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Merge pull request #423 from mdaley/master 

Stop failed timer task from breaking timers.
This commit is contained in:
Jean-Baptiste Onofré 2021-03-23 14:43:43 +01:00 committed by GitHub
parent b6ab868f94 b379879dbf
commit 4c7bb06503
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 41 additions and 1 deletions
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25
activemq-client/src/main/java/org/apache/activemq/thread/SchedulerTimerTask.java
View File

@ -16,6 +16,9 @@
*/
package org.apache.activemq.thread;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.TimerTask;
/**
@ -23,6 +26,8 @@ import java.util.TimerTask;
*
*/
public class SchedulerTimerTask extends TimerTask {
private static final Logger LOGGER = LoggerFactory.getLogger(SchedulerTimerTask.class);
private final Runnable task;
public SchedulerTimerTask(Runnable task) {
@ -30,6 +35,24 @@ public class SchedulerTimerTask extends TimerTask {
}
public void run() {
this.task.run();
try {
this.task.run();
} catch (Error error) {
// Very bad error. Can't swallow this but can log it.
LOGGER.error("Scheduled task error", error);
throw error;
} catch (Exception exception) {
// It is a known issue of java.util.Timer that if a TimerTask.run() method throws an exception, the
// Timer's thread exits as if Timer.cancel() had been called. This makes the Timer completely unusable from
// that point on - whenever the Timer triggers there is an 'IllegalStateException: Timer already cancelled'
// and the task does not get executed.
//
// In practice, this makes the ActiveMQ client unable to refresh connections to brokers. Generally, tasks
// are well coded to not throw exceptions but if they do, problems ensue...
//
// The answer, here, is to log the exception and then carry on without throwing further. This gives the
// added benefit that, having seen the exception thrown, one can then go and fix the offending task!
LOGGER.error("Scheduled task exception", exception);
}
}
}

17
activemq-client/src/test/java/org/apache/activemq/thread/SchedulerTest.java
View File

@ -69,16 +69,33 @@ public class SchedulerTest {
assertFalse(latch.await(1000, TimeUnit.MILLISECONDS));
}
@Test
public void testExecutePeriodicallyTaskExceptionDoesNotBreakTimer() throws Exception {
final CountDownLatch latch = new CountDownLatch(10);
scheduler.executePeriodically(new CountDownRunnable(latch, 5L), 10);
assertTrue(latch.await(5000, TimeUnit.MILLISECONDS));
}
private static class CountDownRunnable implements Runnable {
final CountDownLatch latch;
final Long throwAtCount;
CountDownRunnable(final CountDownLatch latch) {
this(latch, null);
}
CountDownRunnable(final CountDownLatch latch, Long throwAtCount) {
this.latch = latch;
this.throwAtCount = throwAtCount;
}
@Override
public void run() {
latch.countDown();
if (throwAtCount != null && latch.getCount() == throwAtCount) {
throw new RuntimeException("You never want this to happen in a real task!!");
}
}
}