Package io.grpc.util

Class MultiChildLoadBalancer

java.lang.Object

io.grpc.LoadBalancer

io.grpc.util.MultiChildLoadBalancer

@Internal
public abstract class MultiChildLoadBalancer
extends LoadBalancer

A base load balancing policy for those policies which has multiple children such as ClusterManager or the petiole policies. For internal use only.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	MultiChildLoadBalancer.AcceptResolvedAddrRetVal
class	MultiChildLoadBalancer.ChildLbState	This represents the state of load balancer children.
protected static class	MultiChildLoadBalancer.Endpoint	Endpoint is an optimization to quickly lookup and compare EquivalentAddressGroup address sets.

Nested classes/interfaces inherited from class io.grpc.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
protected ConnectivityState	currentConnectivityState
protected final LoadBalancerProvider	pickFirstLbProvider
protected boolean	resolvingAddresses

Fields inherited from class io.grpc.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

Modifier	Constructor	Description
protected	MultiChildLoadBalancer(LoadBalancer.Helper helper)

Method Summary

Modifier and Type	Method	Description
Status	acceptResolvedAddresses(LoadBalancer.ResolvedAddresses resolvedAddresses)	Override to completely replace the default logic or to do additional activities.
protected final MultiChildLoadBalancer.AcceptResolvedAddrRetVal	acceptResolvedAddressesInternal(LoadBalancer.ResolvedAddresses resolvedAddresses)	This does the work to update the child map and calculate which children have been removed.
protected static ConnectivityState	aggregateState(ConnectivityState overallState, ConnectivityState childState)
protected Map<Object,LoadBalancer.ResolvedAddresses>	createChildAddressesMap(LoadBalancer.ResolvedAddresses resolvedAddresses)	Override to utilize parsing of the policy configuration or alternative helper/lb generation.
protected MultiChildLoadBalancer.ChildLbState	createChildLbState(Object key)	Override to create an instance of a subclass.
final Collection<MultiChildLoadBalancer.ChildLbState>	getChildLbStates()
protected final LoadBalancer.Helper	getHelper()
protected final List<MultiChildLoadBalancer.ChildLbState>	getReadyChildren()	Filters out non-ready child load balancers (subchannels).
void	handleNameResolutionError(Status error)	Handle the name resolution error.
void	shutdown()	The channel asks the load-balancer to shutdown.
protected final void	shutdownRemoved(List<MultiChildLoadBalancer.ChildLbState> removedChildren)
protected abstract void	updateOverallBalancingState()	Using the state of all children will calculate the current connectivity state, update fields, generate a picker and then call LoadBalancer.Helper.updateBalancingState(ConnectivityState, SubchannelPicker).

Methods inherited from class io.grpc.LoadBalancer

canHandleEmptyAddressListFromNameResolution, handleResolvedAddresses, handleSubchannelState, requestConnection

Methods inherited from class java.lang.Object

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

Field Details

resolvingAddresses

protected boolean resolvingAddresses

pickFirstLbProvider

protected final LoadBalancerProvider pickFirstLbProvider

currentConnectivityState

protected ConnectivityState currentConnectivityState

Constructor Details

MultiChildLoadBalancer

protected MultiChildLoadBalancer(LoadBalancer.Helper helper)

Method Details

updateOverallBalancingState

protected abstract void updateOverallBalancingState()

Using the state of all children will calculate the current connectivity state, update fields, generate a picker and then call LoadBalancer.Helper.updateBalancingState(ConnectivityState, SubchannelPicker).

createChildAddressesMap

protected Map<Object,LoadBalancer.ResolvedAddresses> createChildAddressesMap(LoadBalancer.ResolvedAddresses resolvedAddresses)

Override to utilize parsing of the policy configuration or alternative helper/lb generation. Override this if keys are not Endpoints or if child policies have configuration. Null map values preserve the child without delivering the child an update.

createChildLbState

protected MultiChildLoadBalancer.ChildLbState createChildLbState(Object key)

Override to create an instance of a subclass.

acceptResolvedAddresses

public Status acceptResolvedAddresses(LoadBalancer.ResolvedAddresses resolvedAddresses)

Override to completely replace the default logic or to do additional activities.

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.

handleNameResolutionError

public void handleNameResolutionError(Status error)

Handle the name resolution error.

Override if you need special handling.

Specified by:

handleNameResolutionError in class LoadBalancer

Parameters:

error - a non-OK status

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

acceptResolvedAddressesInternal

protected final MultiChildLoadBalancer.AcceptResolvedAddrRetVal acceptResolvedAddressesInternal(LoadBalancer.ResolvedAddresses resolvedAddresses)

This does the work to update the child map and calculate which children have been removed. You must call updateOverallBalancingState() to update the picker and call shutdownRemoved(List) to shutdown the endpoints that have been removed.

shutdownRemoved

protected final void shutdownRemoved(List<MultiChildLoadBalancer.ChildLbState> removedChildren)

aggregateState

@Nullable
protected static ConnectivityState aggregateState(@Nullable
 ConnectivityState overallState,
 ConnectivityState childState)

getHelper

protected final LoadBalancer.Helper getHelper()

getChildLbStates

public final Collection<MultiChildLoadBalancer.ChildLbState> getChildLbStates()

getReadyChildren

protected final List<MultiChildLoadBalancer.ChildLbState> getReadyChildren()

Filters out non-ready child load balancers (subchannels).