MySQL Instance Manager is included in MySQL distributions from version 5.0.3, and can be used in place of the mysqld_safe script to start and stop one or more instances of MySQL Server. Because Instance Manager can manage multiple server instances, it can also be used in place of the mysqld_multi script. Instance Manager offers these capabilities:
The following sections describe MySQL Instance Manager operation in more detail.
The MySQL Instance Manager supports a number of command options. For a brief listing, invoke mysqlmanager with the --help option. Options may be given on the command line or in the Instance Manager configuration file. On Windows, the standard configuration file is my.ini in the directory where Instance Manager is installed. On Unix, the standard file is /etc/my.cnf. To specify a different configuration file, start Instance Manager with the --defaults-file option.
mysqlmanager supports the following options:
Display a help message and exit.
The file in which the angel process records its process ID when mysqlmanager runs in daemon mode (that is, when the --run-as-service option is given). The default filename is mysqlmanager.angel.pid.
If the --angel-pid-file option is not given, the default angel PID file has the same name as the PID file except that any PID file extension is replaced with an extension of .angel.pid. (For example, mysqlmanager.pid becomes mysqlmanager.angel.pid.)
This option was added in MySQL 5.0.23.
The IP address to bind to.
The pathname of the MySQL Server binary. This pathname is used for all server instance sections in the configuration file for which no mysqld-path option is present. The default value of this option is the compiled-in pathname, which depends on how the MySQL distribution was configured. Example: --default-mysqld-path=/usr/sbin/mysqld
Read Instance Manager and MySQL Server settings from the given file. All configuration changes made by the Instance Manager will be written to this file. This must be the first option on the command line if it is used, and the file must exist.
If this option is not given, Instance Manager uses its standard configuration file. On Windows, the standard file is my.ini in the directory where Instance Manager is installed. On Unix, the standard file is /etc/my.cnf.
On Windows, install Instance Manager as a Windows service. The service name is MySQL Manager. This option was added in MySQL 5.0.11.
The path to the Instance Manager log file. This option has no effect unless the --run-as-service option is also given. If the filename specified for the option is a relative name, the log file is created under the directory from which Instance Manager is started. To ensure that the file is created in a specific directory, specify it as a full pathname.
If --run-as-service is given without --log, the log file is mysqlmanager.log in the data directory.
If --run-as-service is not given, log messages go to the standard output. To capture log output, you can redirect Instance Manager output to a file:
mysqlmanager > im.log
The interval in seconds for monitoring server instances. The default value is 20 seconds. Instance Manager tries to connect to each monitored (guarded) instance using the non-existing MySQL_Instance_Manager user account to check whether it is alive/not hanging. If the result of the connection attempt indicates that the instance is unavailable, Instance Manager performs several attempts to restart the instance.
Normally, the MySQL_Instance_Manager account does not exist, so the connection attempts by Instance Manager cause the monitored instance to produce messages in its general query log similar to the following:
Access denied for user 'MySQL_Instance_M'@'localhost' (using password: YES)
The nonguarded option in the appropriate server instance section disables monitoring for a particular instance. If the instance dies after being started, Instance Manager will not restart it. Instance Manager tries to connect to a nonguarded instance only when you request the instance's status (for example, with the SHOW INSTANCES status.
See the section called "MYSQL SERVER INSTANCE STATUS MONITORING", for more information.
Prepare an entry for the password file, print it to the standard output, and exit. You can redirect the output from Instance Manager to a file to save the entry in the file.
The name of the file where the Instance Manager looks for users and passwords. On Windows, the default is mysqlmanager.passwd in the directory where Instance Manager is installed. On Unix, the default file is /etc/mysqlmanager.passwd.
The process ID file to use. On Windows, the default file is mysqlmanager.pid in the directory where Instance Manager is installed. On Unix, the default is mysqlmanager.pid in the data directory.
The port number to use when listening for TCP/IP connections from clients. The default port number (assigned by IANA) is 2273.
Print the current defaults and exit. This must be the first option on the command line if it is used.
On Windows, removes Instance Manager as a Windows service. This assumes that Instance Manager has been run with --install previously. This option was added in MySQL 5.0.11.
On Unix, daemonize and start an angel process. The angel process monitors Instance Manager and restarts it if it crashes. (The angel process itself is simple and unlikely to crash.)
On Unix, the socket file to use for incoming connections. The default file is named /tmp/mysqlmanager.sock. This option has no meaning on Windows.
This option is used on Windows to run Instance Manager in standalone mode. You should specify it when you start Instance Manager from the command line. This option was added in MySQL 5.0.13.
On Unix, the username of the system account to use for starting and running mysqlmanager. This option generates a warning and has no effect unless you start mysqlmanager as root (so that it can change its effective user ID), or as the named user. It is recommended that you configure mysqlmanager to run using the same account used to run the mysqld server. ("User" in this context refers to a system login account, not a MySQL user listed in the grant tables.)
Display version information and exit.
The number of seconds to wait for activity on an incoming connection before closing it. The default is 28800 seconds (8 hours).
This option was added in MySQL 5.0.19. Before that, the timeout is 30 seconds and cannot be changed.
Instance Manager uses its standard configuration file unless it is started with a --defaults-file option that specifies a different file. On Windows, the standard file is my.ini in the directory where Instance Manager is installed. On Unix, the standard file is /etc/my.cnf. (Prior to MySQL 5.0.10, the MySQL Instance Manager read the same configuration files as the MySQL Server, including /etc/my.cnf, ~/.my.cnf, and so forth.)
Instance Manager reads options for itself from the [manager] section of the configuration file, and options for server instances from [mysqld] or [mysqldN] sections. The [manager] section contains any of the options listed in the section called "MYSQL INSTANCE MANAGER COMMAND OPTIONS", except for those specified as having to be given as the first option on the command line. Here is a sample [manager] section:
# MySQL Instance Manager options section [manager] default-mysqld-path = /usr/local/mysql/libexec/mysqld socket=/tmp/manager.sock pid-file=/tmp/manager.pid password-file = /home/cps/.mysqlmanager.passwd monitoring-interval = 2 port = 1999 bind-address = 192.168.1.5
Each [mysqld] or [mysqldN] instance section specifies options given by Instance Manager to a server instance at startup. These are mainly common MySQL Server options (see Section 1.2, "Command Options"). In addition, a [mysqldN] section can contain the options in the following list, which are specific to Instance Manager. These options are interpreted by Instance Manager itself; it does not pass them to the server when it attempts to start that server.
The Instance Manager-specific options must not be used in a [mysqld] section. If a server is started without using Instance Manager, it will not recognize these options and will fail to start properly.
The pathname of the mysqld server binary to use for the server instance.
This option disables Instance Manager monitoring functionality for the server instance. By default, an instance is guarded: At Instance Manager start time, it starts the instance. It also monitors the instance status and attempts to restart it if it fails. At Instance Manager exit time, it stops the instance. None of these things happen for nonguarded instances.
The number of seconds Instance Manager should wait for the server instance to shut down. The default value is 35 seconds. After the delay expires, Instance Manager assumes that the instance is hanging and attempts to terminate it. If you use InnoDB with large tables, you should increase this value.
Here are some sample instance sections:
[mysqld1] mysqld-path=/usr/local/mysql/libexec/mysqld socket=/tmp/mysql.sock port=3307 server_id=1 skip-stack-trace core-file skip-bdb log-bin log-error log=mylog log-slow-queries [mysqld2] nonguarded port=3308 server_id=2 mysqld-path= /home/cps/mysql/trees/mysql-5.0/sql/mysqld socket = /tmp/mysql.sock5 pid-file = /tmp/hostname.pid5 datadir= /home/cps/mysql_data/data_dir1 language=/home/cps/mysql/trees/mysql-5.0/sql/share/english log-bin log=/tmp/fordel.log
This section discusses how Instance Manager starts server instances when it starts. However, before you start Instance Manager, you should set up a password file for it. Otherwise, you will not be able to connect to Instance Manager to control it after it starts. For details about creating Instance Manager accounts, see the section called "INSTANCE MANAGER USER AND PASSWORD MANAGEMENT".
On Unix, the mysqld MySQL database server normally is started with the mysql.server script, which usually resides in the /etc/init.d/ directory. In MySQL 5.0.3, this script invokes mysqlmanager (the MySQL Instance Manager binary) to start MySQL. (In prior versions of MySQL the mysqld_safe script is used for this purpose.) Starting from MySQL 5.0.4, the behavior of the startup script was changed again to incorporate both setup schemes. In version 5.0.4, the startup script uses the old scheme (invoking mysqld_safe) by default, but one can set the use_mysqld_safe variable in the script to 0 (zero) to use the MySQL Instance Manager to start a server.
Starting with MySQL 5.0.19, you can use Instance Manager if you modify the my.cnf configuration file by adding use-manager to the [mysql.server] section:
When Instance Manager starts, it reads its configuration file if it exists to find server instance sections and prepare a list of instances. Instance sections have names of the form [mysqld] or [mysqldN], where N is an unsigned integer (for example, [mysqld1], [mysqld2], and so forth).
After preparing the list of instances, Instance Manager starts the guarded instances in the list. If there are no instances, Instance Manager creates an instance named mysqld and attempts to start it with default (compiled-in) configuration values. This means that the Instance Manager cannot find the mysqld program if it is not installed in the default location. (Section 4.6, "Installation Layouts", describes default locations for components of MySQL distributions.) If you have installed the MySQL server in a non-standard location, you should create the Instance Manager configuration file.
Instance Manager also stops all guarded server instances when it shuts down.
The allowable options for [mysqldN] server instance sections are described in the section called "MYSQL INSTANCE MANAGER CONFIGURATION FILES". In these sections, you can use a special mysqld-path=path-to-mysqld-binary option that is recognized only by Instance Manager. Use this option to let Instance Manager know where the mysqld binary resides. If there are multiple instances, it may also be necessary to set other options such as datadir and port, to ensure that each instance has a different data directory and TCP/IP port number. Section 7, "Running Multiple MySQL Servers on the Same Machine", discusses the configuration values that must differ for each instance when you run multiple instance on the same machine.
The [mysqld] instance section, if it exists, must not contain any Instance Manager-specific options.
The typical Unix startup/shutdown cycle for a MySQL server with the MySQL Instance Manager enabled is as follows:
The Instance Manager stores its user information in a password file. On Windows, the default is mysqlmanager.passwd in the directory where Instance Manager is installed. On Unix, the default file is /etc/mysqlmanager.passwd. To specify a different location for the password file, use the --password-file option.
If the password file does not exist or contains no password entries, you cannot connect to the Instance Manager.
Any Instance Manager process that is running to monitor server instances does not notice changes to the password file. You must stop it and restart it after making password entry changes.
Entries in the password file have the following format, where the two fields are the account username and encrypted password, separated by a colon:
Instance Manager password encryption is the same as that used by MySQL Server. It is a one-way operation; no means are provided for decrypting encrypted passwords.
Instance Manager accounts differ somewhat from MySQL Server accounts:
This means that a client can connect to Instance Manager with a given username from any host. To limit connections so that clients can connect only from the local host, start Instance Manager with the --bind-address=127.0.0.1 option so that it listens only to the local network interface. Remote clients will not be able to connect. Local clients can connect like this:
shell> mysql -h 127.0.0.1 -P 2273
To generate a new entry, invoke Instance Manager with the --passwd option and append the output to the /etc/mysqlmanager.passwd file. Here is an example:
shell> mysqlmanager --passwd >> /etc/mysqlmanager.passwd Creating record for new user. Enter user name: mike Enter password: mikepass Re-type password: mikepass
At the prompts, enter the username and password for the new Instance Manager user. You must enter the password twice. It does not echo to the screen, so double entry guards against entering a different password than you intend (if the two passwords do not match, no entry is generated).
The preceding command causes the following line to be added to /etc/mysqlmanager.passwd:
To monitor the status of each guarded server instance, the MySQL Instance Manager attempts to connect to the instance at regular intervals using the [email protected] user account with a password of check_connection.
You are not required to create this account for MySQL Server; in fact, it is expected that it will not exist. Instance Manager can tell that a server is operational if the server accepts the connection attempt but refuses access for the account by returning a login error. However, these failed connection attempts are logged by the server to its general query log (see Section 2.2, "The General Query Log").
Instance Manager also attempts a connection to nonguarded server instances when you use the SHOW INSTANCES or SHOW INSTANCE STATUS command. This is the only status monitoring done for nonguarded instances.
Instance Manager knows if a server instance fails at startup because it receives a status from the attempt. For an instance that starts but later crashes, Instance Manager receives a signal because it is the parent process of the instance.
After you set up a password file for the MySQL Instance Manager and Instance Manager is running, you can connect to it. The MySQL client-server protocol is used to communicate with the Instance Manager. For example, you can connect to it using the standard mysql client program:
shell> mysql --port=2273 --host=im.example.org --user=mysql --password
Instance Manager supports the version of the MySQL client-server protocol used by the client tools and libraries distributed with MySQL 4.1 or later, so other programs that use the MySQL C API also can connect to it.
After you connect to MySQL Instance Manager, you can issue commands. The following general principles apply to Instance Manager command execution:
The following list describes the commands that Instance Manager accepts, with examples.
This command attempts to start an offline instance. The command is asynchronous; it does not wait for the instance to start.
mysql> START INSTANCE mysqld4; Query OK, 0 rows affected (0,00 sec)
This command attempts to stop an instance. The command is synchronous; it waits for the instance to stop.
mysql> STOP INSTANCE mysqld4; Query OK, 0 rows affected (0,00 sec)
Shows the names and status of all loaded instances.
mysql> SHOW INSTANCES; +---------------+---------+ | instance_name | status | +---------------+---------+ | mysqld3 | offline | | mysqld4 | online | | mysqld2 | offline | +---------------+---------+
Shows status and version information for an instance.
mysql> SHOW INSTANCE STATUS mysqld3; +---------------+--------+---------+ | instance_name | status | version | +---------------+--------+---------+ | mysqld3 | online | unknown | +---------------+--------+---------+
Shows the options used by an instance.
mysql> SHOW INSTANCE OPTIONS mysqld3; +---------------+---------------------------------------------------+ | option_name | value | +---------------+---------------------------------------------------+ | instance_name | mysqld3 | | mysqld-path | /home/cps/mysql/trees/mysql-4.1/sql/mysqld | | port | 3309 | | socket | /tmp/mysql.sock3 | | pid-file | hostname.pid3 | | datadir | /home/cps/mysql_data/data_dir1/ | | language | /home/cps/mysql/trees/mysql-4.1/sql/share/english | +---------------+---------------------------------------------------+
The command lists all log files used by the instance. The result set contains the path to the log file and the log file size. If no log file path is specified in the instance section of the configuration file (for example, log=/var/mysql.log), the Instance Manager tries to guess its placement. If Instance Manager is unable to guess the log file placement you should specify the log file location explicitly by using a log option in the appropriate instance section of the configuration file.
mysql> SHOW mysqld LOG FILES; +-------------+------------------------------------+----------+ | Logfile | Path | Filesize | +-------------+------------------------------------+----------+ | ERROR LOG | /home/cps/var/mysql/owlet.err | 9186 | | GENERAL LOG | /home/cps/var/mysql/owlet.log | 471503 | | SLOW LOG | /home/cps/var/mysql/owlet-slow.log | 4463 | +-------------+------------------------------------+----------+
This command retrieves a portion of the specified log file. Because most users are interested in the latest log messages, the size parameter defines the number of bytes to retrieve from the end of the log. To retrieve data from the middle of the log file, specify the optional offset_from_end parameter. The following example retrieves 21 bytes of data, starting 23 bytes before the end of the log file and ending 2 bytes before the end:
mysql> SHOW mysqld LOG GENERAL 21, 2; +---------------------+ | Log | +---------------------+ | using password: YES | +---------------------+
This command edits the specified instance's configuration section to change or add instance options. The option is added to the section is it is not already present. Otherwise, the new setting replaces the existing one.
mysql> SET mysqld2.port=3322; Query OK, 0 rows affected (0.00 sec)
This command removes an option from an instance's configuration section.
mysql> UNSET mysqld2.port; Query OK, 0 rows affected (0.00 sec)
This command forces Instance Manager reread the configuration file and to refresh internal structures. This command should be performed after editing the configuration file. The command does not restart instances.
mysql> FLUSH INSTANCES; Query OK, 0 rows affected (0.04 sec)
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