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https://issues.apache.org/jira/browse/STORM-1253?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15145168#comment-15145168
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ASF GitHub Bot commented on STORM-1253:
---------------------------------------
Github user revans2 commented on a diff in the pull request:
https://github.com/apache/storm/pull/1098#discussion_r52788861
--- Diff: storm-core/src/jvm/org/apache/storm/StormTimer.java ---
@@ -0,0 +1,274 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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 org.apache.storm;
+
+import org.apache.storm.utils.Time;
+import org.apache.storm.utils.Utils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Comparator;
+import java.util.Random;
+import java.util.concurrent.PriorityBlockingQueue;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * The timer defined in this file is very similar to java.util.Timer,
except
+ * it integrates with Storm's time simulation capabilities. This lets us
test
+ * code that does asynchronous work on the timer thread
+ */
+
+public class StormTimer {
+ private static final Logger LOG =
LoggerFactory.getLogger(StormTimer.class);
+
+ public interface TimerFunc {
+ public void run(Object o);
+ }
+
+ public static class QueueEntry {
+ public final Long endTimeMs;
+ public final TimerFunc afn;
+ public final String id;
+
+ public QueueEntry(Long endTimeMs, TimerFunc afn, String id) {
+ this.endTimeMs = endTimeMs;
+ this.afn = afn;
+ this.id = id;
+ }
+ }
+
+ public static class StormTimerTask extends Thread {
+
+ private PriorityBlockingQueue<QueueEntry> queue = new
PriorityBlockingQueue<QueueEntry>(10, new Comparator() {
+ @Override
+ public int compare(Object o1, Object o2) {
+ return ((QueueEntry)o1).endTimeMs.intValue() -
((QueueEntry)o2).endTimeMs.intValue();
+ }
+ });
+
+ // boolean to indicate whether timer is active
+ private AtomicBoolean active = new AtomicBoolean(false);
+
+ // function to call when timer is killed
+ private TimerFunc onKill;
+
+ //random number generator
+ private Random random = new Random();
+
+ // synchronization for cancelling the timer
+ private Semaphore cancelNotifier = new Semaphore(0);
+
+ //used for synchronization
+ private Object lock = new Object();
+
+ @Override
+ public void run() {
+ while (this.active.get()) {
+ QueueEntry queueEntry = null;
+ try {
+ synchronized (this.lock) {
+ queueEntry = this.queue.peek();
+ }
+ if ((queueEntry != null) && (Time.currentTimeMillis()
>= queueEntry.endTimeMs)) {
+ // It is imperative to not run the function
+ // inside the timer lock. Otherwise, it is
+ // possible to deadlock if the fn deals with
+ // other locks, like the submit lock.
+ synchronized (this.lock) {
+ this.queue.poll();
--- End diff --
Crud. There is actually a race here. It is in the original code too We
cannot blindly do a poll and throw away the next thing on the queue, because
something else may have been prioritized ahead of what we just peeked at.
We don't run at a high enough load that I think this is critical, but we
should fix it. Just replacing the queueEntry with the polled one is probably
enough.
```
queueEntry = queue.peek();
if ((queueEntry != null) && (Time.currentTimeMillis() >=
queueEntry.endTimeMs)) {
queueEntry = queue.poll();
queueEntry.afn.run();
}
```
> port backtype.storm.timer to java
> ----------------------------------
>
> Key: STORM-1253
> URL: https://issues.apache.org/jira/browse/STORM-1253
> Project: Apache Storm
> Issue Type: New Feature
> Components: storm-core
> Reporter: Robert Joseph Evans
> Assignee: Boyang Jerry Peng
> Labels: java-migration, jstorm-merger
>
> Timer like class that uses simulated time
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