Package io.grpc.util

Class GracefulSwitchLoadBalancer

java.lang.Object

io.grpc.LoadBalancer

io.grpc.util.ForwardingLoadBalancer

io.grpc.util.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.

Nested Class Summary

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

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

Field Summary

Fields inherited from class io.grpc.LoadBalancer

ATTR_HEALTH_CHECKING_CONFIG, EMPTY_PICKER

Constructor Summary

Constructors

Constructor	Description
GracefulSwitchLoadBalancer(LoadBalancer.Helper helper)

Method Summary

Modifier and Type	Method	Description
protected LoadBalancer	delegate()	Returns the underlying balancer.
void	handleSubchannelState(LoadBalancer.Subchannel subchannel, ConnectivityStateInfo stateInfo)	Deprecated.
void	shutdown()	The channel asks the load-balancer to shutdown.
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.

Methods inherited from class io.grpc.util.ForwardingLoadBalancer

canHandleEmptyAddressListFromNameResolution, handleNameResolutionError, handleResolvedAddresses, requestConnection, toString

Methods inherited from class io.grpc.LoadBalancer

acceptResolvedAddresses

Methods inherited from class java.lang.Object

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

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.

delegate

protected LoadBalancer delegate()

Description copied from class: ForwardingLoadBalancer

Returns the underlying balancer.

Specified by:

delegate in class ForwardingLoadBalancer

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