Re: Memory reclaim problem on Flink Kubernetes pods

Posted by Vinay Patil on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Memory-reclaim-problem-on-Flink-Kubernetes-pods-tp37042p37075.html

Hi Till,

Sure, I will share the logs with you once I run in preprod env. In prod, we are able to reproduce it always.

For now we have shifted to FSStateBackend as the state size is under 1GB. 

> Have you tried whether the same problem occurs with Flink 1.11.1 as well

No, will give it a try in preprod env.

On Thu, Jul 30, 2020 at 3:10 PM Till Rohrmann <[hidden email]> wrote:

Hi Vinay and Akshay,

could you share the logs of the cluster with us? Ideally on DEBUG level if possible. This would help to debug the problem. Have you tried whether the same problem occurs with Flink 1.11.1 as well?

Cheers,

Till

On Thu, Jul 30, 2020 at 11:30 AM Akshay Aggarwal <[hidden email]> wrote:

Hi, We are facing a similar issue in Yarn even with Flink 1.10, the only workaround we have figured is to kill the YARN session before restarting the job. 

~Akshay

On Thu, Jul 30, 2020 at 2:55 PM Vinay Patil <[hidden email]> wrote:

Hi,

Can someone please help here , is it expected that the memory will not go down even after the job is killed. We always have to restart the pods because of this issue.

Since the state size is under 1Gb , I will try with FSStatebackend. But I want to understand why this is the case - I had faced the same issue earlier on YARN - https://issues.apache.org/jira/browse/FLINK-7289  which is fixed in version 1.10

Regards,

Vinay Patil

On Wed, Jul 29, 2020 at 6:55 PM Vinay Patil <[hidden email]> wrote:

Hi Team,

We are facing an issue where the memory is not reclaimed after the job is cancelled on the K8 session cluster, the pods were entirely used by a single job only. So, after re-submitting the same job it fails immediately. We are using RocksDb state backend where the state size is fairly small ranging from 800MB to 1GB. 

Cluster Configurations: Flink 1.10.1 version

8 TM pods with 4 slots each and 16Gb per pod. 

Memory Fraction ratio : 0.6

Few Observations/Concerns:

1.I have observed a weird issue where the memory usage goes beyond 16Gb for the pod , attaching a screenshot in-line.

2. Plotted a graph for `flink_taskmanager_Status_JVM_Memory_NonHeap_Used` and it is under 300MB per pod

3. We thought if there is any memory leak that is causing this to happen but there is normal GC activity going on and TM heap usage is under control

Am I missing any obvious configuration to be set ? 

Regards,

Vinay Patil

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