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 child balancer and configuration is specified using service config. Config objects are generally created by calling parseLoadBalancingPolicyConfig(List) from a provider's parseLoadBalancingPolicyConfig() implementation.

Alternatively, the balancer may switch to a policy prior to handling resolved addresses for the first time. This causes graceful switch to ignore the service config and pass through the resolved addresses directly to the child policy.

Nested Class Summary

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 inherited from class io.grpc.LoadBalancer

ATTR_HEALTH_CHECKING_CONFIG, EMPTY_PICKER, HAS_HEALTH_PRODUCER_LISTENER_KEY, HEALTH_CONSUMER_LISTENER_ARG_KEY, IS_PETIOLE_POLICY

Constructor Summary

Constructors

Constructor	Description
GracefulSwitchLoadBalancer(io.grpc.LoadBalancer.Helper helper)

Method Summary

Modifier and Type	Method	Description
io.grpc.Status	acceptResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)
static Object	createLoadBalancingPolicyConfig(io.grpc.LoadBalancer.Factory childFactory, Object childConfig)	Directly create a config to pass to GracefulSwitch.
protected io.grpc.LoadBalancer	delegate()	Returns the underlying balancer.
String	delegateType()
void	handleResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)
void	handleSubchannelState(io.grpc.LoadBalancer.Subchannel subchannel, io.grpc.ConnectivityStateInfo stateInfo)	Deprecated.
static io.grpc.NameResolver.ConfigOrError	parseLoadBalancingPolicyConfig(List<Map<String,?>> loadBalancingConfigs)	Provided a JSON list of LoadBalancingConfigs, parse it into a config to pass to GracefulSwitch.
static io.grpc.NameResolver.ConfigOrError	parseLoadBalancingPolicyConfig(List<Map<String,?>> loadBalancingConfigs, io.grpc.LoadBalancerRegistry lbRegistry)	Provided a JSON list of LoadBalancingConfigs, parse it into a config to pass to GracefulSwitch.
void	shutdown()
void	switchTo(io.grpc.LoadBalancer.Factory newBalancerFactory)	Deprecated. Use parseLoadBalancingPolicyConfig() and pass the configuration to LoadBalancer.ResolvedAddresses.Builder.setLoadBalancingPolicyConfig(java.lang.Object)

Methods inherited from class io.grpc.util.ForwardingLoadBalancer

canHandleEmptyAddressListFromNameResolution, handleNameResolutionError, requestConnection, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

GracefulSwitchLoadBalancer

public GracefulSwitchLoadBalancer(io.grpc.LoadBalancer.Helper helper)

Method Detail

handleResolvedAddresses

public void handleResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)

Overrides:

handleResolvedAddresses in class ForwardingLoadBalancer

acceptResolvedAddresses

public io.grpc.Status acceptResolvedAddresses(io.grpc.LoadBalancer.ResolvedAddresses resolvedAddresses)

Overrides:

acceptResolvedAddresses in class io.grpc.LoadBalancer

switchTo

@Deprecated
public void switchTo(io.grpc.LoadBalancer.Factory newBalancerFactory)

Deprecated.

Use parseLoadBalancingPolicyConfig() and pass the configuration to LoadBalancer.ResolvedAddresses.Builder.setLoadBalancingPolicyConfig(java.lang.Object)

Gracefully switch to a new policy defined by the given factory, if the given factory isn't equal to the current one.

delegate

protected io.grpc.LoadBalancer delegate()

Description copied from class: ForwardingLoadBalancer

Returns the underlying balancer.

Specified by:

delegate in class ForwardingLoadBalancer

handleSubchannelState

@Deprecated
public void handleSubchannelState(io.grpc.LoadBalancer.Subchannel subchannel,
                                  io.grpc.ConnectivityStateInfo stateInfo)

Deprecated.

Overrides:

handleSubchannelState in class ForwardingLoadBalancer

shutdown

public void shutdown()

Overrides:

shutdown in class ForwardingLoadBalancer

delegateType

public String delegateType()

parseLoadBalancingPolicyConfig

public static io.grpc.NameResolver.ConfigOrError parseLoadBalancingPolicyConfig(List<Map<String,?>> loadBalancingConfigs)

Provided a JSON list of LoadBalancingConfigs, parse it into a config to pass to GracefulSwitch.

parseLoadBalancingPolicyConfig

public static io.grpc.NameResolver.ConfigOrError parseLoadBalancingPolicyConfig(List<Map<String,?>> loadBalancingConfigs,
                                                                                io.grpc.LoadBalancerRegistry lbRegistry)

Provided a JSON list of LoadBalancingConfigs, parse it into a config to pass to GracefulSwitch.

createLoadBalancingPolicyConfig

public static Object createLoadBalancingPolicyConfig(io.grpc.LoadBalancer.Factory childFactory,
                                                     @Nullable
                                                     Object childConfig)

Directly create a config to pass to GracefulSwitch. The object returned is the same as would be found in ConfigOrError.getConfig().