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fix: Implement ChannelCache, which aggregates stubs to a single chann…
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…el, and properly cleans them up on teardown. (#72)
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dpcollins-google committed May 21, 2020
1 parent 603b4a7 commit 502484a
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package com.google.cloud.pubsublite;

import com.google.auth.oauth2.GoogleCredentials;
import com.google.cloud.pubsublite.internal.ChannelCache;
import com.google.common.collect.ImmutableList;
import io.grpc.Channel;
import io.grpc.ManagedChannelBuilder;
import io.grpc.auth.MoreCallCredentials;
import io.grpc.stub.AbstractStub;
import java.io.IOException;
import java.util.function.Function;

public class Stubs {
private static final ChannelCache channels = new ChannelCache();

public static <StubT extends AbstractStub<StubT>> StubT defaultStub(
String target, Function<Channel, StubT> stubFactory) throws IOException {
return stubFactory
.apply(ManagedChannelBuilder.forTarget(target).build())
.apply(channels.get(target))
.withCallCredentials(
MoreCallCredentials.from(
GoogleCredentials.getApplicationDefault()
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/*
* Copyright 2020 Google LLC
*
* 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 com.google.cloud.pubsublite.internal;

import io.grpc.Channel;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

/** A ChannelCache creates and stores default channels for use with api methods. */
public class ChannelCache {
private final ConcurrentHashMap<String, ManagedChannel> channels = new ConcurrentHashMap<>();

public ChannelCache() {
Runtime.getRuntime().addShutdownHook(new Thread(this::onShutdown));
}

private void onShutdown() {
channels.forEachValue(
channels.size(),
channel -> {
try {
channel.shutdownNow().awaitTermination(60, TimeUnit.SECONDS);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
}

public Channel get(String target) {
return channels.computeIfAbsent(target, this::newChannel);
}

private ManagedChannel newChannel(String target) {
return ManagedChannelBuilder.forTarget(target).build();
}
}

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