Re: Trying to figure out why a slot takes a long time to checkpoint

Posted by Till Rohrmann on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Trying-to-figure-out-why-a-slot-takes-a-long-time-to-checkpoint-tp23108p23172.html

This behavior seems very odd Julio. Could you indeed share the debug logs of all Flink processes in order to see why things are taking so long?

The checkpoint size of task #8 is twice as big as the second biggest checkpoint. But this should not cause an increase in checkpoint time of a factor of 8.

Cheers,

Till

On Mon, Sep 17, 2018 at 5:25 AM Renjie Liu <[hidden email]> wrote:

Hi, Julio:

This happens frequently? What state backend do you use? The async checkpoint duration and sync checkpoint duration seems normal compared to others, it seems that most of the time are spent acking the checkpoint.

On Sun, Sep 16, 2018 at 9:24 AM vino yang <[hidden email]> wrote:

Hi Julio,

Yes, it seems that fifty-five minutes is really long. 

However, it is linear with the time and size of the previous task adjacent to it in the diagram. 

I think your real application is concerned about why Flink accesses HDFS so slowly. 

You can call the DEBUG log to see if you can find any clues, or post the log to the mailing list to help others analyze the problem for you.

Thanks, vino.

Julio Biason <[hidden email]> 于2018年9月15日周六 上午7:03写道：

(Just an addendum: Although it's not a huge problem -- we can always increase the checkpoint timeout time -- this anomalous situation makes me think there is something wrong in our pipeline or in our cluster, and that is what is making the checkpoint creation go crazy.)

On Fri, Sep 14, 2018 at 8:00 PM, Julio Biason <[hidden email]> wrote:

Hey guys,

On our pipeline, we have a single slot that it's taking longer to create the checkpoint compared to other slots and we are wondering what could be causing it.

The operator in question is the window metric -- the only element in the pipeline that actually uses the state. While the other slots take 7 mins to create the checkpoint, this one -- and only this one -- takes 55mins.

Is there something I should look at to understand what's going on?

(We are storing all checkpoints in HDFS, in case that helps.)

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