Package io.grpc.util

Class ForwardingLoadBalancer

java.lang.Object
io.grpc.LoadBalancer
io.grpc.util.ForwardingLoadBalancer
Direct Known Subclasses:
GracefulSwitchLoadBalancer
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771") public abstract class ForwardingLoadBalancer extends LoadBalancer

  • Constructor Details

    • ForwardingLoadBalancer

      public ForwardingLoadBalancer()

  • Method Details

    • delegate

      protected abstract LoadBalancer delegate()
      Returns the underlying balancer.

    • handleResolvedAddresses

      public void handleResolvedAddresses(LoadBalancer.ResolvedAddresses resolvedAddresses)
      Description copied from class: LoadBalancer
      Handles newly resolved server groups and metadata attributes from name resolution system. servers contained in EquivalentAddressGroup should be considered equivalent but may be flattened into a single list if needed.

      Implementations should not modify the given servers.

      Overrides:
      handleResolvedAddresses in class LoadBalancer
      Parameters:
      resolvedAddresses - the resolved server addresses, attributes, and config.

    • handleNameResolutionError

      public void handleNameResolutionError(Status error)
      Description copied from class: LoadBalancer
      Handles an error from the name resolution system.
      Specified by:
      handleNameResolutionError in class LoadBalancer
      Parameters:
      error - a non-OK status

    • handleSubchannelState

      @Deprecated public void handleSubchannelState(LoadBalancer.Subchannel subchannel, ConnectivityStateInfo stateInfo)
      Deprecated.
      Description copied from class: LoadBalancer
      Handles a state change on a Subchannel.

      The initial state of a Subchannel is IDLE. You won't get a notification for the initial IDLE state.

      If the new state is not SHUTDOWN, this method should create a new picker and call Helper.updateBalancingState(). Failing to do so may result in unnecessary delays of RPCs. Please refer to PickResult.withSubchannel()'s javadoc for more information.

      SHUTDOWN can only happen in two cases. One is that LoadBalancer called LoadBalancer.Subchannel.shutdown() earlier, thus it should have already discarded this Subchannel. The other is that Channel is doing a forced shutdown or has already terminated, thus there won't be further requests to LoadBalancer. Therefore, the LoadBalancer usually don't need to react to a SHUTDOWN state.

      Overrides:
      handleSubchannelState in class LoadBalancer
      Parameters:
      subchannel - the involved Subchannel
      stateInfo - the new state

    • shutdown

      public void shutdown()
      Description copied from class: LoadBalancer
      The channel asks the load-balancer to shutdown. No more methods on this class will be called after this method. The implementation should shutdown all Subchannels and OOB channels, and do any other cleanup as necessary.
      Specified by:
      shutdown in class LoadBalancer

    • canHandleEmptyAddressListFromNameResolution

      public boolean canHandleEmptyAddressListFromNameResolution()
      Description copied from class: LoadBalancer
      Whether this LoadBalancer can handle empty address group list to be passed to LoadBalancer.handleResolvedAddresses(ResolvedAddresses). The default implementation returns false, meaning that if the NameResolver returns an empty list, the Channel will turn that into an error and call LoadBalancer.handleNameResolutionError(io.grpc.Status). LoadBalancers that want to accept empty lists should override this method and return true.

      This method should always return a constant value. It's not specified when this will be called.

      Overrides:
      canHandleEmptyAddressListFromNameResolution in class LoadBalancer

    • requestConnection

      public void requestConnection()
      Description copied from class: LoadBalancer
      The channel asks the LoadBalancer to establish connections now (if applicable) so that the upcoming RPC may then just pick a ready connection without waiting for connections. This is triggered by ManagedChannel.getState(true).

      If LoadBalancer doesn't override it, this is no-op. If it infeasible to create connections given the current state, e.g. no Subchannel has been created yet, LoadBalancer can ignore this request.

      Overrides:
      requestConnection in class LoadBalancer

    • toString

      public String toString()
      Overrides:
      toString in class Object