Class LeastRequestLoadBalancer

java.lang.Object
io.grpc.LoadBalancer
io.grpc.util.MultiChildLoadBalancer
io.grpc.xds.LeastRequestLoadBalancer
final class LeastRequestLoadBalancer extends io.grpc.util.MultiChildLoadBalancer
A LoadBalancer that provides least request load balancing based on outstanding request counters. It works by sampling a number of subchannels and picking the one with the fewest amount of outstanding requests. The default sampling amount of two is also known as the "power of two choices" (P2C).

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    (package private) static final class 
    LeastRequestLoadBalancer.EmptyPicker
     
    (package private) static final class 
    LeastRequestLoadBalancer.LeastRequestConfig
     
    protected class 
    LeastRequestLoadBalancer.LeastRequestLbState
     
    private static final class 
    LeastRequestLoadBalancer.OutstandingRequestsTracingFactory
     
    (package private) static final class 
    LeastRequestLoadBalancer.ReadyPicker
     

    Nested classes/interfaces inherited from class io.grpc.util.MultiChildLoadBalancer

    io.grpc.util.MultiChildLoadBalancer.AcceptResolvedAddrRetVal, io.grpc.util.MultiChildLoadBalancer.ChildLbState, io.grpc.util.MultiChildLoadBalancer.Endpoint

    Nested classes/interfaces inherited from class io.grpc.LoadBalancer

    io.grpc.LoadBalancer.CreateSubchannelArgs, io.grpc.LoadBalancer.ErrorPicker, io.grpc.LoadBalancer.Factory, io.grpc.LoadBalancer.FixedResultPicker, io.grpc.LoadBalancer.Helper, io.grpc.LoadBalancer.PickDetailsConsumer, io.grpc.LoadBalancer.PickResult, io.grpc.LoadBalancer.PickSubchannelArgs, io.grpc.LoadBalancer.ResolvedAddresses, io.grpc.LoadBalancer.Subchannel, io.grpc.LoadBalancer.SubchannelPicker, io.grpc.LoadBalancer.SubchannelStateListener

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private int
    choiceCount
     
    private io.grpc.LoadBalancer.SubchannelPicker
    currentPicker
     
    private final ThreadSafeRandom
    random
     

    Fields inherited from class io.grpc.util.MultiChildLoadBalancer

    currentConnectivityState, pickFirstLbProvider, resolvingAddresses

    Fields inherited from class io.grpc.LoadBalancer

    ATTR_HEALTH_CHECKING_CONFIG, DISABLE_SUBCHANNEL_RECONNECT_KEY, EMPTY_PICKER, HAS_HEALTH_PRODUCER_LISTENER_KEY, HEALTH_CONSUMER_LISTENER_ARG_KEY, IS_PETIOLE_POLICY

  • Constructor Summary

    Constructors
    Constructor
    Description
    LeastRequestLoadBalancer(io.grpc.LoadBalancer.Helper helper)
     
    LeastRequestLoadBalancer(io.grpc.LoadBalancer.Helper helper, ThreadSafeRandom random)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    io.grpc.Status
    acceptResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)
     
    protected io.grpc.util.MultiChildLoadBalancer.ChildLbState
    createChildLbState(Object key)
     
    private static AtomicInteger
    getInFlights(io.grpc.util.MultiChildLoadBalancer.ChildLbState childLbState)
     
    (package private) void
    setResolvingAddresses(boolean newValue)
    This should ONLY be used by tests.
    private void
    updateBalancingState(io.grpc.ConnectivityState state, io.grpc.LoadBalancer.SubchannelPicker picker)
     
    protected void
    updateOverallBalancingState()
    Updates picker with the list of active subchannels (state == READY).

    Methods inherited from class io.grpc.util.MultiChildLoadBalancer

    acceptResolvedAddressesInternal, aggregateState, createChildAddressesMap, getChildLbState, getChildLbStateEag, getChildLbStates, getHelper, getReadyChildren, handleNameResolutionError, shutdown, shutdownRemoved

    Methods inherited from class io.grpc.LoadBalancer

    canHandleEmptyAddressListFromNameResolution, handleResolvedAddresses, handleSubchannelState, requestConnection

    Methods inherited from class Object

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

  • Field Details

    • random

      private final ThreadSafeRandom random

    • currentPicker

      private io.grpc.LoadBalancer.SubchannelPicker currentPicker

    • choiceCount

      private int choiceCount

  • Constructor Details

    • LeastRequestLoadBalancer

      LeastRequestLoadBalancer(io.grpc.LoadBalancer.Helper helper)

    • LeastRequestLoadBalancer

      LeastRequestLoadBalancer(io.grpc.LoadBalancer.Helper helper, ThreadSafeRandom random)

  • Method Details

    • acceptResolvedAddresses

      public io.grpc.Status acceptResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)
      Overrides:
      acceptResolvedAddresses in class io.grpc.util.MultiChildLoadBalancer

    • updateOverallBalancingState

      protected void updateOverallBalancingState()
      Updates picker with the list of active subchannels (state == READY).

      If no active subchannels exist, but some are in TRANSIENT_FAILURE then returns a picker with all of the children in TF so that the application code will get an error from a varying random one when it tries to get a subchannel.

      Specified by:
      updateOverallBalancingState in class io.grpc.util.MultiChildLoadBalancer

    • createChildLbState

      protected io.grpc.util.MultiChildLoadBalancer.ChildLbState createChildLbState(Object key)
      Overrides:
      createChildLbState in class io.grpc.util.MultiChildLoadBalancer

    • updateBalancingState

      private void updateBalancingState(io.grpc.ConnectivityState state, io.grpc.LoadBalancer.SubchannelPicker picker)

    • setResolvingAddresses

      void setResolvingAddresses(boolean newValue)
      This should ONLY be used by tests.

    • getInFlights

      private static AtomicInteger getInFlights(io.grpc.util.MultiChildLoadBalancer.ChildLbState childLbState)