Class GrpclbLoadBalancer

java.lang.Object

io.grpc.LoadBalancer

io.grpc.grpclb.GrpclbLoadBalancer

class GrpclbLoadBalancer
extends LoadBalancer

A LoadBalancer that uses the GRPCLB protocol.

Optionally, when requested by the naming system, will delegate the work to a local pick-first or round-robin balancer.

Nested Class Summary

Nested classes/interfaces inherited from class LoadBalancer

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

Field Summary

Fields

Modifier and Type	Field	Description
private final BackoffPolicy.Provider	backoffPolicyProvider
private GrpclbConfig	config
private final Context	context
private static final GrpclbConfig	DEFAULT_CONFIG
private GrpclbState	grpclbState
private final LoadBalancer.Helper	helper
private final com.google.common.base.Stopwatch	stopwatch
private final SubchannelPool	subchannelPool
private final TimeProvider	time

Fields inherited from class LoadBalancer

ATTR_HEALTH_CHECKING_CONFIG, DISABLE_SUBCHANNEL_RECONNECT_KEY, EMPTY_PICKER, HAS_HEALTH_PRODUCER_LISTENER_KEY, HEALTH_CONSUMER_LISTENER_ARG_KEY, IS_PETIOLE_POLICY

Constructor Summary

Constructors

Constructor	Description
GrpclbLoadBalancer(LoadBalancer.Helper helper, Context context, SubchannelPool subchannelPool, TimeProvider time, com.google.common.base.Stopwatch stopwatch, BackoffPolicy.Provider backoffPolicyProvider)

Method Summary

Modifier and Type	Method	Description
Status	acceptResolvedAddresses(LoadBalancer.ResolvedAddresses resolvedAddresses)	Accepts newly resolved addresses from the name resolution system.
boolean	canHandleEmptyAddressListFromNameResolution()	Whether this LoadBalancer can handle empty address group list to be passed to LoadBalancer.handleResolvedAddresses(ResolvedAddresses).
(package private) GrpclbState	getGrpclbState()
void	handleNameResolutionError(Status error)	Handles an error from the name resolution system.
private void	recreateStates()
void	requestConnection()	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.
private void	resetStates()
void	shutdown()	The channel asks the load-balancer to shutdown.

Methods inherited from class LoadBalancer

handleResolvedAddresses, handleSubchannelState

Methods inherited from class Object

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

Field Details

DEFAULT_CONFIG

private static final GrpclbConfig DEFAULT_CONFIG

helper

private final LoadBalancer.Helper helper

context

private final Context context

time

private final TimeProvider time

stopwatch

private final com.google.common.base.Stopwatch stopwatch

subchannelPool

private final SubchannelPool subchannelPool

backoffPolicyProvider

private final BackoffPolicy.Provider backoffPolicyProvider

config

private GrpclbConfig config

grpclbState

@Nullable
private GrpclbState grpclbState

Constructor Details

GrpclbLoadBalancer

GrpclbLoadBalancer(LoadBalancer.Helper helper,
 Context context,
 SubchannelPool subchannelPool,
 TimeProvider time,
 com.google.common.base.Stopwatch stopwatch,
 BackoffPolicy.Provider backoffPolicyProvider)

Method Details

acceptResolvedAddresses

public Status acceptResolvedAddresses(LoadBalancer.ResolvedAddresses resolvedAddresses)

Description copied from class: LoadBalancer

Accepts newly resolved addresses from the name resolution system. The EquivalentAddressGroup addresses should be considered equivalent but may be flattened into a single list if needed.

Implementations can choose to reject the given addresses by returning false.

Implementations should not modify the given addresses.

Overrides:

acceptResolvedAddresses in class LoadBalancer

Parameters:

resolvedAddresses - the resolved server addresses, attributes, and config.

Returns:

true if the resolved addresses were accepted. false if rejected.

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

resetStates

private void resetStates()

recreateStates

private void recreateStates()

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

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

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(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

getGrpclbState

@Nullable
GrpclbState getGrpclbState()