io.grpc

Class LoadBalancer.Helper

java.lang.Object

io.grpc.LoadBalancer.Helper

Enclosing class:

LoadBalancer

@ThreadSafe
public abstract static class LoadBalancer.Helper
extends Object

Provides essentials for LoadBalancer implementations.

Constructor Summary

Constructors

Constructor and Description
Helper()

Method Summary

Modifier and Type	Method and Description
abstract ManagedChannel	createOobChannel(EquivalentAddressGroup eag, String authority) Out-of-band channel for LoadBalancer’s own RPC needs, e.g., talking to an external load-balancer service.
abstract LoadBalancer.Subchannel	createSubchannel(EquivalentAddressGroup addrs, Attributes attrs) Creates a Subchannel, which is a logical connection to the given group of addresses which are considered equivalent.
abstract String	getAuthority() Returns the authority string of the channel, which is derived from the DNS-style target name.
abstract NameResolver.Factory	getNameResolverFactory() Returns the NameResolver of the channel.
abstract void	runSerialized(Runnable task) Schedule a task to be run in the Channel Executor, which serializes the task with the callback methods on the LoadBalancer interface.
void	updateBalancingState(ConnectivityState newState, LoadBalancer.SubchannelPicker newPicker) Set a new state with a new picker to the channel.
void	updateOobChannelAddresses(ManagedChannel channel, EquivalentAddressGroup eag) Updates the addresses used for connections in the Channel.
abstract void	updatePicker(LoadBalancer.SubchannelPicker picker) Deprecated. Please migrate ALL usages to updateBalancingState(io.grpc.ConnectivityState, io.grpc.LoadBalancer.SubchannelPicker)
void	updateSubchannelAddresses(LoadBalancer.Subchannel subchannel, EquivalentAddressGroup addrs) Replaces the existing addresses used with subchannel.

Methods inherited from class java.lang.Object

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

Constructor Detail

Helper

public Helper()

Method Detail

createSubchannel

public abstract LoadBalancer.Subchannel createSubchannel(EquivalentAddressGroup addrs,
                                                         Attributes attrs)

Creates a Subchannel, which is a logical connection to the given group of addresses which are considered equivalent. The attrs are custom attributes associated with this Subchannel, and can be accessed later through Subchannel.getAttributes().

The LoadBalancer is responsible for closing unused Subchannels, and closing all Subchannels within LoadBalancer.shutdown().

updateSubchannelAddresses

public void updateSubchannelAddresses(LoadBalancer.Subchannel subchannel,
                                      EquivalentAddressGroup addrs)

Replaces the existing addresses used with subchannel. This method is superior to createSubchannel(io.grpc.EquivalentAddressGroup, io.grpc.Attributes) when the new and old addresses overlap, since the subchannel can continue using an existing connection.

Throws:

IllegalArgumentException - if subchannel was not returned from createSubchannel(io.grpc.EquivalentAddressGroup, io.grpc.Attributes)

createOobChannel

public abstract ManagedChannel createOobChannel(EquivalentAddressGroup eag,
                                                String authority)

Out-of-band channel for LoadBalancer’s own RPC needs, e.g., talking to an external load-balancer service.

The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

updateOobChannelAddresses

public void updateOobChannelAddresses(ManagedChannel channel,
                                      EquivalentAddressGroup eag)

Updates the addresses used for connections in the Channel. This is supperior to createOobChannel(io.grpc.EquivalentAddressGroup, java.lang.String) when the old and new addresses overlap, since the channel can continue using an existing connection.

Throws:

IllegalArgumentException - if channel was not returned from createOobChannel(io.grpc.EquivalentAddressGroup, java.lang.String)

updatePicker

@Deprecated
public abstract void updatePicker(LoadBalancer.SubchannelPicker picker)

Deprecated. Please migrate ALL usages to updateBalancingState(io.grpc.ConnectivityState, io.grpc.LoadBalancer.SubchannelPicker)

Set a new picker to the channel.

When a new picker is provided via updatePicker(), the channel will apply the picker on all buffered RPCs, by calling LoadBalancer.SubchannelPicker.pickSubchannel( LoadBalancer.PickSubchannelArgs).

The channel will hold the picker and use it for all RPCs, until updatePicker() is called again and a new picker replaces the old one. If updatePicker() has never been called, the channel will buffer all RPCs until a picker is provided.

Using this method implies that this load balancer doesn't support channel state, and the application will get exception when trying to get the channel state.

updateBalancingState

public void updateBalancingState(@Nonnull
                                 ConnectivityState newState,
                                 @Nonnull
                                 LoadBalancer.SubchannelPicker newPicker)

Set a new state with a new picker to the channel.

When a new picker is provided via updateBalancingState(), the channel will apply the picker on all buffered RPCs, by calling LoadBalancer.SubchannelPicker.pickSubchannel( LoadBalancer.PickSubchannelArgs).

The channel will hold the picker and use it for all RPCs, until updateBalancingState() is called again and a new picker replaces the old one. If updateBalancingState() has never been called, the channel will buffer all RPCs until a picker is provided.

The passed state will be the channel's new state. The SHUTDOWN state should not be passed and its behavior is undefined.

runSerialized

public abstract void runSerialized(Runnable task)

Schedule a task to be run in the Channel Executor, which serializes the task with the callback methods on the LoadBalancer interface.

getNameResolverFactory

public abstract NameResolver.Factory getNameResolverFactory()

Returns the NameResolver of the channel.

getAuthority

public abstract String getAuthority()

Returns the authority string of the channel, which is derived from the DNS-style target name.