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/*
* Copyright 2018 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.grpc.grpclb;
import io.grpc.Attributes;
import io.grpc.ConnectivityStateInfo;
import io.grpc.EquivalentAddressGroup;
import io.grpc.LoadBalancer.Subchannel;
import javax.annotation.concurrent.NotThreadSafe;
/**
* Manages life-cycle of Subchannels for {@link GrpclbState}.
*
* All methods are run from the ChannelExecutor that the helper uses.
*/
@NotThreadSafe
interface SubchannelPool {
/**
* Registers a listener to received Subchannel status updates.
*/
void registerListener(PooledSubchannelStateListener listener);
/**
* Takes a {@link Subchannel} from the pool for the given {@code eag} if there is one available.
* Otherwise, creates and returns a new {@code Subchannel} with the given {@code eag} and {@code
* defaultAttributes}.
*/
Subchannel takeOrCreateSubchannel(EquivalentAddressGroup eag, Attributes defaultAttributes);
/**
* Puts a {@link Subchannel} back to the pool. From this point the Subchannel is owned by the
* pool, and the caller should stop referencing to this Subchannel.
*/
void returnSubchannel(Subchannel subchannel, ConnectivityStateInfo lastKnownState);
/**
* Shuts down all subchannels in the pool immediately.
*/
void clear();
/**
* Receives state changes for a pooled {@link Subchannel}.
*/
interface PooledSubchannelStateListener {
/**
* Handles a state change on a Subchannel. The behavior is similar to {@link
* io.grpc.LoadBalancer.SubchannelStateListener}.
*
*
When a subchannel is reused, subchannel state change event will be triggered even if the
* underlying status remains same.
*/
void onSubchannelState(Subchannel subchannel, ConnectivityStateInfo newState);
}
}