MariaDB MaxScale 2.5.0 Release Notes -- 2020-06-18

MariaDB MaxScale 2.5.0 Release Notes -- 2020-06-18

Release 2.5.0 is a Beta release.

This document describes the changes in release 2.5.0, when compared to release 2.4.

For any problems you encounter, please consider submitting a bug report at Jira.

Changed Features

  • Network throttling (writeq_high_water and writeq_low_water) is now on by default. This will prevent MaxScale from running out of memory when large database dumps are restored through it. This change will not affect performance in any significant way.

  • Servers with duplicate network details (address and port) are treated as a configuration error. There should exist only one server object in MaxScale for each actual database.

  • Server parameters are now checked and unknown parameters are treated as a configuration error. This can cause old configurations with unknown parameters to fail.

  • Servers without a monitor now start in the Down state instead of the Running state. This means that servers without a monitor need to have their state set manually.


Previously this feature was a readwritesplit feature. In MaxScale 2.5.0 it has been converted into a core MaxScale feature and it can be used with all routers. In addition to this, the keepalive mechanism now also keeps completely idle connections alive (MXS-2505).

User loading timeouts

The default timeout values for user loading have been changed.

  • auth_connect_timeout changed from 3 to 10 second
  • auth_read_timeout deprecated and ignored
  • auth_write_timeout deprecated and ignored

Setting a server to maintenance or draining mode

In the case of a regular MariaDB cluster (monitored by the MariaDB monitor), it is no longer possible to set the the master server to maintenance or draining mode, but a switchover must be performed first.

MariaDB-Monitor deprecated settings

The settings detect_stale_master, detect_standalone_master and detect_stale_slave are replaced by the more flexible master_conditions and slave_conditions. The old settings may still be used, but will be removed in a later version.

Password encryption

The encrypted passwords feature has been updated to be more secure. Users are recommended to generate a new encryption key and and re-encrypt their passwords using the maxkeys and maxpasswd utilities. Old passwords still work.

Authenticator options

Several changes, see here for more details.


  • Listeners are now a separate resource from services. The old listeners entry point is deprecated and its use is discouraged.

Dropped Features

MaxAdmin has been removed.

Use maxctrl or maxgui instead.

No concept of Unix users anymore

As maxadmin, that could be used over a unix domain socket, has been removed it is no longer possible to enable/disable unix users as MaxScale administrators.

Configuration parameters

The following deprecated parameters have been removed.

  • non_blocking_polls
  • poll_sleep
  • log_trace and log_messages that were synonyms for log_info and log_notice respectively.

Removed modules

  • The maxinfo-router and the httpd-protocol have been removed.

Deprecated Features

  • Server parameters protocol and authenticator have been deprecated. Any definitions are ignored.


  • The use of percentage values in max_slave_connections has been deprecated.

New Features

  • The timeout to maxctrl can now be specified using duration suffixes, e.g. --timeout 5s.
  • The new targets parameter for services can be used to list both servers and other services as routing targets. This allows complex setups to be used where one service routes the query to another service.
  • MariaDB connection attributes are now forwarded to the backend servers.


MaxGUI is a new browser based configuration and management tool for MaxScale that complements the command line tool maxctrl.

Please see the documentation for more information.



The MaxScale cache is now capable of performing invalidation of cache entries. See the documentation for more information.

New Cache Storage Modules

The following storage modules have been added: storage_memcached storage_redis

When either of these are used, the cache can be shared between two MaxScale instances.

User specific cache

It is now possible to specify that each user should have a cache of his/her own. Having a user-specific cache ensures that it is impossible for a user to obtain access to data he/she should not have access to, something which may be possible if a shared cache is used, as the cache filter is not aware of grants. Please see the documentation for details.

Load Rebalancing

If the load of the threads of MaxScale differs by a certain amount, MaxScale is now capable of moving sessions from one thread to another so that all threads are evenly utilized. Please refer to rebalance_period and rebalance_threshold for more information.

Columnstore support

The Columnstore monitor is now capable of monitoring Columnstore versions 1.0, 1.2 and 1.5. In addition, some cluster management operations are available for Columnstore 1.5. Please see the documentation for details.

Cooperative monitoring

MariaDB-Monitor supports cooperative monitoring. See cooperative monitoring for more information.

Listener and authenticator settings

  • multiple authenticators per listener
  • connection_init_sql_file
  • mysql_clear_password support for PAM authenticator

See configuration guide and pam plugin documentation for more details.


  • Added support for peer hostname verification in connections that use TLS.

  • Added support for certificate revocation lists


  • The causal reads feature has been extended with a global mode, which uses latest known GTID and waits for slave to replicate, and a fast mode, which routes queries to the master if no up-to-date slave is found.


  • The router now supports setups where multiple servers contain the same database or table. This allows a more resilient setup where a failure of one shard doesn't cause a complete outage.

  • The credentials the clients use to connect to the schemarouter no longer need to exist on all of the databases used by the service. This reduces the amount of access required by the clients that use the schemarouter.

Mirror Router

  • The mirror router is a new router designed for data consistency and database behavior verification during system upgrades. It can export the measured data as JSON into either a file or into a Kafka broker.


  • New module that replicates data changes in a MariaDB master into a Kafka broker formatted as JSON objects. Refer to the KafkaCDC documentation for more details.


  • Token authentication via JWT.

  • Sparse fieldsets allow reduced network overhead for requests.

  • Result filtering allows retrieval of a subset of a resource collection.

  • REST API resources now use the SHA1 of the returned result as the object ETag. This fixes the problem where the ETag was not updated even when the result changed due to internal MaxScale processes.

  • Module parameter types are now described for the server and core MaxScale objects.

  • Listeners are now a separate resource from services. The old listeners entry point is deprecated and its use is discouraged.

Bug fixes

Known Issues and Limitations

There are some limitations and known issues within this version of MaxScale. For more information, please refer to the Limitations document.


RPM and Debian packages are provided for the Linux distributions supported by MariaDB Enterprise.

Packages can be downloaded here.

Source Code

The source code of MaxScale is tagged at GitHub with a tag, which is identical with the version of MaxScale. For instance, the tag of version X.Y.Z of MaxScale is X.Y.Z. Further, master always refers to the latest released non-beta version.

The source code is available here.


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