| /* |
| * Copyright 2016, Google Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| 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.LoadBalancer2}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(); |
| } |
| } |
| } |