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From Jason Brelloch <jb.bc....@gmail.com>
Subject Tuning RocksDB
Date Wed, 03 May 2017 14:46:42 GMT
Hey all,

I am looking for some advice on tuning rocksDB for better performance in
Flink 1.2.  I created a pretty simple job with a single kafka source and
one flatmap function that just stores 50000 events in a single key of
managed keyed state and then drops everything else, to test checkpoint
performance.  Using a basic FsStateBackend configured as:

val backend = new FsStateBackend("file:///home/jason/flink/checkpoint")

With about 30MB of state we see the checkpoints completing in 151ms.  Using
a RocksDBStateBackend configured as:

val backend = new RocksDBStateBackend("file:///home/jason/flink/checkpoint")

Running the same test the checkpoint takes 3 minutes 42 seconds.

I expect it to be slower, but that seems excessive.  I am also a little
confused as to when rocksDB and flink decide to write to disk, because
watching the database the .sst file wasn't created until significantly
after the checkpoint was completed, and the state had not changed.  Is
there anything I can do to increase the speed of the checkpoints, or
anywhere I can look to debug the issue?  (Nothing seems out of the ordinary
in the flink logs or rocksDB logs)


*Jason Brelloch* | Product Developer
3405 Piedmont Rd. NE, Suite 325, Atlanta, GA 30305
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