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From ÇETİNKAYA EBRU ÇETİNKAYA EBRU <b20926...@cs.hacettepe.edu.tr>
Subject Re: Flink memory leak
Date Wed, 08 Nov 2017 08:51:04 GMT
On 2017-11-07 16:53, Ufuk Celebi wrote:
> Do you use any windowing? If yes, could you please share that code? If
> there is no stateful operation at all, it's strange where the list
> state instances are coming from.
> 
> On Tue, Nov 7, 2017 at 2:35 PM, ebru <b20926247@cs.hacettepe.edu.tr> 
> wrote:
>> Hi Ufuk,
>> 
>> We don’t explicitly define any state descriptor. We only use map and 
>> filters
>> operator. We thought that gc handle clearing the flink’s internal 
>> states.
>> So how can we manage the memory if it is always increasing?
>> 
>> - Ebru
>> 
>> On 7 Nov 2017, at 16:23, Ufuk Celebi <uce@apache.org> wrote:
>> 
>> Hey Ebru, the memory usage might be increasing as long as a job is 
>> running.
>> This is expected (also in the case of multiple running jobs). The
>> screenshots are not helpful in that regard. :-(
>> 
>> What kind of stateful operations are you using? Depending on your use 
>> case,
>> you have to manually call `clear()` on the state instance in order to
>> release the managed state.
>> 
>> Best,
>> 
>> Ufuk
>> 
>> On Tue, Nov 7, 2017 at 12:43 PM, ebru <b20926247@cs.hacettepe.edu.tr> 
>> wrote:
>>> 
>>> 
>>> 
>>> Begin forwarded message:
>>> 
>>> From: ebru <b20926247@cs.hacettepe.edu.tr>
>>> Subject: Re: Flink memory leak
>>> Date: 7 November 2017 at 14:09:17 GMT+3
>>> To: Ufuk Celebi <uce@apache.org>
>>> 
>>> Hi Ufuk,
>>> 
>>> There are there snapshots of htop output.
>>> 1. snapshot is initial state.
>>> 2. snapshot is after submitted one job.
>>> 3. Snapshot is the output of the one job with 15000 EPS. And the 
>>> memory
>>> usage is always increasing over time.
>>> 
>>> 
>>> 
>>> 
>>> <1.png><2.png><3.png>
>>> 
>>> On 7 Nov 2017, at 13:34, Ufuk Celebi <uce@apache.org> wrote:
>>> 
>>> Hey Ebru,
>>> 
>>> let me pull in Aljoscha (CC'd) who might have an idea what's causing 
>>> this.
>>> 
>>> Since multiple jobs are running, it will be hard to understand to
>>> which job the state descriptors from the heap snapshot belong to.
>>> - Is it possible to isolate the problem and reproduce the behaviour
>>> with only a single job?
>>> 
>>> – Ufuk
>>> 
>>> 
>>> On Tue, Nov 7, 2017 at 10:27 AM, ÇETİNKAYA EBRU ÇETİNKAYA EBRU
>>> <b20926247@cs.hacettepe.edu.tr> wrote:
>>> 
>>> Hi,
>>> 
>>> We are using Flink 1.3.1 in production, we have one job manager and 3 
>>> task
>>> managers in standalone mode. Recently, we've noticed that we have 
>>> memory
>>> related problems. We use docker container to serve Flink cluster. We 
>>> have
>>> 300 slots and 20 jobs are running with parallelism of 10. Also the 
>>> job
>>> count
>>> may be change over time. Taskmanager memory usage always increases. 
>>> After
>>> job cancelation this memory usage doesn't decrease. We've tried to
>>> investigate the problem and we've got the task manager jvm heap 
>>> snapshot.
>>> According to the jam heap analysis, possible memory leak was Flink 
>>> list
>>> state descriptor. But we are not sure that is the cause of our memory
>>> problem. How can we solve the problem?
>>> 
>>> 
>>> 
>> We have two types of Flink job. One has no state full operator 
>> contains only maps and filters and the other has time window with 
>> count trigger.
* We've analysed the jvm heaps again in different conditions. First we 
analysed the snapshot when no flink jobs running on cluster. (image 1)
* Then, we analysed the jvm heap snapshot when the flink job that has no 
state full operator is running. And according to the results, leak 
suspect was NetworkBufferPool (image 2)
*   Last analys, there were both two types of jobs running and leak 
suspect was again NetworkBufferPool. (image 3)
In our system jobs are regularly cancelled and resubmitted so we noticed 
that when job is submitted some amount of memory allocated and after 
cancelation this allocated memory never freed. So over time memory usage 
is always increasing and exceeded the limits.
>> 
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