FunctionService (Apache Geode 1.8.0)
Date: 2018-11-29

org.apache.geode.cache.execute

## Class FunctionService

- java.lang.Object
- - org.apache.geode.cache.execute.FunctionService

-     public class FunctionService
      extends java.lang.Object

  Provides the entry point into execution of user defined Functions.

  Function execution provides a means to route application behaviour to data or more generically to peers in a `DistributedSystem` or servers in a `Pool`.

  Since:
    GemFire 6.0

- - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Function` | `getFunction(java.lang.String functionId)` Returns the `Function` defined by the functionId, returns null if no function is found for the specified functionId
    `static java.util.Map<java.lang.String,Function>` | `getRegisteredFunctions()` Returns all locally registered functions
    `static boolean` | `isRegistered(java.lang.String functionId)` Returns true if the function is registered to FunctionService
    `static Execution` | `onMember(DistributedMember distributedMember)` Returns an `Execution` object that can be used to execute a data independent function on a `DistributedMember`.
    `static Execution` | `onMember(java.lang.String... groups)` Returns an `Execution` object that can be used to execute a data independent function on one member of each group provided.
    `static Execution` | `onMembers(java.util.Set<DistributedMember> distributedMembers)` Returns an `Execution` object that can be used to execute a data independent function on the set of `DistributedMember`s.
    `static Execution` | `onMembers(java.lang.String... groups)` Returns an `Execution` object that can be used to execute a data independent function on all peer members.
    `static Execution` | `onRegion(Region region)` Returns an `Execution` object that can be used to execute a data dependent function on the specified Region. When invoked from a GemFire client, the method returns an Execution instance that sends a message to one of the connected servers as specified by the `Pool` for the region.
    `static Execution` | `onServer(Pool pool)` Returns an `Execution` object that can be used to execute a data independent function on a server in the provided `Pool`.
    `static Execution` | `onServer(RegionService regionService)` Returns an `Execution` object that can be used to execute a data independent function on a server that the given cache is connected to.
    `static Execution` | `onServers(Pool pool)` Returns an `Execution` object that can be used to execute a data independent function on all the servers in the provided `Pool`.
    `static Execution` | `onServers(RegionService regionService)` Returns an `Execution` object that can be used to execute a data independent function on all the servers that the given cache is connected to.
    `static void` | `registerFunction(Function function)` Registers the given `Function` with the `FunctionService` using `Function.getId()`.
    `static void` | `unregisterFunction(java.lang.String functionId)` Unregisters the given `Function` with the `FunctionService` using `Function.getId()`.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### onRegion

          public static Execution onRegion(Region region)

      Returns an `Execution` object that can be used to execute a data dependent function on the specified Region.
      When invoked from a GemFire client, the method returns an Execution instance that sends a message to one of the connected servers as specified by the `Pool` for the region.
      Depending on the filters setup on the `Execution`, the function is executed on all GemFire members that define the data region, or a subset of members. `Execution.withFilter(Set)`). For DistributedRegions with DataPolicy.NORMAL, it throws UnsupportedOperationException. For DistributedRegions with DataPolicy.EMPTY, execute the function on any random member which has DataPolicy.REPLICATE
      . For DistributedRegions with DataPolicy.REPLICATE, execute the function locally. For Regions with DataPolicy.PARTITION, it executes on members where the data resides as specified by the filter.
      Throws:
        `FunctionException` - if the region passed in is null
      Since:
        GemFire 6.0

    - #### onServer

          public static Execution onServer(Pool pool)

      Returns an `Execution` object that can be used to execute a data independent function on a server in the provided `Pool`.

      If the server goes down while dispatching or executing the function, an Exception will be thrown.

      Parameters:
        `pool` - from which to chose a server for execution
      Throws:
        `FunctionException` - if Pool instance passed in is null
      Since:
        GemFire 6.0

    - #### onServers

          public static Execution onServers(Pool pool)

      Returns an `Execution` object that can be used to execute a data independent function on all the servers in the provided `Pool`. If one of the servers goes down while dispatching or executing the function on the server, an Exception will be thrown.
      Parameters:
        `pool` - the set of servers to execute the function
      Throws:
        `FunctionException` - if Pool instance passed in is null
      Since:
        GemFire 6.0

    - #### onServer

          public static Execution onServer(RegionService regionService)

      Returns an `Execution` object that can be used to execute a data independent function on a server that the given cache is connected to.

      If the server goes down while dispatching or executing the function, an Exception will be thrown.

      Parameters:
        `regionService` - obtained from `ClientCacheFactory.create()` or `ClientCache.createAuthenticatedView(Properties)`.
      Throws:
        `FunctionException` - if cache is null, is not on a client, or it does not have a default pool
      Since:
        GemFire 6.5

    - #### onServers

          public static Execution onServers(RegionService regionService)

      Returns an `Execution` object that can be used to execute a data independent function on all the servers that the given cache is connected to. If one of the servers goes down while dispatching or executing the function on the server, an Exception will be thrown.
      Parameters:
        `regionService` - obtained from `ClientCacheFactory.create()` or `ClientCache.createAuthenticatedView(Properties)`.
      Throws:
        `FunctionException` - if cache is null, is not on a client, or it does not have a default pool
      Since:
        GemFire 6.5

    - #### onMember

          public static Execution onMember(DistributedMember distributedMember)

      Returns an `Execution` object that can be used to execute a data independent function on a `DistributedMember`. If the member is not found, executing the function will throw an Exception. If the member goes down while dispatching or executing the function on the member, an Exception will be thrown.
      Parameters:
        `distributedMember` - defines a member in the distributed system
      Throws:
        `FunctionException` - if distributedMember is null
      Since:
        GemFire 7.0

    - #### onMembers

          public static Execution onMembers(java.lang.String... groups)

      Returns an `Execution` object that can be used to execute a data independent function on all peer members. If the optional groups parameter is provided, function is executed on all members that belong to the provided groups.

      If one of the members goes down while dispatching or executing the function on the member, an Exception will be thrown.

      Parameters:
        `groups` - optional list of GemFire configuration property "groups" (see `groups`) on which to execute the function. Function will be executed on all members of each group
      Throws:
        `FunctionException` - if no members are found belonging to the provided groups
      Since:
        GemFire 7.0

    - #### onMembers

          public static Execution onMembers(java.util.Set<DistributedMember> distributedMembers)

      Returns an `Execution` object that can be used to execute a data independent function on the set of `DistributedMember`s. If one of the members goes down while dispatching or executing the function, an Exception will be thrown.
      Parameters:
        `distributedMembers` - set of distributed members on which `Function` to be executed
      Throws:
        `FunctionException` - if distributedMembers is null
      Since:
        GemFire 7.0

    - #### onMember

          public static Execution onMember(java.lang.String... groups)

      Returns an `Execution` object that can be used to execute a data independent function on one member of each group provided.
      Parameters:
        `groups` - list of GemFire configuration property "groups" (see `groups`) on which to execute the function. Function will be executed on one member of each group
      Throws:
        `FunctionException` - if no members are found belonging to the provided groups
      Since:
        GemFire 7.0

    - #### getFunction

          public static Function getFunction(java.lang.String functionId)

      Returns the `Function` defined by the functionId, returns null if no function is found for the specified functionId
      Throws:
        `FunctionException` - if functionID passed is null
      Since:
        GemFire 6.0

    - #### registerFunction

          public static void registerFunction(Function function)

      Registers the given `Function` with the `FunctionService` using `Function.getId()`.

      Registering a function allows execution of the function using `Execution.execute(String)`. Every member that could execute a function using its `Function.getId()` should register the function.

      Throws:
        `FunctionException` - if function instance passed is null or Function.getId() returns null
      Since:
        GemFire 6.0

    - #### unregisterFunction

          public static void unregisterFunction(java.lang.String functionId)

      Unregisters the given `Function` with the `FunctionService` using `Function.getId()`.

      Throws:
        `FunctionException` - if function instance passed is null or Function.getId() returns null
      Since:
        GemFire 6.0

    - #### isRegistered

          public static boolean isRegistered(java.lang.String functionId)

      Returns true if the function is registered to FunctionService
      Throws:
        `FunctionException` - if function instance passed is null or Function.getId() returns null
      Since:
        GemFire 6.0

    - #### getRegisteredFunctions

          public static java.util.Map<java.lang.String,Function> getRegisteredFunctions()

      Returns all locally registered functions
      Returns:
        A view of registered functions as a Map of `Function.getId()` to `Function`
      Since:
        GemFire 6.0