Syntax:
CHANGE 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
  | MASTER_CONNECT_RETRY = interval
  | MASTER_RETRY_COUNT = count
  | MASTER_DELAY = interval
  | MASTER_HEARTBEAT_PERIOD = interval
  | 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_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'
  | IGNORE_SERVER_IDS = (server_id_list)
}

channel_option:
    FOR CHANNEL channel

server_id_list:
    [server_id [, server_id] ... ]

CHANGE MASTER TO changes the parameters that the replica uses for
connecting to the replication source server, for reading the source's
binary log, and reading the replica's relay log. It also updates the
contents of the replication metadata repositories (see
https://dev.mysql.com/doc/refman/5.7/en/replica-logs.html). CHANGE
MASTER TO requires the SUPER privilege.

Prior to MySQL 5.7.4, the replication threads must be stopped, using
STOP SLAVE if necessary, before issuing this statement. In MySQL 5.7.4
and later, you can issue CHANGE MASTER TO statements on a running
replica without doing this, depending on the states of the replication
SQL thread and replication I/O thread. The rules governing such use are
provided later in this section.

When using a multithreaded replica (in other words
slave_parallel_workers is greater than 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, issuing CHANGE MASTER
TO fails. The solution in this situation is to issue START SLAVE UNTIL
SQL_AFTER_MTS_GAPS which ensures that the gaps are closed.

The optional FOR CHANNEL channel clause enables you to name which
replication channel the statement applies to. Providing a FOR CHANNEL
channel clause applies the 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:

CHANGE MASTER TO MASTER_HOST=host1, MASTER_PORT=3002 FOR CHANNEL 'channel2'

If no clause is named and no extra channels exist, the statement
applies to the default channel.

When using multiple replication channels, if a CHANGE MASTER TO
statement does not name a channel using a FOR CHANNEL channel clause,
an error occurs. See
https://dev.mysql.com/doc/refman/5.7/en/replication-channels.html for
more information.

Options not specified retain their value, except as indicated in the
following discussion. Thus, in most cases, there is no need to specify
options that do not change. For example, if the password to connect to
your replication source server has changed, issue this statement to
tell the replica about the new password:

CHANGE MASTER TO MASTER_PASSWORD='new3cret';

MASTER_HOST, MASTER_USER, MASTER_PASSWORD, and MASTER_PORT provide
information to the replica about how to connect to its replication
source server:

o MASTER_HOST and MASTER_PORT are the host name (or IP address) of the
  master host and its TCP/IP port.

  *Note*:

  Replication cannot use Unix socket files. You must be able to connect
  to the replication source server using TCP/IP.

  If you specify the MASTER_HOST or MASTER_PORT option, the replica
  assumes that the source 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 specify MASTER_LOG_FILE and
  MASTER_LOG_POS in the statement, MASTER_LOG_FILE='' and
  MASTER_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 setting MASTER_HOST at all.
  Beginning with MySQL 5.5, trying to set MASTER_HOST to an empty
  string fails with an error. Previously, setting MASTER_HOST to an
  empty string caused START SLAVE subsequently to fail. (Bug #28796)

  Values used for MASTER_HOST and other CHANGE MASTER TO options are
  checked for linefeed (\n or 0x0A) characters; the presence of such
  characters in these values causes the statement to fail with
  ER_MASTER_INFO
  (https://dev.mysql.com/doc/mysql-errors/5.7/en/server-error-reference
  .html#error_er_master_info). (Bug #11758581, Bug #50801)

o MASTER_USER and MASTER_PASSWORD are the user name and password of the
  account to use for connecting to the source. 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; prior to MySQL 5.7.5, if the password was
  longer, the statement succeeded, but any excess characters were
  silently truncated. In MySQL 5.7.5 and later, trying to use a
  password of more than 32 characters causes CHANGE MASTER TO to fail.
  (Bug #11752299, Bug #43439)

  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. Only set an empty MASTER_USER user name if you need
  to clear previously used credentials from the replica's repositories
  for security purposes, and do not attempt to use the channel
  afterwards.

  The text of a running CHANGE MASTER TO statement, including values
  for MASTER_USER and MASTER_PASSWORD, can be seen in the output of a
  concurrent SHOW PROCESSLIST statement. (The complete text of a START
  SLAVE statement is also visible to SHOW PROCESSLIST.)

The MASTER_SSL_xxx options and the MASTER_TLS_VERSION option 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 MASTER_SSL_xxx and MASTER_TLS_VERSION options perform the
same functions as the --ssl-xxx and --tls-version client options
described in
https://dev.mysql.com/doc/refman/5.7/en/connection-options.html#encrypt
ed-connection-options. The correspondence between the two sets of
options, and the use of the MASTER_SSL_xxx and MASTER_TLS_VERSION
options to set up a secure connection, is explained in
https://dev.mysql.com/doc/refman/5.7/en/replication-solutions-encrypted
-connections.html.

As of MySQL 5.7.3, setting MASTER_SSL=1 means that the replica's
connection to the source must use SSL, or the connection attempt fails.
Before 5.7.3, the use of an SSL connection by the replica was not
enforced with MASTER_SSL=1. This is analogous to the client-side
meaning of the --ssl command-line option; see
https://dev.mysql.com/doc/refman/5.7/en/connection-options.html#encrypt
ed-connection-options.

The MASTER_HEARTBEAT_PERIOD, MASTER_CONNECT_RETRY, and
MASTER_RETRY_COUNT options control how the replica recognizes that the
connection to the source has been lost and makes attempts to reconnect.

o The slave_net_timeout system variable 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). Prior to MySQL 5.7.7, the default was 3600
  seconds (one hour).

o The heartbeat interval, which stops the connection timeout occurring
  in the absence of data if the connection is still good, is controlled
  by the MASTER_HEARTBEAT_PERIOD option. 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. Setting interval to 0 disables heartbeats
  altogether. The heartbeat interval defaults to half the value of the
  slave_net_timeout system variable. It is recorded in the source
  metadata repository and shown in the
  replication_connection_configuration Performance Schema table.
  Issuing RESET SLAVE resets the heartbeat interval to the default
  value.

o Prior to MySQL 5.7.4, not including MASTER_HEARTBEAT_PERIOD caused
  CHANGE MASTER TO to reset the heartbeat interval to the default (half
  the value of the slave_net_timeout system variable), and
  Slave_received_heartbeats to 0. The heartbeat interval is now not
  reset except by RESET SLAVE. (Bug #18185490)

o Note that a change to the value or default setting of
  slave_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
  @@GLOBAL.slave_net_timeout to a value less than that of the current
  heartbeat interval. If slave_net_timeout is changed, you must also
  issue CHANGE 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.

o If the replica does need to reconnect, the first retry occurs
  immediately after the timeout. MASTER_CONNECT_RETRY specifies the
  interval between reconnection attempts, and MASTER_RETRY_COUNT limits
  the number of reconnection attempts. 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 the
  replication_connection_configuration Performance Schema table.
  MASTER_RETRY_COUNT supersedes the --master-retry-count server startup
  option.

MASTER_DELAY 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. The
default is 0. An error occurs if interval is not a nonnegative integer
in the range from 0 to 231−1. For more information, see
https://dev.mysql.com/doc/refman/5.7/en/replication-delayed.html.

From MySQL 5.7, a CHANGE MASTER TO statement employing the MASTER_DELAY
option can be executed on a running replica when the replication SQL
thread is stopped.

MASTER_BIND is for use on replicas having multiple network interfaces,
and determines which of the replica's network interfaces is chosen for
connecting to the source.

The address configured with this option, if any, can be seen in the
Master_Bind column of the output from SHOW SLAVE STATUS. If you are
using a table for the source metadata repository (server started with
master_info_repository=TABLE), the value can also be seen as the
Master_bind column of the mysql.slave_master_info table.

The ability to bind a replica to a specific network interface is also
supported by NDB Cluster.

MASTER_LOG_FILE and MASTER_LOG_POS are the coordinates at which the
replication I/O thread should begin reading from the source the next
time the thread starts. RELAY_LOG_FILE and RELAY_LOG_POS are the
coordinates at which the replication SQL thread should begin reading
from the relay log the next time the thread starts. If you specify
either of MASTER_LOG_FILE or MASTER_LOG_POS, you cannot specify
RELAY_LOG_FILE or RELAY_LOG_POS. If you specify either of
MASTER_LOG_FILE or MASTER_LOG_POS, you also cannot specify
MASTER_AUTO_POSITION = 1 (described later in this section). If neither
of MASTER_LOG_FILE or MASTER_LOG_POS is specified, the replica uses the
last coordinates of the replication SQL thread before CHANGE MASTER TO
was issued. This ensures that there is no discontinuity in replication,
even if the replication SQL thread was late compared to the replication
I/O thread, when you merely want to change, say, the password to use.

From MySQL 5.7, a CHANGE MASTER TO statement employing RELAY_LOG_FILE,
RELAY_LOG_POS, or both options can be executed on a running replica
when the replication SQL thread is stopped. Prior to MySQL 5.7.4,
CHANGE MASTER TO deletes all relay log files and starts a new one,
unless you specify RELAY_LOG_FILE or RELAY_LOG_POS. In that case, relay
log files are kept; the relay_log_purge global variable is set silently
to 0. In MySQL 5.7.4 and later, relay logs are preserved if at least
one of the replication SQL thread and the replication I/O thread is
running. If both threads are stopped, all relay log files are deleted
unless at least one of RELAY_LOG_FILE or RELAY_LOG_POS is specified.
Note that the Group Replication applier channel
(group_replication_applier) has no I/O thread, only an SQL thread. For
this channel, the relay logs are not preserved when the SQL thread is
stopped.

RELAY_LOG_FILE can use either an absolute or relative path, and uses
the same base name as MASTER_LOG_FILE. (Bug #12190)

When MASTER_AUTO_POSITION = 1 is used with CHANGE MASTER TO, the
replica attempts to connect to the source using the GTID-based
replication protocol. From MySQL 5.7, this option can be employed by
CHANGE MASTER TO only if both the replication SQL thread and the
replication I/O thread are stopped. Both the replica and the source
must have GTIDs enabled (GTID_MODE=ON, ON_PERMISSIVE, or OFF_PERMISSIVE
on the replica, and GTID_MODE=ON on the source). Auto-positioning is
used for the connection, so the coordinates represented by
MASTER_LOG_FILE and MASTER_LOG_POS are not used, and the use of either
or both of these options together with MASTER_AUTO_POSITION = 1 causes
an error. If multi-source replication is enabled on the replica, you
need to set the MASTER_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
https://dev.mysql.com/doc/refman/5.7/en/replication-gtids-auto-position
ing.html.

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
error ER_MASTER_HAS_PURGED_REQUIRED_GTIDS to the replica, and
replication does not start. 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 error
ER_SLAVE_HAS_MORE_GTIDS_THAN_MASTER to the replica and replication does
not start. For information on how to handle these situations, see
https://dev.mysql.com/doc/refman/5.7/en/replication-gtids-auto-position
ing.html.

You can see whether replication is running with auto-positioning
enabled by checking the Performance Schema
replication_connection_status table or the output of SHOW SLAVE STATUS.
Disabling the MASTER_AUTO_POSITION option again makes the replica
revert to file-based replication, in which case you must also specify
one or both of the MASTER_LOG_FILE or MASTER_LOG_POS options.

IGNORE_SERVER_IDS takes a comma-separated list of 0 or more server IDs.
Events originating from the corresponding servers are ignored, with the
exception of log rotation and deletion events, which are still 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 the
CHANGE 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 a CHANGE MASTER TO statement is issued without any IGNORE_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:

CHANGE MASTER TO IGNORE_SERVER_IDS = ();

Prior to MySQL 5.7.5, RESET SLAVE ALL has no effect on the server ID
list. In MySQL 5.7.5 and later, RESET SLAVE ALL clears
IGNORE_SERVER_IDS. (Bug #18816897)

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.

The source metadata repository and the output of SHOW SLAVE STATUS
provide the list of servers that are currently ignored. For more
information, see
https://dev.mysql.com/doc/refman/5.7/en/replica-logs-status.html, and
[HELP SHOW SLAVE STATUS].

Invoking CHANGE MASTER TO causes the previous values for MASTER_HOST,
MASTER_PORT, MASTER_LOG_FILE, and MASTER_LOG_POS to be written to the
error log, along with other information about the replica's state prior
to execution.

CHANGE MASTER TO causes an implicit commit of an ongoing transaction.
See https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html.

In MySQL 5.7.4 and later, the strict requirement to execute STOP SLAVE
prior to issuing any CHANGE MASTER TO statement (and START SLAVE
afterward) is removed. Instead of depending on whether the replica is
stopped, the behavior of CHANGE MASTER TO depends (in MySQL 5.7.4 and
later) on the states of the replication SQL thread and the replication
I/O thread; which of these threads is stopped or running now determines
the options that can or cannot be used with a CHANGE MASTER TO
statement at a given point in time. The rules for making this
determination are listed here:

o If the SQL thread is stopped, you can execute CHANGE MASTER TO using
  any combination that is otherwise allowed of RELAY_LOG_FILE,
  RELAY_LOG_POS, and MASTER_DELAY options, even if the replication I/O
  thread is running. No other options may be used with this statement
  when the I/O thread is running.

o If the I/O thread is stopped, you can execute CHANGE MASTER TO using
  any of the options for this statement (in any allowed combination)
  except RELAY_LOG_FILE, RELAY_LOG_POS, MASTER_DELAY, or
  MASTER_AUTO_POSITION = 1 even when the SQL thread is running.

o Both the SQL thread and the I/O thread must be stopped before issuing
  a CHANGE MASTER TO statement that employs MASTER_AUTO_POSITION = 1.

You can check the current state of the replication SQL thread and the
replication I/O thread using SHOW SLAVE STATUS. Note that the Group
Replication applier channel (group_replication_applier) has no I/O
thread, only an SQL thread.

For more information, see
https://dev.mysql.com/doc/refman/5.7/en/replication-solutions-switch.ht
ml.

If you are using statement-based replication and temporary tables, it
is possible for a CHANGE MASTER TO statement following a STOP SLAVE
statement to leave behind temporary tables on the replica. From MySQL
5.7, a warning (ER_WARN_OPEN_TEMP_TABLES_MUST_BE_ZERO
(https://dev.mysql.com/doc/mysql-errors/5.7/en/server-error-reference.h
tml#error_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 the Slave_open_temp_tables system status variable is equal to
0 prior to executing such a CHANGE MASTER TO statement.

CHANGE MASTER TO is useful for setting up a replica when you have the
snapshot of the replication source server 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='log_name', MASTER_LOG_POS=log_pos on the replica to
specify the coordinates at which the replica should begin reading the
source's binary log.

The following example changes the replication source server the replica
uses and establishes the source's binary log coordinates from which the
replica begins reading. This is used when you want to set up the
replica to replicate the source:

CHANGE 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;

The next example shows an operation that is less frequently employed.
It is used when the replica has relay log files that you want it to
execute again for some reason. To do this, the source need not be
reachable. You need only use CHANGE MASTER TO and start the SQL thread
(START SLAVE SQL_THREAD):

CHANGE MASTER TO
  RELAY_LOG_FILE='replica-relay-bin.006',
  RELAY_LOG_POS=4025;

URL: https://dev.mysql.com/doc/refman/5.7/en/change-master-to.html

