MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
CHANGE MASTER TOoption
[,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 CHANNELchannel
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
:
CHANGE 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 of
RELAY_LOG_FILE
,
RELAY_LOG_POS
, and
MASTER_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)
except
RELAY_LOG_FILE
,
RELAY_LOG_POS
,
MASTER_DELAY
, or
MASTER_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 employs
MASTER_AUTO_POSITION = 1
,
GTID_ONLY = 1
, or
ASSIGN_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 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.
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. 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 the
Replica_open_temp_tables
or Slave_open_temp_tables
system status variable is equal to 0 prior to executing such
a CHANGE MASTER TO
statement.
When using a multithreaded replica
(replica_parallel_workers
>
0 or slave_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, 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. 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 is
OFF
, meaning that the feature is not
used.
LOCAL
assigns a GTID including the
replica's own UUID (the
server_uuid
setting).
assigns
a GTID including the specified UUID, such as the
uuid
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
to LOCAL
or
, the
replica must have
uuid
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, so MASTER_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.
A 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 use
ASSIGN_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. If MASTER_PUBLIC_KEY_PATH
is given and specifies a valid public key file, it takes
precedence over GET_MASTER_PUBLIC_KEY
.
If you are using a replication user account that
authenticates with the
caching_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
the MASTER_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. The GTID_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 options REQUIRE_ROW_FORMAT =
1
and SOURCE_AUTO_POSITION =
1
must be set for the replication channel.
When GTID_ONLY = 1
is set, the replica
uses
replica_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 that SOURCE_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
and
SOURCE_LOG_POS
). If you also provide a
relay log file name and position
(RELAY_LOG_FILE
and
RELAY_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 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 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.
When 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. If
gtid_mode=ON
is set for
the server, a deprecation warning is issued if you
include the IGNORE_SERVER_IDS
option
in a CHANGE 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 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 = ();
RESET
REPLICA ALL
clears
IGNORE_SERVER_IDS
.
A deprecation warning is issued if SET
GTID_MODE=ON
is issued when any channel has
existing server IDs set with
IGNORE_SERVER_IDS
. Before starting
GTID-based replication, check for and clear all ignored
server ID lists on the servers involved. The
SHOW
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 after
gtid_mode=ON
is set by
issuing a CHANGE MASTER
TO
statement containing the
IGNORE_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,
or
OFF_PERMISSIVE
on the replica, and
GTID_MODE=ON
on the
source). MASTER_LOG_FILE
,
MASTER_LOG_POS
,
RELAY_LOG_FILE
, and
RELAY_LOG_POS
cannot be specified
together with MASTER_AUTO_POSITION = 1
.
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
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 error
ER_MASTER_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 message
ER_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 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
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 of
SHOW
REPLICA STATUS
. Disabling the
MASTER_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 from
SHOW
REPLICA STATUS
. In the source metadata
repository table
mysql.slave_master_info
, the value can
be seen as the Master_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
, and
uncompressed
, the same as for the
protocol_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 use
zlib
, then zstd
,
then uncompressed
, if they are
specified.
MASTER_COMPRESSION_ALGORITHMS
is
available as of MySQL 8.0.18.
The value of
MASTER_COMPRESSION_ALGORITHMS
applies
only if the
replica_compressed_protocol
or
slave_compressed_protocol
system variable is disabled. If
replica_compressed_protocol
or
slave_compressed_protocol
is enabled, it takes precedence over
MASTER_COMPRESSION_ALGORITHMS
and
connections to the source use zlib
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 the
replication_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
the MASTER_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. Setting
interval
to 0 disables
heartbeats altogether. The heartbeat interval defaults to
half the value of the
replica_net_timeout
or
slave_net_timeout
system
variable. It is recorded in the source metadata repository
and shown in the
replication_connection_configuration
Performance Schema table.
The system variable
replica_net_timeout
(from
MySQL 8.0.26) or
slave_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 of
replica_net_timeout
or
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 the
global value of
replica_net_timeout
or
slave_net_timeout
to a value less than
that of the current heartbeat interval. If
replica_net_timeout
or
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.
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
or
MASTER_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 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. Trying to set
MASTER_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
or
MASTER_LOG_POS
, you cannot specify
MASTER_AUTO_POSITION = 1
, which is for
GTID-based replication.
If neither of MASTER_LOG_FILE
or
MASTER_LOG_POS
is specified, the
replica uses the last coordinates of the
replication SQL (applier) thread
before CHANGE 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 causes CHANGE 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.
Replication cannot use Unix socket files. You must be able to connect to the replication source server using TCP/IP.
If you specify MASTER_HOST
or
MASTER_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 specify MASTER_LOG_FILE
and
MASTER_LOG_POS
in the statement,
MASTER_LOG_FILE=''
and
MASTER_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
or
caching_sha2_password
authentication
plugin. (For sha256_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 the
caching_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
the GET_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
or
slave_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 for MASTER_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
and
MASTER_RETRY_COUNT
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_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 the
MASTER_SSL_
and
xxx
MASTER_TLS_
options.
xxx
Setting MASTER_SSL=1
for a replication
connection and then setting no further
MASTER_SSL_
options corresponds to setting
xxx
--ssl-mode=REQUIRED
for the client, as
described in
Command Options for Encrypted Connections.
With MASTER_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. If MASTER_SSL=0
is set,
this corresponds to
--ssl-mode=DISABLED
.
To 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 settings
xxx
--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_
and
xxx
MASTER_TLS_
options is 511 characters, with the exception of
xxx
MASTER_TLS_CIPHERSUITES
, for which it
is 4000 characters.
The
MASTER_SSL_
and
xxx
MASTER_TLS_
options perform the same functions as the
xxx
--ssl-
and
xxx
--tls-
client options described in
Command Options for Encrypted Connections.
The correspondence between the two sets of options, and
the use of the
xxx
MASTER_SSL_
and
xxx
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 empty
MASTER_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 empty
MASTER_USER
user name and use the
channel afterwards if you always provide user credentials
using the
START
REPLICA
statement or START
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.
To 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. The
caching_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 the
MASTER_PUBLIC_KEY_PATH
option or the
GET_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 the
REPLICATION_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 set
REQUIRE_ROW_FORMAT
to enforce this. For
example, to start privilege checks on the channel
channel_1
on a running replica, issue
the following statements:
mysql> 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
and STOP REPLICA
, and
for releases before MySQL 8.0.22, use START
SLAVE
and STOP 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 as
MASTER_LOG_FILE
. The maximum length of
the string value is 511 characters.
A CHANGE MASTER TO
statement using
RELAY_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 of RELAY_LOG_FILE
or RELAY_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 the
RELAY_LOG_FILE
and
RELAY_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. The REQUIRE_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 value
ON
for the
sql_require_primary_key
system variable in replication operations, requiring a
primary key. When the option is set to
OFF
, the replica always uses the value
OFF
for the
sql_require_primary_key
system variable in replication operations, so that a
primary key is never required, even if the source required
one. When the
REQUIRE_TABLE_PRIMARY_KEY_CHECK
option
is set to STREAM
, 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
to
ON
or OFF
enables a
replica to normalize behavior across the replication
channels for different sources, and keep a consistent
setting for the
sql_require_primary_key
system variable. Using ON
safeguards
against the accidental loss of primary keys when multiple
sources update the same set of tables. Using
OFF
allows sources that can manipulate
primary keys to work alongside sources that cannot.
When PRIVILEGE_CHECKS_USER
is set,
setting REQUIRE_TABLE_PRIMARY_KEY_CHECK
to ON
or OFF
means
that the user account does not need session administration
level privileges to set restricted session variables,
which are required to change the value of
sql_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
and
MASTER_RETRY_COUNT
are exhausted. It
reconnects the replica to an alternative source chosen
from a specified source list, which you manage using the
asynchronous_connection_failover_add_source
and
asynchronous_connection_failover_delete_source
functions. To add and remove managed groups of servers,
use the
asynchronous_connection_failover_add_managed
and
asynchronous_connection_failover_delete_managed
functions instead. For more information, see
Section 19.4.9, “Switching Sources and Replicas with Asynchronous Connection Failover”.
You 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
, set
MASTER_RETRY_COUNT
and
MASTER_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 are
MASTER_RETRY_COUNT=3
and
MASTER_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 the
CHANGE REPLICATION SOURCE
TO
statement with the
MASTER_USER
and
MASTER_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 the
group_replication_disable_member_action
function to disable the Group Replication member
action
mysql_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
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;
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”.
CHANGE 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:
CHANGE 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”.