Hi

From the description and the given figure. the e2e time for one task is longer than $time{sync-snapshot} + $time{async-snapshot}. 
For at least once mode, could you please try to enable the debug log to track the barrier align process?
you can find the debug log such as
"Received barrier for checkpoint {} from channel {}"
"Received cancellation barrier for checkpoint {} "
"Received all barriers for checkpoint {}"

Best,
Congxian


Yun Tang <myasuka@live.com> 于2020年6月19日周五 上午11:48写道:
Hi Sandeep

At-least-once checkpoint mode would not need to align barrier and the longer end-to-end duration is mainly due to barrier cannot be processed by operator as soon as possible.
Operator will only start checkpoint after processed checkpoint barrier, I think you might need to check the back-pressure status of your job[1].
Back-pressure would make the checkpoint barrier move to downstream more slowly in the network channels.

[1] https://ci.apache.org/projects/flink/flink-docs-stable/monitoring/back_pressure.html#back-pressure

Best
Yun Tang

From: Kathula, Sandeep <Sandeep_Kathula@intuit.com>
Sent: Friday, June 19, 2020 9:19
To: user@flink.apache.org <user@flink.apache.org>
Cc: Vora, Jainik <Jainik_Vora@intuit.com>; Rosensweig, JD <JD_Rosensweig@intuit.com>
Subject: S3 Checkpointing taking long time with stateful operations
 

Hi,

We are running a stateful application in Flink with RocksDB as backend and set incremental state to true with checkpoints written to S3

  • 10 task managers each with 2 task slots
  • Checkpoint interval 3 minutes
  • Checkpointing mode – At-least once processing

 

After running app for 2-3 days, we are seeing end to end checkpoint takes almost 2 minutes with Sync time 2 sec and async time 15 sec max. But initially when state is less, it takes 10-15 sec for checkpointing. As checkpointing mode is at least once, align duration is 0. We are seeing a dip in processing during this time. Couldn’t find out what the actual issue is. 

 

We also tried with remote HDFS for checkpointing but observed similar behavior. 

 

We have couple of questions:

  • When sync time is max 2 sec and async time is 15 sec why is end to end checkpointing taking almost 2 minutes?
  • How can we reduce the checkpoint time?

A screenshot of a cell phone

Description automatically generated

 

Any help would be appreciated.

 

 

Thank you

Sandeep Kathula