# MaxAdmin - Admin Interface # The Maxscale Administrative & Monitoring Client Application - [Overview](#overview) - [Configuring MariaDB MaxScale for MaxAdmin](#configuring-mariadb-maxscale-for-maxadmin) - [Running MaxAdmin](#running-maxadmin) - [Working With Administration Interface Users](#working-with-administration-interface-users) - [Getting Help](#getting-help) - [Working with Services](#working-with-services) - [Working with Servers](#working-with-servers) - [Working with Sessions](#working-with-sessions) - [Descriptor Control Blocks](#descriptor-control-blocks) - [Working with Filters](#working-with-filters) - [Working with Monitors](#working-with-monitors) - [MariaDB MaxScale Status Commands](#maxscale-status-commands) - [Administration Commands](#administration-commands) - [Runtime Configuration Changes](#runtime-configuration-changes) - [Servers](#servers) - [Listeners](#listeners) - [Monitors](#monitors) - [Tuning MariaDB MaxScale](#tuning-mariadb-maxscale) # Overview MaxAdmin is a simple client interface that can be used to interact with the MariaDB MaxScale server, it allows the display of internal MariaDB MaxScale statistics, status and control of MariaDB MaxScale operations. MaxAdmin supports * Interactive user sessions * Execution of one-off commands via command line arguments * Execution of command scripts # Configuring MariaDB MaxScale for MaxAdmin In order to be able to use MaxAdmin, MariaDB MaxScale must be configured for it. There are two ways MaxAdmin can connect to to MaxScale. * Using a Unix domain socket. * Using a hostname and port. The first alternative is introduced in MaxScale 2.0 and is the secure and recommended way. The second alternative is available for backward compatibility, but is _insecure_ and **deprecated** and _will be removed in a future version of MaxScale_. An example configuration looks as follows: ``` [MaxAdmin] type=service router=cli [MaxAdmin Unix Listener] type=listener service=MaxAdmin protocol=maxscaled socket=default [MaxAdmin Inet Listener] type=listener service=MaxAdmin protocol=maxscaled address=localhost port=6603 ``` In the configuration above, two listeners are created; one listening on the default Unix domain socket and one listening on the default port. Which approach is used has other implications than just how the communication between MaxAdmin and MariaDB MaxScale is handled. In the former case, the authorization is based upon the Linux identity and in the latter case on explicitly created user accounts that have **no** relationship to the Linux accounts. Note that if the socket path or port are changed, then MaxAdmin has to be invoked with `-S` or `-P` respectively. # Running MaxAdmin Depending on whether MariaDB MaxScale has been configured to use Unix domain sockets or internet sockets, MaxAdmin needs to be invoked slightly differently. If Unix domain sockets are used, then MaxAdmin needs no additional arguments: ``` alice@host$ maxadmin MaxAdmin> ``` The above implies that the Linux user _alice_ has been enabled to use MaxAdmin. If internet sockets are used, then either the host, port, user or password has to be specified explicitly: ``` alice@host$ maxadmin -u maxscale-admin Password: MaxScale> ``` When internet sockets are enabled, initially it is possible to connect using the username `admin` and the password `mariadb`. These remain in effect as long as no other users have been created. As soon as the first user is added, the use of `admin/mariadb` as login credentials is disabled. If Unix domain sockets are used, then initially only `root` has access. MaxAdmin usage can subsequently be enabled for other Linux users. The MaxAdmin client application may be run in two different modes, either as an interactive command shell for executing commands against MariaDB MaxScale or by passing commands on the MaxAdmin command line itself. # Working With Administration Interface Users Both MaxAdmin and the newly added REST API use the administrative users of MaxScale. The network type administrative users are used by the REST API as well as MaxAdmin when it is configured to use a network listener. Linux account type users are only used by MaxAdmin when the UNIX Domain Socket interface is activated. ## Administrative and Read-only Users Administrative users can perform all operations that MaxScale offers. This includes both read-only operations as well as operations that modify the internal state of MaxScale or its modules. The default user for both the network and the UNIX domain socket interfaces is an administrative user. This user will be removed once the first administrative user of that type is created. The default user for the network interface is `admin` with the password `mariadb`. The default user for the UNIX domain socket interface is `root`. Users that can only perform read-only operations are created with `add readonly-user` command. These users can only perform operations that fetch data and do not modify the state of MaxScale. To convert administrative users to read-only users, delete the old administrative user and create it as a read-only user. ## What Users Have Been Defined? In order to see the Linux users for whom MaxAdmin usage has been enabled and any explicitly created accounts, use the command _show users_. ``` MaxScale> show users Enabled Linux accounts (secure) : alice, bob, cecil Created network accounts (insecure): maxscale-admin MaxScale> ``` Please note that `root` will not be shown. ## Enabling a Linux account To enable MaxAdmin usage for a particular Linux account, use the command _enable account_. This command is passed a user name, which should be the same as that of an existing Linux user. ``` MaxScale> enable account bob ``` Note that it is not checked that the provided name indeed corresponds to an existing Linux account, so it is possible to enable an account that does not exist yet. Note also that it is possible to enable a Linux account irrespective of how MaxAdmin has connected to MariaDB MaxScale. That is, the command is not restricted to MaxAdmin users connecting over a Unix domain socket. ## Disabling a Linux account To disable MaxAdmin usage for a particular Linux account, use the command _disable account_. This command is passed a user name, which should be a Linux user for whom MaxAdmin usage earlier has been enabled. ``` MaxScale> disable account bob ``` Note also that it is possible to disable a Linux account irrespective of how MaxAdmin has connected to MariaDB MaxScale. That is, the command is not restricted to MaxAdmin users connecting over a Unix domain socket. Note that it is possible to disable the current user, but that will only affect the next attempt to use MaxAdmin. `root` cannot be removed. ## Add A New User To add a new MaxAdmin user to be used when MaxAdmin connects over an internet socket, use the command _add user_. This command is passed a user name and a password. ``` MaxScale> add user maxscale-admin secretpwd User maxscale-admin has been successfully added. MaxScale> ``` ## Delete A User To remove a user the command _remove user_ is used and it is invoked with the username. ``` MaxScale> remove user maxscale-admin User maxscale-admin has been successfully removed. MaxScale> ``` Note that it is possible to remove the current user, but that will only affect the next attempt to use MaxAdmin. The last administrative account cannot be removed. ## Creating Read-only Users Currently, the `list` and `show` type commands are the only operations that read-only users can perform. To create a read-only network user, use the `add readonly-user` command. To enable a local Linux account as a read-only user, use the `enable readonly-account` command. Both administrative and read-only users can be deleted with the `remove user` and `disable account` commands. # Command Line Switches The MaxAdmin command accepts a number of options. See the output of `maxadmin --help` for more details. ## Interactive Operation If no arguments other than the command line switches are passed to MaxAdmin it will enter its interactive mode of operation. Users will be prompted to enter commands with a **MaxScale>** prompt. The commands themselves are documented in the sections later in this document. A help system is available that will give some minimal details of the commands available. Command history is available on platforms that support the libedit library. This allows the use of the up and down arrow keys to recall previous commands that have been executed by MaxAdmin. The default edit mode for the history is to emulate *emacs* commands, the behavior of libedit may however be customized using the .editrc file. To obtain the history of commands that have been executed use the inbuilt history command. In interactive mode it is possible to execute a set of commands stored in an external file by using the source command. The command takes the argument of a filename which should contain a set of MariaDB MaxScale commands, one per line. These will be executed in the order they appear in the file. ## Command Line Operation MaxAdmin can also be used to execute commands that are passed on the command line, e.g. ``` -bash-4.1$ maxadmin -S /tmp/maxadmin.sock list services Password: Services. --------------------------+----------------------+--------+--------------- Service Name | Router Module | #Users | Total Sessions --------------------------+----------------------+--------+--------------- Test Service | readconnroute | 1 | 1 Split Service | readwritesplit | 1 | 1 Filter Service | readconnroute | 1 | 1 QLA Service | readconnroute | 1 | 1 Debug Service | debugcli | 1 | 1 CLI | cli | 2 | 27 --------------------------+----------------------+--------+--------------- -bash-4.1$ ``` The single command is executed and MaxAdmin then terminates. If the -p option is not given then MaxAdmin will prompt for a password. If a MariaDB MaxScale command requires an argument which contains whitespace, for example a service name, that name should be quoted. The quotes will be preserved and used in the execution of the MariaDB MaxScale command. ``` -bash-4.1$ maxadmin show service "QLA Service" Password: Service 0x70c6a0 Service: QLA Service Router: readconnroute (0x7ffff0f7ae60) Number of router sessions: 0 Current no. of router sessions: 0 Number of queries forwarded: 0 Started: Wed Jun 25 10:08:23 2014 Backend databases 127.0.0.1:3309 Protocol: MariaDBBackend 127.0.0.1:3308 Protocol: MariaDBBackend 127.0.0.1:3307 Protocol: MariaDBBackend 127.0.0.1:3306 Protocol: MariaDBBackend Users data: 0x724340 Total connections: 1 Currently connected: 1 -bash-4.1$ ``` Command files may be executed by redirecting them to MaxAdmin. ``` maxadmin < listall.ms ``` Another option is to use the #! mechanism to make the command file executable from the shell. To do this add a line at the start of your command file that contains the #! directive with the path of the MaxAdmin executable. Command options may also be given in this line. For example to create a script file that runs a set of list commands ``` #!/usr/bin/maxadmin list modules list servers list services list listeners list dcbs list sessions list filters ``` Then simply set this file to have execute permissions and it may be run like any other command in the Linux shell. ## The .maxadmin file MaxAdmin supports a mechanism to set defaults for the command line switches via a file in the home directory of the user. If a file named `.maxadmin` exists, it will be read and parameters set according to the entries in that file. This mechanism can be used to provide defaults to the command line options. If a command line option is provided, it will still override the value in the `.maxadmin` file. The parameters than can be set are: * `1.4`: _hostname_, _port_, _user_ and _passwd_ * `2.0.0` and `2.0.1`: _socket_ * `2.0.2` onwards: _socket_, _hostname_, _port_, _user_ and _passwd_ (and as synonym _password_) An example of a `.maxadmin` file that will alter the default socket path is: ``` socket=/somepath/maxadmin.socket ``` Note that if in `2.0.2` or later, a value for _socket_ as well as any of the internet socket related options, such as _hostname_, is provided in `.maxadmin`, then _socket_ takes precedence. In that case, provide at least one internet socket related option on the command line to force MaxAdmin to use an internet socket and thus the internet socket related options from `.maxadmin`. The `.maxadmin` file may be made read only to protect any passwords written to that file. # Getting Help A help system is available that describes the commands available via the administration interface. To obtain a list of all commands available simply type the command `help`. ``` Available commands: add: add user - Add insecure account for using maxadmin over the network add server - Add a new server to a service remove: remove user - Remove account for using maxadmin over the network remove server - Remove a server from a service or a monitor create: create server - Create a new server create listener - Create a new listener for a service create monitor - Create a new monitor destroy: destroy server - Destroy a server destroy listener - Destroy a listener destroy monitor - Destroy a monitor alter: alter server - Alter server parameters alter monitor - Alter monitor parameters alter service - Alter service parameters alter maxscale - Alter maxscale parameters set: set server - Set the status of a server set pollsleep - Set poll sleep period set nbpolls - Set non-blocking polls set log_throttling - Set the log throttling configuration clear: clear server - Clear server status disable: disable log-priority - Disable a logging priority disable sessionlog-priority - [Deprecated] Disable a logging priority for a particular session disable root - Disable root access disable syslog - Disable syslog logging disable maxlog - Disable MaxScale logging disable account - Disable Linux user enable: enable log-priority - Enable a logging priority enable sessionlog-priority - [Deprecated] Enable a logging priority for a session enable root - Enable root user access to a service enable syslog - Enable syslog logging enable maxlog - Enable MaxScale logging enable account - Activate a Linux user account for MaxAdmin use flush: flush log - Flush the content of a log file and reopen it flush logs - Flush the content of a log file and reopen it list: list clients - List all the client connections to MaxScale list dcbs - List all active connections within MaxScale list filters - List all filters list listeners - List all listeners list modules - List all currently loaded modules list monitors - List all monitors list services - List all services list servers - List all servers list sessions - List all the active sessions within MaxScale list threads - List the status of the polling threads in MaxScale list commands - List registered commands reload: reload config - Reload the configuration reload dbusers - Reload the database users for a service restart: restart monitor - Restart a monitor restart service - Restart a service restart listener - Restart a listener shutdown: shutdown maxscale - Initiate a controlled shutdown of MaxScale shutdown monitor - Stop a monitor shutdown service - Stop a service shutdown listener - Stop a listener show: show dcbs - Show all DCBs show dbusers - [deprecated] Show user statistics show authenticators - Show authenticator diagnostics for a service show epoll - Show the polling system statistics show eventstats - Show event queue statistics show filter - Show filter details show filters - Show all filters show log_throttling - Show the current log throttling setting (count, window (ms), suppression (ms)) show modules - Show all currently loaded modules show monitor - Show monitor details show monitors - Show all monitors show persistent - Show the persistent connection pool of a server show server - Show server details show servers - Show all servers show serversjson - Show all servers in JSON show services - Show all configured services in MaxScale show service - Show a single service in MaxScale show session - Show session details show sessions - Show all active sessions in MaxScale show tasks - Show all active housekeeper tasks in MaxScale show threads - Show the status of the worker threads in MaxScale show users - Show enabled Linux accounts show version - Show the MaxScale version number sync: sync logs - Flush log files to disk call: call command - Call module command Type `help COMMAND` to see details of each command. Where commands require names as arguments and these names contain whitespace either the \ character may be used to escape the whitespace or the name may be enclosed in double quotes ". ``` To see more details on a particular command, and a list of the sub commands of the command, type help followed by the command name. ``` MaxScale> help list Available options to the `list` command: list clients - List all the client connections to MaxScale Usage: list clients ---------------------------------------------------------------------------- list dcbs - List all active connections within MaxScale Usage: list dcbs ---------------------------------------------------------------------------- list filters - List all filters Usage: list filters ---------------------------------------------------------------------------- list listeners - List all listeners Usage: list listeners ---------------------------------------------------------------------------- list modules - List all currently loaded modules Usage: list modules ---------------------------------------------------------------------------- list monitors - List all monitors Usage: list monitors ---------------------------------------------------------------------------- list services - List all services Usage: list services ---------------------------------------------------------------------------- list servers - List all servers Usage: list servers ---------------------------------------------------------------------------- list sessions - List all the active sessions within MaxScale Usage: list sessions ---------------------------------------------------------------------------- list threads - List the status of the polling threads in MaxScale Usage: list threads ---------------------------------------------------------------------------- list commands - List registered commands Usage: list commands [MODULE] [COMMAND] Parameters: MODULE Regular expressions for filtering module names COMMAND Regular expressions for filtering module command names Example: list commands my-module my-command MaxScale> ``` # Working With Services A service is a very important concept in MariaDB MaxScale as it defines the mechanism by which clients interact with MariaDB MaxScale and can attached to the backend databases. A number of commands exist that allow interaction with the services. ## What Services Are Available? The _list services_ command can be used to discover what services are currently available within your MariaDB MaxScale configuration. ``` MaxScale> list services Services. --------------------------+-------------------+--------+----------------+------------------- Service Name | Router Module | #Users | Total Sessions | Backend databases --------------------------+-------------------+--------+----------------+------------------- RWSplit | readwritesplit | 1 | 1 | server1, server2, server3, server4 SchemaRouter | schemarouter | 1 | 1 | server1, server2, server3, server4 RWSplit-Hint | readwritesplit | 1 | 1 | server1, server2, server3, server4 ReadConn | readconnroute | 1 | 1 | server1 CLI | cli | 2 | 2 | --------------------------+-------------------+--------+----------------+------------------- MaxScale> ``` In order to determine which ports services are using then the _list listeners_ command can be used. ``` MaxScale> list listeners Listeners. ----------------------+---------------------+--------------------+-----------------+-------+-------- Name | Service Name | Protocol Module | Address | Port | State ----------------------+---------------------+--------------------+-----------------+-------+-------- RWSplit-Listener | RWSplit | MariaDBClient | * | 4006 | Running SchemaRouter-Listener | SchemaRouter | MariaDBClient | * | 4010 | Running RWSplit-Hint-Listener | RWSplit-Hint | MariaDBClient | * | 4009 | Running ReadConn-Listener | ReadConn | MariaDBClient | * | 4008 | Running CLI-Listener | CLI | maxscaled | default | 0 | Running ----------------------+---------------------+--------------------+-----------------+-------+-------- MaxScale> ``` ## See Service Details It is possible to see the details of an individual service using the _show service_ command. This command should be passed the name of the service you wish to examine as an argument. Where a service name contains spaces characters there should either be escaped or the name placed in quotes. ``` MaxScale> show service RWSplit Service: RWSplit Router: readwritesplit State: Started use_sql_variables_in: all slave_selection_criteria: LEAST_CURRENT_OPERATIONS master_failure_mode: fail_instantly max_slave_replication_lag: -1 retry_failed_reads: true strict_multi_stmt: true disable_sescmd_history: true max_sescmd_history: 0 master_accept_reads: false Number of router sessions: 0 Current no. of router sessions: 1 Number of queries forwarded: 0 Number of queries forwarded to master: 0 (0.00%) Number of queries forwarded to slave: 0 (0.00%) Number of queries forwarded to all: 0 (0.00%) Started: Thu Apr 20 09:45:13 2017 Root user access: Disabled Backend databases: [127.0.0.1]:3000 Protocol: MariaDBBackend Name: server1 [127.0.0.1]:3001 Protocol: MariaDBBackend Name: server2 [127.0.0.1]:3002 Protocol: MariaDBBackend Name: server3 [127.0.0.1]:3003 Protocol: MariaDBBackend Name: server4 Total connections: 1 Currently connected: 1 MaxScale> ``` This allows the set of backend servers defined by the service to be seen along with the service statistics and other information. ## Examining Service Users MariaDB MaxScale provides an authentication model by which the client application authenticates with MariaDB MaxScale using the credentials they would normally use to with the database itself. MariaDB MaxScale loads the user data from one of the backend databases defined for the service. The _show dbusers_ command can be used to examine the user data held by MariaDB MaxScale. ``` MaxScale> show dbusers RWSplit User names: @localhost @localhost.localdomain 14567USER@localhost monuser@localhost monuser@% 14609USER@localhost maxuser@localhost maxuser@% 14651USER@localhost maxtest@localhost maxtest@% 14693USER@localhost skysql@localhost skysql@% 14735USER@localhost cliuser@localhost cliuser@% repuser@localhost repuser@% MaxScale> ``` ## Reloading Service User Data MariaDB MaxScale will automatically reload user data if there are failed authentication requests from client applications. This reloading is rate limited and triggered by missing entries in the MariaDB MaxScale table. If a user is removed from the backend database user table it will not trigger removal from the MariaDB MaxScale internal table. The reload dbusers command can be used to force the reloading of the user table within MariaDB MaxScale. ``` MaxScale> reload dbusers RWSplit Reloaded database users for service RWSplit. MaxScale> ``` ## Stopping A Service It is possible to stop a service from accepting new connections by using the _shutdown service_ command. This will not affect the connections that are already in place for a service, but will stop any new connections from being accepted. ``` MaxScale> shutdown service RWSplit MaxScale> ``` ## Restart A Stopped Service A stopped service may be restarted by using the _restart service_ command. ``` MaxScale> restart service RWSplit MaxScale> ``` # Working With Servers The server represents each of the instances of MariaDB or MySQL that a service may use. ## What Servers Are Configured? The command _list servers_ can be used to display a list of all the servers configured within MariaDB MaxScale. ``` MaxScale> list servers Servers. -------------------+-----------------+-------+-------------+-------------------- Server | Address | Port | Connections | Status -------------------+-----------------+-------+-------------+-------------------- server1 | 127.0.0.1 | 3000 | 0 | Master, Running server2 | 127.0.0.1 | 3001 | 0 | Slave, Running server3 | 127.0.0.1 | 3002 | 0 | Slave, Running server4 | 127.0.0.1 | 3003 | 0 | Slave, Running -------------------+-----------------+-------+-------------+-------------------- MaxScale> ``` ## Server Details It is possible to see more details regarding a given server using the _show server_ command. ``` MaxScale> show server server2 Server 0x6501d0 (server2) Server: 127.0.0.1 Status: Slave, Running Protocol: MariaDBBackend Port: 3001 Server Version: 10.1.22-MariaDB Node Id: 3001 Master Id: 3000 Slave Ids: Repl Depth: 1 Number of connections: 0 Current no. of conns: 0 Current no. of operations: 0 MaxScale> ``` If the server has a non-zero value set for the server configuration item "persistpoolmax", then additional information will be shown: ``` Persistent pool size: 1 Persistent measured pool size: 1 Persistent pool max size: 10 Persistent max time (secs): 3660 ``` The distinction between pool size and measured pool size is that the first is a counter that is updated when operations affect the persistent connections pool, whereas the measured size is the result of checking how many persistent connections are currently in the pool. It can be slightly different, since any expired connections are removed during the check. ## Setting The State Of A Server MariaDB MaxScale maintains a number of status flags for each server that is configured. These status flags are normally maintained by the monitors but there are two commands in the user interface that can be used to manually set these flags; the _set server_ and _clear server_ commands. |Flag |Description | |-----------|-------------------------------------------------------------------------------------------| |running |The server is responding to requests, accepting connections and executing database commands| |master |The server is a master in a replication or it can be used for database writes | |slave |The server is a replication slave or is considered as a read only database | |synced |The server is a fully fledged member of a Galera cluster | |maintenance|The server is in maintenance mode. It won't be used by services or monitored by monitors | |stale |The server is a [stale master server](../Monitors/MariaDB-Monitor.md) | All status flags, with the exception of the maintenance flag, will be set by the monitors that are monitoring the server. If manual control is required the monitor should be stopped. ``` MaxScale> set server server3 maintenance MaxScale> clear server server3 maintenance MaxScale> ``` ## Viewing the persistent pool of DCB The DCBs that are in the pool for a particular server can be displayed (in the format described below in the DCB section) with a command like: ``` MaxScale> show persistent server1 Number of persistent DCBs: 0 ``` # Working With Sessions The MariaDB MaxScale session represents the state within MariaDB MaxScale. Sessions are dynamic entities and not named in the configuration file, this means that sessions can not be easily named within the user interface. The sessions are referenced using ID values, these are actually memory address, however the important thing is that no two session have the same ID. ## What Sessions Are Active in MariaDB MaxScale? There are a number of ways to find out what sessions are active, the most comprehensive being the _list sessions_ command. ``` MaxScale> list sessions -----------------+-----------------+----------------+-------------------------- Session | Client | Service | State -----------------+-----------------+----------------+-------------------------- 10 | localhost | CLI | Session ready for routing 11 | ::ffff:127.0.0.1 | RWSplit | Session ready for routing -----------------+-----------------+----------------+-------------------------- MaxScale> ``` This will give a list of client connections. ## Display Session Details Once the session ID has been determined using one of the above method it is possible to determine more detail regarding a session by using the _show session_ command. ``` MaxScale> show session 11 Session 11 State: Session ready for routing Service: RWSplit Client Address: maxuser@::ffff:127.0.0.1 Connected: Thu Apr 20 09:51:31 2017 Idle: 82 seconds MaxScale> ``` # Descriptor Control Blocks The Descriptor Control Block or DCB is a very important entity within MariaDB MaxScale, it represents the state of each connection within MariaDB MaxScale. A DCB is allocated for every connection from a client, every network listener and every connection to a backend database. Statistics for each of these connections are maintained within these DCB’s. As with session above the DCB’s are not named and are therefore referred to by the use of a unique ID, the memory address of the DCB. ## Finding DCB’s There are several ways to determine what DCB’s are active within a MariaDB MaxScale server, the most straightforward being the _list dcbs_ command. ``` MaxScale> list dcbs Descriptor Control Blocks ------------------+----------------------------+--------------------+---------- DCB | State | Service | Remote ------------------+----------------------------+--------------------+---------- 0x68c0a0 | DCB for listening socket | RWSplit | 0x6e23f0 | DCB for listening socket | CLI | 0x691710 | DCB for listening socket | SchemaRouter | 0x7fffe40130f0 | DCB in the polling loop | CLI | localhost 0x6b7540 | DCB for listening socket | RWSplit-Hint | 0x6cd020 | DCB for listening socket | ReadConn | 0x7fffd80130f0 | DCB in the polling loop | RWSplit | ::ffff:127.0.0.1 0x7fffdc014590 | DCB in the polling loop | RWSplit | 0x7fffdc0148d0 | DCB in the polling loop | RWSplit | 0x7fffdc014c60 | DCB in the polling loop | RWSplit | 0x7fffdc014ff0 | DCB in the polling loop | RWSplit | ------------------+----------------------------+--------------------+---------- MaxScale> ``` A MariaDB MaxScale server that has activity on it will however have many more DCB’s than in the example above, making it hard to find the DCB that you require. The DCB ID is also included in a number of other command outputs, depending on the information you have it may be easier to use other methods to locate a particular DCB. ## DCB Of A Client Connection To find the DCB for a particular client connection it may be best to start with the list clients command and then look at each DCB for a particular client address to determine the one of interest. ## DCB Details The details of DCBs can be obtained by use of the _show dcbs_ command ``` DCB: 0x68c0a0 DCB state: DCB for listening socket Service: RWSplit Role: Service Listener Statistics: No. of Reads: 0 No. of Writes: 0 No. of Buffered Writes: 0 No. of Accepts: 1 No. of High Water Events: 0 No. of Low Water Events: 0 DCB: 0x7fffd80130f0 DCB state: DCB in the polling loop Service: RWSplit Connected to: ::ffff:127.0.0.1 Username: maxuser Role: Client Request Handler Statistics: No. of Reads: 5 No. of Writes: 0 No. of Buffered Writes: 6 No. of Accepts: 0 No. of High Water Events: 0 No. of Low Water Events: 0 DCB: 0x7fffdc014590 DCB state: DCB in the polling loop Service: RWSplit Server name/IP: 127.0.0.1 Port number: 3000 Protocol: MariaDBBackend Server status: Master, Running Role: Backend Request Handler Statistics: No. of Reads: 4 No. of Writes: 0 No. of Buffered Writes: 3 No. of Accepts: 0 No. of High Water Events: 0 No. of Low Water Events: 0 ``` The information Username, Protocol, Server Status are not always relevant, and will not be shown when they are null. The time the DCB was added to the persistent pool is only shown for a DCB that is in a persistent pool. # Working with Filters Filters allow the request contents and result sets from a database to be modified for a client connection, pipelines of filters can be created between the client connection and MariaDB MaxScale router modules. ## What Filters Are Configured? Filters are configured in the configuration file for MariaDB MaxScale, they are given names and may be included in the definition of a service. The _list filters_ command can be used to determine which filters are defined. ``` MaxScale> list filters Filters --------------------+-----------------+---------------------------------------- Filter | Module | Options --------------------+-----------------+---------------------------------------- counter | testfilter | QLA | qlafilter | /tmp/QueryLog Replicate | tee | QLA_BLR | qlafilter | /tmp/QueryLog.blr0 regex | regexfilter | MySQL5.1 | regexfilter | top10 | topfilter | --------------------+-----------------+---------------------------------------- MaxScale> ``` ## Retrieve Details Of A Filter Configuration The command _show filter_ can be used to display information related to a particular filter. ``` MaxScale> show filter QLA Filter 0x719460 (QLA) Module: qlafilter Options: /tmp/QueryLog Limit logging to connections from 127.0.0.1 Include queries that match select.*from.*user.*where MaxScale> ``` ## Filter Usage The _show session_ command will include details for each of the filters in use within a session. First use _list sessions_ or _list clients_ to find the session of interest and then run the _show session_ command ``` MaxScale> list sessions -----------------+-----------------+----------------+-------------------------- Session | Client | Service | State -----------------+-----------------+----------------+-------------------------- 6 | ::ffff:127.0.0.1 | RWSplit-Top | Session ready for routing 7 | localhost | CLI | Session ready for routing -----------------+-----------------+----------------+-------------------------- MaxScale> show session 6 Session 6 State: Session ready for routing Service: RWSplit-Top Client Address: maxuser@::ffff:127.0.0.1 Connected: Thu Apr 20 09:58:38 2017 Idle: 9 seconds Filter: Top Report size 10 Logging to file /tmp/top.1. Current Top 10: 1 place: Execution time: 0.000 seconds SQL: show tables from information_schema 2 place: Execution time: 0.000 seconds SQL: show databases 3 place: Execution time: 0.000 seconds SQL: show tables 4 place: Execution time: 0.000 seconds SQL: select @@version_comment limit 1 ``` The data displayed varies from filter to filter, the example above is the top filter. This filter prints a report of the current top queries at the time the show session command is run. # Working With Monitors Monitors are used to monitor the state of databases within MariaDB MaxScale in order to supply information to other modules, specifically the routers within MariaDB MaxScale. ## What Monitors Are Running? To see what monitors are running within MariaDB MaxScale use the _list monitors_ command. ``` MaxScale> list monitors ---------------------+--------------------- Monitor | Status ---------------------+--------------------- MySQL-Monitor | Running ---------------------+--------------------- MaxScale> ``` ## Details Of A Particular Monitor To see the details of a particular monitor use the _show monitor_ command. ``` MaxScale> show monitor MySQL-Monitor Monitor: 0x6577e0 Name: MySQL-Monitor State: Running Sampling interval: 10000 milliseconds Connect Timeout: 3 seconds Read Timeout: 1 seconds Write Timeout: 2 seconds Monitored servers: [127.0.0.1]:3000, [127.0.0.1]:3001, [127.0.0.1]:3002, [127.0.0.1]:3003 MaxScale MonitorId: 0 Replication lag: disabled Detect Stale Master: enabled Server information Server: server1 Server ID: 3000 Read only: OFF Slave configured: NO Slave IO running: NO Slave SQL running: NO Master ID: -1 Master binlog file: Master binlog position: 0 Server: server2 Server ID: 3001 Read only: OFF Slave configured: YES Slave IO running: YES Slave SQL running: YES Master ID: 3000 Master binlog file: binlog.000001 Master binlog position: 435 Server: server3 Server ID: 3002 Read only: OFF Slave configured: YES Slave IO running: YES Slave SQL running: YES Master ID: 3000 Master binlog file: binlog.000001 Master binlog position: 435 Server: server4 Server ID: 3003 Read only: OFF Slave configured: YES Slave IO running: YES Slave SQL running: YES Master ID: 3000 Master binlog file: binlog.000001 Master binlog position: 435 MaxScale> ``` ## Shutting Down A Monitor A monitor may be shutdown using the _shutdown monitor_ command. This allows for manual control of the status of servers using the _set server_ and _clear server_ commands. ``` MaxScale> shutdown monitor MySQL-Monitor MaxScale> list monitors ---------------------+--------------------- Monitor | Status ---------------------+--------------------- MySQL-Monitor | Stopped ---------------------+--------------------- MaxScale> ``` ## Restarting A Monitor A monitor that has been shutdown may be restarted using the _restart monitor_ command. ``` MaxScale> restart monitor MySQL-Monitor MaxScale> list monitors ---------------------+--------------------- Monitor | Status ---------------------+--------------------- MySQL-Monitor | Running ---------------------+--------------------- MaxScale> ``` # MaxScale Status Commands A number of commands exists that enable the internal MariaDB MaxScale status to be revealed, these commands give an insight to how MariaDB MaxScale is using resource internally and are used to allow the tuning process to take place. ## MariaDB MaxScale Thread Usage MariaDB MaxScale uses a number of threads, as defined in the MariaDB MaxScale configuration file, to execute the processing of requests received from clients and the handling of responses. The _show threads_ command can be used to determine what each thread is currently being used for. ``` MaxScale> show threads Polling Threads. Historic Thread Load Average: 1.06. Current Thread Load Average: 0.00. 15 Minute Average: 0.10, 5 Minute Average: 0.30, 1 Minute Average: 0.67 Pending event queue length averages: 15 Minute Average: 0.00, 5 Minute Average: 0.00, 1 Minute Average: 0.00 ID | State | # fds | Descriptor | Running | Event ----+------------+--------+------------------+----------+--------------- 0 | Polling | | | | 1 | Polling | | | | 2 | Processing | 1 | 0x6e0dd0 | <202400ms | IN|OUT 3 | Polling | | | | MaxScale> ``` The resultant output returns data as to the average thread utilization for the past minutes 5 minutes and 15 minutes. It also gives a table, with a row per thread that shows what DCB that thread is currently processing events for, the events it is processing and how long, to the nearest 100ms has been send processing these events. ## The Housekeeper Tasks Internally MariaDB MaxScale has a housekeeper thread that is used to perform periodic tasks, it is possible to use the command show tasks to see what tasks are outstanding within the housekeeper. ``` MaxScale> show tasks Name | Type | Frequency | Next Due --------------------------+----------+-----------+------------------------- Load Average | Repeated | 10 | Thu Apr 20 10:02:26 2017 MaxScale> ``` # Administration Commands ## What Modules Are In use? In order to determine what modules are in use, and the version and status of those modules the _list modules_ command can be used. ``` MaxScale> list modules Modules. ----------------+-----------------+---------+-------+------------------------- Module Name | Module Type | Version | API | Status ----------------+-----------------+---------+-------+------------------------- qc_sqlite | QueryClassifier | V1.0.0 | 1.1.0 | Beta MySQLAuth | Authenticator | V1.1.0 | 1.1.0 | GA MariaDBClient | Protocol | V1.1.0 | 1.1.0 | GA MaxAdminAuth | Authenticator | V2.1.0 | 1.1.0 | GA maxscaled | Protocol | V2.0.0 | 1.1.0 | GA MySQLBackendAuth| Authenticator | V1.0.0 | 1.1.0 | GA MariaDBBackend | Protocol | V2.0.0 | 1.1.0 | GA mariadbmon | Monitor | V1.5.0 | 3.0.0 | GA schemarouter | Router | V1.0.0 | 2.0.0 | Beta readwritesplit | Router | V1.1.0 | 2.0.0 | GA topfilter | Filter | V1.0.1 | 2.2.0 | GA readconnroute | Router | V1.1.0 | 2.0.0 | GA cli | Router | V1.0.0 | 2.0.0 | GA ----------------+-----------------+---------+-------+------------------------- MaxScale> ``` This command provides important version information for the module. Each module has two versions; the version of the module itself and the version of the module API that it supports. Also included in the output is the status of the module, this may be "In Development", “Alpha”, “Beta”, “GA” or “Experimental”. ## Enabling syslog and maxlog logging MariaDB MaxScale can log messages to syslog, to a log file or to both. The approach can be set in the config file, but can also be changed from maxadmin. Syslog logging is identified by *syslog* and file logging by *maxlog*. ``` MaxScale> enable syslog MaxScale> disable maxlog ``` **NOTE** If you disable both, then you will see no messages at all. ## Rotating the log file MariaDB MaxScale logs messages to a log file in the log directory of MariaDB MaxScale. As the log file grows continuously, it is recommended to periodically rotate it. When rotated, the current log file will be closed and a new one with the *same* name opened. To retain the earlier log entries, you need to first rename the log file and then instruct MaxScale to rotate it. ``` $ mv maxscale.log maxscale1.log $ # MaxScale continues to write to maxscale1.log $ kill -SIGUSR1 $ # MaxScale closes the file (i.e. maxscale1.log) and reopens maxscale.log ``` There are two ways for rotating the log - *flush log maxscale* and *flush logs*; the result is identical. The two alternatives are due to historical reasons; earlier MariaDB MaxScale had several different log files. ``` MaxScale> flush log maxscale MaxScale> flush logs MaxScale> ``` ## Change MariaDB MaxScale Logging Options From version 1.3 onwards, MariaDB MaxScale has a single log file where messages of various priority (aka severity) are logged. Consequently, you no longer enable or disable log files but log priorities. The priorities are the same as those of syslog and the ones that can be enabled or disabled are *debug*, *info*, *notice* and *warning*. *Error* and any more severe messages can not be disabled. ``` MaxScale> enable log-priority info MaxScale> disable log-priority notice MaxScale> ``` Please note that changes made via this interface will not persist across restarts of MariaDB MaxScale. To make a permanent change edit the maxscale.cnf file. ## Adjusting the Log Throttling From 2.0 onwards, MariaDB MaxScale will throttle messages that are logged too frequently, which typically is a sign that MaxScale encounters some error that just keeps on repeating. The aim is to prevent the log from flooding. The configuration specifies how many times a particular error may be logged during a period of a specified length, before it is suppressed for a period of a specified other length. The current log throttling configuration can be queried with ``` MaxScale> show log_throttling 10 1000 100000 ``` where the numbers are the count, the length (in milliseconds) of the period during which the counting is made, and the length (in milliseconds) of the period the message is subsequently suppressed. The configuration can be set with ``` MaxScale> set log_throttling 10 1000 10000 ``` where numbers are specified in the same order as in the *show* case. Setting any of the values to 0, disables the throttling. ## Reloading The Configuration **Note:** This command has been deprecated. Use the MaxScale REST API or the MaxAdmin `alter` commands to change configuration values at runtime. A command, _reload config_, is available that will cause MariaDB MaxScale to reload the maxscale.cnf configuration file. Note that not all configuration changes are taken into effect when the configuration is reloaded. Refer to the [Configuration Guide](../Getting-Started/Configuration-Guide.md) for a list of parameters that can be changed with it. ## Shutting Down MariaDB MaxScale The MariaDB MaxScale server may be shutdown using the _shutdown maxscale_ command. ``` MaxScale> shutdown maxscale MaxScale> ``` # Runtime Configuration Changes Starting with the 2.1 version of MaxScale, you can modify the runtime configuration. This means that new objects (servers, listeners, monitors) can be created, altered and removed at runtime. ## Servers ### Creating a New Server In order to add new servers into MaxScale, they must first be created. They can be created with the `create server` command. Any runtime configuration changes to servers are persisted meaning that they will still be in effect even after a restart. ``` create server - Create a new server Usage: create server NAME HOST [PORT] [PROTOCOL] [AUTHENTICATOR] [OPTIONS] Parameters: NAME Server name HOST Server host address PORT Server port (default 3306) PROTOCOL Server protocol (default MariaDBBackend) AUTHENTICATOR Authenticator module name (default MySQLAuth) OPTIONS Comma separated list of options for the authenticator The first two parameters are required, the others are optional. Example: create server my-db-1 192.168.0.102 3306 ``` ### Adding Servers to Services and Monitors To add a server to a service or a monitor, use the `add server` command. Any changes to the servers of a service or a monitor are persisted meaning that they will still be in effect even after a restart. Servers added to services will only be taken into use by new sessions. Old sessions will only use the servers that were a part of the service when they were created. ``` add server - Add a new server to a service Usage: add server SERVER TARGET... Parameters: SERVER The server that is added to TARGET TARGET List of service and/or monitor names separated by spaces A server can be assigned to a maximum of 11 objects in one command Example: add server my-db my-service "Cluster Monitor" ``` ### Removing Servers from Services and Monitors To remove servers from a service or a monitor, use the `remove server` command. The same rules about server usage for services that apply to `add server` also apply to `remove server`. The servers will only be removed from new sessions created after the command is executed. ``` remove server - Remove a server from a service or a monitor Usage: remove server SERVER TARGET... Parameters: SERVER The server that is removed from TARGET TARGET List of service and/or monitor names separated by spaces A server can be removed from a maximum of 11 objects in one command Example: remove server my-db my-service "Cluster Monitor" ``` ### Altering Servers You can alter server parameters with the `alter server` command. Any changes to the address or port of the server will take effect for new connections only. Changes to other parameters will take effect immediately. Please note that in order for SSL to be enabled for a created server, all of the required SSL parameters (`ssl`, `ssl_key`, `ssl_cert` and `ssl_ca_cert`) must be given in the same command. ``` alter server - Alter server parameters Usage: alter server NAME KEY=VALUE ... Parameters: NAME Server name KEY=VALUE List of `key=value` pairs separated by spaces This will alter an existing parameter of a server. The accepted values for KEY are: address Server address port Server port monuser Monitor user for this server monpw Monitor password for this server ssl Enable SSL, value must be 'required' ssl_key Path to SSL private key ssl_cert Path to SSL certificate ssl_ca_cert Path to SSL CA certificate ssl_version SSL version ssl_cert_verify_depth Certificate verification depth To configure SSL for a newly created server, the 'ssl', 'ssl_cert', 'ssl_key' and 'ssl_ca_cert' parameters must be given at the same time. Example: alter server my-db-1 address=192.168.0.202 port=3307 ``` ### Destroying Servers You can destroy created servers with the `destroy server` command. Only servers created with the `create server` command should be destroyed. A server can only be destroyed once it has been removed from all services and monitors. ``` destroy server - Destroy a server Usage: destroy server NAME Parameters: NAME Server to destroy Example: destroy server my-db-1 ``` ## Listeners ### Creating New Listeners To create a new listener for a service, use the `create listener` command. This will create and start a new listener for a service which will immediately start listening for new connections on the specified port. Please note that in order for SSL to be enabled for a created listeners, all of the required SSL parameters (`ssl`, `ssl_key`, `ssl_cert` and `ssl_ca_cert`) must be given. All the `create listener` parameters do not need to be defined in order for SSL to be enabled. The _default_ parameter can be used to signal that MaxScale should use a default value for the parameter in question. ``` create listener - Create a new listener for a service Usage: create listener SERVICE NAME [HOST] [PORT] [PROTOCOL] [AUTHENTICATOR] [OPTIONS] [SSL_KEY] [SSL_CERT] [SSL_CA] [SSL_VERSION] [SSL_VERIFY_DEPTH] Parameters SERVICE Service where this listener is added NAME Listener name HOST Listener host address (default [::]) PORT Listener port (default 3306) PROTOCOL Listener protocol (default MariaDBClient) AUTHENTICATOR Authenticator module name (default MySQLAuth) OPTIONS Options for the authenticator module SSL_KEY Path to SSL private key SSL_CERT Path to SSL certificate SSL_CA Path to CA certificate SSL_VERSION SSL version (default MAX) SSL_VERIFY_DEPTH Certificate verification depth The first two parameters are required, the others are optional. Any of the optional parameters can also have the value 'default' which will be replaced with the default value. Example: create listener my-service my-new-listener 192.168.0.101 4006 ``` ### Destroying Listeners You can destroy created listeners with the `destroy listener` command. This will remove the persisted configuration and it will not be created on the next startup. The listener is stopped but it will remain a part of the runtime configuration until the next restart. ``` destroy listener - Destroy a listener Usage: destroy listener SERVICE NAME Parameters: NAME Listener to destroy The listener is stopped and it will be removed on the next restart of MaxScale Example: destroy listener my-listener ``` ## Monitors ### Creating New Monitors The `create monitor` command creates a new monitor that is initially stopped. Configure the monitor with the `alter monitor` command and then start it with the `restart monitor` command. The _user_ and _password_ parameters of the monitor must be defined before the monitor is started. ``` create monitor - Create a new monitor Usage: create monitor NAME MODULE Parameters: NAME Monitor name MODULE Monitor module Example: create monitor my-monitor mariadbmon ``` ### Altering Monitors To alter a monitor, use the `alter monitor` command. Module specific parameters can also be altered. ``` alter monitor - Alter monitor parameters Usage: alter monitor NAME KEY=VALUE ... Parameters: NAME Monitor name KEY=VALUE List of `key=value` pairs separated by spaces All monitors support the following values for KEY: user Username used when connecting to servers password Password used when connecting to servers monitor_interval Monitoring interval in milliseconds backend_connect_timeout Server coneection timeout in seconds backend_write_timeout Server write timeout in seconds backend_read_timeout Server read timeout in seconds This will alter an existing parameter of a monitor. To remove parameters, pass an empty value for a key e.g. 'maxadmin alter monitor my-monitor my-key=' Example: alter monitor my-monitor user=maxuser password=maxpwd ``` ### Destroying Monitors To destroy a monitor, use the `destroy monitor` command. All servers need to be removed from the monitor before it can be destroyed. Only created monitors should be destroyed and they will remain a part of the runtime configuration until the next restart. ``` destroy monitor - Destroy a monitor Usage: destroy monitor NAME Parameters: NAME Monitor to destroy The monitor is stopped and it will be removed on the next restart of MaxScale Example: destroy monitor my-monitor ``` ## Services ### Altering Services To alter the common service parameters, use the `alter service` command. Module specific parameters cannot be altered with this command. ``` alter service - Alter service parameters Usage: alter service NAME KEY=VALUE ... Parameters: NAME Service name KEY=VALUE List of `key=value` pairs separated by spaces All services support the following values for KEY: user Username used when connecting to servers password Password used when connecting to servers enable_root_user Allow root user access through this service max_retry_interval Maximum restart retry interval max_connections Maximum connection limit connection_timeout Client idle timeout in seconds auth_all_servers Retrieve authentication data from all servers strip_db_esc Strip escape characters from database names localhost_match_wildcard_host Match wildcard host to 'localhost' address version_string The version string given to client connections weightby Weighting parameter name log_auth_warnings Log authentication warnings retry_on_failure Retry service start on failure Example: alter service my-service user=maxuser password=maxpwd ``` ## MaxScale Core ### Altering MaxScale The core MaxScale parameters that can be modified at runtime can be altered with the `alter maxscale` command. ``` alter maxscale - Alter maxscale parameters Usage: alter maxscale KEY=VALUE ... Parameters: KEY=VALUE List of `key=value` pairs separated by spaces The following configuration values can be altered: auth_connect_timeout Connection timeout for permission checks auth_read_timeout Read timeout for permission checks auth_write_timeout Write timeout for permission checks admin_auth Enable admin interface authentication admin_log_auth_failures Log admin interface authentication failures Example: alter maxscale auth_connect_timeout=10 ``` ## Other Modules Modules can implement custom commands called _module commands_. These are intended to allow modules to perform very specific tasks. To list all module commands, execute `list commands` in maxadmin. This shows all commands that the modules have exposed. It also explains what they do and what sort of arguments they take. ``` list commands - List registered commands Usage: list commands [MODULE] [COMMAND] Parameters: MODULE Regular expressions for filtering module names COMMAND Regular expressions for filtering module command names Example: list commands my-module my-command ``` If no module commands are registered, no output will be generated. Refer to the module specific documentation for more details about module commands. To call a module commands, execute `call command ` in maxadmin. The __ is the name of the module and __ is the command that should be called. The commands take a variable amount of arguments which are explained in the output of `list commands`. ``` call command - Call module command Usage: call command MODULE COMMAND ARGS... Parameters: MODULE The module name COMMAND The command to call ARGS... Arguments for the command To list all registered commands, run 'list commands'. Example: call command my-module my-command hello world! ``` An example of this is the `dbfwfilter` module that implements a rule reloading mechanism as a module command. This command takes a filter name as a parameter. ``` maxadmin call command dbfwfilter rules/reload my-firewall-filter /home/user/rules.txt ``` Here the name of the filter is _my-firewall-filter_ and the optional rule file path is `/home/user/rules.txt`. # Tuning MariaDB MaxScale The way that MariaDB MaxScale does its polling is that each of the polling threads, as defined by the threads parameter in the configuration file, will call epoll_wait to obtain the events that are to be processed. The events are then added to a queue for execution. Any thread can read from this queue, not just the thread that added the event. Once the thread has done an epoll call with no timeout it will either do an epoll_wait call with a timeout or it will take an event from the queue if there is one. These two new parameters affect this behavior. The first parameter, which may be set by using the non_blocking_polls option in the configuration file, controls the number of epoll_wait calls that will be issued without a timeout before MariaDB MaxScale will make a call with a timeout value. The advantage of performing a call without a timeout is that the kernel treats this case as different and will not rescheduled the process in this case. If a timeout is passed then the system call will cause the MariaDB MaxScale thread to be put back in the scheduling queue and may result in lost CPU time to MariaDB MaxScale. Setting the value of this parameter too high will cause MariaDB MaxScale to consume a lot of CPU when there is infrequent work to be done. The default value of this parameter is 3. This parameter may also be set via the maxadmin client using the command _set nbpolls _. The second parameter is the maximum sleep value that MariaDB MaxScale will pass to epoll_wait. What normally happens is that MariaDB MaxScale will do an epoll_wait call with a sleep value that is 10% of the maximum, each time the returns and there is no more work to be done MariaDB MaxScale will increase this percentage by 10%. This will continue until the maximum value is reached or until there is some work to be done. Once the thread finds some work to be done it will reset the sleep time it uses to 10% of the maximum. The maximum sleep time is set in milliseconds and can be placed in the [maxscale] section of the configuration file with the poll_sleep parameter. Alternatively it may be set in the maxadmin client using the command _set pollsleep _. The default value of this parameter is 1000. Setting this value too high means that if a thread collects a large number of events and adds to the event queue, the other threads might not return from the epoll_wait calls they are running for some time resulting in less overall performance. Setting the sleep time too low will cause MariaDB MaxScale to wake up too often and consume CPU time when there is no work to be done. The _show epoll_ command can be used to see how often we actually poll with a timeout, the first two values output are significant. Also the "Number of wake with pending events" is a good measure. This is the count of the number of times a blocking call returned to find there was some work waiting from another thread. If the value is increasing rapidly reducing the maximum sleep value and increasing the number of non-blocking polls should help the situation. ``` MaxScale> show epoll Poll Statistics. No. of epoll cycles: 343 No. of epoll cycles with wait: 66 No. of epoll calls returning events: 19 No. of non-blocking calls returning events: 10 No. of read events: 2 No. of write events: 15 No. of error events: 0 No. of hangup events: 0 No. of accept events: 4 No. of times no threads polling: 4 Total event queue length: 1 Average event queue length: 1 Maximum event queue length: 1 No of poll completions with descriptors No. of descriptors No. of poll completions. 1 19 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 >= 10 0 MaxScale> ``` If the "Number of DCBs with pending events" grows rapidly it is an indication that MariaDB MaxScale needs more threads to be able to keep up with the load it is under. The _show threads_ command can be used to see the historic average for the pending events queue, it gives 15 minute, 5 minute and 1 minute averages. The load average it displays is the event count per poll cycle data. An idea load is 1, in this case MariaDB MaxScale threads and fully occupied but nothing is waiting for threads to become available for processing. The _show eventstats_ command can be used to see statistics about how long events have been queued before processing takes place and also how long the events took to execute once they have been allocated a thread to run on. ``` MaxScale> show eventstats Event statistics. Maximum queue time: 000ms Maximum execution time: 000ms Maximum event queue length: 1 Total event queue length: 4 Average event queue length: 1 | Number of events Duration | Queued | Executed ---------------+------------+----------- < 100ms | 27 | 26 100 - 200ms | 0 | 0 200 - 300ms | 0 | 0 300 - 400ms | 0 | 0 400 - 500ms | 0 | 0 500 - 600ms | 0 | 0 600 - 700ms | 0 | 0 700 - 800ms | 0 | 0 800 - 900ms | 0 | 0 900 - 1000ms | 0 | 0 1000 - 1100ms | 0 | 0 1100 - 1200ms | 0 | 0 1200 - 1300ms | 0 | 0 1300 - 1400ms | 0 | 0 1400 - 1500ms | 0 | 0 1500 - 1600ms | 0 | 0 1600 - 1700ms | 0 | 0 1700 - 1800ms | 0 | 0 1800 - 1900ms | 0 | 0 1900 - 2000ms | 0 | 0 2000 - 2100ms | 0 | 0 2100 - 2200ms | 0 | 0 2200 - 2300ms | 0 | 0 2300 - 2400ms | 0 | 0 2400 - 2500ms | 0 | 0 2500 - 2600ms | 0 | 0 2600 - 2700ms | 0 | 0 2700 - 2800ms | 0 | 0 2800 - 2900ms | 0 | 0 2900 - 3000ms | 0 | 0 > 3000ms | 0 | 0 MaxScale> ``` The statics are defined in 100ms buckets, with the count of the events that fell into that bucket being recorded.