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From Tony Wei <tony19920...@gmail.com>
Subject Re: Stream Task seems to be blocked after checkpoint timeout
Date Thu, 28 Sep 2017 06:18:57 GMT
Hi Stefan,

The checkpoint on my job has been subsumed again. There are some questions
that I don't understand.

Log in JM :
2017-09-27 13:45:15,686 INFO
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Completed checkpoint 1576 (174693180 bytes in 21597 ms).
2017-09-27 13:49:42,795 INFO
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Triggering checkpoint 1577 @ 1506520182795
2017-09-27 13:54:42,795 INFO
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Triggering checkpoint 1578 @ 1506520482795
2017-09-27 13:55:13,105 INFO
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Completed checkpoint 1578 (152621410 bytes in 19109 ms).
2017-09-27 13:56:37,103 WARN
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Received late message for now expired checkpoint attempt 1577 from
2273da50f29b9dee731f7bd749e91c80 of job 7c039572b....
2017-09-27 13:59:42,795 INFO
org.apache.flink.runtime.checkpoint.CheckpointCoordinator
- Triggering checkpoint 1579 @ 1506520782795

Log in TM:
2017-09-27 13:56:37,105 INFO
org.apache.flink.runtime.state.DefaultOperatorStateBackend
- DefaultOperatorStateBackend snapshot (File Stream Factory @
s3://tony-dev/flink-checkpoints/7c039572b13346f1b17dcc0ace2b72c2,
asynchronous part) in thread Thread[pool-7-thread-322,5,Flink Task Threads]
took 240248 ms.

I think the log in TM might be the late message for #1577 in JM, because
#1576, #1578 had been finished and #1579 hadn't been started at 13:56:37.
If there is no mistake on my words, I am wondering why the time it took was
240248 ms (4 min). It seems that it started late than asynchronous tasks in
#1578.
Is there any way to guarantee the previous asynchronous parts of
checkpoints will be executed before the following.

Moreover, I think it will be better to have more information in INFO log,
such as waiting time and checkpoint id, in order to trace the progress of
checkpoint conveniently.

What do you think? Do you have any suggestion for me to deal with these
problems? Thank you.

Best Regards,
Tony Wei

2017-09-27 17:11 GMT+08:00 Tony Wei <tony19920430@gmail.com>:

> Hi Stefan,
>
> Here is the summary for my streaming job's checkpoint after restarting at
> last night.
>
> [image: 內置圖片 1]
>
> This is the distribution of alignment buffered from the last 12 hours.
>
> [image: 內置圖片 3]
>
> And here is the buffer out pool usage during chk #1140 ~ #1142. For chk
> #1245 and #1246, you can check the picture I sent before.
>
>  [image: 內置圖片 2]
>
> AFAIK, the back pressure rate usually is in LOW status, sometimes goes up
> to HIGH, and always OK during the night.
>
> Best Regards,
> Tony Wei
>
>
> 2017-09-27 16:54 GMT+08:00 Stefan Richter <s.richter@data-artisans.com>:
>
>> Hi Tony,
>>
>> are your checkpoints typically close to the timeout boundary? From what I
>> see, writing the checkpoint is relatively fast but the time from the
>> checkpoint trigger to execution seems very long. This is typically the case
>> if your job has a lot of backpressure and therefore the checkpoint barriers
>> take a long time to travel to the operators, because a lot of events are
>> piling up in the buffers. Do you also experience large alignments for your
>> checkpoints?
>>
>> Best,
>> Stefan
>>
>> Am 27.09.2017 um 10:43 schrieb Tony Wei <tony19920430@gmail.com>:
>>
>> Hi Stefan,
>>
>> It seems that I found something strange from JM's log.
>>
>> It had happened more than once before, but all subtasks would finish
>> their checkpoint attempts in the end.
>>
>> 2017-09-26 01:23:28,690 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Triggering checkpoint 1140 @ 1506389008690
>> 2017-09-26 01:28:28,690 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Triggering checkpoint 1141 @ 1506389308690
>> 2017-09-26 01:33:28,690 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Triggering checkpoint 1142 @ 1506389608690
>> 2017-09-26 01:33:28,691 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Checkpoint 1140 expired before completing.
>> 2017-09-26 01:38:28,691 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Checkpoint 1141 expired before completing.
>> 2017-09-26 01:40:38,044 WARN org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Received late message for now expired checkpoint attempt 1140 from
>> c63825d15de0fef55a1d148adcf4467e of job 7c039572b...
>> 2017-09-26 01:40:53,743 WARN org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Received late message for now expired checkpoint attempt 1141 from
>> c63825d15de0fef55a1d148adcf4467e of job 7c039572b...
>> 2017-09-26 01:41:19,332 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Completed checkpoint 1142 (136733704 bytes in 457413 ms).
>>
>> For chk #1245 and #1246, there was no late message from TM. You can refer
>> to the TM log. The full completed checkpoint attempt will have 12
>> (... asynchronous part) logs in general, but #1245 and #1246 only got 10
>> logs.
>>
>> 2017-09-26 10:08:28,690 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Triggering checkpoint 1245 @ 1506420508690
>> 2017-09-26 10:13:28,690 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Triggering checkpoint 1246 @ 1506420808690
>> 2017-09-26 10:18:28,691 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Checkpoint 1245 expired before completing.
>> 2017-09-26 10:23:28,691 INFO org.apache.flink.runtime.checkpoint.CheckpointCoordinator
>> - Checkpoint 1246 expired before completing.
>>
>> Moreover, I listed the directory for checkpoints on S3 and saw there were
>> two states not discarded successfully. In general, there will be 16 parts
>> for a completed checkpoint state.
>>
>> 2017-09-26 18:08:33 36919 tony-dev/flink-checkpoints/7c0
>> 39572b13346f1b17dcc0ace2b72c2/chk-1245/eedd7ca5-ee34-45a5-
>> bf0b-11cc1fc67ab8
>> 2017-09-26 18:13:34 37419 tony-dev/flink-checkpoints/7c0
>> 39572b13346f1b17dcc0ace2b72c2/chk-1246/9aa5c6c4-8c74-465d-
>> 8509-5fea4ed25af6
>>
>> Hope these informations are helpful. Thank you.
>>
>> Best Regards,
>> Tony Wei
>>
>> 2017-09-27 16:14 GMT+08:00 Stefan Richter <s.richter@data-artisans.com>:
>>
>>> Hi,
>>>
>>> thanks for the information. Unfortunately, I have no immediate idea what
>>> the reason is from the given information. I think most helpful could be a
>>> thread dump, but also metrics on the operator operator level to figure out
>>> which part of the pipeline is the culprit.
>>>
>>> Best,
>>> Stefan
>>>
>>> Am 26.09.2017 um 17:55 schrieb Tony Wei <tony19920430@gmail.com>:
>>>
>>> Hi Stefan,
>>>
>>> There is no unknown exception in my full log. The Flink version is 1.3.2.
>>> My job is roughly like this.
>>>
>>> env.addSource(Kafka)
>>>   .map(ParseKeyFromRecord)
>>>   .keyBy()
>>>   .process(CountAndTimeoutWindow)
>>>   .asyncIO(UploadToS3)
>>>   .addSink(UpdateDatabase)
>>>
>>> It seemed all tasks stopped like the picture I sent in the last email.
>>>
>>> I will keep my eye on taking a thread dump from that JVM if this happens
>>> again.
>>>
>>> Best Regards,
>>> Tony Wei
>>>
>>> 2017-09-26 23:46 GMT+08:00 Stefan Richter <s.richter@data-artisans.com>:
>>>
>>>> Hi,
>>>>
>>>> that is very strange indeed. I had a look at the logs and there is no
>>>> error or exception reported. I assume there is also no exception in your
>>>> full logs? Which version of flink are you using and what operators were
>>>> running in the task that stopped? If this happens again, would it be
>>>> possible to take a thread dump from that JVM?
>>>>
>>>> Best,
>>>> Stefan
>>>>
>>>> > Am 26.09.2017 um 17:08 schrieb Tony Wei <tony19920430@gmail.com>:
>>>> >
>>>> > Hi,
>>>> >
>>>> > Something weird happened on my streaming job.
>>>> >
>>>> > I found my streaming job seems to be blocked for a long time and I
>>>> saw the situation like the picture below. (chk #1245 and #1246 were all
>>>> finishing 7/8 tasks then marked timeout by JM. Other checkpoints failed
>>>> with the same state like #1247 util I restarted TM.)
>>>> >
>>>> > <snapshot.png>
>>>> >
>>>> > I'm not sure what happened, but the consumer stopped fetching
>>>> records, buffer usage is 100% and the following task did not seem to fetch
>>>> data anymore. Just like the whole TM was stopped.
>>>> >
>>>> > However, after I restarted TM and force the job restarting from the
>>>> latest completed checkpoint, everything worked again. And I don't know how
>>>> to reproduce it.
>>>> >
>>>> > The attachment is my TM log. Because there are many user logs and
>>>> sensitive information, I only remain the log from `org.apache.flink...`.
>>>> >
>>>> > My cluster setting is one JM and one TM with 4 available slots.
>>>> >
>>>> > Streaming job uses all slots, checkpoint interval is 5 mins and max
>>>> concurrent number is 3.
>>>> >
>>>> > Please let me know if it needs more information to find out what
>>>> happened on my streaming job. Thanks for your help.
>>>> >
>>>> > Best Regards,
>>>> > Tony Wei
>>>> > <flink-root-taskmanager-0-partial.log>
>>>>
>>>>
>>>
>>>
>>
>>
>

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