package org.opendaylight.yangtools.util.concurrent;
-import static com.google.common.base.Preconditions.checkNotNull;
-
-import com.google.common.base.Function;
+import com.google.common.base.Preconditions;
+import com.google.common.base.Supplier;
import com.google.common.util.concurrent.ForwardingListenableFuture;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
-
+import javax.annotation.Nonnull;
import javax.annotation.Nullable;
/**
* An implementation of ListeningExecutorService that attempts to detect deadlock scenarios that
- * could occur if clients invoke the returned Future's <ode>get</code> methods synchronously.
- * <p>
- * Deadlock scenarios are most apt to occur with a backing single-threaded executor where setting of
+ * could occur if clients invoke the returned Future's <code>get</code> methods synchronously.
+ *
+ * <p>Deadlock scenarios are most apt to occur with a backing single-threaded executor where setting of
* the Future's result is executed on the single thread. Here's a scenario:
* <ul>
* <li>Client code is currently executing in an executor's single thread.</li>
* The second submitted task will never execute since the single thread is currently executing
* the client code which is blocked waiting for the submitted task to complete. Thus, deadlock has
* occurred.
- * <p>
- * This class prevents this scenario via the use of a ThreadLocal variable. When a task is invoked,
+ *
+ * <p>This class prevents this scenario via the use of a ThreadLocal variable. When a task is invoked,
* the ThreadLocal is set and, when a task completes, the ThreadLocal is cleared. Futures returned
* from this class override the <code>get</code> methods to check if the ThreadLocal is set. If it is,
* an ExecutionException is thrown with a custom cause.
*
+ * <p>Note that the ThreadLocal is not removed automatically, so some state may be left hanging off of
+ * threads which have encountered this class. If you need to clean that state up, use
+ * {@link #cleanStateForCurrentThread()}.
+ *
* @author Thomas Pantelis
+ * @author Robert Varga
*/
public class DeadlockDetectingListeningExecutorService extends AsyncNotifyingListeningExecutorService {
- private final ThreadLocal<Boolean> deadlockDetector = new ThreadLocal<>();
- private final Function<Void, Exception> deadlockExceptionFunction;
+ /*
+ * We cannot use a static field simply because our API contract allows nesting, which means some
+ * tasks may be submitted to underlay and some to overlay service -- and the two cases need to
+ * be discerned reliably.
+ */
+ private final SettableBooleanThreadLocal deadlockDetector = new SettableBooleanThreadLocal();
+ private final Supplier<Exception> deadlockExceptionFunction;
/**
* Constructor.
*
* @param delegate the backing ExecutorService.
- * @param deadlockExceptionFunction Function that returns an Exception instance to set as the
+ * @param deadlockExceptionSupplier Supplier that returns an Exception instance to set as the
* cause of the ExecutionException when a deadlock is detected.
*/
- public DeadlockDetectingListeningExecutorService( ExecutorService delegate,
- Function<Void,Exception> deadlockExceptionFunction ) {
- this(delegate, deadlockExceptionFunction, null);
+ public DeadlockDetectingListeningExecutorService(final ExecutorService delegate,
+ @Nonnull final Supplier<Exception> deadlockExceptionSupplier) {
+ this(delegate, deadlockExceptionSupplier, null);
}
/**
* Constructor.
*
* @param delegate the backing ExecutorService.
- * @param deadlockExceptionFunction Function that returns an Exception instance to set as the
+ * @param deadlockExceptionSupplier Supplier that returns an Exception instance to set as the
* cause of the ExecutionException when a deadlock is detected.
* @param listenableFutureExecutor the executor used to run listener callbacks asynchronously.
* If null, no executor is used.
*/
- public DeadlockDetectingListeningExecutorService( ExecutorService delegate,
- Function<Void,Exception> deadlockExceptionFunction,
- @Nullable Executor listenableFutureExecutor ) {
+ public DeadlockDetectingListeningExecutorService(final ExecutorService delegate,
+ @Nonnull final Supplier<Exception> deadlockExceptionSupplier,
+ @Nullable final Executor listenableFutureExecutor ) {
super(delegate, listenableFutureExecutor);
- this.deadlockExceptionFunction = checkNotNull(deadlockExceptionFunction);
+ this.deadlockExceptionFunction = Preconditions.checkNotNull(deadlockExceptionSupplier);
}
@Override
- public void execute( Runnable command ){
+ public void execute(@Nonnull final Runnable command) {
getDelegate().execute(wrapRunnable(command));
}
+ @Nonnull
@Override
- public <T> ListenableFuture<T> submit( Callable<T> task ){
+ public <T> ListenableFuture<T> submit(final Callable<T> task) {
return wrapListenableFuture(super.submit(wrapCallable(task)));
}
+ @Nonnull
@Override
- public ListenableFuture<?> submit( Runnable task ){
+ public ListenableFuture<?> submit(final Runnable task) {
return wrapListenableFuture(super.submit(wrapRunnable(task)));
}
+ @Nonnull
@Override
- public <T> ListenableFuture<T> submit( Runnable task, T result ){
+ public <T> ListenableFuture<T> submit(final Runnable task, final T result) {
return wrapListenableFuture(super.submit(wrapRunnable(task), result));
}
+ /**
+ * Remove the state this instance may have attached to the calling thread. If no state
+ * was attached this method does nothing.
+ */
+ public void cleanStateForCurrentThread() {
+ deadlockDetector.remove();
+ }
+
+ private SettableBoolean primeDetector() {
+ final SettableBoolean b = deadlockDetector.get();
+ Preconditions.checkState(!b.isSet(), "Detector for {} has already been primed", this);
+ b.set();
+ return b;
+ }
+
private Runnable wrapRunnable(final Runnable task) {
- return new Runnable() {
- @Override
- public void run() {
- deadlockDetector.set(Boolean.TRUE);
- try {
- task.run();
- } finally {
- deadlockDetector.remove();
- }
+ return () -> {
+ final SettableBoolean b = primeDetector();
+ try {
+ task.run();
+ } finally {
+ b.reset();
}
};
}
private <T> Callable<T> wrapCallable(final Callable<T> delagate) {
- return new Callable<T>() {
- @Override
- public T call() throws Exception {
- deadlockDetector.set(Boolean.TRUE);
- try {
- return delagate.call();
- } finally {
- deadlockDetector.remove();
- }
+ return () -> {
+ final SettableBoolean b = primeDetector();
+ try {
+ return delagate.call();
+ } finally {
+ b.reset();
}
};
}
- private <T> ListenableFuture<T> wrapListenableFuture(final ListenableFuture<T> delegate ) {
+ private <T> ListenableFuture<T> wrapListenableFuture(final ListenableFuture<T> delegate) {
/*
* This creates a forwarding Future that overrides calls to get(...) to check, via the
* ThreadLocal, if the caller is doing a blocking call on a thread from this executor. If
}
@Override
- public T get(final long timeout, final TimeUnit unit)
+ public T get(final long timeout, @Nonnull final TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
checkDeadLockDetectorTL();
return super.get(timeout, unit);
}
void checkDeadLockDetectorTL() throws ExecutionException {
- if (deadlockDetector.get() != null) {
+ if (deadlockDetector.get().isSet()) {
throw new ExecutionException("A potential deadlock was detected.",
- deadlockExceptionFunction.apply(null));
+ deadlockExceptionFunction.get());
}
}
};
Code Review / yangtools.git / blobdiff