| /* |
| * Copyright 2016, gRPC Authors All rights reserved. |
| * |
| * 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 io.grpc.internal; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| import java.util.LinkedList; |
| import java.util.logging.Level; |
| import java.util.logging.Logger; |
| import javax.annotation.concurrent.GuardedBy; |
| import javax.annotation.concurrent.ThreadSafe; |
| |
| /** |
| * The thread-less Channel Executor used to run the state mutation logic in {@link |
| * ManagedChannelImpl}, {@link InternalSubchannel} and {@link io.grpc.LoadBalancer}s. |
| * |
| * <p>Tasks are queued until {@link #drain} is called. Tasks are guaranteed to be run in the same |
| * order as they are submitted. |
| */ |
| @ThreadSafe |
| final class ChannelExecutor { |
| private static final Logger log = Logger.getLogger(ChannelExecutor.class.getName()); |
| |
| private final Object lock = new Object(); |
| |
| @GuardedBy("lock") |
| private final LinkedList<Runnable> queue = new LinkedList<Runnable>(); |
| @GuardedBy("lock") |
| private boolean draining; |
| |
| /** |
| * Run all tasks in the queue in the current thread, if no other thread is in this method. |
| * Otherwise do nothing. |
| * |
| * <p>Upon returning, it guarantees that all tasks submitted by {@code executeLater()} before it |
| * have been or will eventually be run, while not requiring any more calls to {@code drain()}. |
| */ |
| void drain() { |
| boolean drainLeaseAcquired = false; |
| while (true) { |
| Runnable runnable; |
| synchronized (lock) { |
| if (!drainLeaseAcquired) { |
| if (draining) { |
| return; |
| } |
| draining = true; |
| drainLeaseAcquired = true; |
| } |
| runnable = queue.poll(); |
| if (runnable == null) { |
| draining = false; |
| break; |
| } |
| } |
| try { |
| runnable.run(); |
| } catch (Throwable t) { |
| log.log(Level.WARNING, "Runnable threw exception in ChannelExecutor", t); |
| } |
| } |
| } |
| |
| /** |
| * Enqueues a task that will be run when {@link #drain} is called. |
| * |
| * @return this ChannelExecutor |
| */ |
| ChannelExecutor executeLater(Runnable runnable) { |
| synchronized (lock) { |
| queue.add(checkNotNull(runnable, "runnable is null")); |
| } |
| return this; |
| } |
| |
| @VisibleForTesting |
| int numPendingTasks() { |
| synchronized (lock) { |
| return queue.size(); |
| } |
| } |
| } |