com.facebook.presto.jdbc.internal.jetty.util.SharedBlockingCallback Maven / Gradle / Ivy
//
// ========================================================================
// Copyright (c) 1995-2014 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
// ========================================================================
//
package com.facebook.presto.jdbc.internal.jetty.util;
import java.io.Closeable;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.util.concurrent.CancellationException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import com.facebook.presto.jdbc.internal.jetty.util.log.Log;
import com.facebook.presto.jdbc.internal.jetty.util.log.Logger;
import com.facebook.presto.jdbc.internal.jetty.util.thread.NonBlockingThread;
/* ------------------------------------------------------------ */
/** Provides a reusable BlockingCallback.
* A typical usage pattern is:
*
* void someBlockingCall(Object... args) throws IOException
* {
* try(Blocker blocker=sharedBlockingCallback.acquire())
* {
* someAsyncCall(args,blocker);
* blocker.block();
* }
* }
*
*/
public class SharedBlockingCallback
{
private static final Logger LOG = Log.getLogger(SharedBlockingCallback.class);
private static Throwable IDLE = new Throwable()
{
@Override
public String toString()
{
return "IDLE";
}
};
private static Throwable SUCCEEDED = new Throwable()
{
@Override
public String toString()
{
return "SUCCEEDED";
}
};
private static Throwable FAILED = new Throwable()
{
@Override
public String toString()
{
return "FAILED";
}
};
final Blocker _blocker;
public SharedBlockingCallback()
{
this(new Blocker());
}
protected SharedBlockingCallback(Blocker blocker)
{
_blocker=blocker;
}
public Blocker acquire() throws IOException
{
_blocker._lock.lock();
try
{
while (_blocker._state != IDLE)
_blocker._idle.await();
_blocker._state = null;
}
catch (final InterruptedException e)
{
throw new InterruptedIOException()
{
{
initCause(e);
}
};
}
finally
{
_blocker._lock.unlock();
}
return _blocker;
}
/* ------------------------------------------------------------ */
/** A Closeable Callback.
* Uses the auto close mechanism to check block has been called OK.
*/
public static class Blocker implements Callback, Closeable
{
final ReentrantLock _lock = new ReentrantLock();
final Condition _idle = _lock.newCondition();
final Condition _complete = _lock.newCondition();
Throwable _state = IDLE;
public Blocker()
{
}
@Override
public void succeeded()
{
_lock.lock();
try
{
if (_state == null)
{
_state = SUCCEEDED;
_complete.signalAll();
}
else if (_state == IDLE)
throw new IllegalStateException("IDLE");
}
finally
{
_lock.unlock();
}
}
@Override
public void failed(Throwable cause)
{
_lock.lock();
try
{
if (_state == null)
{
_state = cause==null?FAILED:cause;
_complete.signalAll();
}
else if (_state == IDLE)
throw new IllegalStateException("IDLE",cause);
}
finally
{
_lock.unlock();
}
}
/**
* Block until the Callback has succeeded or failed and after the return leave in the state to allow reuse. This is useful for code that wants to
* repeatable use a FutureCallback to convert an asynchronous API to a blocking API.
*
* @throws IOException
* if exception was caught during blocking, or callback was cancelled
*/
public void block() throws IOException
{
if (NonBlockingThread.isNonBlockingThread())
LOG.warn("Blocking a NonBlockingThread: ",new Throwable());
_lock.lock();
try
{
while (_state == null)
{
// TODO remove this debug timout!
// This is here to help debug 435322,
if (!_complete.await(10,TimeUnit.MINUTES))
{
IOException x = new IOException("DEBUG timeout");
LOG.warn("Blocked too long (please report!!!) "+this, x);
_state=x;
}
}
if (_state == SUCCEEDED)
return;
if (_state == IDLE)
throw new IllegalStateException("IDLE");
if (_state instanceof IOException)
throw (IOException)_state;
if (_state instanceof CancellationException)
throw (CancellationException)_state;
if (_state instanceof RuntimeException)
throw (RuntimeException)_state;
if (_state instanceof Error)
throw (Error)_state;
throw new IOException(_state);
}
catch (final InterruptedException e)
{
throw new InterruptedIOException()
{
{
initCause(e);
}
};
}
finally
{
_lock.unlock();
}
}
/**
* Check the Callback has succeeded or failed and after the return leave in the state to allow reuse.
*
* @throws IOException
* if exception was caught during blocking, or callback was cancelled
*/
@Override
public void close() throws IOException
{
_lock.lock();
try
{
if (_state == IDLE)
throw new IllegalStateException("IDLE");
if (_state == null)
LOG.debug("Blocker not complete",new Throwable());
}
finally
{
try
{
_state = IDLE;
_idle.signalAll();
}
finally
{
_lock.unlock();
}
}
}
@Override
public String toString()
{
_lock.lock();
try
{
return String.format("%s@%x{%s}",SharedBlockingCallback.class.getSimpleName(),hashCode(),_state);
}
finally
{
_lock.unlock();
}
}
}
}