MariaDB MaxScale Configuration & Usage Scenarios
MariaDB MaxScale Configuration & Usage Scenarios
This document describes how to configure MariaDB MaxScale and presents some possible usage scenarios. MariaDB MaxScale is designed with flexibility in mind, and consists of an event processing core with various support functions and plugin modules that tailor the behavior of the program.
Table of Contents
- Global Settings
- TLS/SSL Encryption
- Router Modules
- Diagnostic Modules
- Monitor Modules
- Filter Modules
- Reloading Configuration
- Error Reporting
|service||A service represents a set of databases with a specific access mechanism that is offered to clients of MariaDB MaxScale. The access mechanism defines the algorithm that MariaDB MaxScale will use to direct particular requests to the individual databases.|
|server||A server represents an individual database server to which a client can be connected via MariaDB MaxScale.|
|router||A router is a module within MariaDB MaxScale that will route client requests to the various database servers which MariaDB MaxScale provides a service interface to.|
|connection routing||Connection routing is a method of handling requests in which MariaDB MaxScale will accept connections from a client and route data on that connection to a single database using a single connection. Connection based routing will not examine individual requests on a connection and it will not move that connection once it is established.|
|statement routing||Statement routing is a method of handling requests in which each request within a connection will be handled individually. Requests may be sent to one or more servers and connections may be dynamically added or removed from the session.|
|protocol||A protocol is a module of software that is used to communicate with another software entity within the system. MariaDB MaxScale supports the dynamic loading of protocol modules to allow for increased flexibility.|
|module||A module is a separate code entity that may be loaded dynamically into MariaDB MaxScale to increase the available functionality. Modules are implemented as run-time loadable shared objects.|
|monitor||A monitor is a module that can be executed within MariaDB MaxScale to monitor the state of a set of database. The use of an internal monitor is optional, monitoring may be performed externally to MariaDB MaxScale.|
|listener||A listener is the network endpoint that is used to listen for connections to MariaDB MaxScale from the client applications. A listener is associated to a single service, however, a service may have many listeners.|
|connection failover||When a connection currently being used between MariaDB MaxScale and the database server fails a replacement will be automatically created to another server by MariaDB MaxScale without client intervention|
|backend database||A term used to refer to a database that sits behind MariaDB MaxScale and is accessed by applications via MariaDB MaxScale.|
|filter||A module that can be placed between the client and the MariaDB MaxScale router module. All client data passes through the filter module and may be examined or modified by the filter modules. Filters may be chained together to form processing pipelines.|
The MariaDB MaxScale configuration is read from a file that MariaDB MaxScale will look for in the following places:
- By default, the file
maxscale.cnfin the directory
- The location given with the
--configdir=<path>command line argument.
MariaDB MaxScale will further look for a directory with the same name as the
configuration file, followed by
.d (for instance
recursively read all files, having a
.cnf suffix, it finds in the directory
hierarchy. All other files will be ignored.
There are no restrictions on how different configuration sections are arranged, but the strong suggestion is to place global settings into the configuration file MariaDB MaxScale is invoked with, and then, if deemed necessary, create separate configuration files for servers, filters, etc.
The configuration file itself is based on the .ini file format and consists of various sections that are used to build the configuration; these sections define services, servers, listeners, monitors and global settings. Parameters, which expect a comma-separated list of values can be defined on multiple lines. The following is an example of a multi-line definition.
[MyService] type=service router=readconnroute servers=server1, server2, server3
The values of the parameter that are not on the first line need to have at least one whitespace character before them in order for them to be recognized as a part of the multi-line parameter.
Where specifically noted, a number denoting a size can be suffixed by a subset
of the IEC binary prefixes or the SI prefixes. In the former case the number
will be interpreted as a certain multiple of 1024 and in the latter case as a
certain multiple of 1000. The supported IEC binary suffixes are
Ti and the supported SI suffixes are
T. In both cases,
the matching is case insensitive.
For instance, the following entries
max_size=1099511628000 max_size=1073741824Ki max_size=1048576Mi max_size=1024Gi max_size=1Ti
are equivalent, as are the following
max_size=1000000000000 max_size=1000000000k max_size=1000000M max_size=1000G max_size=1T
The global settings, in a section named
[MaxScale], allow various parameters
that affect MariaDB MaxScale as a whole to be tuned.
This parameter controls the number of worker threads that are handling the events coming from the kernel. The default is 1 thread. It is recommended that you start with one thread and increase the number if you require greater performance. Increasing the amount of worker threads beyond the number of processor cores does not improve the performance, rather is likely to degrade it, and can consume resources needlessly.
You can enable automatic configuration of this value by setting the value to
auto. This way MariaDB MaxScale will detect the number of available processors
and set the amount of threads to be equal to that number. This should only be
used for systems dedicated for running MariaDB MaxScale.
# Valid options are: # threads=[<number of threads> | auto ] [MaxScale] threads=1
Additional threads will be created to execute other internal services within MariaDB MaxScale. This setting is used to configure the number of threads that will be used to manage the user connections.
The connection timeout in seconds for the MySQL connections to the backend server when user authentication data is fetched. Increasing the value of this parameter will cause MariaDB MaxScale to wait longer for a response from the backend server before aborting the authentication process. The default is 3 seconds.
The read timeout in seconds for the MySQL connection to the backend database when user authentication data is fetched. Increasing the value of this parameter will cause MariaDB MaxScale to wait longer for a response from the backend server when user data is being actively fetched. If the authentication is failing and you either have a large number of database users and grants or the connection to the backend servers is slow, it is a good idea to increase this value. The default is 1 second.
The write timeout in seconds for the MySQL connection to the backend database when user authentication data is fetched. Currently MariaDB MaxScale does not write or modify the data in the backend server. The default is 2 seconds.
The number of times an interrupted internal query will be retried. This feature was added in MaxScale 2.1.10 and is disabled by default.
An interrupted query is any query that is interrupted by a network
error. Connection timeouts are included in network errors and thus is it
advisable to make sure that the value of
query_retry_timeout is set to an
adequate value. Internal queries are only used to retrieve authentication data
and monitor the servers.
The total timeout in seconds for any retried queries. The default value is 5 seconds.
An interrupted query is retried for either the configured amount of attempts or until the configured timeout is reached.
Enable or disable the high precision timestamps in logfiles. Enabling this adds millisecond precision to all logfile timestamps.
# Valid options are: # ms_timestamp=<0|1> ms_timestamp=1
Skip service and monitor user permission checks. This is useful when you know the permissions are OK and you want to speed up the startup process. This parameter takes a boolean value and is disabled by default.
It is recommended to not disable the permission checks so that any missing privileges are detected when maxscale is starting up. If you are experiencing a slow startup of MaxScale due to large amounts of connection timeouts when permissions are checked, disabling the permission checks could speed up the startup process.
Enable or disable the logging of messages to syslog.
By default logging to syslog is enabled.
# Valid options are: # syslog=<0|1> syslog=1
To enable logging to syslog use the value 1 and to disable use the value 0.
Enable to disable to logging of messages to MariaDB MaxScale's log file.
By default logging to maxlog is enabled.
# Valid options are: # syslog=<0|1> maxlog=1
To enable logging to the MariaDB MaxScale log file use the value 1 and to disable use the value 0.
Enable or disable the writing of the maxscale.log file to shared memory. If
enabled, then the actual log file will be created under
/dev/shm and a
symbolic link to that file will be created in the MaxScale log directory.
Logging to shared memory may be appropriate if log_info and/or log_debug are enabled, as logging to a regular file may in that case cause performance degradation, due to the amount of data logged. However, as shared memory is a scarce resource, logging to shared memory should be used only temporarily and not regularly.
Since MariaDB MaxScale can log to both file and syslog an approach that provides maximum flexibility is to enable syslog and log_to_shm, and to disable maxlog. That way messages will normally be logged to syslog, but if there is something to investigate, log_debug and maxlog can be enabled from maxadmin, in which case informational messages will be logged to the maxscale.log file that resides in shared memory. But note that log_debug messages will only be available if MaxScale has been built in debug mode.
By default, logging to shared memory is disabled.
# Valid options are: # log_to_shm=<0|1> log_to_shm=1
To enable logging to shared memory use the value 1 and to disable use the value 0.
Enable or disable the logging of messages whose syslog priority is warning. Messages of this priority are enabled by default.
# Valid options are: # log_warning=<0|1> log_warning=0
To disable these messages use the value 0 and to enable them use the value 1.
Enable or disable the logging of messages whose syslog priority is notice. Messages of this priority provide information about the functioning of MariaDB MaxScale and are enabled by default.
# Valid options are: # log_notice=<0|1> log_notice=0
To disable these messages use the value 0 and to enable them use the value 1.
Enable or disable the logging of messages whose syslog priority is info. These messages provide detailed information about the internal workings of MariaDB MaxScale and should not, due to their frequency, be enabled, unless there is a specific reason for that. For instance, from these messages it will be evident, e.g., why a particular query was routed to the master instead of to a slave. These informational messages are disabled by default.
# Valid options are: # log_info=<0|1> log_info=1
To disable these messages use the value 0 and to enable them use the value 1.
Enable or disable the logging of messages whose syslog priority is debug. This kind of messages are intended for development purposes and are disabled by default. Note that if MariaDB MaxScale has been built in release mode, then debug messages are excluded from the build and this setting will not have any effect.
# Valid options are: # log_debug=<0|1> log_debug=1
To disable these messages use the value 0 and to enable them use the value 1.
Deprecated Use log_notice instead.
Deprecated Use log_info instead.
Enable or disable the augmentation of messages. If this is enabled, then each logged message is appended with the name of the function where the message was logged. This is primarily for development purposes and hence is disabled by default.
# Valid options are: # log_augmentation=<0|1> log_augmentation=1
To disable the augmentation use the value 0 and to enable it use the value 1.
It is possible that a particular error (or warning) is logged over and over again, if the cause for the error persistently remains. To prevent the log from flooding, it is possible to specify how many times a particular error may be logged within a time period, before the logging of that error is suppressed for a while.
# A valid value looks like # log_throttling = X, Y, Z # # where each value is a positive integer and X means the number of times a # specific error may be logged within a time period of Y milliseconds, before # the logging of that error is suppressed for Z milliseconds. log_throttling=8, 2000, 15000
In the example above, the logging of a particular error will be suppressed for 15 seconds if the error has been logged 8 times in 2 seconds.
The default is
10, 1000, 10000, which means that if the same error is logged
10 times in one second, the logging of that error is suppressed for the
following 10 seconds.
To disable log throttling, add an entry with an empty value
or one where any of the integers is 0.
log_throttling=0, 0, 0
Note that notice, info and debug messages are never throttled.
Set the directory where the logfiles are stored. The folder needs to be both readable and writable by the user running MariaDB MaxScale.
Set the directory where the data files used by MariaDB MaxScale are stored. Modules can write to this directory and for example the binlogrouter uses this folder as the default location for storing binary logs.
Set the directory where MariaDB MaxScale looks for modules. The library directory is the only directory that MariaDB MaxScale uses when it searches for modules. If you have custom modules for MariaDB MaxScale, make sure you have them in this folder.
Configure the directory MariaDB MaxScale uses to store cached data. An example of cached data is the authentication data fetched from the backend servers. MariaDB MaxScale stores this in case a connection to the backend server is not possible.
Configure the directory for the PID file for MariaDB MaxScale. This file contains the Process ID for the running MariaDB MaxScale process.
Configure the directory where the executable files reside. All internal processes which are launched will use this directory to look for executable files.
Location of the MariaDB Connector-C plugin directory. The MariaDB Connector-C used in MaxScale can use this directory to load authentication plugins. The versions of the plugins must be binary compatible with the connector version that MaxScale was built with.
Configure the directory where persisted configurations are stored. When a new server is created via MaxAdmin, it will be stored in this directory. Do not use or modify the contents of this directory, use /etc/maxscale.cnf.d/ instead.
Configure the directory where module configurations are stored. Path arguments are resolved relative to this directory. This directory should be used to store module specific configurations e.g. dbfwfilter rule files.
Any configuration parameter that is not an absolute path will be interpreted as a relative path. The relative paths use the module configuration directory as the working directory.
For example, the configuration parameter
file=my_file.txt would be interpreted
be interpreted as
Set the folder where the errmsg.sys file is located in. MariaDB MaxScale will look for the errmsg.sys file installed with MariaDB MaxScale from this folder.
The module used by MariaDB MaxScale for query classification. The information provided by this module is used by MariaDB MaxScale when deciding where a particular statement should be sent. The default query classifier is qc_sqlite.
Arguments for the query classifier. What arguments are accepted depends on the particular query classifier being used. The default query classifier - qc_sqlite - supports the following arguments:
An integer argument taking the following values: * 0: Nothing is logged. This is the default. * 1: Statements that cannot be parsed completely are logged. They may have been partially parsed, or classified based on keyword matching. * 2: Statements that cannot even be partially parsed are logged. They may have been classified based on keyword matching. * 3: Statements that cannot even be classified by keyword matching are logged.
This will log all statements that cannot be parsed completely. This may be useful if you suspect that MariaDB MaxScale routes statements to the wrong server (e.g. to a slave instead of to a master).
What specific local address/interface to use when connecting to servers.
This can be used for ensuring that MaxScale uses a particular interface when connecting to servers, in case the computer MaxScale is running on has multiple interfaces.
How often, in seconds, MaxScale at most may refresh the users from the backend server.
MaxScale will at startup load the users from the backend server, but if
the authentication of a user fails, MaxScale assumes it is because a new
user has been created and will thus refresh the users. By default, MaxScale
will do that at most once per 30 seconds and with this configuration option
that can be changed. The minimum allowed value is 10 seconds. A negative
value disables the refreshing entirelly. Note that using
maxadmin it is
possible to explicitly cause the users of a service to be reloaded.
A service represents the database service that MariaDB MaxScale offers to the clients. In general a service consists of a set of backend database servers and a routing algorithm that determines how MariaDB MaxScale decides to send statements or route connections to those backend servers.
A service may be considered as a virtual database server that MariaDB MaxScale makes available to its clients.
Several different services may be defined using the same set of backend servers. For example a connection based routing service might be used by clients that already performed internal read/write splitting, whilst a different statement based router may be used by clients that are not written with this functionality in place. Both sets of applications could access the same data in the same databases.
A service is identified by a service name, which is the name of the configuration file section and a type parameter of service.
[Test Service] type=service
In order for MariaDB MaxScale to forward any requests it must have at least one service defined within the configuration file. The definition of a service alone is not enough to allow MariaDB MaxScale to forward requests however, the service is merely present to link together the other configuration elements.
The router parameter of a service defines the name of the router module that will be used to implement the routing algorithm between the client of MariaDB MaxScale and the backend databases. Additionally routers may also be passed a comma separated list of options that are used to control the behavior of the routing algorithm. The two parameters that control the routing choice are router and router_options. The router options are specific to a particular router and are used to modify the behavior of the router. The read connection router can be passed options of master, slave or synced, an example of configuring a service to use this router and limiting the choice of servers to those in slave state would be as follows.
To change the router to connect on to servers in the master state as well as slave servers, the router options can be modified to include the master state.
A more complete description of router options and what is available for a given router is included with the documentation of the router itself.
Option string given to the router module. The value of this parameter should be a comma-separated list of key-value pairs. See router specific documentation for more details.
The filters option allow a set of filters to be defined for a service; requests from the client are passed through these filters before being sent to the router for dispatch to the backend server. The filters parameter takes one or more filter names, as defined within the filter definition section of the configuration file. Multiple filters are separated using the | character.
filters=counter | QLA
The requests pass through the filters from left to right in the order defined in the configuration parameter.
The servers parameter in a service definition provides a comma separated list of the backend servers that comprise the service. The server names are those used in the name section of a block with a type parameter of server (see below).
The user parameter, along with the passwd parameter are used to define the credentials used to connect to the backend servers to extract the list of database users from the backend database that is used for the client authentication.
Authentication of incoming connections is performed by MariaDB MaxScale itself rather than by the database server to which the client is connected. The client will authenticate itself with MariaDB MaxScale, using the username, hostname and password information that MariaDB MaxScale has extracted from the backend database servers. For a detailed discussion of how this impacts the authentication process please see the "Authentication" section below.
The host matching criteria is restricted to IPv4, IPv6 will be added in a future release.
Existing user configuration in the backend databases must be checked and may be updated before successful MariaDB MaxScale authentication:
In order for MariaDB MaxScale to obtain all the data it must be given a username it can use to connect to the database and retrieve that data. This is the parameter that gives MariaDB MaxScale the username to use for this purpose.
The account used must be able to select from the mysql.user table, the following is an example showing how to create this user.
CREATE USER 'maxscale'@'maxscalehost' IDENTIFIED BY 'maxscale-password';
SELECT privileges on the
SHOW DATABASES privileges are required in order to load databases
name and grants suitable for database name authorization.
GRANT SELECT ON mysql.user TO 'maxscale'@'maxscalehost'; GRANT SELECT ON mysql.db TO 'maxscale'@'maxscalehost'; GRANT SELECT ON mysql.tables_priv TO 'maxscale'@'maxscalehost'; GRANT SHOW DATABASES ON *.* TO 'maxscale'@'maxscalehost';
MariaDB MaxScale will execute the following query to retrieve the users. If you suspect that you might have problems with grants, it is recommended to run this query and see the results it returns.
SELECT DISTINCT user.user AS user, user.host AS host, user.password AS password, concat(user.user,user.host,user.password, IF((user.Select_priv+0)||find_in_set('Select',Coalesce(tp.Table_priv,0)),'Y','N') , COALESCE( db.db,tp.db, '')) AS userdata, user.Select_priv AS anydb, COALESCE( db.db,tp.db, NULL) AS db FROM mysql.user LEFT JOIN mysql.db ON user.user=db.user AND user.host=db.host LEFT JOIN mysql.tables_priv tp ON user.user=tp.user AND user.host=tp.host WHERE user.user IS NOT NULL AND user.user <> ''
In versions of MySQL 5.7.6 and later, the
Password column was replaced by
user.password above with
Note: If authentication fails, MaxScale will try to refresh the list of database users used by the service up to 4 times every 30 seconds.
The passwd parameter provides the password information for the above user and may be either a plain text password or it may be an encrypted password. See the section on encrypting passwords for use in the maxscale.cnf file. This user must be capable of connecting to the backend database and executing these SQL statements to load database names and grants from the backends:
SELECT user, host, password,Select_priv FROM mysql.user.
SELECT user, host, db FROM mysql.db
SELECT * FROM INFORMATION_SCHEMA.SCHEMATA
SELECT GRANTEE,PRIVILEGE_TYPE FROM INFORMATION_SCHEMA.USER_PRIVILEGES
This parameter controls the ability of the root user to connect to MariaDB MaxScale and hence onwards to the backend servers via MariaDB MaxScale.
The default value is
0, disabling the ability of the root user to connect to
Example for enabling root user:
true may also be given to enable the root user and
false may be given to disable the use of the root user.
This parameter enables matching of "127.0.0.1" (localhost) against "%" wildcard
host for MySQL protocol authentication. The default value is
0, so in order to
authenticate a connection from the same machine as the one on which MariaDB
MaxScale is running, an explicit user@localhost entry will be required in the
MySQL user table.
This parameter sets a custom version string that is sent in the MySQL Handshake from MariaDB MaxScale to clients.
If not set, the default value is
5.5.5-10.0.0 MaxScale <MaxScale version>
<MaxScale version> is the version of MaxScale. If the provided string
does not start with the number 5, a 5.5.5- prefix will be added to it. This
means that a version_string value of MaxScale-Service would result in a
5.5.5-MaxScale-Service being sent to the client.
The weightby parameter is used in conjunction with server parameters in order to control the load balancing applied in the router in use by the service. This allows varying weights to be applied to each server to create a non-uniform distribution of the load amongst the servers.
An example of this might be to define a parameter for each server that represents the amount of resource available on the server, we could call this serversize. Every server should then have a serversize parameter set for the server.
The service would then have the parameter
weightby=serversize. If there are 4
servers defined in the service (serverA, serverB, serverC and serverD) with the
serversize set as shown in the table below, the connections would balanced using
the percentages in this table.
Note: If the value of the weighting parameter of an individual server is zero or the relative weight rounds down to zero, no queries will be routed to that server as long as a server with a positive weight is available.
Here is an excerpt from an example configuration with the
parameter used as the weighting parameter.
[server1] type=server address=127.0.0.1 port=3000 protocol=MySQLBackend serv_weight=3 [server2] type=server address=127.0.0.1 port=3001 protocol=MySQLBackend serv_weight=1 [Read Service] type=service router=readconnroute servers=server1,server2 weightby=serv_weight
With this configuration and a heavy query load, the server server1 will get most of the connections and about a third of the remaining queries are routed to the second server. With server weights, you can assign secondary servers that are only used when the primary server is under heavy load.
Without the weightby parameter, each connection counts as a single connection. With a weighting parameter, a single connection received its weight from the server's own weighting parameter divided by the sum of all weighting parameters in all the configured servers.
If we use the previous configuration as an example, the sum of the
parameter is 4. Server1 would receive a weight of
3/4=75% and server2
1/4=25%. This means that server1 would get 75% of the connections
and server2 would get 25% of the connections.
This parameter controls whether only a single server or all of the servers are used when loading the users from the backend servers. This takes a boolean value and when enabled, creates a union of all the users and grants on all the servers.
The strip_db_esc parameter strips escape characters from database names of grants when loading the users from the backend server.
This parameter takes a boolean value and when enabled, will strip all backslash (
characters from the database names. The default value for this parameter is true
since MaxScale 2.0.1. In previous version, the default value was false.
Some visual database management tools automatically escape some characters and this might cause conflicts when MariaDB MaxScale tries to authenticate users.
The retry_on_failure parameter controls whether MariaDB MaxScale will try to restart failed services and accepts a boolean value. This functionality is enabled by default to prevent services being permanently disabled if the starting of the service failed due to a network outage. Disabling the restarting of the failed services will cause them to be permanently disabled if the services can't be started when MariaDB MaxScale is started.
Enable or disable the logging of authentication failures and warnings. This parameter takes a boolean value.
MariaDB MaxScale normally suppresses warning messages about failed authentication. Enabling this option will log those messages into the message log with details about who tried to connect to MariaDB MaxScale and from where.
The connection_timeout parameter is used to disconnect sessions to MariaDB MaxScale that have been idle for too long. The session timeouts are disabled by default. To enable them, define the timeout in seconds in the service's configuration section.
[Test Service] connection_timeout=300
The maximum number of simultaneous connections MaxScale should permit to this service. If the parameter is zero or is omitted, there is no limit. Any attempt to make more connections after the limit is reached will result in a "Too many connections" error being returned.
[Test Service] max_connections=100
Server sections are used to define the backend database servers that can be formed into a service. A server may be a member of one or more services within MariaDB MaxScale. Servers are identified by a server name which is the section name in the configuration file. Servers have a type parameter of server, plus address port and protocol parameters.
[server1] type=server address=127.0.0.1 port=3000 protocol=MySQLBackend
The IP address or hostname of the machine running the database server that is being defined. MariaDB MaxScale will use this address to connect to the backend database server.
The port on which the database listens for incoming connections. MariaDB MaxScale will use this port to connect to the database server.
The name for the protocol module to use to connect MariaDB MaxScale to the database. Currently only one backend protocol is supported, the MySQLBackend module.
The monitor has a username and password that is used to connect to all servers for monitoring purposes, this may be overridden by supplying a monitoruser statement for each individual server.
The monitor has a username and password that is used to connect to all servers for monitoring purposes, this may be overridden by supplying a monpasswd statement for the individual servers.
The monpasswd parameter may be either a plain text password or it may be an encrypted password. See the section on encrypting passwords for use in the maxscale.cnf file.
persistpoolmax parameter defaults to zero but can be set to an integer
value for a back end server. If it is non zero, then when a DCB connected to a
back end server is discarded by the system, it will be held in a pool for reuse,
remaining connected to the back end server. If the number of DCBs in the pool
has reached the value given by
persistpoolmax then any further DCB that is
discarded will not be retained, but disconnected and discarded.
persistmaxtime parameter defaults to zero but can be set to an integer
value indicating a number of seconds. A DCB placed in the persistent pool for a
server will only be reused if the elapsed time since it joined the pool is less
than the given value. Otherwise, the DCB will be discarded and the connection
For more information about persistent connections, please read the Administration Tutorial.
The listener defines a port and protocol pair that is used to listen for connections to a service. A service may have multiple listeners associated with it, either to support multiple protocols or multiple ports. As with other elements of the configuration the section name is the listener name and it can be selected freely. A type parameter is used to identify the section as a listener definition. Address is optional and it allows the user to limit connections to certain interface only. Socket is also optional and used for Unix socket connections.
The network socket where the listener listens will have a backlog of connections. The size of this backlog is controlled by the net.ipv4.tcp_max_syn_backlog and net.core.somaxconn kernel parameters.
Increasing the size of the backlog by modifying the kernel parameters helps with sudden connection spikes and rejected connections. For more information see listen(2).
[<Listener name>] type=listener service=<Service name>] protocol=[MySQLClient|HTTPD] address=[IP|hostname] port=<Listen port number> socket=<Socket path>
The service to which the listener is associated. This is the name of a service that is defined elsewhere in the configuration file.
The name of the protocol module that is used for the communication between the client and MariaDB MaxScale itself.
The address option sets the address that will be used to bind the listening socket. The address may be specified as an IP address in 'dot notation' or as a hostname. If the address option is not included in the listener definition the listener will bind to all network interfaces.
The port to use to listen for incoming connections to MariaDB MaxScale from the clients. If the port is omitted from the configuration a default port for the protocol will be used.
socket option may be included in a listener definition, this configures
the listener to use Unix domain sockets to listen for incoming connections. The
parameter value given is the name of the socket to use.
If a socket option and an address option is given then the listener will listen on both the specific IP address and the Unix socket.
The authenticator module to use. Each protocol module defines a default
authentication module which is used if no
authenticator parameter is found
from the configuration.
Option string given to the authenticator module. The value of this parameter should be a comma-separated list of key-value pairs. See authenticator specific documentation for more details.
The protocols supported by MariaDB MaxScale are implemented as external modules that are loaded dynamically into the MariaDB MaxScale core. They allow MariaDB MaxScale to communicate in various protocols both on the client side and the backend side. Each of the protocols can be either a client protocol or a backend protocol. Client protocols are used for client-MariaDB MaxScale communication and backend protocols are for MariaDB MaxScale-database communication.
This is the implementation of the MySQL protocol that is used by clients of MariaDB MaxScale to connect to MariaDB MaxScale.
The MySQLBackend protocol module is the implementation of the protocol that MariaDB MaxScale uses to connect to the backend MariaDB, MySQL and Percona Server databases. This implementation is tailored for the MariaDB MaxScale to MySQL Database traffic and is not a general purpose implementation of the MySQL protocol.
The telnetd protocol module is used for connections to MariaDB MaxScale itself for the purposes of creating interactive user sessions with the MariaDB MaxScale instance itself. Currently this is used in conjunction with a special router implementation, the debugcli.
The protocol used used by the maxadmin client application in order to connect to MariaDB MaxScale and access the command line interface.
This protocol module is currently still under development, it provides a means to create HTTP connections to MariaDB MaxScale for use by web browsers or RESTful API clients.
This section describes configuration parameters for both servers and listeners that control the TLS/SSL encryption method and the various certificate files involved in it.
To enable TLS/SSL for a listener or a server, you must set the
required and provide the three files for
After this, MaxScale connections between the server and/or the client will be encrypted. Note that the database must be configured to use TLS/SSL connections if backend connection encryption is used. When client-side encryption is enabled, only encrypted connections to MaxScale can be created.
This enables SSL connections when set to
required. If enabled, the three
certificate files mentioned below must also be supplied. MaxScale connections
to will then be encrypted with TLS/SSL.
A string giving a file path that identifies an existing readable file. The file must be the SSL client private key MaxScale should use. This is a required parameter for SSL enabled configurations.
A string giving a file path that identifies an existing readable file. The file
must be the SSL client certificate MaxScale should use with the server. This is
a required parameter for SSL enabled configurations. The certificate must match
the key defined in
A string giving a file path that identifies an existing readable file. The file must be the Certificate Authority (CA) certificate for the CA that signed the certificate referred to in the previous parameter. It will be used to verify that the certificate is valid. This is a required parameter for SSL enabled configurations.
This parameter controls the level of encryption used. Accepted values are:
The default is to use the highest level of encryption available. For OpenSSL 1.0 and newer this is TLSv1.2. Older versions use TLSv1.0 as the default transport layer encryption.
Note: It is highly recommended to leave this parameter to the default value of MAX. This will guarantee that the strongest available encryption is used.
The maximum length of the certificate authority chain that will be accepted.
Legal values are positive integers. Note that if the client is to submit an SSL
ssl_cert_verify_depth parameter must not be 0. If no
value is specified, the default is 9.
Peer certificate verification. This functionality is enabled by default.
When this feature is enabled, the certificate sent by the peer is verified against the configured Certificate Authority. If you are using self-signed certificates, disable this feature.
Example SSL enabled server configuration:
[server1] type=server address=10.131.24.62 port=3306 protocol=MySQLBackend ssl=required ssl_cert=/usr/local/mariadb/maxscale/ssl/crt.max-client.pem ssl_key=/usr/local/mariadb/maxscale/ssl/key.max-client.pem ssl_ca_cert=/usr/local/mariadb/maxscale/ssl/crt.ca.maxscale.pem
This example configuration requires all connections to this server to be encrypted with SSL. The paths to the certificate files and the Certificate Authority file are also provided.
Example SSL enabled listener configuration:
[RW Split Listener] type=listener service=RW Split Router protocol=MySQLClient port=3306 ssl=required ssl_cert=/usr/local/mariadb/maxscale/ssl/crt.maxscale.pem ssl_key=/usr/local/mariadb/maxscale/ssl/key.csr.maxscale.pem ssl_ca_cert=/usr/local/mariadb/maxscale/ssl/crt.ca.maxscale.pem
This example configuration requires all connections to be encrypted with SSL. The paths to the certificate files and the Certificate Authority file are also provided.
The main task of MariaDB MaxScale is to accept database connections from client applications and route the connections or the statements sent over those connections to the various services supported by MariaDB MaxScale.
Currently a number of routing modules are available, these are designed for a range of different needs.
Connection based load balancing: * ReadConnRoute
Read/Write aware statement based router: * ReadWriteSplit
Simple sharding on database level: * SchemaRouter
Binary log server: * Binlogrouter
These modules are used for diagnostic purposes and can tell about the status of MariaDB MaxScale and the cluster it is monitoring.
Monitor modules are used by MariaDB MaxScale to internally monitor the state of the backend databases in order to set the server flags for each of those servers. The router modules then use these flags to determine if the particular server is a suitable destination for routing connections for particular query classifications. The monitors are run within separate threads of MariaDB MaxScale and do not affect MariaDB MaxScale's routing performance.
The use of monitors is highly recommended but it is also possible to run MariaDB MaxScale without a monitor module. In this case an external monitoring system which sets the status of each server via MaxAdmin is needed.
Filters provide a means to manipulate or process requests as they pass through MariaDB MaxScale between the client side protocol and the query router. A full explanation of each filter's functionality can be found in its documentation.
The Filter Tutorial document shows how you can add a filter to a service and combine multiple filters in one service.
- Query Log All (QLA) Filter
- Regular Expression Filter
- Tee Filter
- Top Filter
- Database Firewall Filter
- Query Redirection Filter
- RabbitMQ Filter
The current MariaDB MaxScale configuration may be updated by editing the
configuration file and then forcing MariaDB MaxScale to reread the configuration
file. To force MariaDB MaxScale to reread the configuration file, send a SIGHUP
signal to the MariaDB MaxScale process or execute
reload config in the
The following list of service parameters can be updated at runtime.
In addition to these parameters, the server specific user credentials, monuser and monpw, can also be updated at runtime.
Services that are removed via the configuration update mechanism can not be physically removed from MariaDB MaxScale until there are no longer any connections using the service.
When the number of threads is decreased the threads will not actually be terminated until such time as they complete the current operation of that thread.
Monitors can not be completely removed from the running MariaDB MaxScale.
MariaDB uses username, passwords and the client host in order to authenticate a user, so a typical user would be defined as user X at host Y and would be given a password to connect. MariaDB MaxScale uses exactly the same rules as MariaDB when users connect to the MariaDB MaxScale instance, i.e. it will check the address from which the client is connecting and treat this in exactly the same way that MariaDB would. MariaDB MaxScale will pull the authentication data from one of the backend servers and use this to match the incoming connections, the assumption being that all the backend servers for a particular service will share the same set of user credentials.
It is important to understand, however, that when MariaDB MaxScale itself makes connections to the backend servers the backend server will see all connections as originating from the host that runs MariaDB MaxScale and not the original host from which the client connected to MariaDB MaxScale. Therefore the backend servers should be configured to allow connections from the MariaDB MaxScale host for every user that can connect from any host. Since there is only a single password within the database server for a given host, this limits the configuration such that a given user name must have the same password for every host from which they can connect.
To clarify, if a user X is defined as using password pass1 from host a and
pass2 from host b then there must be an entry in the
user table for user
X from the MariaDB MaxScale host, say pass1.
This would result in rows in the user table as follows
In this case the user X would be able to connect to MariaDB MaxScale from host a giving the password of pass1. In addition MariaDB MaxScale would be able to create connections for this user to the backend servers using the username X and password pass1, since the MariaDB MaxScale host is also defined to have password pass1. User X would not however be able to connect from host b since they would need to provide the password pass2 in order to connect to MariaDB MaxScale, but then MariaDB MaxScale would not be able to connect to the backends as it would also use the password pass2 for these connections.
Hostname mapping in MariaDB MaxScale works in exactly the same way as for MariaDB, if the wildcard is used for the host then any host other than the localhost (127.0.0.1) will match. It is important to consider that the localhost check will be performed at the MariaDB MaxScale level and at the MariaDB server level.
If MariaDB MaxScale and the databases are on separate hosts there are two important changes in behavior to consider:
Clients running on the same machine as the backend database now may access the database using the wildcard entry. The localhost check between the client and MariaDB MaxScale will allow the use of the wildcard, since the client is not running on the MariaDB MaxScale host. Also the wildcard entry can be used on the database host as MariaDB MaxScale is making that connection and it is not running on the same host as the database.
Clients running on the same host as MariaDB MaxScale can not access the database via MariaDB MaxScale using the wildcard entry since the connection to MariaDB MaxScale will be from the localhost. These clients are able to access the database directly, as they will use the wildcard entry.
If MariaDB MaxScale is running on the same host as one or more of the database nodes to which it is routing statements then the wildcard host entries can be used to connect to MariaDB MaxScale but not to connect onwards to the database running on the same node.
In all these cases the issue may be solved by adding an explicit entry for the localhost address that has the same password as the wildcard entry. This may be done using a statement as below for each of the databases that are required:
MariaDB [mysql]> GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP ON employee.* 'user1'@'localhost' IDENTIFIED BY 'xxx'; Query OK, 0 rows affected (0.00 sec)
At the time of writing the authentication mechanism within MariaDB MaxScale does not support IPV6 address matching in connections rules. This is also in line with the current protocol modules that do not support IPV6.
Wildcard address supported in the current version of MariaDB MaxScale are:
192.168.3.% 192.168.%.% 192.%.%.%
and short notations
192.% 192.%.% 192.168.%
Note that currently wildcards are only supported in conjunction with IP-addresses, not with domain names.
MariaDB MaxScale is designed to be executed as a service, therefore all error
reports, including configuration errors, are written to the MariaDB MaxScale
error log file. By default, MariaDB MaxScale will log to a file in
/var/log/maxscale, the only exception to this is if the log directory is not
writable, in which case a message is sent to the standard error descriptor.
MariaDB MaxScale binds on TCP ports and UNIX sockets as well.
If there is a local firewall in the server where MariaDB MaxScale is installed, the IP and port must be configured in order to receive connections from outside.
If the firewall is a network facility among all the involved servers, a configuration update is required as well.
[Galera Listener] type=listener address=192.168.3.33 port=4408 socket=/servers/maxscale/galera.sock
TCP/IP Traffic must be permitted to 192.168.3.33 port 4408
For Unix socket, the socket file path (example:
must be writable by the Unix user MariaDB MaxScale runs as.