user storage  514 . Similarly, a copy of MRU items for an entire organization that is a tenant might be stored to the tenant storage area  512 . The UI  530  provides a user interface, and the API  532  provides an application programmer interface to the system  416  resident processes to users and/or developers at the user systems  412 . The tenant data and the system data may be stored in various databases, such as one or more Oracle™ databases. 
     The application platform  418  includes the application setup mechanism  538  that supports application developers&#39; creation and management of applications, which may be saved as metadata into the tenant data storage  422  by the save routines  536  for execution by subscribers as one or more tenant process spaces  504  managed by the tenant management process  510  for example. Invocations to such applications may be coded using the PL/SOQL  534  that provides a programming language style interface extension to the API  532 . A detailed description of some PL/SOQL language embodiments is discussed in commonly owned U.S. Pat. No. 7,730,478 entitled, METHOD AND SYSTEM FOR ALLOWING ACCESS TO DEVELOPED APPLICATIONS VIA A MULTI-TENANT ON-DEMAND DATABASE SERVICE, by Craig Weissman, filed Sep. 21, 2007, which is incorporated in its entirety herein for all purposes. Invocations to applications may be detected by one or more system processes, which manages retrieving the application metadata  516  for the subscriber making the invocation and executing the metadata as an application in a virtual machine. 
     Each application server  500  may be communicably coupled to database systems, e.g., having access to the system data  425  and the tenant data  423 , via a different network connection. For example, one application server  500   1  might be coupled via the network  414  (e.g., the Internet), another application server  500   N-1  might be coupled via a direct network link, and another application server  500   N  might be coupled by yet a different network connection. Transfer Control Protocol and Internet Protocol (TCP/IP) are typical protocols for communicating between application servers  500  and the database system. However, it will be apparent to one skilled in the art that other transport protocols may be used to optimize the system depending on the network interconnect used. 
     In certain embodiments, each application server  500  is configured to handle requests for any user associated with any organization that is a tenant. Because it is desirable to be able to add and remove application servers from the server pool at any time for any reason, there is preferably no server affinity for a user and/or organization to a specific application server  500 . In one embodiment, therefore, an interface system implementing a load balancing function (e.g., an F5 Big-IP load balancer) is communicably coupled between the application servers  500  and the user systems  412  to distribute requests to the application servers  500 . In one embodiment, the load balancer uses a least connections algorithm to route user requests to the application servers  500 . Other examples of load balancing algorithms, such as round robin and observed response time, also may be used. For example, in certain embodiments, three consecutive requests from the same user could hit three different application servers  500 , and three requests from different users could hit the same application server  500 . In this manner, the system  416  is multi-tenant, wherein the system  416  handles storage of, and access to, different objects, data and applications across disparate users and organizations. 
     As an example of storage, one tenant might be a company that employs a sales force where each salesperson uses the system  416  to manage their sales process. Thus, a user might maintain contact data, leads data, customer follow-up data, performance data, goals, and progress data, etc., all applicable to that user&#39;s personal sales process (e.g., in the tenant data storage  422 ). In an example of a MTS arrangement, since all the data and the applications to access, view, modify, report, transmit, calculate, etc., may be maintained and accessed by a user system having nothing more than network access, the user can manage his or her sales efforts and cycles from any of many different user systems. For example, if a salesperson is visiting a customer and the customer has Internet access in their lobby, the salesperson can obtain critical updates as to that customer while waiting for the customer to arrive in the lobby. 
     While each user&#39;s data might be separate from other users&#39; data regardless of the employers of each user, some data might be organization-wide data shared or accessible by a plurality of users or all the users for a given organization that is a tenant. Thus, there might be some data structures managed by the system  416  that are allocated at the tenant level while other data structures might be managed at the user level. Because an MTS might support multiple tenants including possible competitors, the MTS should have security protocols that keep data, applications, and application use separate. Also, because many tenants may opt for access to an MTS rather than maintain their own system, redundancy, up-time, and backup are additional functions that may be implemented in the MTS. In addition to user-specific data and tenant specific data, the system  416  might also maintain system level data usable by multiple tenants or other data. Such system level data might include industry reports, news, postings, and the like that are sharable among tenants. 
     In certain embodiments, the user systems  412  (which may be client systems) communicate with the application servers  500  to request and update system-level and tenant-level data from the system  416  that may require sending one or more queries to the tenant data storage  422  and/or the system data storage  424 . The system  416  (e.g., an application server  500  in the system  416 ) automatically generates one or more SQL statements (e.g., one or more SQL queries) that are designed to access the desired information. The system data storage  424  may generate query plans to access the requested data from the database. 
     Each database can generally be viewed as a collection of objects, such as a set of logical tables, containing data fitted into predefined categories. A “table” is one representation of a data object and may be used herein to simplify the conceptual description of objects and custom objects. It should be understood that “table” and “object” may be used interchangeably herein. Each table generally contains one or more data categories logically arranged as columns or fields in a viewable schema. Each row or record of a table contains an instance of data for each category defined by the fields. For example, a CRM database may include a table that describes a customer with fields for basic contact information such as name, address, phone number, fax number, etc. Another table might describe a purchase order, including fields for information such as customer, product, sale price, date, etc. In some multi-tenant database systems, standard entity tables might be provided for use by all tenants. For CRM database applications, such standard entities might include tables for Account, Contact, Lead, and Opportunity data, each containing pre-defined fields. The word “entity” may also be used interchangeably herein with “object” and “table”. 
     In some multi-tenant database systems, tenants may be allowed to create and store custom objects, or they may be allowed to customize standard entities or objects, for example by creating custom fields for standard objects, including custom index fields. U.S. Pat. No. 7,779,039, filed Apr. 2, 2004, entitled “Custom Entities and Fields in a Multi-Tenant Database System”, which is hereby incorporated herein by reference, teaches systems and methods for creating custom objects as well as customizing standard objects in a multi-tenant database system. In certain embodiments, for example, all custom entity data rows are stored in a single multi-tenant physical table, which may contain multiple logical tables per organization. It is transparent to customers that their multiple “tables” are in fact stored in one large table or that their data may be stored in the same table as the data of other customers. 
     While one or more implementations have been described by way of example and in terms of the specific embodiments, it is to be understood that one or more implementations are not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation to encompass all such modifications and similar arrangements.