Press CTRL+C to copyCHANGE MASTER TO option [, option] ... [ channel_option ] option: { MASTER_BIND = 'interface_name' | MASTER_HOST = 'host_name' | MASTER_USER = 'user_name' | MASTER_PASSWORD = 'password' | MASTER_PORT = port_num | PRIVILEGE_CHECKS_USER = {'account' | NULL} | REQUIRE_ROW_FORMAT = {0|1} | REQUIRE_TABLE_PRIMARY_KEY_CHECK = {STREAM | ON | OFF} | ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS = {OFF | LOCAL | uuid} | MASTER_LOG_FILE = 'source_log_name' | MASTER_LOG_POS = source_log_pos | MASTER_AUTO_POSITION = {0|1} | RELAY_LOG_FILE = 'relay_log_name' | RELAY_LOG_POS = relay_log_pos | MASTER_HEARTBEAT_PERIOD = interval | MASTER_CONNECT_RETRY = interval | MASTER_RETRY_COUNT = count | SOURCE_CONNECTION_AUTO_FAILOVER = {0|1} | MASTER_DELAY = interval | MASTER_COMPRESSION_ALGORITHMS = 'algorithm[,algorithm][,algorithm]' | MASTER_ZSTD_COMPRESSION_LEVEL = level | 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_TLS_VERSION = 'protocol_list' | MASTER_TLS_CIPHERSUITES = 'ciphersuite_list' | MASTER_PUBLIC_KEY_PATH = 'key_file_name' | GET_MASTER_PUBLIC_KEY = {0|1} | NETWORK_NAMESPACE = 'namespace' | IGNORE_SERVER_IDS = (server_id_list), | GTID_ONLY = {0|1} } channel_option: FOR CHANNEL channel server_id_list: [server_id [, server_id] ... ]
CHANGE MASTER TO
changes the
parameters that the replica server uses for connecting to the
source and for reading data from the source. It also updates the
contents of the replication metadata repositories (see
Section 19.2.4, “Relay Log and Replication Metadata Repositories”). From MySQL 8.0.23, use
CHANGE REPLICATION SOURCE TO
in
place of CHANGE MASTER
TO
, which is deprecated from that release. In releases
before MySQL 8.0.23, use CHANGE MASTER
TO
.
CHANGE MASTER TO
requires the
REPLICATION_SLAVE_ADMIN
privilege
(or the deprecated SUPER
privilege).
Options that you do not specify on a CHANGE
MASTER TO
statement retain their value, except as
indicated in the following discussion. In most cases, there is
therefore no need to specify options that do not change.
Values used for SOURCE_HOST
and other
CHANGE REPLICATION SOURCE TO
options are checked for linefeed (\n
or
0x0A
) characters. The presence of such
characters in these values causes the statement to fail with an
error.
The optional FOR CHANNEL
clause enables you
to name which replication channel the statement applies to.
Providing a channel
FOR CHANNEL
clause applies the
channel
CHANGE MASTER TO
statement to a specific
replication channel, and is used to add a new channel or modify
an existing channel. For example, to add a new channel called
channel2
:
Press CTRL+C to copyCHANGE MASTER TO MASTER_HOST=host1, MASTER_PORT=3002 FOR CHANNEL 'channel2'
If no clause is named and no extra channels exist, a
CHANGE MASTER TO
statement
applies to the default channel, whose name is the empty string
(""). When you have set up multiple replication channels, every
CHANGE MASTER TO
statement must
name a channel using the FOR CHANNEL
clause. See
Section 19.2.2, “Replication Channels” for more information.
channel
For some of the options of the CHANGE
MASTER TO
statement, you must issue a
STOP
SLAVE
statement prior to issuing a
CHANGE MASTER TO
statement (and a
START
SLAVE
statement afterwards). Sometimes, you only need
to stop the replication SQL (applier) thread or the replication
I/O (receiver) thread, not both:
When the applier thread is stopped, you can execute
CHANGE MASTER TO
using any combination that is otherwise allowed ofRELAY_LOG_FILE
,RELAY_LOG_POS
, andMASTER_DELAY
options, even if the replication receiver thread is running. No other options may be used with this statement when the receiver thread is running.When the receiver thread is stopped, you can execute
CHANGE MASTER TO
using any of the options for this statement (in any allowed combination) exceptRELAY_LOG_FILE
,RELAY_LOG_POS
,MASTER_DELAY
, orMASTER_AUTO_POSITION = 1
even when the applier thread is running.Both the receiver thread and the applier thread must be stopped before issuing a
CHANGE MASTER TO
statement that employsMASTER_AUTO_POSITION = 1
,GTID_ONLY = 1
, orASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
.
You can check the current state of the replication applier
thread and replication receiver thread using
SHOW SLAVE
STATUS
. Note that the Group Replication applier
channel (group_replication_applier
) has no
receiver thread, only an applier thread.
CHANGE MASTER TO
statements have
a number of side-effects and interactions that you should be
aware of beforehand:
CHANGE MASTER TO
causes an implicit commit of an ongoing transaction. See Section 15.3.3, “Statements That Cause an Implicit Commit”.CHANGE MASTER TO
causes the previous values forMASTER_HOST
,MASTER_PORT
,MASTER_LOG_FILE
, andMASTER_LOG_POS
to be written to the error log, along with other information about the replica's state prior to execution.If you are using statement-based replication and temporary tables, it is possible for a
CHANGE MASTER TO
statement following aSTOP SLAVE
statement to leave behind temporary tables on the replica. A warning (ER_WARN_OPEN_TEMP_TABLES_MUST_BE_ZERO
) is issued whenever this occurs. You can avoid this in such cases by making sure that the value of theReplica_open_temp_tables
orSlave_open_temp_tables
system status variable is equal to 0 prior to executing such aCHANGE MASTER TO
statement.When using a multithreaded replica (
replica_parallel_workers
> 0 orslave_parallel_workers
> 0), stopping the replica can cause gaps in the sequence of transactions that have been executed from the relay log, regardless of whether the replica was stopped intentionally or otherwise. When such gaps exist, issuingCHANGE MASTER TO
fails. The solution in this situation is to issueSTART SLAVE UNTIL SQL_AFTER_MTS_GAPS
which ensures that the gaps are closed. From MySQL 8.0.26, the process of checking for gaps in the sequence of transactions is skipped entirely when GTID-based replication and GTID auto-positioning are in use, because gaps in transactions can be resolved using GTID auto-positioning. In that situation,CHANGE MASTER TO
can still be used.
The following options are available for
CHANGE MASTER TO
statements:
-
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS = {OFF | LOCAL |
uuid
} Makes the replication channel assign a GTID to replicated transactions that do not have one, enabling replication from a source that does not use GTID-based replication, to a replica that does. For a multi-source replica, you can have a mix of channels that use
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
, and channels that do not. The default isOFF
, meaning that the feature is not used.LOCAL
assigns a GTID including the replica's own UUID (theserver_uuid
setting).
assigns a GTID including the specified UUID, such as theuuid
server_uuid
setting for the replication source server. Using a nonlocal UUID lets you differentiate between transactions that originated on the replica and transactions that originated on the source, and for a multi-source replica, between transactions that originated on different sources. The UUID you choose only has significance for the replica's own use. If any of the transactions sent by the source do have a GTID already, that GTID is retained.Channels specific to Group Replication cannot use
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
, but an asynchronous replication channel for another source on a server instance that is a Group Replication group member can do so. In that case, do not specify the Group Replication group name as the UUID for creating the GTIDs.To set
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
toLOCAL
or
, the replica must haveuuid
gtid_mode=ON
set, and this cannot be changed afterwards. This option is for use with a source that has binary log file position based replication, soMASTER_AUTO_POSITION=1
cannot be set for the channel. Both the replication SQL thread and the replication I/O (receiver) thread must be stopped before setting this option.ImportantA replica set up with
ASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
on any channel cannot be promoted to replace the replication source server in the event that a failover is required, and a backup taken from the replica cannot be used to restore the replication source server. The same restriction applies to replacing or restoring other replicas that useASSIGN_GTIDS_TO_ANONYMOUS_TRANSACTIONS
on any channel.For further restrictions and information, see Section 19.1.3.6, “Replication From a Source Without GTIDs to a Replica With GTIDs”.
-
GET_MASTER_PUBLIC_KEY = {0|1}
Enables RSA key pair-based password exchange by requesting the public key from the source. The option is disabled by default.
This option applies to replicas that authenticate with the
caching_sha2_password
authentication plugin. For connections by accounts that authenticate using this plugin, the source does not send the public key unless requested, so it must be requested or specified in the client. IfMASTER_PUBLIC_KEY_PATH
is given and specifies a valid public key file, it takes precedence overGET_MASTER_PUBLIC_KEY
. If you are using a replication user account that authenticates with thecaching_sha2_password
plugin (which is the default from MySQL 8.0), and you are not using a secure connection, you must specify either this option or theMASTER_PUBLIC_KEY_PATH
option to provide the RSA public key to the replica.-
GTID_ONLY = {0|1}
Stops the replication channel persisting file names and file positions in the replication metadata repositories.
GTID_ONLY
is available as of MySQL 8.0.27. TheGTID_ONLY
option is disabled by default for asynchronous replication channels, but it is enabled by default for Group Replication channels, and it cannot be disabled for them.For replication channels with this setting, in-memory file positions are still tracked, and file positions can still be observed for debugging purposes in error messages and through interfaces such as
SHOW REPLICA STATUS
statements (where they are shown as being invalid if they are out of date). However, the writes and reads required to persist and check the file positions are avoided in situations where GTID-based replication does not actually require them, including the transaction queuing and application process.This option can be used only if both the replication SQL (applier) thread and replication I/O (receiver) thread are stopped. To set
GTID_ONLY = 1
for a replication channel, GTIDs must be in use on the server (gtid_mode = ON
), and row-based binary logging must be in use on the source (statement-based replication is not supported). The optionsREQUIRE_ROW_FORMAT = 1
andSOURCE_AUTO_POSITION = 1
must be set for the replication channel.When
GTID_ONLY = 1
is set, the replica usesreplica_parallel_workers=1
if that system variable is set to zero for the server, so it is always technically a multi-threaded applier. This is because a multi-threaded applier uses saved positions rather than the replication metadata repositories to locate the start of a transaction that it needs to reapply.If you disable
GTID_ONLY
after setting it, the existing relay logs are deleted and the existing known binary log file positions are persisted, even if they are stale. The file positions for the binary log and relay log in the replication metadata repositories might be invalid, and a warning is returned if this is the case. Provided thatSOURCE_AUTO_POSITION
is still enabled, GTID auto-positioning is used to provide the correct positioning.If you also disable
SOURCE_AUTO_POSITION
, the file positions for the binary log and relay log in the replication metadata repositories are used for positioning if they are valid. If they are marked as invalid, you must provide a valid binary log file name and position (SOURCE_LOG_FILE
andSOURCE_LOG_POS
). If you also provide a relay log file name and position (RELAY_LOG_FILE
andRELAY_LOG_POS
), the relay logs are preserved and the applier position is set to the stated position. GTID auto-skip ensures that any transactions already applied are skipped even if the eventual applier position is not correct.-
IGNORE_SERVER_IDS = (
server_id_list
) Makes the replica ignore events originating from the specified servers. The option takes a comma-separated list of 0 or more server IDs. Log rotation and deletion events from the servers are not ignored, and are recorded in the relay log.
In circular replication, the originating server normally acts as the terminator of its own events, so that they are not applied more than once. Thus, this option is useful in circular replication when one of the servers in the circle is removed. Suppose that you have a circular replication setup with 4 servers, having server IDs 1, 2, 3, and 4, and server 3 fails. When bridging the gap by starting replication from server 2 to server 4, you can include
IGNORE_SERVER_IDS = (3)
in theCHANGE MASTER TO
statement that you issue on server 4 to tell it to use server 2 as its source instead of server 3. Doing so causes it to ignore and not to propagate any statements that originated with the server that is no longer in use.If
IGNORE_SERVER_IDS
contains the server's own ID and the server was started with the--replicate-same-server-id
option enabled, an error results.NoteWhen global transaction identifiers (GTIDs) are used for replication, transactions that have already been applied are automatically ignored, so the
IGNORE_SERVER_IDS
function is not required and is deprecated. Ifgtid_mode=ON
is set for the server, a deprecation warning is issued if you include theIGNORE_SERVER_IDS
option in aCHANGE MASTER TO
statement.The source metadata repository and the output of
SHOW REPLICA STATUS
provide the list of servers that are currently ignored. For more information, see Section 19.2.4.2, “Replication Metadata Repositories”, and Section 15.7.7.35, “SHOW REPLICA STATUS Statement”.If a
CHANGE MASTER TO
statement is issued without anyIGNORE_SERVER_IDS
option, any existing list is preserved. To clear the list of ignored servers, it is necessary to use the option with an empty list:Press CTRL+C to copyCHANGE MASTER TO IGNORE_SERVER_IDS = ();
RESET REPLICA ALL
clearsIGNORE_SERVER_IDS
.NoteA deprecation warning is issued if
SET GTID_MODE=ON
is issued when any channel has existing server IDs set withIGNORE_SERVER_IDS
. Before starting GTID-based replication, check for and clear all ignored server ID lists on the servers involved. TheSHOW REPLICA STATUS
statement displays the list of ignored IDs, if there is one. If you do receive the deprecation warning, you can still clear a list aftergtid_mode=ON
is set by issuing aCHANGE MASTER TO
statement containing theIGNORE_SERVER_IDS
option with an empty list.-
MASTER_AUTO_POSITION = {0|1}
Makes the replica attempt to connect to the source using the auto-positioning feature of GTID-based replication, rather than a binary log file based position. This option is used to start a replica using GTID-based replication. The default is 0, meaning that GTID auto-positioning and GTID-based replication are not used. This option can be used with
CHANGE MASTER TO
only if both the replication SQL (applier) thread and replication I/O (receiver) thread are stopped.Both the replica and the source must have GTIDs enabled (
GTID_MODE=ON
,ON_PERMISSIVE,
orOFF_PERMISSIVE
on the replica, andGTID_MODE=ON
on the source).MASTER_LOG_FILE
,MASTER_LOG_POS
,RELAY_LOG_FILE
, andRELAY_LOG_POS
cannot be specified together withMASTER_AUTO_POSITION = 1
. If multi-source replication is enabled on the replica, you need to set theMASTER_AUTO_POSITION = 1
option for each applicable replication channel.With
MASTER_AUTO_POSITION = 1
set, in the initial connection handshake, the replica sends a GTID set containing the transactions that it has already received, committed, or both. The source responds by sending all transactions recorded in its binary log whose GTID is not included in the GTID set sent by the replica. This exchange ensures that the source only sends the transactions with a GTID that the replica has not already recorded or committed. If the replica receives transactions from more than one source, as in the case of a diamond topology, the auto-skip function ensures that the transactions are not applied twice. For details of how the GTID set sent by the replica is computed, see Section 19.1.3.3, “GTID Auto-Positioning”.If any of the transactions that should be sent by the source have been purged from the source's binary log, or added to the set of GTIDs in the
gtid_purged
system variable by another method, the source sends the errorER_SOURCE_HAS_PURGED_REQUIRED_GTIDS
to the replica, and replication does not start. The GTIDs of the missing purged transactions are identified and listed in the source's error log in the warning messageER_FOUND_MISSING_GTIDS
. Also, if during the exchange of transactions it is found that the replica has recorded or committed transactions with the source's UUID in the GTID, but the source itself has not committed them, the source sends the errorER_REPLICA_HAS_MORE_GTIDS_THAN_SOURCE
to the replica and replication does not start. For information on how to handle these situations, see Section 19.1.3.3, “GTID Auto-Positioning”.You can see whether replication is running with GTID auto-positioning enabled by checking the Performance Schema
replication_connection_status
table or the output ofSHOW REPLICA STATUS
. Disabling theMASTER_AUTO_POSITION
option again makes the replica revert to file-based replication.-
MASTER_BIND = '
interface_name
' Determines which of the replica's network interfaces is chosen for connecting to the source, for use on replicas that have multiple network interfaces. Specify the IP address of the network interface. The maximum length of the string value is 255 characters.
The IP address configured with this option, if any, can be seen in the
Master_Bind
column of the output fromSHOW REPLICA STATUS
. In the source metadata repository tablemysql.slave_master_info
, the value can be seen as theMaster_bind
column. The ability to bind a replica to a specific network interface is also supported by NDB Cluster.-
MASTER_COMPRESSION_ALGORITHMS = '
algorithm
[,algorithm
][,algorithm
]' Specifies one, two, or three of the permitted compression algorithms for connections to the replication source server, separated by commas. The maximum length of the string value is 99 characters. The default value is
uncompressed
.The available algorithms are
zlib
,zstd
, anduncompressed
, the same as for theprotocol_compression_algorithms
system variable. The algorithms can be specified in any order, but it is not an order of preference - the algorithm negotiation process attempts to usezlib
, thenzstd
, thenuncompressed
, if they are specified.MASTER_COMPRESSION_ALGORITHMS
is available as of MySQL 8.0.18.The value of
MASTER_COMPRESSION_ALGORITHMS
applies only if thereplica_compressed_protocol
orslave_compressed_protocol
system variable is disabled. Ifreplica_compressed_protocol
orslave_compressed_protocol
is enabled, it takes precedence overMASTER_COMPRESSION_ALGORITHMS
and connections to the source usezlib
compression if both source and replica support that algorithm. For more information, see Section 6.2.8, “Connection Compression Control”.Binary log transaction compression (available as of MySQL 8.0.20), which is activated by the
binlog_transaction_compression
system variable, can also be used to save bandwidth. If you do this in combination with connection compression, connection compression has less opportunity to act on the data, but can still compress headers and those events and transaction payloads that are uncompressed. For more information on binary log transaction compression, see Section 7.4.4.5, “Binary Log Transaction Compression”.-
MASTER_CONNECT_RETRY =
interval
Specifies the interval in seconds between the reconnection attempts that the replica makes after the connection to the source times out. The default interval is 60.
The attempts are limited by the
MASTER_RETRY_COUNT
option. If both the default settings are used, the replica waits 60 seconds between reconnection attempts (MASTER_CONNECT_RETRY=60
), and keeps attempting to reconnect at this rate for 60 days (MASTER_RETRY_COUNT=86400
). These values are recorded in the source metadata repository and shown in thereplication_connection_configuration
Performance Schema table.-
MASTER_DELAY =
interval
Specifies how many seconds behind the source the replica must lag. An event received from the source is not executed until at least
interval
seconds later than its execution on the source.interval
must be a nonnegative integer in the range from 0 to 231−1. The default is 0. For more information, see Section 19.4.11, “Delayed Replication”.A
CHANGE MASTER TO
statement employing theMASTER_DELAY
option can be executed on a running replica when the replication SQL thread is stopped.-
MASTER_HEARTBEAT_PERIOD =
interval
Controls the heartbeat interval, which stops the connection timeout occurring in the absence of data if the connection is still good. A heartbeat signal is sent to the replica after that number of seconds, and the waiting period is reset whenever the source's binary log is updated with an event. Heartbeats are therefore sent by the source only if there are no unsent events in the binary log file for a period longer than this.
The heartbeat interval
interval
is a decimal value having the range 0 to 4294967 seconds and a resolution in milliseconds; the smallest nonzero value is 0.001. Settinginterval
to 0 disables heartbeats altogether. The heartbeat interval defaults to half the value of thereplica_net_timeout
orslave_net_timeout
system variable. It is recorded in the source metadata repository and shown in thereplication_connection_configuration
Performance Schema table.The system variable
replica_net_timeout
(from MySQL 8.0.26) orslave_net_timeout
(before MySQL 8.0.26) specifies the number of seconds that the replica waits for either more data or a heartbeat signal from the source, before the replica considers the connection broken, aborts the read, and tries to reconnect. The default value is 60 seconds (one minute). Note that a change to the value or default setting ofreplica_net_timeout
orslave_net_timeout
does not automatically change the heartbeat interval, whether that has been set explicitly or is using a previously calculated default. A warning is issued if you set the global value ofreplica_net_timeout
orslave_net_timeout
to a value less than that of the current heartbeat interval. Ifreplica_net_timeout
orslave_net_timeout
is changed, you must also issueCHANGE MASTER TO
to adjust the heartbeat interval to an appropriate value so that the heartbeat signal occurs before the connection timeout. If you do not do this, the heartbeat signal has no effect, and if no data is received from the source, the replica can make repeated reconnection attempts, creating zombie dump threads.-
MASTER_HOST = '
host_name
' The host name or IP address of the replication source server. The replica uses this to connect to the source. The maximum length of the string value is 255 characters. Before MySQL 8.0.17 it was 60 characters.
If you specify
MASTER_HOST
orMASTER_PORT
, the replica assumes that the source server is different from before (even if the option value is the same as its current value.) In this case, the old values for the source's binary log file name and position are considered no longer applicable, so if you do not specifyMASTER_LOG_FILE
andMASTER_LOG_POS
in the statement,MASTER_LOG_FILE=''
andMASTER_LOG_POS=4
are silently appended to it.Setting
MASTER_HOST=''
(that is, setting its value explicitly to an empty string) is not the same as not settingMASTER_HOST
at all. Trying to setMASTER_HOST
to an empty string fails with an error.-
MASTER_LOG_FILE = '
,source_log_name
'MASTER_LOG_POS =
source_log_pos
The binary log file name, and the location in that file, at which the replication I/O (receiver) thread begins reading from the source's binary log the next time the thread starts. Specify these options if you are using binary log file position based replication.
MASTER_LOG_FILE
must include the numeric suffix of a specific binary log file that is available on the source server, for example,MASTER_LOG_FILE='binlog.000145'
. The maximum length of the string value is 511 characters.MASTER_LOG_POS
is the numeric position for the replica to start reading in that file.MASTER_LOG_POS=4
represents the start of the events in a binary log file.If you specify either of
MASTER_LOG_FILE
orMASTER_LOG_POS
, you cannot specifyMASTER_AUTO_POSITION = 1
, which is for GTID-based replication.If neither of
MASTER_LOG_FILE
orMASTER_LOG_POS
is specified, the replica uses the last coordinates of the replication SQL (applier) thread beforeCHANGE MASTER TO
was issued. This ensures that there is no discontinuity in replication, even if the replication SQL (applier) thread was late compared to the replication I/O (receiver) thread.-
MASTER_PASSWORD = '
password
' The password for the replication user account to use for connecting to the replication source server. The maximum length of the string value is 32 characters. If you specify
MASTER_PASSWORD
,MASTER_USER
is also required.The password used for a replication user account in a
CHANGE MASTER TO
statement is limited to 32 characters in length. Trying to use a password of more than 32 characters causesCHANGE MASTER TO
to fail.The password is masked in MySQL Server’s logs, Performance Schema tables, and
SHOW PROCESSLIST
statements.-
MASTER_PORT =
port_num
The TCP/IP port number that the replica uses to connect to the replication source server.
NoteReplication cannot use Unix socket files. You must be able to connect to the replication source server using TCP/IP.
If you specify
MASTER_HOST
orMASTER_PORT
, the replica assumes that the source server is different from before (even if the option value is the same as its current value). In this case, the old values for the source's binary log file name and position are considered no longer applicable, so if you do not specifyMASTER_LOG_FILE
andMASTER_LOG_POS
in the statement,MASTER_LOG_FILE=''
andMASTER_LOG_POS=4
are silently appended to it.-
MASTER_PUBLIC_KEY_PATH = '
key_file_name
' Enables RSA key pair-based password exchange by providing the path name to a file containing a replica-side copy of the public key required by the source. The file must be in PEM format. The maximum length of the string value is 511 characters.
This option applies to replicas that authenticate with the
sha256_password
orcaching_sha2_password
authentication plugin. (Forsha256_password
,MASTER_PUBLIC_KEY_PATH
can be used only if MySQL was built using OpenSSL.) If you are using a replication user account that authenticates with thecaching_sha2_password
plugin (which is the default from MySQL 8.0), and you are not using a secure connection, you must specify either this option or theGET_MASTER_PUBLIC_KEY=1
option to provide the RSA public key to the replica.-
MASTER_RETRY_COUNT =
count
Sets the maximum number of reconnection attempts that the replica makes after the connection to the source times out, as determined by the
replica_net_timeout
orslave_net_timeout
system variable. If the replica does need to reconnect, the first retry occurs immediately after the timeout. The default is 86400 attempts.The interval between the attempts is specified by the
MASTER_CONNECT_RETRY
option. If both the default settings are used, the replica waits 60 seconds between reconnection attempts (MASTER_CONNECT_RETRY=60
), and keeps attempting to reconnect at this rate for 60 days (MASTER_RETRY_COUNT=86400
). A setting of 0 forMASTER_RETRY_COUNT
means that there is no limit on the number of reconnection attempts, so the replica keeps trying to reconnect indefinitely.The values for
MASTER_CONNECT_RETRY
andMASTER_RETRY_COUNT
are recorded in the source metadata repository and shown in thereplication_connection_configuration
Performance Schema table.MASTER_RETRY_COUNT
supersedes the--master-retry-count
server startup option.-
MASTER_SSL = {0|1}
Specify whether the replica encrypts the replication connection. The default is 0, meaning that the replica does not encrypt the replication connection. If you set
MASTER_SSL=1
, you can configure the encryption using theMASTER_SSL_
andxxx
MASTER_TLS_
options.xxx
Setting
MASTER_SSL=1
for a replication connection and then setting no furtherMASTER_SSL_
options corresponds to settingxxx
--ssl-mode=REQUIRED
for the client, as described in Command Options for Encrypted Connections. WithMASTER_SSL=1
, the connection attempt only succeeds if an encrypted connection can be established. A replication connection does not fall back to an unencrypted connection, so there is no setting corresponding to the--ssl-mode=PREFERRED
setting for replication. IfMASTER_SSL=0
is set, this corresponds to--ssl-mode=DISABLED
.ImportantTo help prevent sophisticated man-in-the-middle attacks, it is important for the replica to verify the server’s identity. You can specify additional
MASTER_SSL_
options to correspond to the settingsxxx
--ssl-mode=VERIFY_CA
and--ssl-mode=VERIFY_IDENTITY
, which are a better choice than the default setting to help prevent this type of attack. With these settings, the replica checks that the server’s certificate is valid, and checks that the host name the replica is using matches the identity in the server’s certificate. To implement one of these levels of verification, you must first ensure that the CA certificate for the server is reliably available to the replica, otherwise availability issues will result. For this reason, they are not the default setting.-
MASTER_SSL_
,xxx
MASTER_TLS_
xxx
Specify how the replica uses encryption and ciphers to secure the replication connection. These options can be changed even on replicas that are compiled without SSL support. They are saved to the source metadata repository, but are ignored if the replica does not have SSL support enabled. The maximum length of the value for the string-valued
MASTER_SSL_
andxxx
MASTER_TLS_
options is 511 characters, with the exception ofxxx
MASTER_TLS_CIPHERSUITES
, for which it is 4000 characters.The
MASTER_SSL_
andxxx
MASTER_TLS_
options perform the same functions as thexxx
--ssl-
andxxx
--tls-
client options described in Command Options for Encrypted Connections. The correspondence between the two sets of options, and the use of thexxx
MASTER_SSL_
andxxx
MASTER_TLS_
options to set up a secure connection, is explained in Section 19.3.1, “Setting Up Replication to Use Encrypted Connections”.xxx
-
MASTER_USER = '
user_name
' The user name for the replication user account to use for connecting to the replication source server. The maximum length of the string value is 96 characters.
For Group Replication, this account must exist on every member of the replication group. It is used for distributed recovery if the XCom communication stack is in use for the group, and also used for group communication connections if the MySQL communication stack is in use for the group. With the MySQL communication stack, the account must have the
GROUP_REPLICATION_STREAM
permission.It is possible to set an empty user name by specifying
MASTER_USER=''
, but the replication channel cannot be started with an empty user name. In releases before MySQL 8.0.21, only set an emptyMASTER_USER
user name if you need to clear previously used credentials from the replication metadata repositories for security purposes. Do not use the channel afterwards, due to a bug in these releases that can substitute a default user name if an empty user name is read from the repositories (for example, during an automatic restart of a Group Replication channel). From MySQL 8.0.21, it is valid to set an emptyMASTER_USER
user name and use the channel afterwards if you always provide user credentials using theSTART REPLICA
statement orSTART GROUP_REPLICATION
statement that starts the replication channel. This approach means that the replication channel always needs operator intervention to restart, but the user credentials are not recorded in the replication metadata repositories.ImportantTo connect to the source using a replication user account that authenticates with the
caching_sha2_password
plugin, you must either set up a secure connection as described in Section 19.3.1, “Setting Up Replication to Use Encrypted Connections”, or enable the unencrypted connection to support password exchange using an RSA key pair. Thecaching_sha2_password
authentication plugin is the default for new users created from MySQL 8.0 (for details, see Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”). If the user account that you create or use for replication uses this authentication plugin, and you are not using a secure connection, you must enable RSA key pair-based password exchange for a successful connection. You can do this using either theMASTER_PUBLIC_KEY_PATH
option or theGET_MASTER_PUBLIC_KEY=1
option for this statement.-
MASTER_ZSTD_COMPRESSION_LEVEL =
level
The compression level to use for connections to the replication source server that use the
zstd
compression algorithm. The permitted levels are from 1 to 22, with larger values indicating increasing levels of compression. The default level is 3.MASTER_ZSTD_COMPRESSION_LEVEL
is available as of MySQL 8.0.18.The compression level setting has no effect on connections that do not use
zstd
compression. For more information, see Section 6.2.8, “Connection Compression Control”.-
NETWORK_NAMESPACE = '
namespace
' The network namespace to use for TCP/IP connections to the replication source server or, if the MySQL communication stack is in use, for Group Replication’s group communication connections. The maximum length of the string value is 64 characters. If this option is omitted, connections from the replica use the default (global) namespace. On platforms that do not implement network namespace support, failure occurs when the replica attempts to connect to the source. For information about network namespaces, see Section 7.1.14, “Network Namespace Support”.
NETWORK_NAMESPACE
is available as of MySQL 8.0.22.-
PRIVILEGE_CHECKS_USER = {NULL | '
account
'} Names a user account that supplies a security context for the specified channel.
NULL
, which is the default, means no security context is used.PRIVILEGE_CHECKS_USER
is available as of MySQL 8.0.18.The user name and host name for the user account must follow the syntax described in Section 8.2.4, “Specifying Account Names”, and the user must not be an anonymous user (with a blank user name) or the
CURRENT_USER
. The account must have theREPLICATION_APPLIER
privilege, plus the required privileges to execute the transactions replicated on the channel. For details of the privileges required by the account, see Section 19.3.3, “Replication Privilege Checks”. When you restart the replication channel, the privilege checks are applied from that point on. If you do not specify a channel and no other channels exist, the statement is applied to the default channel.The use of row-based binary logging is strongly recommended when
PRIVILEGE_CHECKS_USER
is set, and you can setREQUIRE_ROW_FORMAT
to enforce this. For example, to start privilege checks on the channelchannel_1
on a running replica, issue the following statements:Press CTRL+C to copymysql> STOP REPLICA FOR CHANNEL 'channel_1'; mysql> CHANGE MASTER TO PRIVILEGE_CHECKS_USER = 'priv_repl'@'%.example.com', REQUIRE_ROW_FORMAT = 1, FOR CHANNEL 'channel_1'; mysql> START REPLICA FOR CHANNEL 'channel_1';
For releases from MySQL 8.0.22, use
START REPLICA
andSTOP REPLICA
, and for releases before MySQL 8.0.22, useSTART SLAVE
andSTOP SLAVE
. The statements work in the same way, only the terminology has changed.-
RELAY_LOG_FILE = '
,relay_log_file
'RELAY_LOG_POS = '
relay_log_pos
' The relay log file name, and the location in that file, at which the replication SQL thread begins reading from the replica's relay log the next time the thread starts.
RELAY_LOG_FILE
can use either an absolute or relative path, and uses the same base name asMASTER_LOG_FILE
. The maximum length of the string value is 511 characters.A
CHANGE MASTER TO
statement usingRELAY_LOG_FILE
,RELAY_LOG_POS
, or both options can be executed on a running replica when the replication SQL thread is stopped. Relay logs are preserved if at least one of the replication SQL (applier) thread and the replication I/O (receiver) thread is running. If both threads are stopped, all relay log files are deleted unless at least one ofRELAY_LOG_FILE
orRELAY_LOG_POS
is specified. For the Group Replication applier channel (group_replication_applier
), which only has an applier thread and no receiver thread, this is the case if the applier thread is stopped, but with that channel you cannot use theRELAY_LOG_FILE
andRELAY_LOG_POS
options.-
REQUIRE_ROW_FORMAT = {0|1}
Permits only row-based replication events to be processed by the replication channel. This option prevents the replication applier from taking actions such as creating temporary tables and executing
LOAD DATA INFILE
requests, which increases the security of the channel. TheREQUIRE_ROW_FORMAT
option is disabled by default for asynchronous replication channels, but it is enabled by default for Group Replication channels, and it cannot be disabled for them. For more information, see Section 19.3.3, “Replication Privilege Checks”.REQUIRE_ROW_FORMAT
is available as of MySQL 8.0.19.-
REQUIRE_TABLE_PRIMARY_KEY_CHECK = {STREAM | ON | OFF}
Enables a replica to select its own policy for primary key checks. The default is
STREAM
.REQUIRE_TABLE_PRIMARY_KEY_CHECK
is available as of MySQL 8.0.20.When the option is set to
ON
for a replication channel, the replica always uses the valueON
for thesql_require_primary_key
system variable in replication operations, requiring a primary key. When the option is set toOFF
, the replica always uses the valueOFF
for thesql_require_primary_key
system variable in replication operations, so that a primary key is never required, even if the source required one. When theREQUIRE_TABLE_PRIMARY_KEY_CHECK
option is set toSTREAM
, which is the default, the replica uses whatever value is replicated from the source for each transaction.For multisource replication, setting
REQUIRE_TABLE_PRIMARY_KEY_CHECK
toON
orOFF
enables a replica to normalize behavior across the replication channels for different sources, and keep a consistent setting for thesql_require_primary_key
system variable. UsingON
safeguards against the accidental loss of primary keys when multiple sources update the same set of tables. UsingOFF
allows sources that can manipulate primary keys to work alongside sources that cannot.When
PRIVILEGE_CHECKS_USER
is set, settingREQUIRE_TABLE_PRIMARY_KEY_CHECK
toON
orOFF
means that the user account does not need session administration level privileges to set restricted session variables, which are required to change the value ofsql_require_primary_key
to match the source's setting for each transaction. For more information, see Section 19.3.3, “Replication Privilege Checks”.-
SOURCE_CONNECTION_AUTO_FAILOVER = {0|1}
Activates the asynchronous connection failover mechanism for a replication channel if one or more alternative replication source servers are available (so when there are multiple MySQL servers or groups of servers that share the replicated data).
SOURCE_CONNECTION_AUTO_FAILOVER
is available as of MySQL 8.0.22. The default is 0, meaning that the mechanism is not activated. For full information and instructions to set up this feature, see Section 19.4.9.2, “Asynchronous Connection Failover for Replicas”.The asynchronous connection failover mechanism takes over after the reconnection attempts controlled by
MASTER_CONNECT_RETRY
andMASTER_RETRY_COUNT
are exhausted. It reconnects the replica to an alternative source chosen from a specified source list, which you manage using theasynchronous_connection_failover_add_source
andasynchronous_connection_failover_delete_source
functions. To add and remove managed groups of servers, use theasynchronous_connection_failover_add_managed
andasynchronous_connection_failover_delete_managed
functions instead. For more information, see Section 19.4.9, “Switching Sources and Replicas with Asynchronous Connection Failover”.ImportantYou can only set
SOURCE_CONNECTION_AUTO_FAILOVER = 1
when GTID auto-positioning is in use (MASTER_AUTO_POSITION = 1
).When you set
SOURCE_CONNECTION_AUTO_FAILOVER = 1
, setMASTER_RETRY_COUNT
andMASTER_CONNECT_RETRY
to minimal numbers that just allow a few retry attempts with the same source in a short time, in case the connection failure is caused by a transient network outage. Otherwise the asynchronous connection failover mechanism cannot be activated promptly. Suitable values areMASTER_RETRY_COUNT=3
andMASTER_CONNECT_RETRY=10
, which make the replica retry the connection 3 times with 10-second intervals between.When you set
SOURCE_CONNECTION_AUTO_FAILOVER = 1
, the replication metadata repositories must contain the credentials for a replication user account that can be used to connect to all the servers on the source list for the replication channel. These credentials can be set using theCHANGE REPLICATION SOURCE TO
statement with theMASTER_USER
andMASTER_PASSWORD
options. For more information, see Section 19.4.9, “Switching Sources and Replicas with Asynchronous Connection Failover”.From MySQL 8.0.27, when you set
SOURCE_CONNECTION_AUTO_FAILOVER = 1
, asynchronous connection failover for replicas is automatically activated if this replication channel is on a Group Replication primary in a group in single-primary mode. With this function active, if the primary that is replicating goes offline or into an error state, the new primary starts replication on the same channel when it is elected. If you want to use the function, this replication channel must also be set up on all the secondary servers in the replication group, and on any new joining members. (If the servers are provisioned using MySQL’s clone functionality, this all happens automatically.) If you do not want to use the function, disable it by using thegroup_replication_disable_member_action
function to disable the Group Replication member actionmysql_start_failover_channels_if_primary
, which is enabled by default. For more information, see Section 19.4.9.2, “Asynchronous Connection Failover for Replicas”.
CHANGE MASTER TO
is
useful for setting up a replica when you have the snapshot of
the source and have recorded the source's binary log
coordinates corresponding to the time of the snapshot. After
loading the snapshot into the replica to synchronize it with
the source, you can run CHANGE MASTER TO
MASTER_LOG_FILE='
on
the replica to specify the coordinates at which the replica
should begin reading the source's binary log. The following
example changes the source server the replica uses and
establishes the source's binary log coordinates from which the
replica begins reading:
log_name
',
MASTER_LOG_POS=log_pos
Press CTRL+C to copyCHANGE MASTER TO MASTER_HOST='source2.example.com', MASTER_USER='replication', MASTER_PASSWORD='password', MASTER_PORT=3306, MASTER_LOG_FILE='source2-bin.001', MASTER_LOG_POS=4, MASTER_CONNECT_RETRY=10;
For the procedure to switch an existing replica to a new source during failover, see Section 19.4.8, “Switching Sources During Failover”.
When GTIDs are in use on the source and the replica, specify GTID auto-positioning instead of giving the binary log file position, as in the following example. For full instructions to configure and start GTID-based replication on new or stopped servers, online servers, or additional replicas, see Section 19.1.3, “Replication with Global Transaction Identifiers”.
Press CTRL+C to copyCHANGE MASTER TO MASTER_HOST='source3.example.com', MASTER_USER='replication', MASTER_PASSWORD='password', MASTER_PORT=3306, MASTER_AUTO_POSITION = 1, FOR CHANNEL "source_3";
In this example, multi-source replication is in use, and the
CHANGE MASTER TO
statement is
applied to the replication channel
"source_3"
that connects the replica to the
specified host. For guidance on setting up multi-source
replication, see Section 19.1.5, “MySQL Multi-Source Replication”.
The next example shows how to make the replica apply
transactions from relay log files that you want to repeat. To
do this, the source need not be reachable. You can use
CHANGE MASTER TO
to locate the
relay log position where you want the replica to start
reapplying transactions, and then start the SQL thread:
Press CTRL+C to copyCHANGE MASTER TO RELAY_LOG_FILE='replica-relay-bin.006', RELAY_LOG_POS=4025; START SLAVE SQL_THREAD;
CHANGE MASTER TO
can also be
used to skip over transactions in the binary log that are
causing replication to stop. The appropriate method to do this
depends on whether GTIDs are in use or not. For instructions
to skip transactions using CHANGE MASTER
TO
or another method, see
Section 19.1.7.3, “Skipping Transactions”.