Re: Fault tolerance guarantees of Elasticsearch sink in flink-elasticsearch2?

Posted by Tzu-Li (Gordon) Tai on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Fault-tolerance-guarantees-of-Elasticsearch-sink-in-flink-elasticsearch2-tp10982p11132.html

Hi Andrew!

There’s nothing special about extending the checkpointing interfaces for the SinkFunction; for Flink they’re essentially user functions that have user state to be checkpointed.

So yes, you’ll just implement is as you would for a flatMap / map / etc. function.

Fell free to let me know if you bump into any questions.

Cheers,

Gordon

On January 16, 2017 at 11:37:30 PM, Andrew Roberts ([hidden email]) wrote:

Hi Gordon,

Thanks for getting back to me. The ticket looks good, but I’m going to need to do something similar for our homegrown sinks. It sounds like just having the affected sinks participate in checkpointing is enough of a solution - is there anything special about `SinkFunction[T]` extending `Checkpointed[S]`, or can I just implement it as I would for e.g. a mapping function?

Thanks,

Andrew

On Jan 13, 2017, at 4:34 PM, Tzu-Li (Gordon) Tai <[hidden email]> wrote:

Hi Andrew,

Your observations are correct. Like you mentioned, the current problem circles around how we deal with the pending buffered requests with accordance to Flink’s checkpointing.

I’ve filed a JIRA for this, as well as some thoughts for the solution in the description: https://issues.apache.org/jira/browse/FLINK-5487. What do you think?

Thank you for bringing this up! We should probably fix this soon.

There’s already some on-going effort in fixing some other aspects of proper at-least-once support in the Elasticsearch sinks, so I believe this will be brought to attention very soon too.

Cheers,

Gordon

On January 11, 2017 at 3:49:06 PM, Andrew Roberts ([hidden email]) wrote:

I’m trying to understand the guarantees made by Flink’s Elasticsearch sink in terms of message delivery. according to (1), the ES sink offers at-least-once guarantees. This page doesn’t differentiate between flink-elasticsearch and flink-elasticsearch2, so I have to assume for the moment that they both offer that guarantee. However, a look at the code (2) shows that the invoke() method puts the record into a buffer, and then that buffer is flushed to elasticsearch some time later.