CHANGE MASTER TO
The terms master and slave have historically been used in replication, and MariaDB has begun the process of adding primary and replica synonyms. The old terms will continue to be used to maintain backward compatibility - see MDEV-18777 to follow progress on this effort.
Syntax
CHANGE MASTER ['connection_name'] TO master_def [, master_def] ... [FOR CHANNEL 'channel_name'] master_def: MASTER_BIND = 'interface_name' | MASTER_HOST = 'host_name' | MASTER_USER = 'user_name' | MASTER_PASSWORD = 'password' | MASTER_PORT = port_num | MASTER_CONNECT_RETRY = interval | MASTER_HEARTBEAT_PERIOD = interval | MASTER_LOG_FILE = 'master_log_name' | MASTER_LOG_POS = master_log_pos | RELAY_LOG_FILE = 'relay_log_name' | RELAY_LOG_POS = relay_log_pos | MASTER_DELAY = interval | MASTER_SSL = {0|1} | MASTER_SSL_CA = 'ca_file_name' | MASTER_SSL_CAPATH = 'ca_directory_name' | MASTER_SSL_CERT = 'cert_file_name' | MASTER_SSL_CRL = 'crl_file_name' | MASTER_SSL_CRLPATH = 'crl_directory_name' | MASTER_SSL_KEY = 'key_file_name' | MASTER_SSL_CIPHER = 'cipher_list' | MASTER_SSL_VERIFY_SERVER_CERT = {0|1} | MASTER_USE_GTID = {current_pos|slave_pos|no} | MASTER_DEMOTE_TO_SLAVE = bool | IGNORE_SERVER_IDS = (server_id_list) | DO_DOMAIN_IDS = ([N,..]) | IGNORE_DOMAIN_IDS = ([N,..])
Contents
Description
CHANGE MASTER
is used on a replica to setup or change replication settings for connecting to the primary.
MariaDB starting with 10.7.0
The FOR CHANNEL
keyword was added for MySQL compatibility. This is identical to
using the channel_name directly after CHANGE MASTER
.
Multi-Source Replication
If you are using multi-source replication, then you need to specify a connection name when you execute CHANGE MASTER
. There are two ways to do this:
- Setting the default_master_connection system variable prior to executing
CHANGE MASTER
. - Setting the
connection_name
parameter when executingCHANGE MASTER
.
default_master_connection
SET default_master_connection = 'gandalf'; STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE;
connection_name
STOP SLAVE 'gandalf'; CHANGE MASTER 'gandalf' TO MASTER_PASSWORD='new3cret'; START SLAVE 'gandalf';
Options
Connection Options
MASTER_USER
The MASTER_USER
option for CHANGE MASTER
defines the user account that the replica will use to connect to the primary.
This user account will need the REPLICATION SLAVE privilege (or, from MariaDB 10.5.1, the REPLICATION REPLICA on the primary.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_USER='repl', MASTER_PASSWORD='new3cret'; START SLAVE;
The maximum length of the MASTER_USER
string is 96 characters until MariaDB 10.5, and 128 characters from MariaDB 10.6.
MASTER_PASSWORD
The MASTER_PASSWORD
option for CHANGE MASTER
defines the password that the replica will use to connect to the primary as the user account defined by the MASTER_USER option.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE;
The maximum length of the MASTER_PASSWORD
string is 32 characters. The effective maximum length of the string depends on how many bytes are used per character and can be up to 96 characters.
Due to MDEV-29994, the password can be silently truncated to 41 characters when MariaDB is restarted. For this reason it is recommended to use a password that is shorter than this.
MASTER_HOST
The MASTER_HOST
option for CHANGE MASTER
defines the hostname or IP address of the primary.
If you set the value of the MASTER_HOST
option to the empty string, then that is not the same as not setting the option's value at all. If you set the value of the MASTER_HOST
option to the empty string, then the CHANGE MASTER
command will fail with an error. In MariaDB 5.3 and before, if you set the value of the MASTER_HOST
option to the empty string, then the CHANGE MASTER
command would succeed, but the subsequent START SLAVE command would fail.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_HOST='dbserver1.example.com', MASTER_USER='repl', MASTER_PASSWORD='new3cret', MASTER_USE_GTID=slave_pos; START SLAVE;
If you set the value of the MASTER_HOST
option in a CHANGE MASTER
command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary
log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE=''
and MASTER_LOG_POS=4
. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no
in the statement, then these values will effectively be ignored anyway.
Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.
The maximum length of the MASTER_HOST
string is 60 characters until MariaDB 10.5, and 255 characters from MariaDB 10.6.
MASTER_PORT
The MASTER_PORT
option for CHANGE MASTER
defines the TCP/IP port of the primary.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_HOST='dbserver1.example.com', MASTER_PORT=3307, MASTER_USER='repl', MASTER_PASSWORD='new3cret', MASTER_USE_GTID=slave_pos; START SLAVE;
If you set the value of the MASTER_PORT
option in a CHANGE MASTER
command, then the replica assumes that the primary is different from before, even if you set the value of this option to the same value it had previously. In this scenario, the replica will consider the old values for the primary's binary
log file name and position to be invalid for the new primary. As a side effect, if you do not explicitly set the values of the MASTER_LOG_FILE and MASTER_LOG_POS options in the statement, then the statement will be implicitly appended with MASTER_LOG_FILE=''
and MASTER_LOG_POS=4
. However, if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no
in the statement, then these values will effectively be ignored anyway.
Replicas cannot connect to primaries using Unix socket files or Windows named pipes. The replica must connect to the primary using TCP/IP.
MASTER_CONNECT_RETRY
The MASTER_CONNECT_RETRY
option for CHANGE MASTER
defines how many seconds that the replica will wait between connection retries. The default is 60
.
STOP SLAVE; CHANGE MASTER TO MASTER_CONNECT_RETRY=20; START SLAVE;
The number of connection attempts is limited by the master_retry_count option. It can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:
[mariadb] ... master_retry_count=4294967295
MASTER_BIND
The MASTER_BIND
option for CHANGE MASTER
is only supported by MySQL 5.6.2 and later and by MySQL NDB Cluster 7.3.1 and later. This option is not supported by MariaDB. See MDEV-19248 for more information.
MASTER_HEARTBEAT_PERIOD
The MASTER_HEARTBEAT_PERIOD
option for CHANGE MASTER
can be used to set the interval in seconds between replication heartbeats. Whenever the primary's binary log is updated with an event, the waiting period for the next heartbeat is reset.
This option's interval argument has the following characteristics:
- It is a decimal value with a range of
0
to4294967
seconds. - It has a resolution of hundredths of a second.
- Its smallest valid non-zero value is
0.001
. - Its default value is the value of the slave_net_timeout system variable divided by 2.
- If it's set to
0
, then heartbeats are disabled.
Heartbeats are sent by the primary only if there are no unsent events in the binary log file for a period longer than the interval.
If the RESET SLAVE statement is executed, then the heartbeat interval is reset to the default.
If the slave_net_timeout system variable is set to a value that is lower than the current heartbeat interval, then a warning will be issued.
TLS Options
The TLS options are used for providing information about TLS. The options can be set even on replicas that are compiled without TLS support. The TLS options are saved to either the default master.info
file or the file that is configured by the master_info_file option, but these TLS options are ignored unless the replica supports TLS.
See Replication with Secure Connections for more information.
MASTER_SSL
The MASTER_SSL
option for CHANGE MASTER
tells the replica whether to force TLS for the connection. The valid values are 0
or 1
. Required to be set to 1
for the other MASTER_SSL*
options to have any effect.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL=1; START SLAVE;
MASTER_SSL_CA
The MASTER_SSL_CA
option for CHANGE MASTER
defines a path to a PEM file that should contain one or more X509 certificates for trusted Certificate Authorities (CAs) to use for TLS. This option requires that you use the absolute path, not a relative path.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE;
See Secure Connections Overview: Certificate Authorities (CAs) for more information.
The maximum length of MASTER_SSL_CA
string is 511 characters.
MASTER_SSL_CAPATH
The MASTER_SSL_CAPATH
option for CHANGE MASTER
defines a path to a directory that contains one or more PEM files that should each contain one X509 certificate for a trusted Certificate Authority (CA) to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this option needs to be run through the openssl rehash command.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CAPATH='/etc/my.cnf.d/certificates/ca/', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE;
See Secure Connections Overview: Certificate Authorities (CAs) for more information.
The maximum length of MASTER_SSL_CA_PATH
string is 511 characters.
MASTER_SSL_CERT
The MASTER_SSL_CERT
option for CHANGE MASTER
defines a path to the X509 certificate file to use for TLS. This option requires that you use the absolute path, not a relative path.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE;
The maximum length of MASTER_SSL_CERT
string is 511 characters.
MASTER_SSL_CRL
The MASTER_SSL_CRL
option for CHANGE MASTER
defines a path to a PEM file that should contain one or more revoked X509 certificates to use for TLS. This option requires that you use the absolute path, not a relative path.
This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CRL='/etc/my.cnf.d/certificates/crl.pem'; START SLAVE;
See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.
The maximum length of MASTER_SSL_CRL
string is 511 characters.
MASTER_SSL_CRLPATH
The MASTER_SSL_CRLPATH
option for CHANGE MASTER
defines a path to a directory that contains one or more PEM files that should each contain one revoked X509 certificate to use for TLS. This option requires that you use the absolute path, not a relative path. The directory specified by this variable needs to be run through the openssl rehash command.
This option is only supported if the server was built with OpenSSL. If the server was built with yaSSL, then this option is not supported. See TLS and Cryptography Libraries Used by MariaDB for more information about which libraries are used on which platforms.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CRLPATH='/etc/my.cnf.d/certificates/crl/'; START SLAVE;
See Secure Connections Overview: Certificate Revocation Lists (CRLs) for more information.
The maximum length of MASTER_SSL_CRL_PATH
string is 511 characters.
MASTER_SSL_KEY
The MASTER_SSL_KEY
option for CHANGE MASTER
defines a path to a private key file to use for TLS. This option requires that you use the absolute path, not a relative path.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE;
The maximum length of MASTER_SSL_KEY
string is 511 characters.
MASTER_SSL_CIPHER
The MASTER_SSL_CIPHER
option for CHANGE MASTER
defines the list of permitted ciphers or cipher suites to use for TLS. Besides cipher names, if MariaDB was compiled with OpenSSL, this option could be set to "SSLv3" or "TLSv1.2" to allow all SSLv3 or all TLSv1.2 ciphers. Note that the TLSv1.3 ciphers cannot be excluded when using OpenSSL, even by using this option. See Using TLSv1.3 for details.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1, MASTER_SSL_CIPHER='TLSv1.2'; START SLAVE;
The maximum length of MASTER_SSL_CIPHER
string is 511 characters.
MASTER_SSL_VERIFY_SERVER_CERT
The MASTER_SSL_VERIFY_SERVER_CERT
option for CHANGE MASTER
enables server certificate verification. This option is disabled by default prior to MariaDB 11.3.0, and enabled by default from MariaDB 11.3.0.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem', MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem', MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem', MASTER_SSL_VERIFY_SERVER_CERT=1; START SLAVE;
See Secure Connections Overview: Server Certificate Verification for more information.
Binary Log Options
These options are related to the binary log position on the primary.
MASTER_LOG_FILE
The MASTER_LOG_FILE
option for CHANGE MASTER
can be used along with MASTER_LOG_POS
to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE;
The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.
The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no
in the statement.
MASTER_LOG_POS
The MASTER_LOG_POS
option for CHANGE MASTER
can be used along with MASTER_LOG_FILE
to specify the coordinates at which the replica's I/O thread should begin reading from the primary's binary logs the next time the thread starts.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE;
The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be specified if the RELAY_LOG_FILE and RELAY_LOG_POS options were also specified.
The MASTER_LOG_FILE and MASTER_LOG_POS options are effectively ignored if you enable GTID mode for replication by setting the MASTER_USE_GTID option to some value other than no
in the statement.
Relay Log Options
These options are related to the relay log position on the replica.
RELAY_LOG_FILE
The RELAY_LOG_FILE
option for CHANGE MASTER
can be used along with the RELAY_LOG_POS option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.
The CHANGE MASTER
statement usually deletes all relay log files. However, if the RELAY_LOG_FILE
and/or RELAY_LOG_POS
options are specified, then existing relay log files are kept.
When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD
option for this scenario. For example:
STOP SLAVE SQL_THREAD; CHANGE MASTER TO RELAY_LOG_FILE='slave-relay-bin.006', RELAY_LOG_POS=4025; START SLAVE SQL_THREAD;
When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info
file or the file that is configured by the relay_log_info_file system variable.
The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.
RELAY_LOG_POS
The RELAY_LOG_POS
option for CHANGE MASTER
can be used along with the RELAY_LOG_FILE option to specify the coordinates at which the replica's SQL thread should begin reading from the relay log the next time the thread starts.
The CHANGE MASTER
statement usually deletes all relay log files. However, if the RELAY_LOG_FILE
and/or RELAY_LOG_POS
options are specified, then existing relay log files are kept.
When you want to change the relay log position, you only need to stop the replica's SQL thread. The replica's I/O thread can continue running. The STOP SLAVE and START SLAVE statements support the SQL_THREAD
option for this scenario. For example:
STOP SLAVE SQL_THREAD; CHANGE MASTER TO RELAY_LOG_FILE='slave-relay-bin.006', RELAY_LOG_POS=4025; START SLAVE SQL_THREAD;
When the value of this option is changed, the metadata about the replica's SQL thread's position in the relay logs will also be changed in the relay-log.info
file or the file that is configured by the relay_log_info_file system variable.
The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be specified if the MASTER_LOG_FILE and MASTER_LOG_POS options were also specified.
GTID Options
MASTER_USE_GTID
The MASTER_USE_GTID
option for CHANGE MASTER
can be used to configure the replica to use the global transaction ID (GTID) when connecting to a primary. The possible values are:
current_pos
- Replicate in GTID mode and use gtid_current_pos as the position to start downloading transactions from the primary. Using to transition to primary can break the replication state if the replica executes local transactions due to actively updating gtid_current_pos with gtid_binlog_pos and gtid_slave_pos. Use the new, safe, MASTER_DEMOTE_TO_SLAVE=<bool> option instead.slave_pos
- Replicate in GTID mode and use gtid_slave_pos as the position to start downloading transactions from the primary. From MariaDB 10.5.1,replica_pos
is an alias forslave_pos
.no
- Don't replicate in GTID mode.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_USE_GTID = current_pos; START SLAVE;
Or:
STOP SLAVE; SET GLOBAL gtid_slave_pos='0-1-153'; CHANGE MASTER TO MASTER_USE_GTID = slave_pos; START SLAVE;
MASTER_DEMOTE_TO_SLAVE
MariaDB starting with 10.10
Used to transition a primary to become a replica. Replaces the old MASTER_USE_GTID=current_pos with a safe alternative by forcing users to set Using_Gtid=Slave_Pos
and merging gtid_binlog_pos
into gtid_slave_pos
once at CHANGE MASTER TO
time. If gtid_slave_pos
is more
recent than gtid_binlog_pos
(as in the case of chain replication), the replication state should be preserved.
For example:
STOP SLAVE; CHANGE MASTER TO MASTER_DEMOTE_TO_SLAVE = 1; START SLAVE;
Replication Filter Options
Also see Replication filters.
IGNORE_SERVER_IDS
The IGNORE_SERVER_IDS
option for CHANGE MASTER
can be used to configure a replica to ignore binary log events that originated from certain servers. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.
The option's value can be specified by providing a comma-separated list of server_id values. For example:
STOP SLAVE; CHANGE MASTER TO IGNORE_SERVER_IDS = (3,5); START SLAVE;
If you would like to clear a previously set list, then you can set the value to an empty list. For example:
STOP SLAVE; CHANGE MASTER TO IGNORE_SERVER_IDS = (); START SLAVE;
DO_DOMAIN_IDS
The DO_DOMAIN_IDS
option for CHANGE MASTER
can be used to configure a replica to only apply binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.
The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:
STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (1,2); START SLAVE;
If you would like to clear a previously set list, then you can set the value to an empty list. For example:
STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (); START SLAVE;
The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the DO_DOMAIN_IDS option, and the IGNORE_DOMAIN_IDS option was previously set, then you need to clear the value of the IGNORE_DOMAIN_IDS option. For example:
STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (), DO_DOMAIN_IDS = (1,2); START SLAVE;
The DO_DOMAIN_IDS
option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no
in order to use this option.
IGNORE_DOMAIN_IDS
The IGNORE_DOMAIN_IDS
option for CHANGE MASTER
can be used to configure a replica to ignore binary log events if the transaction's GTID is in a specific gtid_domain_id value. Filtered binary log events will not get logged to the replica’s relay log, and they will not be applied by the replica.
The option's value can be specified by providing a comma-separated list of gtid_domain_id values. Duplicate values are automatically ignored. For example:
STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (1,2); START SLAVE;
If you would like to clear a previously set list, then you can set the value to an empty list. For example:
STOP SLAVE; CHANGE MASTER TO IGNORE_DOMAIN_IDS = (); START SLAVE;
The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option cannot both be set to non-empty values at the same time. If you want to set the IGNORE_DOMAIN_IDS option, and the DO_DOMAIN_IDS option was previously set, then you need to clear the value of the DO_DOMAIN_IDS option. For example:
STOP SLAVE; CHANGE MASTER TO DO_DOMAIN_IDS = (), IGNORE_DOMAIN_IDS = (1,2); START SLAVE;
The IGNORE_DOMAIN_IDS
option can only be specified if the replica is replicating in GTID mode. Therefore, the MASTER_USE_GTID option must also be set to some value other than no
in order to use this option.
Delayed Replication Options
MASTER_DELAY
The MASTER_DELAY
option for CHANGE MASTER
can be used to enable delayed replication. This option specifies the time in seconds (at least) that a replica should lag behind the primary up to a maximum value of 2147483647, or about 68 years. Before executing an event, the replica will first wait, if necessary, until the given time has passed since the event was created on the primary. The result is that the replica will reflect the state of the primary some time back in the past. The default is zero, no delay.
STOP SLAVE; CHANGE MASTER TO MASTER_DELAY=3600; START SLAVE;
Changing Option Values
If you don't specify a given option when executing the CHANGE MASTER
statement, then the option keeps its old value in most cases. Most of the time, there is no need to specify the options that do not need to change. For example, if the password for the user account that the replica uses to connect to its primary has changed, but no other options need to change, then you can just change the MASTER_PASSWORD option by executing the following commands:
STOP SLAVE; CHANGE MASTER TO MASTER_PASSWORD='new3cret'; START SLAVE;
There are some cases where options are implicitly reset, such as when the MASTER_HOST and MASTER_PORT options are changed.
Option Persistence
The values of the MASTER_LOG_FILE and MASTER_LOG_POS options (i.e. the binary log position on the primary) and most other options are written to either the default master.info
file or the file that is configured by the master_info_file option. The replica's I/O thread keeps this binary log position updated as it downloads events only when MASTER_USE_GTID option
is set to NO
. Otherwise the file is not updated on a per event basis.
The master_info_file option can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:
[mariadb] ... master_info_file=/mariadb/myserver1-master.info
The values of the RELAY_LOG_FILE and RELAY_LOG_POS options (i.e. the relay log position) are written to either the default relay-log.info
file or the file that is configured by the relay_log_info_file system variable. The replica's SQL thread keeps this relay log position updated as it applies events.
The relay_log_info_file system variable can be set either on the command-line or in a server option group in an option file prior to starting up the server. For example:
[mariadb] ... relay_log_info_file=/mariadb/myserver1-relay-log.info
GTID Persistence
If the replica is replicating binary log events that contain GTIDs, then the replica's SQL thread will write every GTID that it applies to the mysql.gtid_slave_pos table. This GTID can be inspected and modified through the gtid_slave_pos system variable.
If the replica has the log_slave_updates system variable enabled and if the replica has the binary log enabled, then every write by the replica's SQL thread will also go into the replica's binary log. This means that GTIDs of replicated transactions would be reflected in the value of the gtid_binlog_pos system variable.
Creating a Replica from a Backup
The CHANGE MASTER
statement is useful for setting up a replica when you have a backup of the primary and you also have the binary log position or GTID position corresponding to the backup.
After restoring the backup on the replica, you could execute something like this to use the binary log position:
CHANGE MASTER TO MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4; START SLAVE;
Or you could execute something like this to use the GTID position:
SET GLOBAL gtid_slave_pos='0-1-153'; CHANGE MASTER TO MASTER_USE_GTID=slave_pos; START SLAVE;
See Setting up a Replication Slave with Mariabackup for more information on how to do this with Mariabackup.
Example
The following example changes the primary and primary's binary log coordinates. This is used when you want to set up the replica to replicate the primary:
CHANGE MASTER TO MASTER_HOST='master2.mycompany.com', MASTER_USER='replication', MASTER_PASSWORD='bigs3cret', MASTER_PORT=3306, MASTER_LOG_FILE='master2-bin.001', MASTER_LOG_POS=4, MASTER_CONNECT_RETRY=10; START SLAVE;
See Also
- Setting up replication
- START SLAVE
- Multi-source replication
- RESET SLAVE. Removes a connection created with
CHANGE MASTER TO
. - Global Transaction ID