org.apache.hadoop.fs.s3a.commit.Tasks Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.hadoop.fs.s3a.commit;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.AtomicBoolean;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Utility class for parallel execution, takes closures for the various
* actions.
* There is no retry logic: it is expected to be handled by the closures.
*/
public final class Tasks {
private static final Logger LOG = LoggerFactory.getLogger(Tasks.class);
private Tasks() {
}
/**
* Callback invoked to process an item.
* @param item type being processed
* @param exception class which may be raised
*/
@FunctionalInterface
public interface Task {
void run(I item) throws E;
}
/**
* Callback invoked on a failure.
* @param item type being processed
* @param exception class which may be raised
*/
@FunctionalInterface
public interface FailureTask {
/**
* process a failure.
* @param item item the task is processing
* @param exception the exception which was raised.
* @throws E Exception of type E
*/
void run(I item, Exception exception) throws E;
}
/**
* Builder for task execution.
* @param item type
*/
public static class Builder {
private final Iterable items;
private Submitter service = null;
private FailureTask onFailure = null;
private boolean stopOnFailure = false;
private boolean suppressExceptions = false;
private Task revertTask = null;
private boolean stopRevertsOnFailure = false;
private Task abortTask = null;
private boolean stopAbortsOnFailure = false;
/**
* Create the builder.
* @param items items to process
*/
Builder(Iterable items) {
this.items = items;
}
/**
* Declare executor service: if null, the tasks are executed in a single
* thread.
* @param submitter service to schedule tasks with.
* @return this builder.
*/
public Builder executeWith(Submitter submitter) {
this.service = submitter;
return this;
}
public Builder onFailure(FailureTask task) {
this.onFailure = task;
return this;
}
public Builder stopOnFailure() {
this.stopOnFailure = true;
return this;
}
public Builder suppressExceptions() {
return suppressExceptions(true);
}
public Builder suppressExceptions(boolean suppress) {
this.suppressExceptions = suppress;
return this;
}
public Builder revertWith(Task task) {
this.revertTask = task;
return this;
}
public Builder stopRevertsOnFailure() {
this.stopRevertsOnFailure = true;
return this;
}
public Builder abortWith(Task task) {
this.abortTask = task;
return this;
}
public Builder stopAbortsOnFailure() {
this.stopAbortsOnFailure = true;
return this;
}
public boolean run(Task task) throws E {
if (service != null) {
return runParallel(task);
} else {
return runSingleThreaded(task);
}
}
private boolean runSingleThreaded(Task task)
throws E {
List succeeded = new ArrayList<>();
List exceptions = new ArrayList<>();
Iterator iterator = items.iterator();
boolean threw = true;
try {
while (iterator.hasNext()) {
I item = iterator.next();
try {
task.run(item);
succeeded.add(item);
} catch (Exception e) {
exceptions.add(e);
if (onFailure != null) {
try {
onFailure.run(item, e);
} catch (Exception failException) {
LOG.error("Failed to clean up on failure", e);
// keep going
}
}
if (stopOnFailure) {
break;
}
}
}
threw = false;
} finally {
// threw handles exceptions that were *not* caught by the catch block,
// and exceptions that were caught and possibly handled by onFailure
// are kept in exceptions.
if (threw || !exceptions.isEmpty()) {
if (revertTask != null) {
boolean failed = false;
for (I item : succeeded) {
try {
revertTask.run(item);
} catch (Exception e) {
LOG.error("Failed to revert task", e);
failed = true;
// keep going
}
if (stopRevertsOnFailure && failed) {
break;
}
}
}
if (abortTask != null) {
boolean failed = false;
while (iterator.hasNext()) {
try {
abortTask.run(iterator.next());
} catch (Exception e) {
failed = true;
LOG.error("Failed to abort task", e);
// keep going
}
if (stopAbortsOnFailure && failed) {
break;
}
}
}
}
}
if (!suppressExceptions && !exceptions.isEmpty()) {
Tasks.throwOne(exceptions);
}
return !threw && exceptions.isEmpty();
}
private boolean runParallel(final Task task)
throws E {
final Queue succeeded = new ConcurrentLinkedQueue<>();
final Queue exceptions = new ConcurrentLinkedQueue<>();
final AtomicBoolean taskFailed = new AtomicBoolean(false);
final AtomicBoolean abortFailed = new AtomicBoolean(false);
final AtomicBoolean revertFailed = new AtomicBoolean(false);
List> futures = new ArrayList<>();
for (final I item : items) {
// submit a task for each item that will either run or abort the task
futures.add(service.submit(new Runnable() {
@Override
public void run() {
if (!(stopOnFailure && taskFailed.get())) {
// run the task
boolean threw = true;
try {
LOG.debug("Executing task");
task.run(item);
succeeded.add(item);
LOG.debug("Task succeeded");
threw = false;
} catch (Exception e) {
taskFailed.set(true);
exceptions.add(e);
LOG.info("Task failed", e);
if (onFailure != null) {
try {
onFailure.run(item, e);
} catch (Exception failException) {
LOG.error("Failed to clean up on failure", e);
// swallow the exception
}
}
} finally {
if (threw) {
taskFailed.set(true);
}
}
} else if (abortTask != null) {
// abort the task instead of running it
if (stopAbortsOnFailure && abortFailed.get()) {
return;
}
boolean failed = true;
try {
LOG.info("Aborting task");
abortTask.run(item);
failed = false;
} catch (Exception e) {
LOG.error("Failed to abort task", e);
// swallow the exception
} finally {
if (failed) {
abortFailed.set(true);
}
}
}
}
}));
}
// let the above tasks complete (or abort)
waitFor(futures);
int futureCount = futures.size();
futures.clear();
if (taskFailed.get() && revertTask != null) {
// at least one task failed, revert any that succeeded
LOG.info("Reverting all {} succeeded tasks from {} futures",
succeeded.size(), futureCount);
for (final I item : succeeded) {
futures.add(service.submit(() -> {
if (stopRevertsOnFailure && revertFailed.get()) {
return;
}
boolean failed = true;
try {
revertTask.run(item);
failed = false;
} catch (Exception e) {
LOG.error("Failed to revert task", e);
// swallow the exception
} finally {
if (failed) {
revertFailed.set(true);
}
}
}));
}
// let the revert tasks complete
waitFor(futures);
}
if (!suppressExceptions && !exceptions.isEmpty()) {
Tasks.throwOne(exceptions);
}
return !taskFailed.get();
}
}
/**
* Wait for all the futures to complete; there's a small sleep between
* each iteration; enough to yield the CPU.
* @param futures futures.
*/
private static void waitFor(Collection> futures) {
int size = futures.size();
LOG.debug("Waiting for {} tasks to complete", size);
int oldNumFinished = 0;
while (true) {
int numFinished = (int) futures.stream().filter(Future::isDone).count();
if (oldNumFinished != numFinished) {
LOG.debug("Finished count -> {}/{}", numFinished, size);
oldNumFinished = numFinished;
}
if (numFinished == size) {
// all of the futures are done, stop looping
break;
} else {
try {
Thread.sleep(10);
} catch (InterruptedException e) {
futures.forEach(future -> future.cancel(true));
Thread.currentThread().interrupt();
break;
}
}
}
}
public static Builder foreach(Iterable items) {
return new Builder<>(items);
}
public static Builder foreach(I[] items) {
return new Builder<>(Arrays.asList(items));
}
@SuppressWarnings("unchecked")
private static void throwOne(
Collection exceptions)
throws E {
Iterator iter = exceptions.iterator();
Exception e = iter.next();
Class exceptionClass = e.getClass();
while (iter.hasNext()) {
Exception other = iter.next();
if (!exceptionClass.isInstance(other)) {
e.addSuppressed(other);
}
}
Tasks.castAndThrow(e);
}
@SuppressWarnings("unchecked")
private static void castAndThrow(Exception e) throws E {
if (e instanceof RuntimeException) {
throw (RuntimeException) e;
}
throw (E) e;
}
/**
* Interface to whatever lets us submit tasks.
*/
public interface Submitter {
/**
* Submit work.
* @param task task to execute
* @return the future of the submitted task.
*/
Future submit(Runnable task);
}
}