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Percona XtraDB Cluster 5.7.16-27.19

Percona is glad to announce the release of Percona XtraDB Cluster 5.7.16-27.19 on December 15, 2016. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.7.16-27.19 is now the current release, based on the following:

All Percona software is open-source and free. Details of this release can be found in the 5.7.16-27.19 milestone on Launchpad.


  • The following encryption modes:

    • encrypt=1

    • encrypt=2

    • encrypt=3

The default is encrypt=0 with encryption disabled. The recommended mode now is the new encrypt=4, which uses SSL files generated by MySQL.

For more information, see Encrypting PXC Traffic.

New Features

  • Added encrypt=4 mode for SST encryption that uses SSL files generated by MySQL. Modes 1, 2, and 3 will soon be deprecated.

  • ProxySQL assisted maintenance mode that enables you to take a node down without adjusting ProxySQL manually. The mode is controlled using the pxc_maint_mode variable, which can be set to one of the following values:

    • DISABLED: This is the default state that tells ProxySQL to route traffic to the node as usual.

    • SHUTDOWN: This state is set automatically when you initiate node shutdown.

    • MAINTENANCE: You can change to this state if you need to perform maintenace on a node without shutting it down.

For more information, see Assisted Maintenance Mode.

  • Simplified SSL configuration for Galera/SST traffic with pxc-encrypt-cluster-traffic option, which auto-configures SSL encryption.

For more information, see SSL Automatic Configuration.

  • Added the wsrep_flow_control_interval status variable that displays the lower and upper limits of the flow control system used for the Galera receive queue.

Fixed Bugs

  • Optimized IST donor selection logic to avoid SST. Child processes are now cleaned-up and node state is resumed if SST fails.

  • Added init.ok to the list of files that do not get removed during SST.

  • Fixed error with ASIO library not acknowledging an EPOLLIN event when building Galera.

  • Fixed stalling of DML workload on slave node caused by FLUSH TABLE executed on master.

For more information, see #1629296.

  • Fixed super_read_only to not apply to Galera replication applier.

For more information, see #1634295.

  • Redirected netcat output to stdout to avoid it in the log.

For more information, see #1625968.

  • Enabled replication of ALTER USER statements.

For more information, see #1376269.

  • Changed the wsrep_max_ws_rows variable to ignore non-replicated write-sets generated by DML action on temporary tables (explict or implicit).

For more information, see #1638138.

  • Fixed SST to fail with an error if SSL is not supported by socat, instead of switching to unencrypted mode.

  • Fixed SST with SSL to auto-generate a 2048-bit dhparams file for versions of socat before 1.7.3. These older versions use 512-bit dhparams file by default that get rejected by newer clients with dh key too small error.

  • PXC-731: Changed the wsrep_cluster_name variable to read-only, because changing it dynamically leads to high overhead.

For more information, see #1620439.

  • PXC-732: Improved error message when any of the SSL files required for SST are missing.

  • PXC-735: Fixed SST to fail with an error when netcat is used (transferfmt set to nc) with SSL encryption (encrypt set to 2, 3 or 4), instead of silently switching to unencrypted mode.

  • Fixed faulty switch case that caused cluster to stall when the repl.commit_order variable was set to 2 (LOCAL_OOOC mode that should allow out-of-order committing for local transactions).