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core: thread-less ChannelExecutor. (#2493) 

Dedicated for mutating states of ManagedChannelImpl, InternalSubchannel and LoadBalancer.
This commit is contained in:
Kun Zhang 2016-12-08 18:38:29 -08:00 committed by GitHub
parent ecb79ce36f
commit fd33a72174
2 changed files with 279 additions and 0 deletions
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core/src/main/java/io/grpc/internal/ChannelExecutor.java Normal file
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/*
* 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 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(runnable);
}
return this;
}
@VisibleForTesting
int numPendingTasks() {
synchronized (lock) {
return queue.size();
}
}
}

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core/src/test/java/io/grpc/internal/ChannelExecutorTest.java Normal file
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/*
* 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 org.junit.Assert.assertSame;
import static org.junit.Assert.assertTrue;
import static org.mockito.Mockito.doAnswer;
import static org.mockito.Mockito.inOrder;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
import org.mockito.InOrder;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
/**
* Unit tests for {@link ChannelExecutor}.
*/
@RunWith(JUnit4.class)
public class ChannelExecutorTest {
private final ChannelExecutor executor = new ChannelExecutor();
@Mock
private Runnable task1;
@Mock
private Runnable task2;
@Mock
private Runnable task3;
@Before public void setUp() {
MockitoAnnotations.initMocks(this);
}
@Test
public void singleThread() {
executor.executeLater(task1);
executor.executeLater(task2);
InOrder inOrder = inOrder(task1, task2, task3);
inOrder.verifyNoMoreInteractions();
executor.drain();
inOrder.verify(task1).run();
inOrder.verify(task2).run();
executor.executeLater(task3);
inOrder.verifyNoMoreInteractions();
executor.drain();
inOrder.verify(task3).run();
}
@Test
public void multiThread() throws Exception {
InOrder inOrder = inOrder(task1, task2);
final CountDownLatch task1Added = new CountDownLatch(1);
final CountDownLatch task1Running = new CountDownLatch(1);
final CountDownLatch task1Proceed = new CountDownLatch(1);
final CountDownLatch sideThreadDone = new CountDownLatch(1);
final AtomicReference<Thread> task1Thread = new AtomicReference<Thread>();
final AtomicReference<Thread> task2Thread = new AtomicReference<Thread>();
doAnswer(new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) {
task1Thread.set(Thread.currentThread());
task1Running.countDown();
try {
assertTrue(task1Proceed.await(5, TimeUnit.SECONDS));
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
return null;
}
}).when(task1).run();
doAnswer(new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) {
task2Thread.set(Thread.currentThread());
return null;
}
}).when(task2).run();
Thread sideThread = new Thread() {
@Override
public void run() {
executor.executeLater(task1);
task1Added.countDown();
executor.drain();
sideThreadDone.countDown();
}
};
sideThread.start();
assertTrue(task1Added.await(5, TimeUnit.SECONDS));
executor.executeLater(task2);
assertTrue(task1Running.await(5, TimeUnit.SECONDS));
// This will do nothing because task1 is running until task1Proceed is set
executor.drain();
inOrder.verify(task1).run();
inOrder.verifyNoMoreInteractions();
task1Proceed.countDown();
// drain() on the side thread has returned, which runs task2
assertTrue(sideThreadDone.await(5, TimeUnit.SECONDS));
inOrder.verify(task2).run();
assertSame(sideThread, task1Thread.get());
assertSame(sideThread, task2Thread.get());
}
@Test
public void taskThrows() {
InOrder inOrder = inOrder(task1, task2, task3);
doAnswer(new Answer<Void>() {
@Override
public Void answer(InvocationOnMock invocation) {
throw new RuntimeException("Simulated");
}
}).when(task2).run();
executor.executeLater(task1);
executor.executeLater(task2);
executor.executeLater(task3);
executor.drain();
inOrder.verify(task1).run();
inOrder.verify(task2).run();
inOrder.verify(task3).run();
}
}