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// Copyright 2017 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.lib.remote;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import io.grpc.Status;
import io.grpc.StatusException;
import io.grpc.StatusRuntimeException;
import java.time.Duration;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadLocalRandom;
import java.util.function.Predicate;
import java.util.function.Supplier;
/**
* Specific retry logic for remote execution/caching.
*
* <p>A call can disable retries by throwing a {@link PassThroughException}. <code>
* RemoteRetrier r = ...;
* try {
* r.execute(() -> {
* // Not retried.
* throw PassThroughException(new IOException("fail"));
* }
* } catch (RetryException e) {
* // e.getCause() is the IOException
* System.out.println(e.getCause());
* }
* </code>
*/
public class RemoteRetrier extends Retrier {
/**
* Wraps around an {@link Exception} to make it pass through a single layer of retries.
*/
public static class PassThroughException extends Exception {
public PassThroughException(Exception e) {
super(e);
}
}
public static final Predicate<? super Exception> RETRIABLE_GRPC_ERRORS =
e -> {
if (!(e instanceof StatusException) && !(e instanceof StatusRuntimeException)) {
return false;
}
Status s = Status.fromThrowable(e);
switch (s.getCode()) {
case CANCELLED:
return !Thread.currentThread().isInterrupted();
case UNKNOWN:
case DEADLINE_EXCEEDED:
case ABORTED:
case INTERNAL:
case UNAVAILABLE:
case UNAUTHENTICATED:
case RESOURCE_EXHAUSTED:
return true;
default:
return false;
}
};
public RemoteRetrier(
RemoteOptions options,
Predicate<? super Exception> shouldRetry,
ListeningScheduledExecutorService retryScheduler,
CircuitBreaker circuitBreaker) {
this(
options.experimentalRemoteRetry
? () -> new ExponentialBackoff(options)
: () -> RETRIES_DISABLED,
shouldRetry,
retryScheduler,
circuitBreaker);
}
public RemoteRetrier(
Supplier<Backoff> backoff,
Predicate<? super Exception> shouldRetry,
ListeningScheduledExecutorService retryScheduler,
CircuitBreaker circuitBreaker) {
super(backoff, supportPassthrough(shouldRetry), retryScheduler, circuitBreaker);
}
@VisibleForTesting
RemoteRetrier(
Supplier<Backoff> backoff,
Predicate<? super Exception> shouldRetry,
ListeningScheduledExecutorService retryScheduler,
CircuitBreaker circuitBreaker,
Sleeper sleeper) {
super(backoff, supportPassthrough(shouldRetry), retryScheduler, circuitBreaker, sleeper);
}
@Override
public <T> T execute(Callable<T> call) throws RetryException, InterruptedException {
try {
return super.execute(call);
} catch (RetryException e) {
if (e.getCause() instanceof PassThroughException) {
PassThroughException passThrough = (PassThroughException) e.getCause();
throw new RetryException("Retries aborted because of PassThroughException",
e.getAttempts(), (Exception) passThrough.getCause());
}
throw e;
}
}
private static Predicate<? super Exception> supportPassthrough(
Predicate<? super Exception> delegate) {
// PassThroughException is not retriable.
return e -> !(e instanceof PassThroughException) && delegate.test(e);
}
static class ExponentialBackoff implements Retrier.Backoff {
private final long maxMillis;
private long nextDelayMillis;
private int attempts = 0;
private final double multiplier;
private final double jitter;
private final int maxAttempts;
/**
* Creates a Backoff supplier for an optionally jittered exponential backoff. The supplier is
* ThreadSafe (non-synchronized calls to get() are fine), but the returned Backoff is not.
*
* @param initial The initial backoff duration.
* @param max The maximum backoff duration.
* @param multiplier The amount the backoff should increase in each iteration. Must be >1.
* @param jitter The amount the backoff should be randomly varied (0-1), with 0 providing no
* jitter, and 1 providing a duration that is 0-200% of the non-jittered duration.
* @param maxAttempts Maximal times to attempt a retry 0 means no retries.
*/
ExponentialBackoff(Duration initial, Duration max, double multiplier, double jitter,
int maxAttempts) {
Preconditions.checkArgument(multiplier > 1, "multipler must be > 1");
Preconditions.checkArgument(jitter >= 0 && jitter <= 1, "jitter must be in the range (0, 1)");
Preconditions.checkArgument(maxAttempts >= 0, "maxAttempts must be >= 0");
nextDelayMillis = initial.toMillis();
maxMillis = max.toMillis();
this.multiplier = multiplier;
this.jitter = jitter;
this.maxAttempts = maxAttempts;
}
ExponentialBackoff(RemoteOptions options) {
this(Duration.ofMillis(options.experimentalRemoteRetryStartDelayMillis),
Duration.ofMillis(options.experimentalRemoteRetryMaxDelayMillis),
options.experimentalRemoteRetryMultiplier,
options.experimentalRemoteRetryJitter,
options.experimentalRemoteRetryMaxAttempts);
}
@Override
public long nextDelayMillis() {
if (attempts == maxAttempts) {
return -1;
}
attempts++;
double jitterRatio = jitter * (ThreadLocalRandom.current().nextDouble(2.0) - 1);
long result = (long) (nextDelayMillis * (1 + jitterRatio));
// Advance current by the non-jittered result.
nextDelayMillis = (long) (nextDelayMillis * multiplier);
if (nextDelayMillis > maxMillis) {
nextDelayMillis = maxMillis;
}
return result;
}
@Override
public int getRetryAttempts() {
return attempts;
}
}
}
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