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From Josh <jof...@gmail.com>
Subject Re: ExpiredIteratorException when reading from a Kinesis stream
Date Thu, 03 Nov 2016 14:08:13 GMT
Hi Gordon,

Thanks for the fast reply!
You're right about the expired iterator exception occurring just before
each spike. I can't see any signs of long GC on the task managers... CPU
has been <15% the whole time when the spikes were taking place and I can't
see anything unusual in the task manager logs.

But actually I just noticed that the Flink UI showed no successful
checkpoints during the time of the problem even though my checkpoint
interval is 15 minutes. So I guess this is probably some kind of Flink
problem rather than a problem with the Kinesis consumer. Unfortunately I
can't find anything useful in the logs so not sure what happened!


On Thu, Nov 3, 2016 at 12:44 PM, Tzu-Li (Gordon) Tai <tzulitai@apache.org>

> Hi Josh,
> That warning message was added as part of FLINK-4514. It pops out whenever
> a shard iterator was used after 5 minutes it was returned from Kinesis.
> The only time spent between after a shard iterator was returned and before
> it was used to fetch the next batch of records, is on deserializing and
> emitting of the records of the last fetched batch.
> So unless processing of the last fetched batch took over 5 minutes, this
> normally shouldn’t happen.
> Have you noticed any sign of long, constant full GC for your Flink task
> managers? From your description and check in code, the only possible guess
> I can come up with now is that
> the source tasks completely seized to be running for a period of time, and
> when it came back, the shard iterator was unexpectedly found to be expired.
> According to the graph you attached,
> when the iterator was refreshed and tasks successfully fetched a few more
> batches, the source tasks again halted, and so on.
> So you should see that same warning message right before every small peak
> within the graph.
> Best Regards,
> Gordon
> On November 3, 2016 at 7:46:42 PM, Josh (jofo90@gmail.com) wrote:
> Hey Gordon,
> I've been using Flink 1.2-SNAPSHOT for the past week (with FLINK-4514)
> with no problems, but yesterday the Kinesis consumer started behaving
> strangely... My Kinesis data stream is fairly constant at around 1.5MB/sec,
> however the Flink Kinesis consumer started to stop consuming for periods of
> time (see the spikes in graph attached which shows data consumed by the
> Flink Kinesis consumer)
> Looking in the task manager logs, there are no exceptions however there is
> this log message which I believe is related to the problem:
> 2016-11-03 09:27:53,782 WARN  org.apache.flink.streaming.
> connectors.kinesis.internals.ShardConsumer  - Encountered an unexpected
> expired iterator AAAAAAAAAAF8OJyh+X3yBnbtzUgIfXv+phS7PKppd7q09/
> tduXG3lOhCmBGPUOlZul24tzSSM6KjHsQ+AbZY8MThKcSvGax/
> EoOIYoTELYbZmuwY4hgeqUsndxLIM0HL55iejroBV8YFmUmGwHsW8qkHsz//
> Ci4cxcLrGArHex3n+4E+aoZ9AtgTPEZOBjXY49g+VGsDb0bQN5FJUoUVEfnbupk96ore for
> shard KinesisStreamShard{streamName='stream001', shard='{ShardId:
> shardId-000000000000,HashKeyRange: {StartingHashKey: 0,EndingHashKey:
> 85070511730234615865841151857942042863},SequenceNumberRange:
> {StartingSequenceNumber: 495665429169236488921642479266
> 79091159472198219567464450,}}'}; refreshing the iterator ...
> Having restarted the job from my last savepoint, it's consuming the stream
> fine again with no problems.
> Do you have any idea what might be causing this, or anything I should do
> to investigate further?
> Cheers,
> Josh
> On Wed, Oct 5, 2016 at 4:55 AM, Tzu-Li (Gordon) Tai <tzulitai@apache.org>
> wrote:
>> Hi Steffen,
>> Turns out that FLINK-4514 just missed Flink 1.1.2 and wasn’t included in
>> the release (I’ll update the resolve version in JIRA to 1.1.3, thanks for
>> noticing this!).
>> The Flink community is going to release 1.1.3 asap, which will include
>> the fix.
>> If you don’t want to wait for the release and want to try the fix now,
>> you can also build on the current “release-1.1” branch, which already has
>> FLINK-4514 merged.
>> Sorry for the inconvenience. Let me know if you bump into any other
>> problems afterwards.
>> Best Regards,
>> Gordon
>> On October 5, 2016 at 2:56:21 AM, Steffen Hausmann (
>> steffen@hausmann-family.de) wrote:
>> Hi there,
>> I'm running a Flink 1.1.2 job on EMR and Yarn that is reading events
>> from a Kinesis stream. However, after a while (the exact duration varies
>> and is in the order of minutes) the Kinesis source doesn't emit any
>> further events and hence Flink doesn't produce any further output.
>> Eventually, an ExpiredIteratorException occurs in one of the task,
>> causing the entire job to fail:
>> > com.amazonaws.services.kinesis.model.ExpiredIteratorException:
>> Iterator expired. The iterator was created at time Mon Oct 03 18:40:30 UTC
>> 2016 while right now it is Mon Oct 03 18:45:33 UTC 2016 which is further in
>> the future than the tolerated delay of 300000 milliseconds. (Service:
>> AmazonKinesis; Status Code: 400; Error Code: ExpiredIteratorException;
>> Request ID: dace9532-9031-54bc-8aa2-3cbfb136d590)
>> This seems to be related to FLINK-4514, which is marked as resovled for
>> Flink 1.1.2. In contrast to what is describe in the ticket, the job I'm
>> running isn't suspended but hangs just a few minutes after the job has
>> been started.
>> I've attached a log file showing the described behavior.
>> Any idea what may be wrong?
>> Thanks,
>> Steffen

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