package org.jgroups.blocks.executor;
import java.io.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.Future;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.RunnableFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import org.jgroups.JChannel;
import org.jgroups.protocols.Executing;
import org.jgroups.util.FutureListener;
import org.jgroups.util.NotifyingFuture;
import org.jgroups.util.Streamable;
import org.jgroups.util.Util;
/**
* This is a jgroups implementation of an ExecutorService, where the consumers
* are running on any number of nodes. The nodes should run
* {@link ExecutionRunner} to start picking up requests.
* <p>
* Every future object returned will be a {@link NotifyingFuture} which
* allows for not having to query the future and have a callback instead. This
* can then be used as a workflow to submit other tasks sequentially or also to
* query the future for the value at that time.
* <p>
* Every callable or runnable submitted must be either {@link Serializable} or
* {@link Streamable}. Also the value returned from
* a callable must {@link Serializable} or
* {@link Streamable}. Unfortunately if the value returned is not serializable
* then a {@link NotSerializableException} will be thrown as the cause.
* @author wburns
* @since 2.12.0
*/
public class ExecutionService extends AbstractExecutorService {
protected JChannel ch;
protected Executing _execProt;
protected Lock _unfinishedLock = new ReentrantLock();
protected Condition _unfinishedCondition = _unfinishedLock.newCondition();
protected Set<Future<?>> _unfinishedFutures = new HashSet<Future<?>>();
protected AtomicBoolean _shutdown = new AtomicBoolean(false);
public ExecutionService() {
}
public ExecutionService(JChannel ch) {
setChannel(ch);
}
public void setChannel(JChannel ch) {
this.ch=ch;
_execProt=(Executing)ch.getProtocolStack().findProtocol(Executing.class);
if(_execProt == null)
throw new IllegalStateException("Channel configuration must include a executing protocol " +
"(subclass of " + Executing.class.getName() + ")");
}
// @see java.util.concurrent.AbstractExecutorService#submit(java.lang.Runnable, java.lang.Object)
@Override
public <T> NotifyingFuture<T> submit(Runnable task, T result) {
// This cast is okay cause we control creation of the task
return (NotifyingFuture<T>)super.submit(task, result);
}
// @see java.util.concurrent.AbstractExecutorService#submit(java.util.concurrent.Callable)
@Override
public <T> NotifyingFuture<T> submit(Callable<T> task) {
// This cast is okay cause we control creation of the task
return (NotifyingFuture<T>)super.submit(task);
}
/**
* This is basically a copy of the FutureTask in java.util.concurrent but
* added serializable to it. Also added in the NotifyingFuture
* so that the channel can update the future when the value is calculated.
*
* @param <V>
* @author wburns
*/
public static class DistributedFuture<V> implements RunnableFuture<V>,
ExecutorNotification, NotifyingFuture<V> {
// @see java.lang.Object#toString()
@Override
public String toString() {
return "DistributedFuture [callable=" + sync.callable + "]";
}
/** Synchronization control for FutureTask */
protected final Sync<V> sync;
/** The following values are only used on the client side */
private final JChannel channel;
private final Set<Future<?>> _unfinishedFutures;
private final Lock _unfinishedLock;
private final Condition _unfinishedCondition;
private volatile FutureListener<V> _listener;
/**
* Creates a <tt>FutureTask</tt> that will upon running, execute the
* given <tt>Callable</tt>.
*
* @param channel The channel that messages are sent down
* @param unfinishedLock The lock which protects the futuresToFinish
* set object.
* @param condition The condition to signal when this future finishes
* @param futuresToFinish The set to remove this future from when
* it is finished.
* @param callable The callable to actually run on the server side
*/
public DistributedFuture(JChannel channel, Lock unfinishedLock,
Condition condition,
Set<Future<?>> futuresToFinish,
Callable<V> callable) {
if (callable == null)
throw new NullPointerException();
sync = new Sync<V>(this, callable);
this.channel = channel;
// We keep the real copy to update the outside
_unfinishedFutures = futuresToFinish;
_unfinishedLock = unfinishedLock;
_unfinishedCondition = condition;
}
/**
* Creates a <tt>FutureTask</tt> that will upon running, execute the
* given <tt>Runnable</tt>, and arrange that <tt>get</tt> will return the
* given result on successful completion.
*
* @param channel The channel that messages are sent down
* @param unfinishedLock The lock which protects the futuresToFinish
* set object.
* @param condition The condition to signal when this future finishes
* @param futuresToFinish The set to remove this future from when
* it is finished.
* @param runnable the runnable task
* @param result the result to return on successful completion. If
* you don't need a particular result, consider using
* constructions of the form:
* <tt>Future<?> f = new FutureTask<Object>(runnable, null)</tt>
* @throws NullPointerException if runnable is null
*/
public DistributedFuture(JChannel channel, Lock unfinishedLock,
Condition condition, Set<Future<?>> futuresToFinish,
Runnable runnable, V result) {
sync = new Sync<V>(this, new RunnableAdapter<V>(runnable, result));
this.channel = channel;
// We keep the real copy to update the outside
_unfinishedFutures = futuresToFinish;
_unfinishedLock = unfinishedLock;
_unfinishedCondition = condition;
}
public Callable<V> getCallable() {
return sync.callable;
}
public boolean isCancelled() {
return sync.innerIsCancelled();
}
public boolean isDone() {
return sync.innerIsDone();
}
public boolean cancel(boolean mayInterruptIfRunning) {
if (sync.innerIsDone()) {
return false;
}
// This will only happen on calling side since it is transient
if (channel != null) {
return (Boolean)channel.down(new ExecutorEvent(
ExecutorEvent.TASK_CANCEL, new Object[] {this, mayInterruptIfRunning}));
}
return sync.innerCancel(mayInterruptIfRunning);
}
/**
* @throws CancellationException {@inheritDoc}
*/
public V get() throws InterruptedException, ExecutionException {
return sync.innerGet();
}
/**
* @throws CancellationException {@inheritDoc}
*/
public V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return sync.innerGet(unit.toNanos(timeout));
}
/**
* Protected method invoked when this task transitions to state
* <tt>isDone</tt> (whether normally or via cancellation). The
* default implementation does nothing. Subclasses may override
* this method to invoke completion callbacks or perform
* bookkeeping. Note that you can query status inside the
* implementation of this method to determine whether this task
* has been cancelled.
*/
protected void done() {
_unfinishedLock.lock();
try {
_unfinishedFutures.remove(this);
_unfinishedCondition.signalAll();
}
finally {
_unfinishedLock.unlock();
}
// We assign the listener to a local variable so we don't have to
// worry about it becoming null inside the if
FutureListener<V> listener = _listener;
// We don't want this to run on server
if (listener != null) {
listener.futureDone(this);
}
}
@Override
public NotifyingFuture<V> setListener(FutureListener<V> listener) {
_listener = listener;
if (sync.innerIsDone()) {
_listener.futureDone(this);
}
return this;
}
/**
* Sets the result of this Future to the given value unless
* this future has already been set or has been cancelled.
* This method is invoked internally by the <tt>run</tt> method
* upon successful completion of the computation.
* @param v the value
*/
protected void set(V v) {
sync.innerSet(v);
}
/**
* Causes this future to report an <tt>ExecutionException</tt>
* with the given throwable as its cause, unless this Future has
* already been set or has been cancelled.
* This method is invoked internally by the <tt>run</tt> method
* upon failure of the computation.
* @param t the cause of failure
*/
protected void setException(Throwable t) {
sync.innerSetException(t);
}
// The following (duplicated) doc comment can be removed once
//
// 6270645: Javadoc comments should be inherited from most derived
// superinterface or superclass
// is fixed.
/**
* Sets this Future to the result of its computation
* unless it has been cancelled.
*/
public void run() {
sync.innerRun();
}
/**
* Synchronization control for FutureTask. Note that this must be
* a non-static inner class in order to invoke the protected
* <tt>done</tt> method. For clarity, all inner class support
* methods are same as outer, prefixed with "inner".
*
* Uses AQS sync state to represent run status
*/
protected static final class Sync<V> extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = -7828117401763700385L;
/** State value representing that task is running */
protected static final int RUNNING = 1;
/** State value representing that task ran */
protected static final int RAN = 2;
/** State value representing that task was cancelled */
protected static final int CANCELLED = 4;
/** The containing future */
protected final DistributedFuture<V> future;
/** The underlying callable */
protected final Callable<V> callable;
/** The result to return from get() */
protected V result;
/** The exception to throw from get() */
protected Throwable exception;
/**
* The thread running task. When nulled after set/cancel, this
* indicates that the results are accessible. Must be
* volatile, to ensure visibility upon completion.
*/
protected transient volatile Thread runner;
public Sync(DistributedFuture<V> future, Callable<V> callable) {
this.future = future;
this.callable = callable;
}
private static boolean ranOrCancelled(int state) {
return (state & (RAN | CANCELLED)) != 0;
}
/**
* Implements AQS base acquire to succeed if ran or cancelled
*/
protected int tryAcquireShared(int ignore) {
return innerIsDone()? 1 : -1;
}
/**
* Implements AQS base release to always signal after setting
* final done status by nulling runner thread.
*/
protected boolean tryReleaseShared(int ignore) {
runner = null;
return true;
}
boolean innerIsCancelled() {
return getState() == CANCELLED;
}
boolean innerIsDone() {
return ranOrCancelled(getState()) && runner == null;
}
V innerGet() throws InterruptedException, ExecutionException {
acquireSharedInterruptibly(0);
if (getState() == CANCELLED)
throw new CancellationException();
if (exception != null)
throw new ExecutionException(exception);
return result;
}
V innerGet(long nanosTimeout) throws InterruptedException, ExecutionException, TimeoutException {
if (!tryAcquireSharedNanos(0, nanosTimeout))
throw new TimeoutException();
if (getState() == CANCELLED)
throw new CancellationException();
if (exception != null)
throw new ExecutionException(exception);
return result;
}
void innerSet(V v) {
for (;;) {
int s = getState();
if (s == RAN)
return;
if (s == CANCELLED) {
// aggressively release to set runner to null,
// in case we are racing with a cancel request
// that will try to interrupt runner
releaseShared(0);
return;
}
if (compareAndSetState(s, RAN)) {
result = v;
releaseShared(0);
future.done();
return;
}
}
}
void innerSetException(Throwable t) {
for (;;) {
int s = getState();
if (s == RAN)
return;
if (s == CANCELLED) {
// aggressively release to set runner to null,
// in case we are racing with a cancel request
// that will try to interrupt runner
releaseShared(0);
return;
}
if (compareAndSetState(s, RAN)) {
exception = t;
result = null;
releaseShared(0);
future.done();
return;
}
}
}
boolean innerCancel(boolean mayInterruptIfRunning) {
for (;;) {
int s = getState();
if (ranOrCancelled(s))
return false;
if (compareAndSetState(s, CANCELLED))
break;
}
if (mayInterruptIfRunning) {
Thread r = runner;
if (r != null)
r.interrupt();
}
releaseShared(0);
future.done();
return true;
}
void innerRun() {
if (!compareAndSetState(0, RUNNING))
return;
try {
runner = Thread.currentThread();
if (getState() == RUNNING) // recheck after setting thread
innerSet(callable.call());
else
releaseShared(0); // cancel
} catch (Throwable ex) {
innerSetException(ex);
}
}
boolean innerRunAndReset() {
if (!compareAndSetState(0, RUNNING))
return false;
try {
runner = Thread.currentThread();
if (getState() == RUNNING)
callable.call(); // don't set result
runner = null;
return compareAndSetState(RUNNING, 0);
} catch (Throwable ex) {
innerSetException(ex);
return false;
}
}
}
// @see org.jgroups.blocks.executor.ExecutorNotification#resultReturned(java.lang.Object)
@SuppressWarnings("unchecked")
@Override
public void resultReturned(Object obj) {
set((V)obj);
}
// @see org.jgroups.blocks.executor.ExecutorNotification#throwableEncountered(java.lang.Throwable)
@Override
public void throwableEncountered(Throwable t) {
setException(t);
}
@Override
public void interrupted(Runnable runnable) {
_unfinishedLock.lock();
try {
_unfinishedFutures.remove(this);
_unfinishedCondition.signalAll();
}
finally {
_unfinishedLock.unlock();
}
// We assign the listener to a local variable so we don't have to
// worry about it becoming null inside the if
FutureListener<V> listener = _listener;
// We don't want this to run on server
if (listener != null) {
listener.futureDone(this);
}
}
}
// @see java.util.concurrent.ExecutorService#shutdown()
@Override
public void shutdown() {
_realShutdown(false);
}
@SuppressWarnings("unchecked")
private List<Runnable> _realShutdown(boolean interrupt) {
_shutdown.set(true);
_unfinishedLock.lock();
Set<Future<?>> futures;
try {
futures = new HashSet<Future<?>>(_unfinishedFutures);
}
finally {
_unfinishedLock.unlock();
}
return (List<Runnable>)ch.down(new ExecutorEvent(
ExecutorEvent.ALL_TASK_CANCEL, new Object[]{futures, interrupt}));
}
// @see java.util.concurrent.ExecutorService#shutdownNow()
@Override
public List<Runnable> shutdownNow() {
return _realShutdown(true);
}
// @see java.util.concurrent.ExecutorService#isShutdown()
@Override
public boolean isShutdown() {
return _shutdown.get();
}
// @see java.util.concurrent.ExecutorService#isTerminated()
@Override
public boolean isTerminated() {
if (_shutdown.get()) {
_unfinishedLock.lock();
try {
return _unfinishedFutures.isEmpty();
}
finally {
_unfinishedLock.unlock();
}
}
return false;
}
// @see java.util.concurrent.ExecutorService#awaitTermination(long, java.util.concurrent.TimeUnit)
@Override
public boolean awaitTermination(long timeout, TimeUnit unit)
throws InterruptedException {
long nanoTimeWait = unit.toNanos(timeout);
_unfinishedLock.lock();
try {
while (!_unfinishedFutures.isEmpty()) {
if ((nanoTimeWait = _unfinishedCondition.awaitNanos(
nanoTimeWait)) <= 0) {
return false;
}
}
}
finally {
_unfinishedLock.unlock();
}
return true;
}
// @see java.util.concurrent.AbstractExecutorService#invokeAny(java.util.Collection)
@Override
public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
throws InterruptedException, ExecutionException {
try {
return doInvokeAny(tasks, false, 0);
} catch (TimeoutException cannotHappen) {
assert false;
return null;
}
}
// @see java.util.concurrent.AbstractExecutorService#invokeAny(java.util.Collection, long, java.util.concurrent.TimeUnit)
@Override
public <T> T invokeAny(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
return doInvokeAny(tasks, true, unit.toNanos(timeout));
}
/**
* the main mechanics of invokeAny.
* This was essentially copied from {@link AbstractExecutorService}
* doInvokeAny except that we replaced the {@link ExecutorCompletionService}
* with an {@link ExecutionCompletionService}.
*/
private <T> T doInvokeAny(Collection<? extends Callable<T>> tasks,
boolean timed, long nanos)
throws InterruptedException, ExecutionException, TimeoutException {
if (tasks == null)
throw new NullPointerException();
int ntasks = tasks.size();
if (ntasks == 0)
throw new IllegalArgumentException();
List<Future<T>> futures= new ArrayList<Future<T>>(ntasks);
CompletionService<T> ecs =
new ExecutionCompletionService<T>(this);
// For efficiency, especially in executors with limited
// parallelism, check to see if previously submitted tasks are
// done before submitting more of them. This interleaving
// plus the exception mechanics account for messiness of main
// loop.
try {
// Record exceptions so that if we fail to obtain any
// result, we can throw the last exception we got.
ExecutionException ee = null;
long lastTime = (timed)? System.nanoTime() : 0;
Iterator<? extends Callable<T>> it = tasks.iterator();
// Start one task for sure; the rest incrementally
futures.add(ecs.submit(it.next()));
--ntasks;
int active = 1;
for (;;) {
Future<T> f = ecs.poll();
if (f == null) {
if (ntasks > 0) {
--ntasks;
futures.add(ecs.submit(it.next()));
++active;
}
else if (active == 0)
break;
else if (timed) {
f = ecs.poll(nanos, TimeUnit.NANOSECONDS);
if (f == null)
throw new TimeoutException();
long now = System.nanoTime();
nanos -= now - lastTime;
lastTime = now;
}
else
f = ecs.take();
}
if (f != null) {
--active;
try {
return f.get();
} catch (InterruptedException ie) {
throw ie;
} catch (ExecutionException eex) {
ee = eex;
} catch (RuntimeException rex) {
ee = new ExecutionException(rex);
}
}
}
if (ee == null)
ee = new ExecutionException() {
private static final long serialVersionUID = 200818694545553992L;
};
throw ee;
} finally {
for (Future<T> f : futures)
f.cancel(true);
}
}
// @see java.util.concurrent.Executor#execute(java.lang.Runnable)
@Override
public void execute(Runnable command) {
if (!_shutdown.get()) {
Object serializeCheck;
DistributedFuture<?> distFuture = null;
// If it is wrapped by our future, then we have to make sure to
// check the actual callable/runnable given to us for serialization
if (command instanceof DistributedFuture) {
distFuture = (DistributedFuture<?>)command;
serializeCheck = distFuture.getCallable();
if (serializeCheck instanceof RunnableAdapter) {
serializeCheck = ((RunnableAdapter<?>)serializeCheck).task;
}
}
else {
serializeCheck = command;
}
if (serializeCheck instanceof Serializable ||
serializeCheck instanceof Streamable) {
if (distFuture != null) {
_execProt.addExecutorListener(distFuture, distFuture);
_unfinishedLock.lock();
try {
_unfinishedFutures.add(distFuture);
}
finally {
_unfinishedLock.unlock();
}
}
ch.down(new ExecutorEvent(ExecutorEvent.TASK_SUBMIT, command));
}
else {
throw new IllegalArgumentException(
"Command was not Serializable or Streamable - "
+ serializeCheck);
}
}
else {
throw new RejectedExecutionException();
}
}
/**
* This is copied from {@see java.util.concurrent.Executors} class which
* contains RunnableAdapter. However that adapter isn't serializable, and
* is final and package level so we can' reference.
*/
protected static final class RunnableAdapter<T> implements Callable<T>, Streamable {
protected Runnable task;
protected T result;
public RunnableAdapter() {
}
protected RunnableAdapter(Runnable task, T result) {
this.task = task;
this.result = result;
}
public T call() {
task.run();
return result;
}
@Override
public void writeTo(DataOutput out) throws Exception {
try {
Util.writeObject(task, out);
}
catch (IOException e) {
throw e;
}
catch (Exception e) {
throw new IOException("Exception encountered while writing execution runnable", e);
}
try {
Util.writeObject(result, out);
}
catch (IOException e) {
throw e;
}
catch (Exception e) {
throw new IOException("Exception encountered while writing execution result", e);
}
}
@SuppressWarnings("unchecked")
@Override
public void readFrom(DataInput in) throws Exception {
// We can't use Util.readObject since it's size is limited to 2^15-1
// The runner could be larger than that possibly
try {
task = (Runnable)Util.readObject(in);
}
catch (IOException e) {
throw e;
}
catch (Exception e) {
throw new IOException("Exception encountered while reading execution runnable", e);
}
try {
result = (T)Util.readObject(in);
}
catch (IOException e) {
throw e;
}
catch (Exception e) {
throw new IOException("Exception encountered while reading execution result", e);
}
}
}
// @see java.util.concurrent.AbstractExecutorService#newTaskFor(java.lang.Runnable, java.lang.Object)
@Override
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
DistributedFuture<T> future = new DistributedFuture<T>(ch, _unfinishedLock,
_unfinishedCondition, _unfinishedFutures, runnable, value);
return future;
}
// @see java.util.concurrent.AbstractExecutorService#newTaskFor(java.util.concurrent.Callable)
@Override
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
DistributedFuture<T> future = new DistributedFuture<T>(ch, _unfinishedLock,
_unfinishedCondition, _unfinishedFutures, callable);
return future;
}
}