com.firefly.utils.concurrent.SharedBlockingCallback Maven / Gradle / Ivy
package com.firefly.utils.concurrent;
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.TimeoutException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
/**
* Provides a reusable {@link Callback} that can block the thread while waiting
* to be completed.
*
* 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 Throwable IDLE = new Throwable() {
private static final long serialVersionUID = 2839201304149405751L;
@Override
public String toString() {
return "IDLE";
}
};
private static Throwable SUCCEEDED = new Throwable() {
private static final long serialVersionUID = 3201333456423359501L;
@Override
public String toString() {
return "SUCCEEDED";
}
};
private static Throwable FAILED = new Throwable() {
private static final long serialVersionUID = 7378407146943258362L;
@Override
public String toString() {
return "FAILED";
}
};
private final ReentrantLock _lock = new ReentrantLock();
private final Condition _idle = _lock.newCondition();
private final Condition _complete = _lock.newCondition();
private Blocker _blocker = new Blocker();
protected long getIdleTimeout() {
return -1;
}
public Blocker acquire() throws IOException {
_lock.lock();
long idle = getIdleTimeout();
try {
while (_blocker._state != IDLE) {
if (idle > 0 && (idle < Long.MAX_VALUE / 2)) {
// Wait a little bit longer than the blocker might block
if (!_idle.await(idle * 2, TimeUnit.MILLISECONDS))
throw new IOException(new TimeoutException());
} else
_idle.await();
}
_blocker._state = null;
} catch (final InterruptedException e) {
throw new InterruptedIOException();
} finally {
_lock.unlock();
}
return _blocker;
}
protected void notComplete(Blocker blocker) {
}
/**
* A Closeable Callback. Uses the auto close mechanism to check block has
* been called OK.
*
* Implements {@link Callback.NonBlocking} because calls to this callback do
* not blocak, rather they wakeup the thread that is blocked in
* {@link #block()}
*/
public class Blocker implements Callback.NonBlocking, Closeable {
private Throwable _state = IDLE;
protected Blocker() {
}
@Override
public void succeeded() {
_lock.lock();
try {
if (_state == null) {
_state = SUCCEEDED;
_complete.signalAll();
} else
throw new IllegalStateException(_state);
} finally {
_lock.unlock();
}
}
@Override
public void failed(Throwable cause) {
_lock.lock();
try {
if (_state == null) {
if (cause == null)
_state = FAILED;
else if (cause instanceof BlockerTimeoutException)
// Not this blockers timeout
_state = new IOException(cause);
else
_state = cause;
_complete.signalAll();
} else
throw new IllegalStateException(_state);
} 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 {
_lock.lock();
long idle = getIdleTimeout();
try {
while (_state == null) {
if (idle > 0 && (idle < Long.MAX_VALUE / 2)) {
// Wait a little bit longer than expected callback idle
// timeout
if (!_complete.await(idle + idle / 2, TimeUnit.MILLISECONDS))
// The callback has not arrived in sufficient time.
// We will synthesize a TimeoutException
_state = new BlockerTimeoutException();
} else {
_complete.await();
}
}
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();
} finally {
_lock.unlock();
}
}
/**
* Check the Callback has succeeded or failed and after the return leave
* in the state to allow reuse.
*/
@Override
public void close() {
_lock.lock();
try {
if (_state == IDLE)
throw new IllegalStateException("IDLE");
if (_state == null)
notComplete(this);
} finally {
try {
// If the blocker timed itself out, remember the state
if (_state instanceof BlockerTimeoutException)
// and create a new Blocker
_blocker = new Blocker();
else
// else reuse Blocker
_state = IDLE;
_idle.signalAll();
_complete.signalAll();
} finally {
_lock.unlock();
}
}
}
@Override
public String toString() {
_lock.lock();
try {
return String.format("%s@%x{%s}", Blocker.class.getSimpleName(), hashCode(), _state);
} finally {
_lock.unlock();
}
}
}
private static class BlockerTimeoutException extends TimeoutException {
private static final long serialVersionUID = -3538089426850786553L;
}
}