io.grpc

Interface LoadBalancer.SubchannelStateListener

Enclosing class:

LoadBalancer

public static interface LoadBalancer.SubchannelStateListener

Receives state changes for one LoadBalancer.Subchannel. All methods are run under LoadBalancer.Helper.getSynchronizationContext().

Since:

1.22.0

Method Summary

Modifier and Type	Method and Description
void	onSubchannelState(ConnectivityStateInfo newState) Handles a state change on a Subchannel.

Method Detail

onSubchannelState

void onSubchannelState(ConnectivityStateInfo newState)

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.

When a subchannel's state is IDLE or TRANSIENT_FAILURE and the address for the subchannel was received in LoadBalancer.handleResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses), load balancers should call LoadBalancer.Helper.refreshNameResolution() to inform polling name resolvers that it is an appropriate time to refresh the addresses. Without the refresh, changes to the addresses may never be detected.

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.

Parameters:

newState - the new state

Since:

1.22.0