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Issue #1924 - ManagedSelector livelock. 

* Actually using the MAX_ACTION_PERIOD value rather than a harcoded one.
* Waking up the selector outside the sync block.
This commit is contained in:
Simone Bordet 2017-10-30 00:36:01 +01:00
parent d90eeba233
commit 333c22d670
2 changed files with 54 additions and 33 deletions
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42
jetty-client/src/test/java/org/eclipse/jetty/client/LivelockTest.java
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@ -25,18 +25,15 @@ import java.util.concurrent.atomic.AtomicBoolean;
import org.eclipse.jetty.client.http.HttpClientTransportOverHTTP;
import org.eclipse.jetty.http.HttpStatus;
import org.eclipse.jetty.io.ManagedSelector;
import org.eclipse.jetty.io.SelectorManager;
import org.eclipse.jetty.server.Handler;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.ServerConnector;
import org.eclipse.jetty.toolchain.test.annotation.Slow;
import org.eclipse.jetty.util.SocketAddressResolver;
import org.eclipse.jetty.util.thread.Invocable;
import org.eclipse.jetty.util.thread.QueuedThreadPool;
import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;
public class LivelockTest
@ -61,19 +58,20 @@ public class LivelockTest
@After
public void after() throws Exception
{
client.stop();
server.stop();
if (client != null)
client.stop();
if (server != null)
server.stop();
}
@Test
@Slow
public void testLivelock() throws Exception
{
// This test applies a moderate connect/request load (5/s) over 5 seconds,
// with a connect timeout of 100, so any delayed connects will be detected.
// NonBlocking runnables are submitted to both the client and server
// with a connect timeout of 1000, so any delayed connects will be detected.
// NonBlocking actions are submitted to both the client and server
// ManagedSelectors that submit themselves in an attempt to cause a live lock
// as there will always be an action available to run
// as there will always be an action available to run.
int count = 25;
HttpClientTransport transport = new HttpClientTransportOverHTTP(1);
@ -96,7 +94,7 @@ public class LivelockTest
@Override
public void run()
{
try { Thread.sleep(10);} catch(Exception e) {}
sleep(10);
if (busy.get())
clientSelector.submit(this);
}
@ -109,13 +107,15 @@ public class LivelockTest
@Override
public void run()
{
try { Thread.sleep(10);} catch(Exception e) {}
sleep(10);
if (busy.get())
serverSelector.submit(this);
}
};
serverSelector.submit(serverLivelock);
int requestRate = 5;
long pause = 1000 / requestRate;
CountDownLatch latch = new CountDownLatch(count);
for (int i = 0; i < count; ++i)
{
@ -126,9 +126,23 @@ public class LivelockTest
if (result.isSucceeded() && result.getResponse().getStatus() == HttpStatus.OK_200)
latch.countDown();
});
Thread.sleep(200);
sleep(pause);
}
Assert.assertTrue(latch.await(5000, TimeUnit.MILLISECONDS));
Assert.assertTrue(latch.await(2 * pause * count, TimeUnit.MILLISECONDS));
// Exit the livelocks.
busy.set(false);
}
private void sleep(long time)
{
try
{
Thread.sleep(time);
}
catch (InterruptedException x)
{
throw new RuntimeException(x);
}
}
}

45
jetty-io/src/main/java/org/eclipse/jetty/io/ManagedSelector.java
View File

@ -69,7 +69,6 @@ public class ManagedSelector extends ContainerLifeCycle implements Dumpable
private Selector _selector;
private long _actionTime = -1;
public ManagedSelector(SelectorManager selectorManager, int id)
{
_selectorManager = selectorManager;
@ -305,11 +304,11 @@ public class ManagedSelector extends ContainerLifeCycle implements Dumpable
private Runnable nextAction()
{
Runnable action;
long now = System.nanoTime();
Selector selector = null;
Runnable action = null;
try (Locker.Lock lock = _locker.lock())
{
// It is important to avoid live-lock (busy blocking) here. If too many actions
// are submitted, this can indefinitely defer selection happening. Similarly if
// we give too much priority to selection, it may prevent actions from being run.
@ -317,30 +316,38 @@ public class ManagedSelector extends ContainerLifeCycle implements Dumpable
// so that this method will fall through to selection if more than MAX_ACTION_PERIOD_MS
// is spent running actions. The time period is cleared whenever a selection occurs,
// so that a full period can be spent on actions after every select.
if (_actionTime==-1)
_actionTime = now;
else if ((now-_actionTime)>TimeUnit.MILLISECONDS.toNanos(100) && _actions.size()>0)
if (_actionTime == -1)
{
// Too long spent handling actions, give selection a go by,
// immediate wakeup (as if remaining action were just added).
_selector.wakeup();
_actionTime = now;
}
else if ((now - _actionTime) > TimeUnit.MILLISECONDS.toNanos(MAX_ACTION_PERIOD_MS) && _actions.size() > 0)
{
// Too much time spent handling actions, give selection a go,
// immediately waking up (as if remaining action were just added).
selector = _selector;
_selecting = false;
_actionTime = -1;
if (LOG.isDebugEnabled())
LOG.debug("force select q={}",_actions.size());
return null;
LOG.debug("Forcing selection, actions={}",_actions.size());
}
action = _actions.poll();
if (action == null)
if (selector == null)
{
// No more actions, so we time to do some selecting
_selecting = true;
_actionTime = -1;
action = _actions.poll();
if (action == null)
{
// No more actions, so we time to do some selecting
_selecting = true;
_actionTime = -1;
}
}
return action;
}
if (selector != null)
selector.wakeup();
return action;
}
private boolean select()