The Question
Recently, a customer asked us:
What is the meaning of this error message found in
trepsvc.log?2019/05/14 01:48:04.973 | mysql02.prod.example.com | [east - binlog-to-q-0] INFO pipeline.SingleThreadStageTask Performing rollback of possible partial transaction: seqno=(unavailable)
Simple Overview
The Skinny
This message is an indication that we are dropping any uncommitted or incomplete data read from the MySQL binary logs due to a pending error.
The Answer
Safety First
This error is often seen before another error and is an indication that we are rolling back anything uncommitted, for safety. On a master this is normally very little and would likely be internal transactions in the trep_commit_seqno table, for example.
As you may know with the replicator we always extract complete transactions, and so this particular message is specific to the reading of the MySQL binlog into the internal memory queue (binlog-to-q).
This queue then feeds into the q-to-thl pipeline. We only want to write a complete transaction into the THL, so anything not completed when a failure like this happens gets rolled back.
Summary
The Wrap-Up
In this blog post we discussed the Tungsten Replicator rollback error.
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The Library
Please read the docs!
For more information about monitoring Tungsten clusters, please visit https://docs.continuent.com.
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