[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[asfgit]

Github user asfgit closed the pull request at:

https://github.com/apache/flink/pull/3644


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[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[kl0u]

Github user kl0u commented on a diff in the pull request:

https://github.com/apache/flink/pull/3644#discussion_r108958127
  
--- Diff: 
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/operator/AbstractKeyedCEPPatternOperator.java
 ---
@@ -196,19 +213,45 @@ public void processElement(StreamRecord element) 
throws Exception {
updateNFA(nfa);
 
} else {
-   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
 
-   PriorityQueue priorityQueue = 
getPriorityQueue();
+   // In event-time processing we assume correctness of 
the watermark.
+   // Events with timestamp smaller than the last seen 
watermark are considered late.
+   // Late events are put in a dedicated side output, if 
the user has specified one.
+
+   if (element.getTimestamp() >= lastWatermark) {
 
-   // event time processing
-   // we have to buffer the elements until we receive the 
proper watermark
-   if (getExecutionConfig().isObjectReuseEnabled()) {
-   // copy the StreamRecord so that it cannot be 
changed
-   priorityQueue.offer(new 
StreamRecord(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   // we have an event with a valid timestamp, so
+   // we buffer it until we receive the proper 
watermark.
+
+   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
+
+   PriorityQueue priorityQueue = 
getPriorityQueue();
+   if 
(getExecutionConfig().isObjectReuseEnabled()) {
+   // copy the StreamRecord so that it 
cannot be changed
+   priorityQueue.offer(new 
StreamRecord<>(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   } else {
+   priorityQueue.offer(element);
+   }
+   updatePriorityQueue(priorityQueue);
} else {
-   priorityQueue.offer(element);
+   sideOutputLateElement(element);
}
-   updatePriorityQueue(priorityQueue);
+   }
+   }
+
+   private void updateLastSeenWatermark(Watermark watermark) {
+   this.lastWatermark = watermark.getTimestamp();
--- End diff --

I believe that the `Watermark` handling should be the responsibility of the 
sources. Checkpointing it here would mean special logic for handling it in case 
of scaling down for example. In addition, when scaling down e.g from 2 tasks to 
1 and the 2 tasks had different last watermarks, then we still may have issues 
with elements being processed out-of-order.


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[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[dawidwys]

Github user dawidwys commented on a diff in the pull request:

https://github.com/apache/flink/pull/3644#discussion_r108866698
  
--- Diff: 
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/operator/AbstractKeyedCEPPatternOperator.java
 ---
@@ -196,19 +213,45 @@ public void processElement(StreamRecord element) 
throws Exception {
updateNFA(nfa);
 
} else {
-   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
 
-   PriorityQueue priorityQueue = 
getPriorityQueue();
+   // In event-time processing we assume correctness of 
the watermark.
+   // Events with timestamp smaller than the last seen 
watermark are considered late.
+   // Late events are put in a dedicated side output, if 
the user has specified one.
+
+   if (element.getTimestamp() >= lastWatermark) {
 
-   // event time processing
-   // we have to buffer the elements until we receive the 
proper watermark
-   if (getExecutionConfig().isObjectReuseEnabled()) {
-   // copy the StreamRecord so that it cannot be 
changed
-   priorityQueue.offer(new 
StreamRecord(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   // we have an event with a valid timestamp, so
+   // we buffer it until we receive the proper 
watermark.
+
+   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
+
+   PriorityQueue priorityQueue = 
getPriorityQueue();
+   if 
(getExecutionConfig().isObjectReuseEnabled()) {
+   // copy the StreamRecord so that it 
cannot be changed
+   priorityQueue.offer(new 
StreamRecord<>(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   } else {
+   priorityQueue.offer(element);
+   }
+   updatePriorityQueue(priorityQueue);
} else {
-   priorityQueue.offer(element);
+   sideOutputLateElement(element);
}
-   updatePriorityQueue(priorityQueue);
+   }
+   }
+
+   private void updateLastSeenWatermark(Watermark watermark) {
+   this.lastWatermark = watermark.getTimestamp();
--- End diff --

Anyway would be nice to see a testcase like watermark(10) 
restoreFromCheckpoint event(7)


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[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[dawidwys]

Github user dawidwys commented on a diff in the pull request:

https://github.com/apache/flink/pull/3644#discussion_r108741567
  
--- Diff: 
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/operator/AbstractKeyedCEPPatternOperator.java
 ---
@@ -196,19 +213,45 @@ public void processElement(StreamRecord element) 
throws Exception {
updateNFA(nfa);
 
} else {
-   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
 
-   PriorityQueue priorityQueue = 
getPriorityQueue();
+   // In event-time processing we assume correctness of 
the watermark.
+   // Events with timestamp smaller than the last seen 
watermark are considered late.
+   // Late events are put in a dedicated side output, if 
the user has specified one.
+
+   if (element.getTimestamp() >= lastWatermark) {
 
-   // event time processing
-   // we have to buffer the elements until we receive the 
proper watermark
-   if (getExecutionConfig().isObjectReuseEnabled()) {
-   // copy the StreamRecord so that it cannot be 
changed
-   priorityQueue.offer(new 
StreamRecord(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   // we have an event with a valid timestamp, so
+   // we buffer it until we receive the proper 
watermark.
+
+   
getInternalWatermarkCallbackService().registerKeyForWatermarkCallback(keySelector.getKey(element.getValue()));
+
+   PriorityQueue priorityQueue = 
getPriorityQueue();
+   if 
(getExecutionConfig().isObjectReuseEnabled()) {
+   // copy the StreamRecord so that it 
cannot be changed
+   priorityQueue.offer(new 
StreamRecord<>(inputSerializer.copy(element.getValue()), 
element.getTimestamp()));
+   } else {
+   priorityQueue.offer(element);
+   }
+   updatePriorityQueue(priorityQueue);
} else {
-   priorityQueue.offer(element);
+   sideOutputLateElement(element);
}
-   updatePriorityQueue(priorityQueue);
+   }
+   }
+
+   private void updateLastSeenWatermark(Watermark watermark) {
+   this.lastWatermark = watermark.getTimestamp();
--- End diff --

Shouldn't the lastWatermark be stored in a StateBackend? How will it behave 
after restoring from a checkpoint?


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[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[dawidwys]

Github user dawidwys commented on a diff in the pull request:

https://github.com/apache/flink/pull/3644#discussion_r108742662
  
--- Diff: docs/dev/libs/cep.md ---
@@ -711,6 +711,57 @@ DataStream[Either[TimeoutEvent, ComplexEvent]] result 
= patternStream.flatSelect
 
 
 
+### Handling Lateness in Event Time
+
+In `CEP` the order in which elements are processed matters. To this end 
and when working in event time, an incoming 
--- End diff --

I don't get the first part of the sentence : "To this end and when working 
in event time"


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[GitHub] flink pull request #3644: [FLINK-6205] [FLINK-6069] [cep] Correct watermark/...

[kl0u]

GitHub user kl0u opened a pull request:

https://github.com/apache/flink/pull/3644

[FLINK-6205] [FLINK-6069] [cep] Correct watermark/late events in side-output

With this, the CEP library assumes correctness of the watermark
and considers as late, events that arrive having a timestamp
smaller than that of the last seen watermark. Late events are not
silently dropped, but the user can specify to send them to a side
output.

You can merge this pull request into a Git repository by running:

$ git pull https://github.com/kl0u/flink late-element-cep

Alternatively you can review and apply these changes as the patch at:

https://github.com/apache/flink/pull/3644.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

This closes #3644


commit 827bd85916206e36ed23564e77e5ff119bfadead
Author: kl0u 
Date:   2017-03-23T18:01:15Z

[FLINK-6205] [FLINK-6069] [cep] Correct watermark/late events in side 
output.

With this, the CEP library assumes correctness of the watermark
and considers as late, events that arrive having a timestamp
smaller than that of the last seen watermark. Late events are not
silently dropped, but the user can specify to send them to a side
output.




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