google-nomulus/java/google/registry/util/AppEngineTimeLimiter.java
Justine Tunney 5012893c1d mv com/google/domain/registry google/registry
This change renames directories in preparation for the great package
rename. The repository is now in a broken state because the code
itself hasn't been updated. However this should ensure that git
correctly preserves history for each file.
2016-05-13 18:55:08 -04:00

83 lines
2.8 KiB
Java

// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
//
// 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.domain.registry.util;
import static com.google.appengine.api.ThreadManager.currentRequestThreadFactory;
import com.google.common.util.concurrent.SimpleTimeLimiter;
import com.google.common.util.concurrent.TimeLimiter;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.TimeUnit;
/**
* A factory for {@link TimeLimiter} instances that use request threads, which carry the namespace
* and live only as long as the request that spawned them.
* <p>
* It is safe to reuse instances of this class, but there is no benefit in doing so over creating a
* fresh instance each time.
*/
public class AppEngineTimeLimiter {
/**
* An {@code ExecutorService} that uses a new thread for every task.
* <p>
* We need to use fresh threads for each request so that we can use App Engine's request threads.
* If we cached these threads in a thread pool (and if we were executing on a backend, where there
* is no time limit on requests) the caching would cause the thread to keep the task that opened
* it alive even after returning an http response, and would also cause the namespace that the
* original thread was created in to leak out to later reuses of the thread.
* <p>
* Since there are no cached resources, this class doesn't have to support being shutdown.
*/
private static class NewRequestThreadExecutorService extends AbstractExecutorService {
@Override
public void execute(Runnable command) {
currentRequestThreadFactory().newThread(command).start();
}
@Override
public boolean isShutdown() {
return false;
}
@Override
public boolean isTerminated() {
return false;
}
@Override
public void shutdown() {
throw new UnsupportedOperationException();
}
@Override
public List<Runnable> shutdownNow() {
throw new UnsupportedOperationException();
}
@Override
public boolean awaitTermination(long timeout, TimeUnit unit) {
throw new UnsupportedOperationException();
}
}
public static TimeLimiter create() {
return new SimpleTimeLimiter(new NewRequestThreadExecutorService());
}
}