Package io.grpc.util

Class GracefulSwitchLoadBalancer


  • @ExperimentalApi("https://github.com/grpc/grpc-java/issues/5999")
    @NotThreadSafe
    public final class GracefulSwitchLoadBalancer
    extends ForwardingLoadBalancer
    A load balancer that gracefully swaps to a new lb policy. If the channel is currently in a state other than READY, the new policy will be swapped into place immediately. Otherwise, the channel will keep using the old policy until the new policy reports READY or the old policy exits READY.

    The balancer must switch to a policy prior to handling resolved addresses for the first time.

    • Constructor Detail

      • GracefulSwitchLoadBalancer

        public GracefulSwitchLoadBalancer​(LoadBalancer.Helper helper)
    • Method Detail

      • switchTo

        public void switchTo​(LoadBalancer.Factory newBalancerFactory)
        Gracefully switch to a new policy defined by the given factory, if the given factory isn't equal to the current one.
      • 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 ForwardingLoadBalancer
        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.
        Overrides:
        shutdown in class ForwardingLoadBalancer