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The Important Role of a Tungsten Rollback Error

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.

To learn about Continuent solutions in general, check out https://www.continuent.com/solutions

The Library

Please read the docs!

For more information about monitoring Tungsten clusters, please visit https://docs.continuent.com.

Tungsten Clustering is the most flexible, performant global database layer available today - use it underlying your SaaS offering as a strong base upon which to grow your worldwide business!

For more information, please visit https://www.continuent.com/solutions

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About the Author

Eric M. Stone
COO

Eric is a veteran of fast-paced, large-scale enterprise environments with 35 years of Information Technology experience. With a focus on HA/DR, from building data centers and trading floors to world-wide deployments, Eric has architected, coded, deployed and administered systems for a wide variety of disparate customers, from Fortune 500 financial institutions to SMB’s.

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