You Can Now Use Binary Log Checksums with Group Replication

Group Replication enables you to create fault-tolerant systems with redundancy by replicating the system state to a set of servers. Even if some of the servers subsequently fail, as long it is not all or a majority, the system is still available.
This blog post will focus on the fact that after 8.0.21 you can use Group Replication with binary log event checksums turned on. Therefore, you do not have to explicitly set binlog-checksum=NONE before starting Group Replication.

The fact that Group Replication supports binary log checksums makes archiving/backing up the binary logs more resilient when it comes to validity and integrity checking. When they are pulled from the archive to be used at a later point in time, checksums will be checked when these are replayed. Furthermore, during distributed recovery, donors shall have checksums in their binary logs, so these will also be double checked at that stage. This is a good thing.

From MySQL 8.0.21, the extra configuration

is no more required.

Note that binary log event checksums are generated when writing to the binary log. In Group Replication, coordination between servers (i.e., replication and agreement) happens before writing transactions out to the binary log and as such checksums are generated after being replicated. Consequently, the relay log for the group_replication_applier channel shall contain transactions that have events without checksums.

Conclusion

Following our tradition of steady improvements, we are once again making Group Replication simpler to use by using the server default values.

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About Nuno Carvalho

Nuno Carvalho is a Principal Software Engineer and MySQL Replication Service Team lead at Oracle, the team in charge of MySQL Group Replication plugin. His research interests include replication technologies, dependable systems and high availability. Before joining the MySQL team, he was a post-graduate student and a researcher at the University of Minho, Portugal, where he designed and implemented techniques to improve distributed systems scalability.

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