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Percona XtraDB Cluster Documentation

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Percona XtraDB Cluster 8.0.26-16.1

Percona XtraDB Cluster (PXC) supports critical business applications in your public, private, or hybrid cloud environment. Our free, open source, enterprise-grade solution includes the high availability and security features your business requires to meet your customer expectations and business goals.

Release Highlights

The following are a number of the notable fixes for MySQL 8.0.26, provided by Oracle, and included in this release:

  • The TLSv1 and TLSv1.1 connection protocols are deprecated.

  • Identifiers with specific terms, such as “master” or “slave” are deprecated and replaced. See the Functionality Added or Changed section in the 8.0.26 Release Notes for a list of updated identifiers. The following terms have been changed:

  • The identifier master is changed to source

  • The identifier slave is changed to replica

  • The identifier multithreaded slave (mts) is changed to multithreaded applier (mta)

  • When using semisynchronous replication, either the old version or the new version of system variables and status variables are available. You cannot have both versions installed on an instance. The old system variables are available when you use the old version, but the new ones are not. The new system variables are available when you use the new version, but the old values are not.

In an upgrade from an earlier version to 8.0.26, enable the rpl_semi_sync_source plugin and the rpl_semi_sync_replica plugin after the upgrade has been completed. Enabling these plugins before all of the nodes are upgraded may cause data inconsistency between the nodes.

For the source, the rpl_semi_sync_master plugin (seminsync_master.so library) is the old version and the rpl_semi_sync_source plugin(semisync_source.so library) is the new version.

For the client, the rpl_semi_sync_slave plugin (semisync_slave.so library) is the old version and the rpl_semi_sync_replica plugin (semisync_replica.so library) is the new version

For more information, see the MySQL 8.0.26 Release Notes.

Bugs Fixed

  • PXC-3824: An incorrect directive in Systemd Unit File (Thanks to Jim Lohiser for reporting this issue)

  • PXC-3706: A fix for a race condition in group commit queue (Thanks to Kevin Sauter for reporting this issue)

  • PXC-3739: The FLUSH TABLES FOR EXPORT lock is released when the session ends.

  • PXC-3628: The server allowed altering the storage engine to MyISAM for mysql.wsrep_* tables.

  • PXC-3731: A fix for when the user deletes data from the source but does not want that data deleted from the replica. The sql_log_bin=0 command had no effect and the deleted rows were replicated and written into the binary log.

  • PXC-3857: The following system variables are renamed. The old variables are deprecated and may be removed in a future version.

  • wsrep_slave_threads renamed as wsrep_applier_threads

  • wsrep_slave_FK_checks renamed as wsrep_applier_FK_checks

  • wsrep_slave_UK_checks renamed as wsrep_applier_UK_checks

  • wsrep_restart_slave renamed as wsrep_restart_replica

Known Issues (unfixed problems that you should be aware of)

  • PXC-3039: No useful error messages if an SSL-disabled node tried to join an SSL-enabled cluster

  • PXC-3093: A completed SST Transfer is incorrectly logged by garbd. The timing is incorrect.