Automated rollback of changelist 178323108
Test: tap
PiperOrigin-RevId: 181196939
Change-Id: I97405c5356814fe3ad02d498cfa96c210921c477
diff --git a/java/com/android/dialer/common/concurrent/DialerFutureSerializer.java b/java/com/android/dialer/common/concurrent/DialerFutureSerializer.java
index de37a29..2629abb 100644
--- a/java/com/android/dialer/common/concurrent/DialerFutureSerializer.java
+++ b/java/com/android/dialer/common/concurrent/DialerFutureSerializer.java
@@ -16,24 +16,83 @@
package com.android.dialer.common.concurrent;
+import static com.google.common.util.concurrent.Futures.immediateCancelledFuture;
+import static com.google.common.util.concurrent.Futures.immediateFuture;
+import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
+
import com.google.common.util.concurrent.AsyncCallable;
+import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
/**
* Serializes execution of a set of operations. This class guarantees that a submitted callable will
* not be called before previously submitted callables have completed.
*/
public final class DialerFutureSerializer {
+ /** This reference acts as a pointer tracking the head of a linked list of ListenableFutures. */
+ private final AtomicReference<ListenableFuture<?>> ref =
+ new AtomicReference<>(immediateFuture(null));
/** Enqueues a task to run when the previous task (if any) completes. */
+ public <T> ListenableFuture<T> submit(final Callable<T> callable, Executor executor) {
+ return submitAsync(() -> immediateFuture(callable.call()), executor);
+ }
+
+ /**
+ * Enqueues a task to run when the previous task (if any) completes.
+ *
+ * <p>Cancellation does not propagate from the output future to the future returned from {@code
+ * callable}, but if the output future is cancelled before {@link AsyncCallable#call()} is
+ * invoked, {@link AsyncCallable#call()} will not be invoked.
+ */
public <T> ListenableFuture<T> submitAsync(final AsyncCallable<T> callable, Executor executor) {
- // TODO(zachh): This is just a dummy implementation until we fix guava API level issues.
- try {
- return callable.call();
- } catch (Exception e) {
- e.printStackTrace();
- }
- return null;
+ AtomicBoolean wasCancelled = new AtomicBoolean(false);
+ final AsyncCallable<T> task =
+ () -> {
+ if (wasCancelled.get()) {
+ return immediateCancelledFuture();
+ }
+ return callable.call();
+ };
+ /*
+ * Three futures are at play here:
+ * taskFuture is the future that comes from the callable.
+ * newFuture is the future we use to track the serialization of our task.
+ * oldFuture is the previous task's newFuture.
+ *
+ * newFuture is guaranteed to only complete once all tasks previously submitted to this instance
+ * once the futures returned from those submissions have completed.
+ */
+ final SettableFuture<Object> newFuture = SettableFuture.create();
+
+ final ListenableFuture<?> oldFuture = ref.getAndSet(newFuture);
+
+ // Invoke our task once the previous future completes.
+ final ListenableFuture<T> taskFuture =
+ Futures.nonCancellationPropagating(
+ Futures.submitAsync(task, runnable -> oldFuture.addListener(runnable, executor)));
+ // newFuture's lifetime is determined by taskFuture, unless taskFuture is cancelled, in which
+ // case it falls back to oldFuture's. This is to ensure that if the future we return is
+ // cancelled, we don't begin execution of the next task until after oldFuture completes.
+ taskFuture.addListener(
+ () -> {
+ if (taskFuture.isCancelled()) {
+ // Since the value of oldFuture can only ever be immediateFuture(null) or setFuture of a
+ // future that eventually came from immediateFuture(null), this doesn't leak throwables
+ // or completion values.
+ wasCancelled.set(true);
+ newFuture.setFuture(oldFuture);
+ } else {
+ newFuture.set(null);
+ }
+ },
+ directExecutor());
+
+ return taskFuture;
}
}