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https://issues.apache.org/jira/browse/FLINK-6290?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15978453#comment-15978453
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ASF GitHub Bot commented on FLINK-6290:
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Github user StephanEwen commented on the issue:
https://github.com/apache/flink/pull/3706
Thanks for the patch @dawidwys - good fix, nice test.
Merging this...
> SharedBuffer is improperly released when multiple edges between entries
> -----------------------------------------------------------------------
>
> Key: FLINK-6290
> URL: https://issues.apache.org/jira/browse/FLINK-6290
> Project: Flink
> Issue Type: Bug
> Components: CEP
> Affects Versions: 1.3.0
> Reporter: Dawid Wysakowicz
> Assignee: Dawid Wysakowicz
> Priority: Critical
> Fix For: 1.3.0
>
>
> Below test right now fails:
> {code}
> @Test
> public void testClearingSharedBufferWithMultipleEdgesBetweenEntries() {
> SharedBuffer<String, Event> sharedBuffer = new
> SharedBuffer<>(Event.createTypeSerializer());
> int numberEvents = 8;
> Event[] events = new Event[numberEvents];
> final long timestamp = 1L;
> for (int i = 0; i < numberEvents; i++) {
> events[i] = new Event(i + 1, "e" + (i + 1), i);
> }
> sharedBuffer.put("start", events[1], timestamp,
> DeweyNumber.fromString("1"));
> sharedBuffer.put("branching", events[2], timestamp, "start",
> events[1], timestamp, DeweyNumber.fromString("1.0"));
> sharedBuffer.put("branching", events[3], timestamp, "start",
> events[1], timestamp, DeweyNumber.fromString("1.1"));
> sharedBuffer.put("branching", events[3], timestamp,
> "branching", events[2], timestamp, DeweyNumber.fromString("1.0.0"));
> sharedBuffer.put("branching", events[4], timestamp,
> "branching", events[3], timestamp, DeweyNumber.fromString("1.0.0.0"));
> sharedBuffer.put("branching", events[4], timestamp,
> "branching", events[3], timestamp, DeweyNumber.fromString("1.1.0"));
> //simulate IGNORE (next event can point to events[2])
> sharedBuffer.lock("branching", events[2], timestamp);
> sharedBuffer.release("branching", events[4], timestamp);
> //There should be still events[1] and events[2] in the buffer
> assertFalse(sharedBuffer.isEmpty());
> }
> {code}
> The problem is with the {{SharedBuffer#internalRemove}} method:
> {code}
> private void internalRemove(final SharedBufferEntry<K, V> entry) {
> Stack<SharedBufferEntry<K, V>> entriesToRemove = new Stack<>();
> entriesToRemove.add(entry);
> while (!entriesToRemove.isEmpty()) {
> SharedBufferEntry<K, V> currentEntry =
> entriesToRemove.pop();
> if (currentEntry.getReferenceCounter() == 0) {
> currentEntry.remove();
> for (SharedBufferEdge<K, V> edge:
> currentEntry.getEdges()) {
> if (edge.getTarget() != null) {
>
> edge.getTarget().decreaseReferenceCounter();
>
> entriesToRemove.push(edge.getTarget());
> }
> }
> }
> }
> }
> {code}
> When currentEntry has multiple edges to the same entry. The entry will be
> added twice to the entriesToRemove and it's edges will be removed twice and
> the second edge can potentially change the referenceCounter for both of those
> entries to 0. Resulting in removing this entry twice.
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