Patent Publication Number: US-10761829-B2

Title: Rolling version update deployment utilizing dynamic node allocation

Description:
CROSS REFERENCES 
     The present Application for Patent claims priority to U.S. patent application Ser. No. 15/221,496 by Roy et al., entitled “Rolling Version Update Deployment Utilizing Dynamic Node Allocation,” filed Jul. 27, 2016, which is related to U.S. patent application Ser. No. 15/221,486 by Roy et al., entitled “Dynamic Allocation of Stateful Nodes or Healing and Load Balancing,” filed Jul. 27, 2016, assigned to the assignee hereof. 
     FIELD OF TECHNOLOGY 
     The field of the disclosed technology is dynamic node allocation for delivering business analytics live, for large volumes of data—with dynamic visualization of data from huge datasets, for creating compelling dynamic answers for businesses. 
     BACKGROUND 
     The subject matter discussed in the background section should not be assumed to be prior art merely as a result 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 claim inventions. 
     Both developers and end users are dealing with large numbers of clients and huge data volumes, popularly referred to as “Big Data” in today&#39;s world. Web applications that serve and manage millions of Internet users, such as Facebook™, Instagram™, Twitter™, banking websites, or even online retail shops, such as Amazon.com™ or eBay™ are faced with the challenge of delivering information as fast as possible so that the end users can be provided with a real-time experience. 
     Businesses need the ability to query and to view query results in real time, large data sets being analyzed, in order to make informed business decisions. An enterprise system that provides business analytics live, for large volumes of data, performs visual data analysis and live data rendering, with flexible display options for analyzing the data and conveying analysis results. Workflow handling for queries is a significant consideration when configuring server node allocation—to optimize for speed and minimize the expense of providing live business analytics. 
     Existing worker node clusters for an example enterprise system operate as described next. Requests enter the system via a load balancer and get routed to one of a pool of several data structure server nodes. In one implementation, the data structure servers may be Redis nodes. Requests for a given org are hashed to a specific queue number and placed on that queue. Each worker node is assigned a fixed set of queues to monitor. For example, worker one on rack one might be assigned queues 1, 5, 7 and 9. Thus, worker one will service any requests for org IDs that get hashed to one of those queue numbers. To meet the need for assured reliability, at any time of any day, at least three backend servers are configured to monitor the Redis node assigned to process the generated queue. One of the backend servers picks up the work, processes it, and provides results. To ensure availability and maximize throughput, all workers listen to their assigned queues on all Redis nodes. 
     A salient issue for node configuration is how to spread queue assignments among the nodes available in the backend system. Existing systems are configured by manually running a configuration tool that extracts, from a database that contains a reliable list of information about the hardware, host server systems and their locations for example, what server is where, on which racks. This configuration data gets extracted from the database, to produce a static set of configuration files, per data center. The configuration files of attribute-value pairs explicitly describe which server is going to handle which queue. In one implementation, the attribute-value pairs can be expressed in JSON, and the JSON results are usable as input to a revision control system, such as Perforce. After going through a coordinated release process, including obtaining the necessary signoffs, a series of server restarts can be carefully orchestrated to make changes to the configuration of the backend server nodes. The generated configurations are written in stone until new configuration files are deployed, which requires a repeat of the process just described. 
     The existing configuration approach, described above, for spreading queue assignments for big data among the nodes in the backend, is limited. Any configuration change, including adding additional server capacity, removing server capacity from the cluster, or reallocation of queues to better service hotspots in the system, requires a full release pipeline. 
     If any server in the system goes down for any reason, then the orgs that would have hashed to those queues go into degraded mode. The only available fix is for a human to take action and fix the node. Therefore, nodes operate very much as pets, instead of as cattle. If the system loses multiple nodes with queue overlaps, the service may become entirely unavailable for a set of orgs even if plenty of usable capacity is available in the cluster of servers. The requirement for a release cycle to implement configuration changes results in a lack of runtime adaptability, so that every single server gets treated like a precious pet, instead of the preferable perspective of having “cattle”. That is, if a server goes down, ideally a different server would be substituted without a need to nurse the “pet” back to health before proceeding. 
     For the system described above, because node allocation is a slow and manual process, it is impossible to maximize hardware utilization for the end user&#39;s benefit. A large org could be experiencing a very high load with three servers running at maximum capacity, while another fifty servers are doing very little. Temporarily shifting resources around to better balance the load could greatly improve the average end user experience, but the existing configuration system for servers is inflexible at runtime. There is no ability to employ underutilized hardware to adapt to performance hotspots. 
     Therefore, an opportunity arises for dynamic node allocation for a server system that can automatically heal on failure—a system that minimizes the need for static configuration and is capable of dynamically adjusting server resources to match load, and minimize end user wait times. The disclosed technology relates to dynamically allocating nodes to increase capacity for a platform that accepts data queries and completes ultra-fast, ad-hoc data exploration and faceted navigation on integrated, heterogeneous data sets. The analytic data structures, also referred to as “edgemarts,” are compressed data forms produced from transactional databases, which represent specific form functions of transactional database objects. Sometimes analytic data structures are produced by merging data from multiple database systems or platforms. For instance, prospect and opportunity closing data may come from one enterprise system and order fulfillment data can come from a software-as-a-system. An analytic data structure may combine sales and fulfillment data for particular opportunities, merging data from systems that run on different database platforms, in separate applications from different vendors, applying divergent security models. Dozens of analysts may work on subsets of an overall analytic data structure, both for periodic and ad hoc investigations. 
     SUMMARY 
     A simplified summary is provided herein to help enable a basic or general understanding of various aspects of exemplary, non-limiting implementations that follow in the more detailed description and the accompanying drawings. This summary is not intended, however, as an extensive or exhaustive overview. Instead, the sole purpose of this summary is to present some concepts related to some exemplary non-limiting implementations in a simplified form as a prelude to the more detailed description of the various implementations that follow. 
     Disclosed systems and methods are usable for dynamic allocation of stateful nodes for healing and load balancing. A disclosed system of networked racks with management devices and worker devices includes sufficient management devices to establish a redundancy factor and having management devices redundantly located in disjoint racks. The disclosed system responds to querying devices that query immutable data sets for orgs to which the querying devices belong; and the system handles the queries and the immutable data sets based on org-affinities. An org-affinity is implemented by data structures linking allocated workers that run on the worker devices and service the queries, with each allocated worker using a configuration agent to manage the worker&#39;s org-affinities. Immutable data sets belong to orgs, the immutable data sets are cached locally to the allocated workers, and the allocated workers listen to org-task-queues. Org-tasks are received by the allocated workers from the org-task-queues, and the allocated workers report status updates as they process the org-tasks. The disclosed system is further organized with redundant workers allocated to service particular org-task-queues, with the redundant workers for a particular org-task-queue selected to run on worker devices in disjoint racks; and a leader process runs on one of the management devices or worker devices. The leader process dynamically allocates workers to the org-task-queues and targets the workers to obtain and locally cache the immutable data sets used to respond to tasks in the org-task-queues. Management devices refer to the hardware on which a leader process, org-task-queue and configuration store management can be implemented. 
     The disclosed technology also includes a system with rolling version update deployment, which includes workers on a set of devices in the system, that maintain lists of org-task-queues to be serviced by the workers. Org-affinities between the workers and the org-task-queues provide access to local copies of org-data-sets to service org-tasks from the org-task-queues of the orgs that they service; a configuration leader running on a worker or management device implements a healing and balancing service that maintains worker redundancy, that manages the workers&#39; org-affinities, and that causes workers to accumulate orgs on their respective org-lists and to have heterogeneous org-affinities, such that two workers both servicing a first org will have different lists of org-affinities. The configuration leader implements messaging to the workers to update from a legacy software version to a new software version and implements monitoring of completion of updates, in cycles: the configuration leader selects workers to update in a cycle, taking care that a selected level of worker redundancy to service particular org-task-queues is not compromised, by coordinating the selection of workers taken out of service during the update cycle based on the selected workers&#39; org-affinities; the configuration leader informs the selected workers in the cycle to proceed with updating; and the configuration leader learns that the selected workers have successfully completed updating, updates version accounting over the selected workers; and moves on to another cycle of updating; and the configuration leader repeats the cycle to update all update-eligible workers. 
     Other aspects and advantages of the technology disclosed can be seen on review of the drawings, the detailed description and the claims, which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The included drawings are for illustrative purposes and serve only to provide examples of possible structures and process operations for one or more implementations of this disclosure. These drawings in no way limit any changes in form and detail that may be made by one skilled in the art without departing from the spirit and scope of this disclosure. A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
         FIG. 1  illustrates an example environment capable of implementing dynamic allocation of stateful nodes for healing and load balancing. 
         FIG. 2  shows an example global data center block diagram for implementing dynamic allocation of stateful nodes for healing and load balancing, and for rolling version update deployment. 
         FIG. 3  shows a superpod as a cluster of racks. 
         FIG. 4  shows a cluster of racks with org-status-stores (for example, Redis), a leader, configuration agents, a centralized service for maintaining configuration information (for example, Zookeeper) and workers. 
         FIG. 5  shows an example of a leader becoming disabled. 
         FIG. 6  shows an example in which three workers become unavailable. 
         FIG. 7  shows a load balancing example of workers across racks, as the number of racks or number of workers changes. 
         FIG. 8  shows an overview of the flow for a method for implementing dynamic allocation of stateful nodes for healing and load balancing. 
         FIG. 9  is a block diagram of an example multi-tenant computer system capable of implementing dynamic allocation of stateful nodes for healing and load balancing. 
         FIG. 10  shows an overview of the flow for a method for implementing rolling version update deployment. 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     The following detailed description is made with reference to the figures. Sample implementations are described to illustrate the technology disclosed, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a variety of equivalent variations on the description that follows. 
     Existing node allocation approaches for spreading queue assignments for big data among the server nodes in a data center are limited: even the smallest server configuration change requires a full release pipeline, which is slow and expensive. Additionally, data center operations need to be able to plug in or remove server hardware and the system needs to be able to adjust. 
     The disclosed technology includes methods and systems for dynamically allocating nodes to increase capacity for a platform. The importance of any single server can be minimized, and static configuration can be limited to what is needed to support the configuration structure. 
     Enterprise multi-tenant cloud-based entities need to be able to respond to shifts in customer demand in near real time, so need an ability to employ underutilized hardware to adapt to performance hotspots. That is, a demand exists for being able to grow and shrink the hardware pool for a data center by adding servers, as needed, or removing some servers from service. In a static configuration, some servers will be overextended while other servers sit underutilized. In one example, at ten am on a Monday, a group of insurance and financial services companies, such as an insurance conglomerate, must run an extensive number of reports. This scenario motivates the need to be able to dynamically adjust resources to match changing conditions and load, to minimize end user wait times. 
     Runtime adaptability also requires that a single server can be treated like a head of cattle instead of being treated like a precious pet. That is, if a server goes down, a different server can be substituted without a need to nurse the precious pet back to health in real time. 
     The disclosed dynamic node allocation environment for an analytics platform, described next, is usable to make it possible for data centers to automatically heal when a failure occurs, so they can deliver dynamic visualizations of data from huge datasets, for creating compelling dynamic answers for business enterprises. For some implementations of the disclosed dynamic node allocation environment, the system collects metrics about the state of each member of the cluster of servers, and can make the metrics available to external monitoring systems used by operations personnel. 
     The disclosed dynamic node allocation also makes it possible for system upgrades for a cluster of servers to be coordinated as rolling code upgrades across the cluster, without any user-facing down time, and without any human intervention other than choosing to initiate a release via a user interface. 
     Dynamic Node Allocation Environment 
       FIG. 1  shows an architectural level schematic of an environment for dynamic allocation of stateful nodes for healing and load balancing—dynamically allocating nodes for delivering analytics for enterprise users. Because  FIG. 1  is an architectural diagram, certain details are intentionally omitted to improve the clarity of the description.  FIG. 1  15 includes global data center  126 , GUI client engine  152  and data store  124 . Global data center  126  is described in detail infra, relative to  FIG. 2 . Additionally the system includes network  145 , mobile device user interface  154  and computer device user interface  156 . GUI client engine  152  includes visualization display engine  162 , which updates the display for end users, to reflect live business analytics query results for large volumes of data, with flexible display options for analyzing the data and conveying analysis results. Additionally, GUI client engine  152  includes allocation UI  172 , which includes a user interface for human-triggered dynamic reconfiguration, such as choosing to allocate more capacity for a specific client for a period of time. In some implementations, allocation UI  172  can include features for selecting deployment options for system upgrades. 
     Data store  124  includes read-only datasets, with attributes of multiple users, usable for querying and viewing query results in real time, for large data sets being analyzed—including datasets extracted from multi-tenant CRM computing services on a batch basis, in one example. The data extracted from large data repositories can be compiled into analytical read-only data and stored in data store  124 , and is usable to create “raw” datasets-read-only data structures for analytics—that can be augmented, transformed, flattened, etc. and published as customer-visible datasets for business entities. 
     Data store  124  can be implemented using a general-purpose distributed memory caching system. In some implementations, data structures can store information from one or more tenants into tables of a common database image to form an on-demand database service (ODDS), which can be implemented in many ways, such as a multitenant database system (MTDS). A database image can include one or more database objects. In other implementations, the databases can be relational database management systems (RDBMSs), object oriented database management systems (OODBMSs), distributed file systems (DFS), no-schema database, or any other data storing systems or computing devices. Analytical, read-only databases can implement response times of under two seconds when searching over twenty million records and compiling aggregate statistics from selected records. 
     In some implementations, user computing device  164  can be a personal computer, a laptop computer, tablet computer, smartphone or other mobile computing device, personal digital assistant (PDA), digital image capture devices, and the like. In some implementations, user mobile device  165  can be a tablet computer, smartphone or other mobile computing device, personal digital assistant (PDA), digital image capture devices, and the like. 
     GUI client engine  152  can take one of a number of forms, running in a browser or as an application, including user interfaces, dashboard interfaces, engagement consoles, and other interfaces, such as mobile interfaces, tablet interfaces, summary interfaces, or wearable interfaces. In some implementations, it can be hosted on a web-based or cloud-based server in an on premise environment. In one implementation, GUI client engine  152  can be accessed from a browser running on a computing device. The browser can be CHROME™, INTERNET EXPLORER™, FIREFOX™, SAFARI™, OPERA™, ANDROID™ BLACKBERRY™ and the like. In other implementations, GUI client engine  152  can run on a computer desktop application. 
     Network  145  can be any network or combination of networks of devices that communicate with one another, and communicate among the data stores, servers, and engines described herein. For example, network  145  can be implemented using one or any combination of a LAN (local area network), WAN (wide area network), telephone network (Public Switched Telephone Network (PSTN), Session Initiation Protocol (SIP), 3G, 4G LTE), wireless network, point-to-point network, star network, token ring network, hub network, WiMAX, Wi-Fi, peer-to-peer connections like Bluetooth, Near Field Communication (NFC), Z-Wave, ZigBee, or other appropriate configuration of data networks, including the Internet. In other implementations, other networks can be used such as an intranet, an extranet, a virtual private network (VPN), a non-TCP/IP based network, any LAN or WAN or the like. 
     In other implementations, environment  100  for dynamically allocating nodes for delivering analytics for enterprise users, multi-tenant cloud applications may not have the same elements or components as those listed above and/or may have other/different elements or components instead of, or in addition to, those listed above, such as a web server and template database. The different elements or components can be combined into single software modules and multiple software modules can run on the same hardware. Communication between component-driven multi-tenant cloud applications and application servers is considered at multiple levels in the data flow for a system; one example is described next. 
     The disclosed technology for dynamic node allocation for a server system that can automatically heal on failure includes a static configuration component that causes pre-selection of specific nodes in some servers to run an org-status store for maintaining configuration information, naming, providing distributed synchronization, and providing group services for the servers in the rack. In one implementation, the org-status store can be implemented as a Zookeeper cluster that includes sets of servers working together, including a server&#39;s root node. The Zookeeper file system is organized as a tree of nodes referred to as znodes, each of which has values within, usable for coordination among services. An example implementation is described in detail infra. 
       FIG. 2  shows global data center  126  which includes systems of networked racks, referred to as clusters, shown as superpods  215 ,  225  and  235 . Superpod  215  contains rack- 1   214 , rack- 2   224  and rack- 3   234 , and each rack includes a Redis server node: Redis A  222 , Redis B  226  and Redis C  228 ; and a logical grouping of hosts: worker A  232 , worker B  236  and worker C  238  for handling requests. Each superpod includes similar functional blocks. To ensure availability and maximize throughput, all workers in a system of networked racks listen to all Redis nodes for notifications. To meet the need for assured reliability at any time of any day, at least three workers are configured to monitor each Redis node, in one use case. 
     Continuing the description of  FIG. 2 , Worker A  232  maintains communication with a process which can implemented as a Zookeeper service, and decides, by analyzing the data from the process, when changes to the allocation of nodes need to be propagated to the worker process executed by edge control engine  246 . Extract, load, transform (ELT) engine  252  manipulates data served by backend system servers to populate the data set  1   248  and data set  2   258 . Edge control engine  246  listens to the Redis nodes, acting as a traffic arbitrator. In one example, edge control engine  246  handles thirty-two requests in near real time, handing off requests to transport coordinator  256 . Transport coordinator  256  executes algorithms for retrieving immutable data sets based on org-affinities for orgs to which the querying devices belong—needed for completing fast queries, and caches the retrieved immutable data sets in local data copy  266 . Worker B  236  and Worker C  238  each include similar functional blocks as those described for Worker A  232 . 
     In one implementation, a company allocates a customer to specific racks where their data resides. In common use, multiple customers rely on each rack—a self-contained unit that contains everything required to run an instantiation of a company&#39;s services. In one implementation, edge control engine  246  can analyze measured metrics and use the analytics to direct queued tasks to workers. 
       FIG. 3  shows superpod  215  as a cluster of racks, including rack  1   362 , rack  2   365  and rack  3   368  at startup, with Zookeeper services ZK- 1   322 , ZK- 2   325  and ZK- 3   25   328 . Each of the four servers (workers) in each of racks  362 ,  365  and  368  is booted, and as the servers are booted, a configuration agent boots up and uses the Zookeeper address known to it to register the server with the Zookeeper service. In one implementation of the example of  FIG. 3 , configuration agents  324 ,  334 ,  344  and  354  register with Zookeeper service ZK- 1   322 . Configuration agents  327 ,  337 ,  347  and  357  register with Zookeeper service ZK- 2   325 . Configuration agents  329 ,  339 ,  349  and  359  register with Zookeeper service ZK- 3   328 . The ZK registrations are coordinated through the current ZK leader. Each of these registered ephemeral znodes exists as long as the session that created the znode is active; and when the session ends, the znode is deleted. After a server registers itself with a Zookeeper service, the server receives an event if the status of the servers in the rack changes. 
     An example Zookeeper service data model is listed next. 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                   
                 /wave-agent 0 
               
               
                   
                  /global-config 
               
               
                   
                  /commands 
               
               
                   
                  /cluster-members 
               
               
                   
                   /iworker4-1-2-chi 
               
               
                   
                   /i worker4-2-2-chi 
               
               
                   
                   /i worker4-3-2-chi 
               
               
                   
                   /i worker4-4-2-chi 
               
               
                   
                  /configs 
               
               
                   
                   /iworker4-1-2-chi 
               
               
                   
                     /commands 
               
               
                   
                    /roles 
               
               
                   
                      /worker [ { State = Initializing I Ready I Updating } ] 
               
               
                   
                       /actual-config [ {j son configuration data} ] 
               
               
                   
                       /target-config [ {j son configuration data} ] 
               
               
                   
                      /redis 
               
               
                   
               
            
           
         
       
     
     In one use case, the startup sequence for the configuration agents includes determining the server coordinates within the data center—that is, the superpod and rack coordinates; and connecting to the appropriate Zookeeper service within the specified system of networked racks. The startup sequence also includes checking the local disk to retrieve the existing configuration, for example, after a server restart; and registering a new ephemeral server node in the appropriate Zookeeper service, writing existing configuration information, and setting a watch. Upon notification of an updated configuration, the node can launch a startup sequence for each type of process it needs to run. For example, in the case of a worker node, it can launch edge control services and edge query services. The edge control service can examine the queue configuration, contact Redis, and download any edgemarts that it does not already have locally. Once it has the needed immutable data set files cached locally, the edge control service for a worker can attach to work queues and start pulling query jobs. Atomic locking is implemented to ensure that a single worker pulls and processes a single task from the org-task-queue. 
     Continuing with the disclosed technology for dynamic node allocation, one of the configuration agents is elected to be leader. The elected configuration leader decides what servers will run what processes, and with what configuration. Many of the servers in the cluster could fulfill the role of leader, but only a single agent will do it at any one time. 
     The leader process listens for events that signal when changes to the servers root node have occurred. That is, the configuration leader has a dynamic global view of what servers are in the cluster.  FIG. 4  shows that agent  347 , shown in  FIG. 3 , has been elected leader  447 . Leader  447  puts a watch on the server&#39;s root node, so that the leader receives an event from the Zookeeper service when a change happens—such as when a new server is added or other servers are removed. Leader  447  can write configuration changes into the configuration agents of the individual nodes. Because the individual servers are monitoring events, watching for changes, they receive notifications from the Zookeeper services when changes happen. At any single moment in time, a cluster has a single leader for the superpod. 
     The leader process can write to the nodes for the servers, as appropriate. After leader  447  evaluates the situation based on what servers are active, the leader  447  specifies which servers will have Redis  423 ,  426  and  428 —or an equivalent data structure store as a database, cache and message broker, and which will have edge control processes  432 ,  442 ,  452 ,  436 ,  446 ,  456 ,  438 ,  448 , and  458 . Local configuration agents launch and communicate with local edge control processes based on their assigned configurations, with the configuration agents for individual servers watching for events to learn of changes. 
     The configuration agents in a cluster synchronize with the local edge control processes, which include edge query background processes. For some use cases, to ensure that the configuration agents are synchronized with the edge control processes, each of the background processes can implement a healthy check URL, bound to the local host only. The configuration agent can poll these URLs frequently to ensure that the services continue to report a healthy status. If the node is not able to serve customer requests properly, then the leader  447  will de-register the worker from the cluster, triggering the appropriate cluster reconfiguration for the superpod. If the leader process crashes, a new leader is elected immediately. The new leader process then begins executing the perpetual analysis and update loop to ensure optimal cluster configuration. 
     The disclosed technology, which includes the described configuration management process and leader election, makes it possible to dynamically manage resource allocation at runtime, without requiring a release process. The disclosed system does not include a single point of failure, which if it fails, will stop the overall cluster from continuing to operate.  FIG. 5  shows an example use case scenario in which configuration leader  447  goes offline  515 . In this scenario, a new configuration leader  539  gets elected and any load rebalancing for queues is handled by the new leader. 
     If one or more Zookeeper service nodes in the superpod go offline, the system can reassign the affected Zookeeper services to different servers and shift the work in the affected queues to other worker nodes as needed, without human intervention. This includes cases in which hardware is removed from the cluster. The disclosed technology can automatically adapt and rebalance queues across the remaining hardware. A cluster can lose up to n−2 configuration management service nodes (ZK in one implementation), where n is the number of racks in the system. For the superpod shown in  FIG. 5 , the number of racks is equal to three, so the system could lose two Zookeeper service nodes and continue to dynamically balance the workload queues among the racks. 
       FIG. 6  shows a case in which superpod  215  loses one worker  612 ,  614  and  616  in each of the three racks: edge control  442  and configuration agent  344 , edge control process  436  and agent  337 , and edge control  448  and agent  349  all go offline. The individual server config nodes are ephemeral nodes so they disappear automatically when the config agent sessions terminate. The leader process notices, and writes updated configurations back to the Zookeeper processes, auto-healing the cluster. 
     Redundancy levels can be specified for worker queues across multiple servers. In one use case, the disclosed technology includes continuously and automatically maintaining a redundancy level of at least three different worker queue assignments, one on each of three different racks, servicing each node in the cluster. This fault tolerant design makes it viable to tolerate the failure of multiple servers or top of rack (TOR) switches and continue to serve customer requests, though perhaps with degraded performance. In some implementations, redundancy is implemented by implementing workers such that two workers both servicing a specific org will have different lists of org-affinities on disjoint racks. 
       FIG. 7  shows examples of changes in load distribution for the use case described earlier, based on changes detected. Cluster  722  includes rack  1 , rack  2  and rack  3 , each of which includes a single active server, so the load is duplicated across the three servers to meet the redundancy requirement of three, specified for the use case. A second cluster  742  includes rack  1 , rack  2  and rack  3 , each with a single active server, and includes three added racks: rack  4 , rack  5  and rack  6 , each with a single worker. Note that the load gets balanced across the six servers, with each queue covered on three distinct servers, to meet the redundancy level requirement of three, for the queue. A third server cluster  762  includes six racks, with three workers on rack  1 , and a single active server on each of the remaining five racks. Note that the load gets balanced across the three servers of rack  1 , and the remaining load gets balanced across rack  2  through rack  6 . This example shows one scenario in which the dynamic allocation engine  204  automatically absorbs new capacity and optimizes usage when additional hardware gets added to the cluster. 
     In some implementations the system can analyze received metrics to monitor for hotspots and attempt to automatically adjust its resource allocation to compensate. The ultimate goal is to maximize hardware utilization in order to minimize the time an end user must wait for a result. 
     System Flow 
       FIG. 8  illustrates a flowchart of one implementation  600  of implementing dynamic allocation of stateful nodes for healing and load balancing. Flowchart  800  can be implemented at least partially with a database system, e.g., by one or more processors configured to receive or retrieve information, process the information, store results, and transmit the results. Other implementations may perform the steps in different orders and/or with different, fewer or additional steps than the ones illustrated in  FIG. 8 . The actions described below can be subdivided into more steps or combined into fewer steps to carry out the method described using a different number or arrangement of steps. 
     At action  810 , the leader process, running on one of the management devices or the worker devices, dynamically allocates workers to org-task-queues and targets the workers to obtain and locally cache immutable data sets used to respond to tasks in org-task-queues. 
     At action  820 , the transport coordinator runs on one of the management devices or the worker devices, with the transport coordinator interacting with the workers to migrate respective immutable data sets used to respond to queries by respective orgs to storage that is local to respective worker devices, while limiting a total resources committed to migration of the respective immutable data sets. 
     At action  830 , allocated workers run on the worker devices and service the queries, each allocated worker using a configuration agent to manage the worker&#39;s org-affinities. 
     At action  840 , immutable data sets belong to orgs, the immutable data sets cached locally to the allocated workers. 
     At action  850 , org-task-queues provide org-tasks to the allocated workers and receive updates from the allocated workers as they process the org-tasks. 
       FIG. 10  illustrates a flowchart of one implementation  600  of implementing rolling version update deployment, with workers on worker devices, org-affinities between the workers and org-task-queues, and a configuration leader running on a worker or management device. Flowchart  1000  can be implemented at least partially with a database system, e.g., by one or more processors configured to receive or retrieve information, process the information, store results, and transmit the results. Other implementations may perform the steps in different orders and/or with different, fewer or additional steps than the ones illustrated in  FIG. 10 . The actions described below can be subdivided into more steps or combined into fewer steps to carry out the method described using a different number or arrangement of steps. 
     At action  1010 , org-affinities between the workers and the org-task-queues provide access to local copies of org-data-sets to service org-tasks from the org-task-queues serviced by the workers. 
     At action  1020 , the configuration leader running on a worker or management device implements a healing and balancing service that maintains worker redundancy, that manages the workers&#39; org-affinities, and that causes workers to accumulate orgs on their respective org-lists and to have heterogeneous org-affinities, such that two workers both servicing a first org can have different lists of org-affinities. 
     At action  1030 , a messaging service, implemented by the configuration leader, messages the workers to update to a new software version and monitoring completion of updates, in cycles. 
     At action  1040 , the configuration leader selects workers to update in a cycle, ensuring that a selected level of worker redundancy to service particular org-task-queues is not compromised, by coordinating the selection of workers taken out of service during the update cycle based on the selected workers&#39; org-affinities. 
     At action  1050 , the configuration leader informs the selected workers in the cycle to proceed with updating. 
     At action  1060 , the configuration leader learns that the selected workers have successfully completed updating, updates version accounting over the selected workers; and moves on to another cycle of updating. 
     At action  1070 , the configuration leader repeats the cycle to update all update-eligible workers. 
     The technology disclosed can be implemented in the context of any computer-implemented system including a database system, a multi-tenant environment, or the like. Moreover, this technology can be implemented using two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. This technology can be implemented in numerous ways, including as a process, a method, an apparatus, a system, a device, a computer readable medium such as a computer readable storage medium that stores computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein. 
     Multi-Tenant Integration 
       FIG. 9  presents a block diagram of an exemplary multi-tenant system  900  suitable for implementing dynamic allocation of stateful nodes for healing and load balancing in environment  100  of  FIG. 1 . In general, the illustrated multi-tenant system  900  of  FIG. 9  includes a server  904  that dynamically creates and supports virtual applications  916  and  918 , based upon data  932  from a common multi-tenant database  930  that is shared between multiple tenants, alternatively referred to herein as a “multi-tenant database”. Data and services generated by the virtual applications  916  and  918 , including GUI clients, are provided via a network  945  to any number of client devices  948  or  958 , as desired. 
     As used herein, a “tenant” or an “organization” refers to a group of one or more users that shares access to common subset of the data within the multi-tenant database  930 . In this regard, each tenant includes one or more users associated with, assigned to, or otherwise belonging to that respective tenant. Stated another way, each respective user within the multi-tenant system  900  is associated with, assigned to, or otherwise belongs to a particular tenant of the plurality of tenants supported by the multitenant system  900 . Tenants may represent users, user departments, work or legal organizations, and/or any other entities that maintain data for particular sets of users within the multi-tenant system  900 . Although multiple tenants may share access to the server  904  and the database  930 , the particular data and services provided from the server  904  to each tenant can be securely isolated from those provided to other tenants. The multi-tenant architecture therefore allows different sets of users to share functionality and hardware resources without necessarily sharing any of the data  932  belonging to or otherwise associated with other tenants. 
     The multi-tenant database  930  is any sort of repository or other data storage system capable of storing and managing the data  932  associated with any number of tenants. The database  930  may be implemented using any type of conventional database server hardware. In various implementations, the database  930  shares processing hardware with the server  904 . In other implementations, the database  930  is implemented using separate physical and/or virtual database server hardware that communicates with the server  904  to perform the various functions described herein. The multi-tenant database  930  may alternatively be referred to herein as an on-demand database, in that the multi-tenant database  930  provides (or is available to provide) data at run-time to on-demand virtual applications  916  or  918  generated by the application platform  910 , with tenant 1  metadata  912  and tenant 2  metadata  914  securely isolated. 
     In practice, the data  932  may be organized and formatted in any manner to support the application platform  910 . In various implementations, conventional data relationships are established using any number of pivot tables  913  that establish indexing, uniqueness, relationships between entities, and/or other aspects of conventional database organization as desired. 
     The server  904  is implemented using one or more actual and/or virtual computing systems that collectively provide the dynamic application platform  910  for generating the virtual applications. For example, the server  904  may be implemented using a cluster of actual and/or virtual servers operating in conjunction with each other, typically in association with conventional network communications, cluster management, load balancing and other features as appropriate. The server  904  operates with any sort of conventional processing hardware such as a processor  936 , memory  938 , input/output features  934  and the like. The input/output devices  934  generally represent the interface(s) to networks (e.g., to the network  945 , or any other local area, wide area or other network), mass storage, display devices, data entry devices and/or the like. User interface input devices  934  can include a keyboard; pointing devices such as a mouse, trackball, touchpad, or graphics tablet; a scanner; a touch screen incorporated into the display; audio input devices such as voice recognition systems and microphones; and other types of input devices. In general, use of the term “input device” is intended to include possible types of devices and ways to input information into server  904 . 
     User interface output devices can include a display subsystem, a printer, a fax machine, or non-visual displays such as audio output devices. The display subsystem can include a cathode ray tube (CRT), a flat-panel device such as a liquid crystal display (LCD), a projection device, or some other mechanism for creating a visible image. The display subsystem can also provide a non-visual display such as audio output devices. In general, use of the term “output device” is intended to include all possible types of devices and ways to output information from processor  936  to the user or to another machine or computer system. 
     The processor  936  may be implemented using any suitable processing system, such as one or more processors, controllers, microprocessors, microcontrollers, processing cores and/or other computing resources spread across any number of distributed or integrated systems, including any number of “cloud-based” or other virtual systems. The memory  938  represents any non-transitory short or long term storage or other computer-readable media capable of storing programming instructions for execution on the processor  936 , including any sort of random access memory (RAM), read only memory (ROM), flash memory, magnetic or optical mass storage, and/or the like. The computer-executable programming instructions, when read and executed by the server  904  and/or processor  936 , cause the server  904  and/or processor  936  to create, generate, or otherwise facilitate the application platform  910  and/or virtual applications  916  and  918 , and perform one or more additional tasks, operations, functions, and/or processes described herein. It should be noted that the memory  938  represents one suitable implementation of such computer-readable media, and alternatively or additionally, the server  904  could receive and cooperate with external computer-readable media that is realized as a portable or mobile component or application platform, e.g., a portable hard drive, a USB flash drive, an optical disc, or the like. 
     The application platform  910  is any sort of software application or other data processing engine that generates the virtual applications  916  and  918  that provide data and/or services to the client devices  948  and  958 . In a typical implementation, the application platform  910  gains access to processing resources, communications interfaces and other features of the processing hardware using any sort of conventional or proprietary operating system  928 . The virtual applications  916  and  918  are typically generated at run-time in response to input received from the client devices  948  and  958 . 
     With continued reference to  FIG. 9 , the data and services provided by the server  904  can be retrieved using any sort of personal computer, mobile telephone, tablet or other network-enabled client device  948  or  958  on the network  945 . In an exemplary implementation, the client device  948  or  958  includes a display device, such as a monitor, screen, or another conventional electronic display capable of graphically presenting data and/or information retrieved from the multi-tenant database  930 . 
     In some implementations, network(s)  945  can be any one or any combination of Local Area Network (LAN), Wide Area Network (WAN), WiMAX, Wi-Fi telephone network, wireless network, point-to-point network, star network, token ring network, hub network, mesh network, peer-to-peer connections like Bluetooth, Near Field Communication (NFC), Z-Wave, ZigBee, or other appropriate configuration of data networks, including the Internet. 
     The foregoing description is merely illustrative in nature and is not intended to limit the implementations of the subject matter or the application and uses of such implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the technical field, background, or the detailed description. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations, and the exemplary implementations described herein are not intended to limit the scope or applicability of the subject matter in any way. 
     The technology disclosed can be implemented in the context of any computer-implemented system including a database system, a multi-tenant environment, or a relational database implementation like an ORACLE™ compatible database implementation, an IBM DB2 Enterprise Server compatible relational database implementation, a MySQL or PostgreSQL compatible relational database implementation or a Microsoft SQL Server compatible relational database implementation or a NoSQL non-relational database implementation such as a Vampire™ compatible non-relational database implementation, an Apache Cassandra™ compatible non-relational database implementation, a BigTable compatible non-relational database implementation or an HBase or DynamoDB compatible non-relational database implementation. 
     Moreover, the technology disclosed can be implemented using two or more separate and distinct computer-implemented systems that cooperate and communicate with one another. The technology disclosed can be implemented in numerous ways, including as a process, a method, an apparatus, a system, a device, a computer readable medium such as a computer readable storage medium that stores computer readable instructions or computer program code, or as a computer program product comprising a computer usable medium having a computer readable program code embodied therein. 
     Particular Implementations 
     In one implementation, a disclosed system of networked racks, with the racks having management devices and worker devices, includes the system having sufficient management devices to establish a redundancy factor and having management devices redundantly located in disjoint racks; querying devices that query the system for immutable data sets for orgs to which the querying devices belong, wherein the system handles the queries and the immutable data sets based on org-affinities. The disclosed system further includes an org-affinity implemented by data structures linking: allocated workers that run on the worker devices and service the queries from the querying devices, each allocated worker using a configuration agent to manage the worker&#39;s org-affinities, immutable data sets that belong to orgs, the immutable data sets cached locally to the allocated workers, and org-task-queues to which the allocated workers listen for org-tasks and to which workers report status updates as they process the org-tasks. The system is further organized with redundant workers allocated to service particular org-task-queues, with the redundant workers for a particular org-task-queue selected to run on worker devices in disjoint racks; and a leader process that runs on one of the management devices or worker devices. The leader process dynamically allocates workers to the org-task-queues and targets the workers to obtain and locally cache the immutable data sets used to respond to tasks in the org-task-queues. 
     The disclosed system further includes a transport coordinator running on one of the management devices or the worker devices that interact with the workers to migrate respective immutable data sets used to respond to queries by respective orgs to storage local to respective worker devices, while limiting “total resources committed” to migration of the respective immutable data sets. For the disclosed system, the immutable data sets are cached locally within hardware in the rack holding the worker device on which the allocated worker runs. In some implementations, the established redundancy factor has an integer value of at least three. For one implementation, the established redundancy factor is administrator configurable and automatically implemented by the leader process through allocation of new redundant workers or deallocation of existing redundant workers. 
     For some implementations, a disclosed method of organizing workers in a system includes networked racks, the racks having management devices and worker devices, workers running on the worker devices, an elected leader process running on one of the management devices or the worker devices, and storage local to the workers. The disclosed method includes the leader process running on one of the management device or the worker devices, with the leader process dynamically allocating workers to org-task-queues and targeting the workers to obtain and locally cache immutable data sets used to respond to tasks in org-task-queues; and a transport coordinator running on one of the management devices or the worker devices, the transport coordinator interacting with the workers to migrate respective immutable data sets used to respond to queries by respective orgs to storage that is local to respective worker devices, while limiting a total resources committed to migration of the respective immutable data sets. For the disclosed method allocated workers run on the worker devices and service the queries, each allocated worker using a configuration agent to manage the worker&#39;s org-affinities; immutable data sets belong to orgs, the immutable data sets cached locally to the allocated workers; org-task-queues provide org-tasks to the allocated workers; and receive updates from the allocated workers as they process the org-tasks. For the disclosed method, the immutable data sets are cached locally, at least in the same rack, to the allocated workers. 
     This method and other implementations of the technology disclosed can include one or more of the following features and/or features described in connection with additional methods disclosed. In the interest of conciseness, the combinations of features disclosed in this application are not individually enumerated and are not repeated with each base set of features. The reader will understand how features identified in this section can readily be combined with sets of base features identified as implementations. 
     The disclosed method can further include the leader process detecting that a dead worker is not currently responsive; and the leader process deallocating the dead worker and dynamically allocating other workers to take over the org-task-queues previously serviced by the dead worker. Some implementations of the method further include the leader determining that the allocated worker cannot properly service the org-task-queues assigned to it; and the leader deregistering the allocated worker from the org-task-queues that it cannot properly service. The method can further include the leader deregistering the allocated worker from the org-task-queues that it cannot properly service. 
     For some implementations of the disclosed method, a worker working redundantly and flexibly in a system that includes networked racks, the racks having management devices and worker devices, workers running on the worker devices, an elected leader process running on one of the management devices or the worker devices, and storage local to the workers, the method includes the worker running on a worker device in a rack; and the worker receiving from a leader process running on a management or worker device, a dynamic allocation message that targets the worker to service tasks from an org-task-queue and that directs the worker to obtain and locally cache immutable data sets belonging to an org serviced from the org-task-queue. The disclosed method further includes, upon being targeted to a respective org-task-queue, the worker interacts with a transport coordinator running on one of the management or worker devices, from which the worker receives one or more respective immutable data sets used by the worker to respond to queries by a respective org. The method additionally includes the worker processing service tasks including queries from the respective org-task-queue against the migrated respective immutable data sets and returning query response sets and from other org-task-queue assigned to it by the leader process; and the worker reports performance statistics to at least one redundant org-status store that monitor the worker&#39;s health and work load for healing and redundancy across workers. 
     For yet other implementations, the disclosed method further includes the transport coordinator limiting a total resources committed to migration of the respective immutable data sets. The disclosed method includes workers that process service tasks, including queries, from the respective org-task-queue on a first come, first served basis. 
     In one implementation a disclosed system with rolling version update deployment includes workers on worker devices, the workers maintain org lists of org-task-queues that they service; org-affinities between the workers and the org-task-queues require the workers to have access to local copies of org-data-sets to service org-tasks from the org-task-queues of the orgs that they service; and a configuration leader running on a worker or management device implements a healing and balancing service that maintains worker redundancy, that manages the workers&#39; org-affinities, and that causes workers to accumulate orgs on their respective org-lists and to have heterogeneous org-affinities, such that two workers both servicing a first org can have different lists of org-affinities. In other implementation workers can accumulate orgs on their respective org-lists will have similar lists of org-affinities. The disclosed system further includes a messaging service, implemented by the configuration leader, messaging workers to update from a legacy software version to a new software version and to implement monitoring of completion of updates in a set of update cycles. The configuration leader selects workers to update in a cycle, ensuring that a selected level of redundancy in worker availability to service particular org-task-queues is not compromised, by coordinating the selection of workers taken out of service during the update cycle based on the selected workers&#39; org-affinities. The configuration leader informs the selected workers in the cycle to proceed with updating; and the configuration leader learns that the selected workers have successfully completed updating, updates version accounting over the selected workers; and moves on to another cycle of updating. The configuration leader repeats the cycle to update all update-eligible workers. 
     Some implementations of the disclosed system further include the worker devices being organized by racks and redundant workers running on worker devices in disjoint racks. In other implementations, the configuration leader suspends the healing and balancing service during updating. The disclosed system can further include satisfying the selected level of worker redundancy in worker availability by updating to the new software version on a rack-by-rack basis; and further includes the worker redundancy maintained by the healing and balancing service having a flexible integer value of at least three redundant workers. In yet other implementations, the configuration leader increases redundancy of workers servicing the org-task-queues with which the selected workers have org-affinities, including provisioning the org-data sets to increased redundancy workers to establish org-affinities. In some implementations, the workers stop taking new tasks, complete pending tasks, shut off services, update to the new software version, restart, and report available for duty. In other implementations of the disclosed system, the workers wait for instructions from an administrator to proceed before reporting available for duty. The human administrator can allow for regression testing before signaling that the workers are ready to restart and report available for duty. For some implementations, the configuration leader for at least one cycle of updating reports results from the cycle of updating and waits for instructions from an administrator to proceed before repeating the cycle of updating. 
     Some implementations may include a system that includes devices organized in racks, each device including a processor and memory coupled to the processor, the memory loaded with instructions that, when executed, implement the methods described earlier. 
     Other implementations may include a tangible non-transitory computer readable medium impressed with instructions that are combinable with a processor and memory coupled to the processor. The instructions, when executed on a computer device and one or more servers, perform any of the methods described earlier. In yet other implementations, a tangible non-transitory computer readable medium with instructions that are combinable with a processor and memory coupled to the processor carry out the systems described earlier. 
     Yet another implementation may include a computing system including at least one server comprising one or more processors and memory, coupled to the processors, containing computer instructions that, when executed on the processors, cause the computing system to perform any of the processes described earlier. 
     While the technology disclosed is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than in a limiting sense. It is contemplated that modifications and combinations will readily occur to those skilled in the art, which modifications and combinations will be within the spirit of the invention and the scope of the following claims.