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MariaDB MaxScale 2.4.0 Release Notes
Release 2.4.0 is a Beta release.
This document describes the changes in release 2.4.0, when compared to release 2.3.
For any problems you encounter, please consider submitting a bug report at Jira.
Changed Features
Section and object names
Section and object names starting with @@ are now reserved for
use by MaxScale itself. If any such names are encountered in
configuration files, then MaxScale will not start.
Whitespace in section names that was deprecated in 2.2 will now be rejected and cause the startup of MaxScale to fail.
Binding on network ports
MaxScale 2.4.0 will now use the SO_REUSEPORT capability offered by newer kernels that allows reuse of network listener ports. In practice this means improved connection creation speed with more dynamic balancing of connections.
As a side-effect of this, it is possible for two MaxScale instances to bind on
the same listener port on systems that have Linux kernels newer than 3.9. This
can only happen if the MaxScale instances use completely different directory
structures (i.e. different --basedir arguments). Normal use of MaxScale still
detects multiple MaxScales trying to bind to the same ports. Almost always, this
will not have any negative side-effects.
Dropped Features
New Features
Servers can be drained
It is now possible to drain a server, which means that existing connections to the server can continue to be used but new connections are no longer created to the server.
In the output of maxctrl, the fact that a server is being drained
is visible in the State column as the value Draining.
┌─────────┬─────────────────┬──────┬─────────────┬───────────────────────────────┬───────┐
│ Server │ Address │ Port │ Connections │ State │ GTID │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server1 │ 192.168.121.159 │ 3306 │ 2 │ Master, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server2 │ 192.168.121.80 │ 3306 │ 1 │ Draining, Slave, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server3 │ 192.168.121.122 │ 3306 │ 2 │ Slave, Running │ 0-1-6 │
├─────────┼─────────────────┼──────┼─────────────┼───────────────────────────────┼───────┤
│ Server4 │ 192.168.121.144 │ 3306 │ 2 │ Slave, Running │ 0-1-6 │
└─────────┴─────────────────┴──────┴─────────────┴───────────────────────────────┴───────┘
A server is set in the Draining state the same way as it is set in the Maintenance state:
$ maxctrl set server Server2 drain
Note that although the state is displayed as Draining, when setting
and clearing the state, the word drain is used.
Note that the full implication of draining a server depends upon both on the role of the server and on the router being used, and its configuration.
For instance, if readwritesplit is used and the server being drained
is a slave, then from a client's perspective there will be no difference;
readwritesplit will simply not use that server. However, if the server
being drained is the master, then it will not be possible to connect
unless master_failure_mode has been set to something else but the
default fail_instantly.
Once the server has been drained, the state will be Drained.
Cluster
The servers a service uses can now be specified using the cluster
parameter of the service.
[TheService]
...
cluster=TheMonitor
In this case, the servers of the service will be defined by the
referred to monitor. Note that the parameters servers and cluster
are mutually exclusive.
Durations
In the MaxScale configuration file, durations can now be suffixed with
h, m, s or ms to indicate that the duration is specified as
hours, minutes, seconds or milliseconds.
Please see the configuration guide for details.
Not providing an explicit unit has been deprecated in MaxScale 2.4.
Query Classifier Cache
It is now possible to examine the contents of the query classifier cache. The REST-API endpoint is
/v1/maxscale/query_classifier/cache
and the equivalent maxctrl command
maxctrl show qc_cache
The output shows the statements (the canonical version) in the cache, the number of times they have been encountered and how they have been classified.
Bug fixes
Here is a list of bugs fixed in MaxScale 2.4.0.
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.
Packaging
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.