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// Copyright 2014 The Bazel 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.devtools.build.skyframe;
import static com.google.common.truth.Truth.assertThat;
import com.google.common.base.Throwables;
import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.Uninterruptibles;
import com.google.devtools.build.lib.testutil.TestUtils;
import com.google.devtools.build.lib.util.Pair;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
/**
* Safely await {@link CountDownLatch}es in tests, storing any exceptions that happen. Callers
* should call {@link #assertNoErrors} at the end of each test method, either manually or using an
* {@code @After} hook.
*/
public class TrackingAwaiter {
public static final TrackingAwaiter INSTANCE = new TrackingAwaiter();
private TrackingAwaiter() {}
private final ConcurrentLinkedQueue<Pair<String, Throwable>> exceptionsThrown =
new ConcurrentLinkedQueue<>();
/**
* This method fixes a race condition with simply calling {@link CountDownLatch#await}. If this
* thread is interrupted before {@code latch.await} is called, then {@code latch.await} will throw
* an {@link InterruptedException} without checking the value of the latch at all. This leads to a
* race condition in which this thread will throw an InterruptedException if it is slow calling
* {@code latch.await}, but it will succeed normally otherwise.
*
* <p>To avoid this, we wait for the latch uninterruptibly. In the end, if the latch has in fact
* been released, we do nothing, although the interrupted bit is set, so that the caller can
* decide to throw an InterruptedException if it wants to. If the latch was not released, then
* this was not a race condition, but an honest-to-goodness interrupt, and we propagate the
* exception onward.
*/
private static void waitAndMaybeThrowInterrupt(CountDownLatch latch, String errorMessage)
throws InterruptedException {
if (Uninterruptibles.awaitUninterruptibly(latch, TestUtils.WAIT_TIMEOUT_SECONDS,
TimeUnit.SECONDS)) {
// Latch was released. We can ignore the interrupt state.
return;
}
if (!Thread.currentThread().isInterrupted()) {
// Nobody interrupted us, but latch wasn't released. Failure.
throw new AssertionError(errorMessage);
} else {
// We were interrupted before the latch was released. Propagate this interruption.
throw new InterruptedException();
}
}
/** Threadpools can swallow exceptions. Make sure they don't get lost. */
public void awaitLatchAndTrackExceptions(CountDownLatch latch, String errorMessage) {
try {
waitAndMaybeThrowInterrupt(latch, errorMessage);
} catch (Throwable e) {
// We would expect e to be InterruptedException or AssertionError, but we leave it open so
// that any throwable gets recorded.
exceptionsThrown.add(Pair.of(errorMessage, e));
// Caller will assert exceptionsThrown is empty at end of test and fail, even if this is
// swallowed.
Throwables.propagate(e);
}
}
/** Allow arbitrary errors to be recorded here for later throwing. */
public void injectExceptionAndMessage(Throwable throwable, String message) {
exceptionsThrown.add(Pair.of(message, throwable));
}
public void assertNoErrors() {
List<Pair<String, Throwable>> thisEvalExceptionsThrown = ImmutableList.copyOf(exceptionsThrown);
exceptionsThrown.clear();
assertThat(thisEvalExceptionsThrown).isEmpty();
}
}
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