| /* |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.iotdb.db.mpp.execution; |
| |
| import com.google.common.collect.ImmutableSet; |
| import com.google.common.util.concurrent.ListenableFuture; |
| import com.google.common.util.concurrent.SettableFuture; |
| |
| import javax.annotation.concurrent.GuardedBy; |
| import javax.annotation.concurrent.ThreadSafe; |
| |
| import java.util.HashSet; |
| import java.util.Set; |
| import java.util.concurrent.Executor; |
| |
| import static com.google.common.util.concurrent.MoreExecutors.directExecutor; |
| import static java.util.Objects.requireNonNull; |
| |
| @ThreadSafe |
| public class FutureStateChange<T> { |
| // Use a separate future for each listener so canceled listeners can be removed |
| @GuardedBy("listeners") |
| private final Set<SettableFuture<T>> listeners = new HashSet<>(); |
| |
| public ListenableFuture<T> createNewListener() { |
| SettableFuture<T> listener = SettableFuture.create(); |
| synchronized (listeners) { |
| listeners.add(listener); |
| } |
| |
| // remove the listener when the future completes |
| listener.addListener( |
| () -> { |
| synchronized (listeners) { |
| listeners.remove(listener); |
| } |
| }, |
| directExecutor()); |
| |
| return listener; |
| } |
| |
| public void complete(T newState) { |
| fireStateChange(newState, directExecutor()); |
| } |
| |
| public void complete(T newState, Executor executor) { |
| fireStateChange(newState, executor); |
| } |
| |
| private void fireStateChange(T newState, Executor executor) { |
| requireNonNull(executor, "executor is null"); |
| Set<SettableFuture<T>> futures; |
| synchronized (listeners) { |
| futures = ImmutableSet.copyOf(listeners); |
| listeners.clear(); |
| } |
| |
| for (SettableFuture<T> future : futures) { |
| executor.execute(() -> future.set(newState)); |
| } |
| } |
| } |