SHOW SLAVE STATUS
This statement provides status information on essential
parameters of the slave threads. It requires either the
SUPER or
REPLICATION CLIENT privilege.
If you issue this statement using the mysql
client, you can use a \G statement terminator
rather than a semicolon to obtain a more readable vertical
layout:
mysql> SHOW SLAVE STATUS\G
*************************** 1. row ***************************
Slave_IO_State: Waiting for master to send event
Master_Host: localhost
Master_User: root
Master_Port: 3306
Connect_Retry: 3
Master_Log_File: gbichot-bin.005
Read_Master_Log_Pos: 79
Relay_Log_File: gbichot-relay-bin.005
Relay_Log_Pos: 548
Relay_Master_Log_File: gbichot-bin.005
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 79
Relay_Log_Space: 552
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 8
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids: 0
Master_Server_Id: 1
The following list describes the fields returned by
SHOW SLAVE STATUS. For additional
information about interpreting their meanings, see
Section 8.14.6, “Replication Slave I/O Thread States”.
Slave_IO_State
A copy of the State field of the
SHOW PROCESSLIST output for
the slave I/O thread. This tells you what the thread is
doing: trying to connect to the master, waiting for events
from the master, reconnecting to the master, and so on. For
a listing of possible states, see
Section 8.14.6, “Replication Slave I/O Thread States”.
Master_Host
The master host that the slave is connected to.
Master_User
The user name of the account used to connect to the master.
Master_Port
The port used to connect to the master.
Connect_Retry
The number of seconds between connect retries (default 60).
This can be set with the CHANGE MASTER
TO statement.
Master_Log_File
The name of the master binary log file from which the I/O thread is currently reading.
Read_Master_Log_Pos
The position in the current master binary log file up to which the I/O thread has read.
Relay_Log_File
The name of the relay log file from which the SQL thread is currently reading and executing.
Relay_Log_Pos
The position in the current relay log file up to which the SQL thread has read and executed.
Relay_Master_Log_File
The name of the master binary log file containing the most recent event executed by the SQL thread.
Slave_IO_Running
Whether the I/O thread is started and has connected successfully to the master. Internally, the state of this thread is represented by one of the following three values:
MYSQL_SLAVE_NOT_RUN.
The slave I/O thread is not running. For this state,
Slave_IO_Running is
No.
MYSQL_SLAVE_RUN_NOT_CONNECT.
The slave I/O thread is running, but is not connected
to a replication master. For this state,
Slave_IO_Running depends on the
server version as shown in the following table.
| MySQL Version | Slave_IO_Running |
|---|---|
| 4.1 (4.1.13 and earlier); 5.0 (5.0.11 and earlier) | Yes |
| 4.1 (4.1.14 and later); 5.0 (5.0.12 and later) | No |
| 5.1 (5.1.45 and earlier) | No |
| 5.1 (5.1.46 and later); 5.5 | Connecting |
MYSQL_SLAVE_RUN_CONNECT.
The slave I/O thread is running, and is connected to a
replication master. For this state,
Slave_IO_Running is
Yes.
The value of the
Slave_running system
status variable corresponds with this value.
Slave_SQL_Running
Whether the SQL thread is started.
Replicate_Do_DB,
Replicate_Ignore_DB
The lists of databases that were specified with the
--replicate-do-db and
--replicate-ignore-db
options, if any.
Replicate_Do_Table,
Replicate_Ignore_Table,
Replicate_Wild_Do_Table,
Replicate_Wild_Ignore_Table
The lists of tables that were specified with the
--replicate-do-table,
--replicate-ignore-table,
--replicate-wild-do-table,
and
--replicate-wild-ignore-table
options, if any.
Last_Errno, Last_Error
These columns are aliases for
Last_SQL_Errno and
Last_SQL_Error.
Issuing RESET MASTER or
RESET SLAVE resets the values
shown in these columns.
When the slave SQL thread receives an error, it reports
the error first, then stops the SQL thread. This means
that there is a small window of time during which
SHOW SLAVE STATUS shows a
nonzero value for Last_SQL_Errno even
though Slave_SQL_Running still displays
Yes.
Skip_Counter
The current value of the
sql_slave_skip_counter
system variable. See
Section 13.4.2.4, “SET GLOBAL sql_slave_skip_counter Syntax”.
Exec_Master_Log_Pos
The position in the current master binary log file to which
the SQL thread has read and executed, marking the start of
the next transaction or event to be processed. You can use
this value with the CHANGE MASTER
TO statement's
MASTER_LOG_POS option when starting a new
slave from an existing slave, so that the new slave reads
from this point. The coordinates given by
(Relay_Master_Log_File,
Exec_Master_Log_Pos) in the master's
binary log correspond to the coordinates given by
(Relay_Log_File,
Relay_Log_Pos) in the relay log.
Relay_Log_Space
The total combined size of all existing relay log files.
Until_Condition,
Until_Log_File,
Until_Log_Pos
The values specified in the UNTIL clause
of the START SLAVE statement.
Until_Condition has these values:
None if no UNTIL
clause was specified
Master if the slave is reading until
a given position in the master's binary log
Relay if the slave is reading until a
given position in its relay log
Until_Log_File and
Until_Log_Pos indicate the log file name
and position that define the coordinates at which the SQL
thread stops executing.
Master_SSL_Allowed,
Master_SSL_CA_File,
Master_SSL_CA_Path,
Master_SSL_Cert,
Master_SSL_Cipher,
Master_SSL_Key,
Master_SSL_Verify_Server_Cert
These fields show the SSL parameters used by the slave to connect to the master, if any.
Master_SSL_Allowed has these values:
Yes if an SSL connection to the
master is permitted
No if an SSL connection to the master
is not permitted
Ignored if an SSL connection is
permitted but the slave server does not have SSL support
enabled
The values of the other SSL-related fields correspond to the
values of the MASTER_SSL_CA,
MASTER_SSL_CAPATH,
MASTER_SSL_CERT,
MASTER_SSL_CIPHER,
MASTER_SSL_KEY, and
MASTER_SSL_VERIFY_SERVER_CERT options to
the CHANGE MASTER TO
statement. See Section 13.4.2.1, “CHANGE MASTER TO Syntax”.
Seconds_Behind_Master
This field is an indication of how “late” the slave is:
When the slave is actively processing updates, this field shows the difference between the current timestamp on the slave and the original timestamp logged on the master for the event currently being processed on the slave.
When no event is currently being processed on the slave, this value is 0.
In essence, this field measures the time difference in
seconds between the slave SQL thread and the slave I/O
thread. If the network connection between master and slave
is fast, the slave I/O thread is very close to the master,
so this field is a good approximation of how late the slave
SQL thread is compared to the master. If the network is
slow, this is not a good approximation;
the slave SQL thread may quite often be caught up with the
slow-reading slave I/O thread, so
Seconds_Behind_Master often shows a value
of 0, even if the I/O thread is late compared to the master.
In other words, this column is useful only for
fast networks.
This time difference computation works even if the master
and slave do not have identical clock times, provided that
the difference, computed when the slave I/O thread starts,
remains constant from then on. Any changes—including
NTP updates—can lead to clock skews that can make
calculation of Seconds_Behind_Master less
reliable.
This field is NULL (undefined or unknown)
if the slave SQL thread is not running, or if the slave I/O
thread is not running or is not connected to the master. For
example, if the slave I/O thread is running but is not
connected to the master and is sleeping for the number of
seconds given by the CHANGE MASTER
TO statement or
--master-connect-retry option
(default 60) before reconnecting, the value is
NULL. This is because the slave cannot
know what the master is doing, and so cannot say reliably
how late it is.
The value of Seconds_Behind_Master is
based on the timestamps stored in events, which are
preserved through replication. This means that if a master
M1 is itself a slave of M0, any event from M1's binary log
that originates from M0's binary log has M0's timestamp for
that event. This enables MySQL to replicate
TIMESTAMP successfully.
However, the problem for
Seconds_Behind_Master is that if M1 also
receives direct updates from clients, the
Seconds_Behind_Master value randomly
fluctuates because sometimes the last event from M1
originates from M0 and sometimes is the result of a direct
update on M1.
Last_IO_Errno,
Last_IO_Error
The error number and error message of the most recent error
that caused the I/O thread to stop. An error number of 0 and
message of the empty string mean “no error.” If
the Last_IO_Error value is not empty, the
error values also appear in the slave's error log.
Prior to MySQL 5.5, Last_IO_Error and
Last_IO_Errno were not set in the event
that replication failed due to exceeding
max_allowed_packet (Bug
#42914).
Issuing RESET MASTER or
RESET SLAVE resets the values
shown in these columns.
Last_SQL_Errno,
Last_SQL_Error
The error number and error message of the most recent error
that caused the SQL thread to stop. An error number of 0 and
message of the empty string mean “no error.” If
the Last_SQL_Error value is not empty,
the error values also appear in the slave's error log.
Example:
Last_SQL_Errno: 1051 Last_SQL_Error: error 'Unknown table 'z'' on query 'drop table z'
The message indicates that the table z
existed on the master and was dropped there, but it did not
exist on the slave, so DROP
TABLE failed on the slave. (This might occur, for
example, if you forget to copy the table to the slave when
setting up replication.)
Issuing RESET MASTER or
RESET SLAVE resets the values
shown in these columns.
Replicate_Ignore_Server_Ids
Beginning with MySQL 5.5, you can tell a slave to ignore
events from 0 or more masters using the
IGNORE_SERVER_IDS option of the
CHANGE MASTER TO statement.
This is normally of interest only when using a circular or
other multi-master replication setup.
The message shown for
Replicate_Ignore_Server_Ids consists of a
space-delimited list of one or more numbers, the first value
indicating the number of servers to be ignored; if not 0
(the default), this server-count value is followed by the
actual server IDs. For example, if a
CHANGE MASTER TO statement
containing the IGNORE_SERVER_IDS =
(2,6,9) option has been issued to tell a slave to
ignore masters having the server ID 2, 6, or 9, that
information appears as shown here:
Replicate_Ignore_Server_Ids: 3 2 6 9
Replicate_Ignore_Server_Ids filtering is
performed by the I/O thread, rather than by the SQL thread,
which means that events which are filtered out are not
written to the relay log. This differs from the filtering
actions taken by server options such
--replicate-do-table, which
apply to the SQL thread.
Master_Server_Id
The server_id value from
the master.