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From "Gyula Fora (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-3431) Add retrying logic for RocksDB snapshots
Date Wed, 17 Feb 2016 12:22:18 GMT
Gyula Fora created FLINK-3431:
---------------------------------

             Summary: Add retrying logic for RocksDB snapshots
                 Key: FLINK-3431
                 URL: https://issues.apache.org/jira/browse/FLINK-3431
             Project: Flink
          Issue Type: Improvement
          Components: Streaming
            Reporter: Gyula Fora
            Priority: Critical


Currently the RocksDB snapshots rely on hdfs copy not failing while taking the snapshots.
In some cases when the state size is big enough the HDFS nodes might get so overloaded that
the copy operation fails on errors like this:

AsynchronousException{java.io.IOException: All datanodes 172.26.86.90:50010 are bad. Aborting...}
at org.apache.flink.streaming.runtime.tasks.StreamTask$1.run(StreamTask.java:545)
Caused by: java.io.IOException: All datanodes 172.26.86.90:50010 are bad. Aborting...
at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.setupPipelineForAppendOrRecovery(DFSOutputStream.java:1023)
at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.processDatanodeError(DFSOutputStream.java:838)
at org.apache.hadoop.hdfs.DFSOutputStream$DataStreamer.run(DFSOutputStream.java:483)

I think it would be important that we don't immediately fail the job in these cases but retry
the copy operation after some random sleep time. It might be also good to do a random sleep
before the copy depending on the state size to smoothen out IO a little bit.



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