MariaDB MaxScale 2.1.0 Release Notes -- 2017-02-16

Release 2.1.0 is a Beta release.

This document describes the changes in release 2.1.0, when compared to release 2.0.4.

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

License

The license of MaxScale has been changed from MariaDB BSL 1.0 to MariaDB BSL 1.1.

For more information about MariaDB BSL 1.1, please refer to MariaDB BSL11.

Changed Features

router_options to Parameters

The router_options values can also be given as parameters to the service for the readwritesplit, schemarouter and binlogrouter modules.

What this means is that in MaxScale 2.1 the following readwritesplit configration.

[RW Split Router]
type=service
router=readwritesplit
servers=server1
user=maxuser
passwd=maxpwd
router_options=slave_selection_criteria=LEAST_ROUTER_CONNECTIONS,max_sescmd_history=10,disable_sescmd_history=false

Can also be written in the following form.

[RW Split Router]
type=service
router=readwritesplit
servers=server1
user=maxuser
passwd=maxpwd
slave_selection_criteria=LEAST_ROUTER_CONNECTIONS
max_sescmd_history=10
disable_sescmd_history=false

Configuration Files

From 2.1.0 onwards MariaDB MaxScale supports hierarchical configuration files. When invoked with a configuration file, e.g. maxscale.cnf, MariaDB MaxScale looks for a directory maxscale.cnf.d in the same directory as the configuration file, and reads all .cnf files it finds in that directory hierarchy. All other files will be ignored.

Please see the Configuration Guide for details.

Readwritesplit disable_sescmd_history option

The default value for disable_sescmd_history is now true. This new default value will prevent the excessive memory use of long-lived connections. In addition to this, it was not optimal to enable this option while the default value for max_slave_connections was 100%, effectively making it useless.

Module configurations

MaxScale 2.1 introduces a new directory for module configurations. This new directory can be used to store module specific configuration files.

Any configuration parameter that accepts a path will also support relative paths. If a relative path is given, the path is interpreted relative to the module configuration directory. The default value is /etc/maxscale.modules.d.

For example, the dbfwfilter rule files could be stored in /etc/maxscale.modules.d/my_rules.txt and referred to with rules=my_rules.txt.

For more details, refer to the documentation of module_configdir in the Configuration Guide

Logging

Before version 2.1.0, MaxScale created in the log directory a log file maxscaleN.log, where N initially was 1 and then was increased every time MaxScale was instructed (by sending the signal SIGUSR1 or via maxadmin) to rotate the log file.

That has now been changed so that the name of the log file is always maxscale.log and when MaxScale is instructed to rotate the log file, MaxScale simply closes it and then reopens and truncates it.

To retain the existing log entries, you should first move the file to another name (MaxScale continues writing to it) and then instruct MaxScale to rotate the the log file.

    $ mv maxscale.log maxscale1.log
    $ # MaxScale continues to write to maxscale1.log
    $ kill -SIGUSR1 <maxscale-pid>
    $ # MaxScale closes the file (i.e. maxscale1.log) and reopens maxscale.log

This behaviour is now compatible with logrotate(8).

Further, if MaxScale is configured to use shared memory for the log file, the file is created into the directory /dev/shm/maxscale. Earlier the log file was created into the directory /dev/shm/maxscale.PID, where PID was the pid of the MaxScale process.

In addition, there is now a mechanism that prevents the flooding of the log, in case the same error occurs over and over again. That mechanism, which is enabled by default, is configured using the new global configuration entry log_throttling. For more information about this configuration entry, please see Global Settings.

Readwritesplit Read Retry

In 2.1, Readwritesplit will retry failed SELECT statements that are executed outside of transaction and with autocommit enabled. This allows seamless slave failover and makes it transparent to the client.

Read the Readwritesplit documentation on retry_failed_reads for more details.

Persistent Connections

Starting with the 2.1 version of MariaDB MaxScale, when a MySQL protocol persistent connection is taken from the persistent connection pool, the state of the MySQL session will be reset when the the connection is used for the first time. This allows persistent connections to be used with no functional limitations and makes them behave like normal MySQL connections.

For more information about persistent connections, please read the Administration Tutorial.

User data cache

The user data cache stores the cached credentials that are used by some router modules. In 2.1.0, the authenticator modules are responsible for the persisting of the user data cache. Currently, only the MySQLAuth module implements user data caching.

The user data loaded from the backend databases is now stored on a per listener basis instead of a per service basis. In earlier versions, each service had its own cache directory in /var/cache/maxscale. This directory contains cached user data which is used there is no connectivity to the backend cluster.

In 2.1.0, each listener has its own sub-directory in the service cache directory. The old caches in /var/cache/maxscale will need to be manually removed if they are no longer used by older versions of MaxScale.

Galeramon Monitoring Algorithm

The galeramon monitor will only choose nodes with a wsrep_local_index value of 0 as the master. This allows multiple MaxScales to always choose the same node as the write master node for the cluster. The old behavior can be taken into use by disabling the new root_node_as_master option.

For more details, read the Galeramon documentation.

MaxAdmin editing mode

MaxAdmin now defaults to Emacs editing mode instead of VIM. To activate with VIM-mode start MaxAdmin with option -i.

Named Server Filter

The source option can now handle wildcards such as: 192.168.%.%

For more details, read the Named Server Filter documentation.

New Features

Dynamic configuration

MaxScale 2.1 supports dynamic configuration of servers, monitors and listeners. A set of new commands were added to maxadmin. See output of maxadmin help and maxadmin help { create | destroy | alter | add | remove } for more details.

Dynamic server configuration

MaxScale can now change the servers of a service or a monitor at run-time. New servers can also be created and they will persisted even after a restart.

• create server: Creates a new server
• destroy server: Destroys a created server
• add server: Adds a server to a service or a monitor
• remove server: Removes a server from a service or a monitor
• alter server: Alter server configuration
• alter monitor: Alter monitor configuration

With these new features, you can start MaxScale without the servers and define them later.

Dynamic listener configuration

New listeners for services can be created and destroyed at runtime. This allows the services to adapt to changes in client traffic.

• create listener: Create a new listener
• destroy listener: Destroy a created listener. The listener will stop handling client requests and will be removed after the next restart of MaxScale.

In addition to these commands, individual listeners can now be stopped and started.

• shutdown listener: Stop a listener
• restart listener: Restart a listener

Dynamic monitor configuration

New monitors can be created, modified and destroyed at runtime. This allows new clusters to be added into MaxScale by defining new monitors for them. The monitor parameters can also be changed at runtime making them more adaptive and allowing runtime tuning of parameters.

• create monitor: Create a new monitor
• destroy monitor: Destroy a created monitor
• alter monitor: Alter monitor parameters

Module commands

Introduced in MaxScale 2.1, the module commands are special, module-specific commands. They allow the modules to expand beyound the capabilities of the module API. Currently, only MaxAdmin implements an interface to the module commands.

All registered module commands can be shown with maxadmin list commands and they can be executed with maxadmin call command <module> <name> ARGS... where <module> is the name of the module and <name> is the name of the command. ARGS is a command specific list of arguments.

Read Module Commands documentation for more details.

In the 2.1 release of MaxScale, the [dbfwfilter}(../Filters/Database-Firewall-Filter.md), avrorouter, cache and masking modules implement module commands.

Amazon RDS Aurora monitor

The new Aurora Monitor module allows monitoring of Aurora clusters. The monitor detects which of the nodes are read replicas and which of them is the real write node and assigns the appropriate status for each node. This module also supports launchable scripts on monitored events. Read the Monitor Common Documentation for more details.

Multi-master mode for MySQL Monitor

The MySQL monitor now detects complex multi-master replication topologies. This allows the mysqlmon module to be used as a replacement for the mmmon module. For more details, please read the MySQL Monitor Documentation.

Failover mode for MySQL Monitor

A simple failover mode has been added to the MySQL Monitor. This mode is aimed for two node master-slave clusters where the slave can act as a master in case the original master fails. For more details, please read the MySQL Monitor Documentation.

Permissive authentication mode for MySQLAuth

The MySQL authentication module supports the skip_authentication option which allows authentication to always succedd in MaxScale. This option offloads the actual authentication to the backend server and it can be used to implement a secure version of a wildcard user.

Consistent Critical Reads

MaxScale 2.1 comes with a new filter module, ccrfilter, which allows critical reads to be routed to master after inserts. This will make reads after inserts consistent while still allowing read scaling.

For more information, refer to the CCRFilter documentation.

Database Cache

A new filter module, cache, allows MaxScale to cache the results of SELECT statements. This improves the performance of read-heavy workloads by reducing the work the backend databases have to perform.

For more information, refer to the Cache documentation.

Result set masking

The new masking filter can mask sensitive information from result sets. This is commonly done to hide sensitive information while still allowing the database to efficiently process the actual data.

For more information, refer to the Masking documentation.

Result set limiting

The newly added maxrows filter can restrict the maximum size of a returned result set. This can be used to reduce the negative effects of unexpectedly large result sets. It can also be used to improve security by preventing access to large sets of data with a single query.

For more information, refer to the Maxrows documentation.

Insert stream filter

The insertstream filter converts bulk inserts into CSV data streams that are consumed by the backend server via the LOAD DATA LOCAL INFILE mechanism. This leverages the speed advantage of LOAD DATA LOCAL INFILE over regular inserts while also reducing the overall network traffic by condensing the inserted values into CSV.

For more information, refer to the Insert Stream Filter documentation.

Galeramon Monitor new option

The set_donor_nodes option allows the setting of global variable wsrep_sst_donor with a list the preferred donor nodes (among slave ones).

For more details, read the Galeramon documentation.

Binlog Server encrypted binlogs

The binlog server can optionally encrypt the events received from the master server: the setup requires MariaDB 10.1 master (with Encryption active) and the mariadb10-compatibility=1 option set.

For more details, read the Binlogrouter documentation.

Bug fixes

Here is a list of bugs fixed since the release of MaxScale 2.0.4.

• MXS-1025 qc_sqlite always reports " Statement was parsed, but not classified"
• MXS-977 MaxAdmin show monitor output missing formatting
• MXS-951 Using utf8mb4 on galera hosts stops maxscale connections
• MXS-889 "Ungrade Test" Jenkins job fails with CeentOS/RHEL 5 and SLES11
• MXS-887 create_env Jenkin job fails
• MXS-873 Changing server status via maxadmin is not atomic
• MXS-832 Problem with Regex filter as readconnroute doesn't wait for complete packets
• MXS-831 new_master event not triggered by galeramon
• MXS-828 Remove "Syslog logging is disabled." to stdout when starting without syslog
• MXS-825 --execdir option does not work
• MXS-805 Server weights don't work with LEAST_BEHIND_MASTER
• MXS-804 Grants for user@IP/Netmask doesn't work
• MXS-799 fatal signal 11 when socket could not be opened
• MXS-769 Malloc return value must be checked.
• MXS-711 All service ports use the same user data
• MXS-650 Connection attempt w/o SSL to SSL service gives confusing error
• MXS-626 Don't log anything to maxlog until it is known whether that is wanted.
• MXS-590 MaxScale doesn't log an error when .secrets file is not owned by current user
• MXS-586 Tee filter hangs when using range
• MXS-576 Maxscale does not generate warning/error if incorrect values is set for persistpoolmax
• MXS-397 Unsafe handling of dcb_readqueue
• MXS-390 Lack of checks of dynamic memory allocation
• MXS-350 Return value of realloc must not be assigned to provided pointer.
• MXS-348 Incorrect use of strncat
• MXS-253 Use of strncpy is dangerous
• MXS-126 debug assert in TEE filter test

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.