co.paralleluniverse.fibers.FiberAsync Maven / Gradle / Ivy
/*
* Quasar: lightweight threads and actors for the JVM.
* Copyright (c) 2013-2014, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.fibers;
import co.paralleluniverse.common.util.CheckedCallable;
import co.paralleluniverse.strands.Strand;
import co.paralleluniverse.strands.Timeout;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
/**
* A general helper class that transforms asynchronous requests to synchronous (fiber-blocking) calls.
*
* Usage example
*
* Assume that operation {@code Foo.asyncOp(FooCompletion callback)} is an asynchronous operation, where {@code Completion} is defined as:
*
* {@code
* interface FooCompletion {
* void success(String result);
* void failure(FooException exception);
* }
* }
*
* We then define the following subclass:
*
* {@code
* class FooAsync extends FiberAsync implements FooCompletion {
* {@literal @}Override
* public void success(String result) {
* asyncCompleted(result);
* }
*
* {@literal @}Override
* public void failure(FooException exception) {
* asyncFailed(exception);
* }
* }
* }
*
* Then, to turn the operation into a fiber-blocking one, we can define:
*
* {@code
* String op() {
* return new FooAsync() {
* protected void requestAsync() {
* Foo.asyncOp(this);
* }
* }.run();
* }
* }
*
* @param The value returned by the async request
* @param An exception class that could be thrown by the async request
*
* @author pron
*/
public abstract class FiberAsync implements java.io.Serializable {
private final Fiber fiber;
private final boolean immediateExec;
private volatile boolean completed;
private Throwable exception;
private V result;
private transient Thread registrationThread;
private transient volatile boolean registrationComplete;
private long timeoutNanos;
private transient long deadline;
/**
* Same as `FiberAsync(false)`
*/
public FiberAsync() {
this(false);
}
/**
*
* @param immediateExec Whether the fiber should be executed in the same thread as the callback. Should generally be set to `false`.
*/
public FiberAsync(boolean immediateExec) {
this.fiber = Fiber.currentFiber();
this.immediateExec = immediateExec;
}
/**
* Runs the asynchronous operation, blocks until it completes and returns its result. Throws an exception if the operation has failed.
*
* In immediate exec mode, when this method returns we are running within the handler, and will need to call {@link Fiber#yield()}
* to return from the handler.
*
* @return the result of the async operation as set in the call to {@link #asyncCompleted(java.lang.Object) asyncCompleted}.
* @throws E if the async computation failed and an exception was set in a call to {@link #asyncFailed(java.lang.Throwable) asyncFailed}.
* @throws InterruptedException
*/
@SuppressWarnings("empty-statement")
public V run() throws E, SuspendExecution, InterruptedException {
if (fiber == null)
return runSync();
if (registrationComplete)
throw new IllegalStateException("This FiberAsync instance has already been used");
// We call the verifySuspend first here, because instrumentation problems may corrupt
// the second call inside Fiber.park
Fiber.verifySuspend(fiber);
fiber.record(1, "FiberAsync", "run", "Blocking fiber %s on FiberAsync %s", fiber, this);
while (!Fiber.park(this, new Fiber.ParkAction() {
@Override
public void run(Fiber current) {
try {
current.record(1, "FiberAsync", "run", "Calling requestAsync on class %s", this);
registrationThread = Thread.currentThread();
requestAsync();
current.record(1, "FiberAsync", "run", "requestAsync on %s done", FiberAsync.this);
} catch (Throwable t) {
asyncFailed(t);
} finally {
registrationComplete = true;
}
}
})) {
checkInterrupted();
}
while (!completed) { // the fiber can be awakened spuriously, in particular, from calls to getStackTrace
checkInterrupted();
Fiber.park(this);
}
assert isCompleted() : "Unblocker: " + Fiber.currentFiber().getUnparker() + " " + Strand.toString(Fiber.currentFiber().getUnparkStackTrace());
// while (!isCompleted() || (immediateExec && !Fiber.currentFiber().isInExec())) {
// Fiber.park((Object) this);
// throw new InterruptedException();
// }
return getResult();
}
/**
* Runs the asynchronous operation, blocks until it completes (but only up to the given timeout duration) and returns its result.
* Throws an exception if the operation has failed.
*
* In immediate exec mode, when this method returns we are running within the handler, and will need to call {@link Fiber#yield()}
* to return from the handler.
*
* @param timeout the maximum duration to wait for the result
* @param unit {@code timeout}'s time unit
* @return the result of the async operation as set in the call to {@link #asyncCompleted(java.lang.Object) asyncCompleted}.
* @throws E if the async computation failed and an exception was set in a call to {@link #asyncFailed(java.lang.Throwable) asyncFailed}.
* @throws TimeoutException if the operation had not completed by the time the timeout has elapsed.
* @throws InterruptedException
*/
@SuppressWarnings("empty-statement")
public V run(final long timeout, final TimeUnit unit) throws E, SuspendExecution, InterruptedException, TimeoutException {
if (Fiber.currentFiber() == null)
return runSync(timeout, unit);
if (registrationComplete)
throw new IllegalStateException("This FiberAsync instance has already been used");
if (unit == null)
return run();
if (timeout <= 0)
throw new TimeoutException();
this.timeoutNanos = unit.toNanos(timeout);
this.deadline = System.nanoTime() + timeoutNanos;
fiber.record(1, "FiberAsync", "run", "Blocking fiber %s on FibeAsync %s", fiber, this);
while (!Fiber.park(this, new Fiber.ParkAction() {
@Override
public void run(Fiber current) {
try {
current.getScheduler().schedule(current, FiberAsync.this, timeout, unit);
current.record(1, "FiberAsync", "run", "Calling requestAsync on class %s", this);
registrationThread = Thread.currentThread();
requestAsync();
current.record(1, "FiberAsync", "run", "requestAsync on %s done", FiberAsync.this);
} catch (Throwable t) {
asyncFailed(t);
} finally {
registrationComplete = true;
}
}
})) {
checkInterrupted();
}
if (timeoutNanos > 0 && deadline == 0) // must have been deserialized
this.deadline = System.nanoTime() + timeoutNanos;
while (!completed) { // the fiber can be awakened spuriously, in particular, from calls to getStackTrace
checkInterrupted();
final long now = System.nanoTime();
if (now >= deadline) {
exception = new TimeoutException();
completed = true;
fiber.record(1, "FiberAsync", "run", "FibeAsync %s on fiber %s has timed out", this, fiber);
throw (TimeoutException) exception;
}
Fiber.park(this, deadline - now, TimeUnit.NANOSECONDS);
}
return getResult();
}
protected void checkInterrupted() throws InterruptedException {
if (Fiber.interrupted()) {
interrupted();
throw new InterruptedException();
}
}
/**
* Runs the asynchronous operation, blocks until it completes (but only up to the given timeout duration) and returns its result.
* Throws an exception if the operation has failed.
*
* In immediate exec mode, when this method returns we are running within the handler, and will need to call {@link Fiber#yield()}
* to return from the handler.
*
* @param timeout the method will not block for longer than the amount remaining in the {@link Timeout}
* @return the result of the async operation as set in the call to {@link #asyncCompleted(java.lang.Object) asyncCompleted}.
* @throws E if the async computation failed and an exception was set in a call to {@link #asyncFailed(java.lang.Throwable) asyncFailed}.
* @throws TimeoutException if the operation had not completed by the time the timeout has elapsed.
* @throws InterruptedException
*/
public V run(Timeout timeout) throws E, SuspendExecution, InterruptedException, TimeoutException {
return run(timeout.nanosLeft(), TimeUnit.NANOSECONDS);
}
private V runSync(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException, E {
try {
return requestSync(timeout, unit);
} catch (ExecutionException e) {
if (e.getCause() instanceof RuntimeException)
throw (RuntimeException) e.getCause();
throw (E) e.getCause();
}
}
private V runSync() throws InterruptedException, E {
try {
return requestSync();
} catch (ExecutionException e) {
if (e.getCause() instanceof RuntimeException)
throw (RuntimeException) e.getCause();
throw (E) e.getCause();
}
}
/**
* Spins until {@code requestAsync} returns. Can be called from overrides of {@code run} (and must be called by the fiber that's
* calling {@code run}).
*/
protected final void waitForRegistration() {
if (registrationThread != null && Thread.currentThread() != registrationThread) {
while (!registrationComplete)
; // spin
}
}
/**
* Called when the fiber calling {@link run} is interrupted during the call.
*/
protected void interrupted() {
}
/**
* A user of this class must override this method to start the asynchronous operation and register the callback.
* This method may not use any {@link ThreadLocal}s.
*/
protected abstract void requestAsync();
/**
* Called if {@link #run()} is not being executed in a fiber. Should perform the operation synchronously and return its result.
* The default implementation of this method throws an `IllegalThreadStateException`.
*
* @return The operation's result.
* @throws E
* @throws InterruptedException
*/
protected V requestSync() throws E, InterruptedException, ExecutionException {
throw new IllegalThreadStateException("Method called not from within a fiber");
}
/**
* Called if {@link #run(long, TimeUnit)} is not being executed in a fiber. Should perform the operation synchronously and return its result.
* The default implementation of this method throws an `IllegalThreadStateException`.
*
* @return The operation's result.
* @param timeout the maximum duration to wait for the result
* @param unit {@code timeout}'s time unit
* @throws E
* @throws InterruptedException
*/
protected V requestSync(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException, E {
throw new IllegalThreadStateException("Method called not from within a fiber");
}
/**
* This method must be called by the callback upon successful completion of the asynchronous operation.
*
* @param result The operation's result
*/
protected void asyncCompleted(V result) {
if (completed) // probably timeout
return;
this.result = result;
completed = true;
// a race can happen at this point in the immediateExec case, hence the test Fiber.currentFiber().isInExec() in run()
fire(fiber);
}
/**
* This method must be called by the callback upon a failure of the asynchronous operation.
*
* @param t The exception that caused the failure, or an exception to be associated with it. Must not be `null`.
*/
protected void asyncFailed(Throwable t) {
if (t == null)
throw new IllegalArgumentException("t must not be null");
if (completed) // probably timeout
return;
this.exception = t;
completed = true;
// a race can happen at this point in the immediateExec case, hence the test Fiber.currentFiber().isInExec() in run()
fire(fiber);
}
private void fire(Fiber fiber) {
// if (Thread.currentThread() != registrationThread)
// while (!registrationComplete); // spin
if (immediateExec) {
fiber.record(1, "FiberAsync", "fire", "%s - Immediate exec of fiber %s", this, fiber);
if (!fiber.exec(this, new Fiber.ParkAction() {
public void run(Fiber current) {
prepark();
}
})) {
final boolean timeout = (deadline > 0 && System.nanoTime() >= deadline);
final Exception ex = timeout ? new TimeoutException() : new RuntimeException("Failed to exec fiber " + fiber + " in thread " + Thread.currentThread());
this.exception = ex;
fiber.unpark(this);
if (!timeout)
throw (RuntimeException) ex;
}
} else
fiber.unpark(this);
}
/**
* Called by the fiber if this `FiberAsync` is in immediate-exec mode, immediately before attempting to block while running
* in the callback's thread.
* Can be overridden by subclasses running in immediate-exec mode to verify whether a park is allowed.
*/
protected void prepark() {
}
/**
* Tests whether or not the asynchronous operation represented by this `FiberAsyc` has completed.
*/
public final boolean isCompleted() {
return completed;
}
/**
* Returns the result of the asynchronous operation if it has completed, or throws an exception if it completed unsuccessfully.
* If the operation has not yet completed, this method throws an `IllegalStateException`.
*
* @return the result of the asynchronous operation if it has completed.
* @throws E if the async computation failed and an exception was set in a call to {@link #asyncFailed(java.lang.Throwable) asyncFailed}.
* @throws IllegalStateException if the operation has not yet completed.
*/
public final V getResult() throws E {
if (!completed)
throw new IllegalStateException("Not completed");
if (exception != null)
throw wrapException(exception);
return result;
}
/**
* Takes the exception generated by the async operation and possibly wraps it in an exception
* that will be thrown by the {@code run} method.
*/
protected E wrapException(Throwable t) {
return (E) t;
}
/**
* Runs a thread-blocking operation on a given thread pool, blocks (the fiber) until the operation completes and returns
* its result.
* This method is useful to transform thread-blocking calls that don't have corresponding asynchronous operations
* into a fiber-blocking operation.
*
* @param exec the thread-pool on which the thread-blocking operation will be run
* @param callable the operation
* @return the result of the operation
* @throws E if the operation has thrown an exception
*/
public static V runBlocking(final ExecutorService exec, final CheckedCallable callable) throws E, SuspendExecution, InterruptedException {
return new ThreadBlockingFiberAsync<>(exec, callable).run();
}
/**
* Runs a thread-blocking operation on a given thread pool, blocks (the fiber) until the operation completes
* (but no longer than the specified timeout) and returns its result.
* This method is useful to transform thread-blocking calls that don't have corresponding asynchronous operations
* into a fiber-blocking operation.
*
* @param exec the thread-pool on which the thread-blocking operation will be run
* @param timeout the maximum duration to wait for the operation to complete
* @param unit {@code timeout}'s time unit.
* @param callable the operation
* @return the result of the operation
* @throws E if the operation has thrown an exception
* @throws TimeoutException if the timeout expires before the operation completes.
*/
public static V runBlocking(final ExecutorService exec, long timeout, TimeUnit unit, final CheckedCallable callable) throws E, SuspendExecution, InterruptedException, TimeoutException {
return new ThreadBlockingFiberAsync<>(exec, callable).run(timeout, unit);
}
/**
* Runs a thread-blocking operation on a given thread pool, blocks (the fiber) until the operation completes
* (but no longer than the specified timeout) and returns its result.
* This method is useful to transform thread-blocking calls that don't have corresponding asynchronous operations
* into a fiber-blocking operation.
*
* @param exec the thread-pool on which the thread-blocking operation will be run
* @param timeout the maximum duration to wait for the operation to complete
* @param callable the operation
* @return the result of the operation
* @throws E if the operation has thrown an exception
* @throws TimeoutException if the timeout expires before the operation completes.
*/
public static V runBlocking(final ExecutorService exec, Timeout timeout, final CheckedCallable callable) throws E, SuspendExecution, InterruptedException, TimeoutException {
return new ThreadBlockingFiberAsync<>(exec, callable).run(timeout);
}
private static class ThreadBlockingFiberAsync extends FiberAsync {
private final ExecutorService exec;
private final CheckedCallable action;
private Future fut;
public ThreadBlockingFiberAsync(ExecutorService exec, CheckedCallable action) {
this.exec = exec;
this.action = action;
}
@Override
protected void requestAsync() {
this.fut = exec.submit(new Runnable() {
@Override
public void run() {
try {
V res = action.call();
asyncCompleted(res);
} catch (Throwable e) {
asyncFailed(e);
}
}
});
}
@Override
protected V requestSync() throws E, InterruptedException {
return action.call();
}
@Override
protected void interrupted() {
if (fut != null)
fut.cancel(true);
super.interrupted();
}
}
}