mirror of
https://github.com/google/nomulus.git
synced 2025-04-30 12:07:51 +02:00
c458c05801
The dark lord Gosling designed the Java package naming system so that ownership flows from the DNS system. Since we own the domain name registry.google, it seems only appropriate that we should use google.registry as our package name.
102 lines
3.9 KiB
Java
102 lines
3.9 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 google.registry.util;
|
|
|
|
import static com.google.appengine.api.ThreadManager.currentRequestThreadFactory;
|
|
import static com.google.common.base.Preconditions.checkNotNull;
|
|
import static java.lang.Math.max;
|
|
import static java.lang.Math.min;
|
|
import static java.util.concurrent.Executors.newFixedThreadPool;
|
|
|
|
import com.google.common.base.Function;
|
|
import com.google.common.collect.FluentIterable;
|
|
import com.google.common.collect.ImmutableList;
|
|
import com.google.common.util.concurrent.UncheckedExecutionException;
|
|
import com.google.common.util.concurrent.Uninterruptibles;
|
|
|
|
import java.util.ArrayList;
|
|
import java.util.Collection;
|
|
import java.util.List;
|
|
import java.util.concurrent.Callable;
|
|
import java.util.concurrent.ExecutionException;
|
|
import java.util.concurrent.ExecutorService;
|
|
import java.util.concurrent.Future;
|
|
import java.util.concurrent.ThreadFactory;
|
|
|
|
/** Utilities for multithreaded operations in App Engine requests. */
|
|
public final class Concurrent {
|
|
|
|
/** Maximum number of threads per pool. The actual GAE per-request limit is 50. */
|
|
private static final int MAX_THREADS = 10;
|
|
|
|
/**
|
|
* Runs transform with the default number of threads.
|
|
*
|
|
* @see #transform(Collection, int, Function)
|
|
*/
|
|
public static <A, B> ImmutableList<B> transform(Collection<A> items, final Function<A, B> funk) {
|
|
return transform(items, max(1, min(items.size(), MAX_THREADS)), funk);
|
|
}
|
|
|
|
/**
|
|
* Processes {@code items} in parallel using {@code funk}, with the specified number of threads.
|
|
*
|
|
* <p><b>Note:</b> Spawned threads will inherit the same namespace.
|
|
*
|
|
* @throws UncheckedExecutionException to wrap the exception thrown by {@code funk}. This will
|
|
* only contain the exception information for the first exception thrown.
|
|
* @return transformed {@code items} in the same order.
|
|
*/
|
|
public static <A, B> ImmutableList<B> transform(
|
|
Collection<A> items,
|
|
int threadCount,
|
|
final Function<A, B> funk) {
|
|
checkNotNull(funk);
|
|
checkNotNull(items);
|
|
ThreadFactory threadFactory = currentRequestThreadFactory();
|
|
if (threadFactory == null) {
|
|
// Fall back to non-concurrent transform if we can't get an App Engine thread factory (most
|
|
// likely caused by hitting this code from a command-line tool). Default Java system threads
|
|
// are not compatible with code that needs to interact with App Engine (such as Objectify),
|
|
// which we often have in funk when calling Concurrent.transform().
|
|
// For more info see: http://stackoverflow.com/questions/15976406
|
|
return FluentIterable.from(items).transform(funk).toList();
|
|
}
|
|
ExecutorService executor = newFixedThreadPool(threadCount, threadFactory);
|
|
try {
|
|
List<Future<B>> futures = new ArrayList<>();
|
|
for (final A item : items) {
|
|
futures.add(executor.submit(new Callable<B>() {
|
|
@Override
|
|
public B call() {
|
|
return funk.apply(item);
|
|
}}));
|
|
}
|
|
ImmutableList.Builder<B> results = new ImmutableList.Builder<>();
|
|
for (Future<B> future : futures) {
|
|
try {
|
|
results.add(Uninterruptibles.getUninterruptibly(future));
|
|
} catch (ExecutionException e) {
|
|
throw new UncheckedExecutionException(e.getCause());
|
|
}
|
|
}
|
|
return results.build();
|
|
} finally {
|
|
executor.shutdownNow();
|
|
}
|
|
}
|
|
|
|
private Concurrent() {}
|
|
}
|