• MySQL 5.1 Reference Manual :: 12 SQL Statement Syntax :: 12.4 Database Administration Statements :: 12.4.5 SHOW Syntax :: 12.4.5.36 SHOW SLAVE STATUS Syntax

  • 12.4.5.36. SHOW SLAVE STATUS Syntax

    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:

    The following list describes the fields returned by SHOW SLAVE STATUS. For additional information about interpreting their meanings, see Section 16.1.4.1, “Checking Replication Status”.

    • 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. Possible states are listed in Section 16.2.1, “Replication Implementation Details”.

    • 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 or --master-connect-retry option.

    • 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); 5.4 No
        5.1 (5.1.46 and later); 5.5 Connecting
        6.0 (6.0.10 and earlier) No
        6.0 (6.0.11 and later) 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.

      Beginning with MySQL 5.1.46, the value of the Slave_running system status variable corresponds with this value. (Bug#30703)

    • 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

      As of MySQL 5.1.20, these columns are aliases for Last_SQL_Errno and Last_SQL_Error. Before 5.1.20, they indicate the error number and error message returned by the most recently executed statement. An error number of 0 and message of the empty string mean “no error.” If the Last_Error value is not empty, the error values also appear in the slave's error log.

      Beginning with MySQL 5.1.37, and with MySQL Cluster NDB 6.2.17, MySQL Cluster NDB 6.3.23, and MySQL Cluster NDB 6.4.3: Issuing RESET MASTER or RESET SLAVE resets the values shown in these columns. (Bug#34654, Bug#44270)

      Note

      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 12.5.2.6, “SET GLOBAL sql_slave_skip_counter Syntax”.

    • Exec_Master_Log_Pos

      The position in the current master binary file up to which the SQL thread has read and executed. 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 12.5.2.1, “CHANGE MASTER TO Syntax”. MASTER_SSL_VERIFY_SERVER_CERT was added in MySQL 5.1.18.

    • Seconds_Behind_Master

      This field is an indication of how “late” the slave is:

      • When the slave SQL thread is actively processing updates, this field is the number of seconds that have elapsed since the timestamp of the most recent event on the master executed by that thread.

      • When the SQL thread has caught up to the slave I/O thread and is idle waiting for more events from the I/O thread, this field is zero.

      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 though the master and slave do not have identical clocks (the clock difference is computed when the slave I/O thread starts, and assumed to remain constant from then on). Seconds_Behind_Master is NULL (“unknown”) if the slave SQL thread is not running, or if the slave I/O thread is not running or not connected to 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 this field 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 last 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. These columns were added in MySQL 5.1.20.

      MySQL Cluster.  Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3: Issuing RESET MASTER or RESET SLAVE resets the values shown in these columns. This applies to MySQL Cluster only. (Bug#34654)

    • Last_SQL_Errno, Last_SQL_Error

      The error number and error message of the last 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. These columns were added in MySQL 5.1.20.

      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.)

      MySQL Cluster.  Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3: Issuing RESET MASTER or RESET SLAVE resets the values shown in these columns. This applies to MySQL Cluster only. (Bug#34654)