Can we capture only Slave_IO_Running in SHOW SLAVE STATUS in MySQL

Question

I wanted to capture only status/result of Slave_IO_Running and Slave_SQL_Running column values, which I will be using to integrate into our application.

Is there any way to get only the values of those fields instead of getting values of all fields of SHOW SLAVE STATUS.

My OS is windows.

I am using MySQL 5.0.24

Answer 1

Executing

mysql> SHOW STATUS LIKE 'Slave_running';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| Slave_running | ON    |
+---------------+-------+
1 row in set (0.04 sec)

From the manual:

This is ON if this server is a replication slave that is connected to a replication master, and both the I/O and SQL threads are running; otherwise, it is OFF.

Caveat: If you're running MySQL prior to version 5.1.46 or 5.5.4, it's possible the slave IO thread could not be running, and the status variable indicate the slave is running. (MySQL Bug 51089)

---

As of MySQL 5.7, the above solution will not work by default. This is because many of the status variables from information_schema are being moved into performance_schema:

As of MySQL 5.7.6, the Performance Schema also contains system and status variable tables (see Section 23.9.13, “Performance Schema System Variable Tables”, and Section 23.9.14, “Performance Schema Status Variable Tables”). The Performance Schema tables are intended to replace the INFORMATION_SCHEMA tables, which are deprecated as of MySQL 5.7.6 and will be removed in a future MySQL release. [src]

and

These Slave_xxx status variables become unavailable through SHOW STATUS:

• Slave_heartbeat_period
• Slave_last_heartbeat
• Slave_received_heartbeats
• Slave_retried_transactions
• Slave_running

Applications that use these status variables should be revised to obtain this information using the replication-related Performance Schema tables.

There are two options to get the slave_running status outside of SHOW SLAVE STATUS

1. The preferred method, as mentioned by the doc, is to update the application to pull from replication-connection-status.SERVICE_STATE and replication-applier-status.SERVICE_STATE in performance_schema:

// this is the SLAVE IO THREAD status
SELECT SERVICE_STATE FROM performance_schema.replication_connection_status;

// this is the SLAVE SQL THREAD status
SELECT SERVICE_STATE FROM performance_schema.replication_applier_status;

NOTE: This is for single master replication. Multi-master replication should be in replication_applier_coordinator.SERVICE_STATE

2. The second option is to turn on show_compatibility_56. This is a temporary fix to get you by without modifying the application, but will go away in a future release.

Answer 2

SELECT t.PROCESSLIST_TIME, t.* 
FROM    performance_schema.threads t
WHERE NAME IN('thread/sql/slave_io', 'thread/sql/slave_sql')

Answer 3

A useful command to display the result in a more inteligible way is

mysql> show slave STATUS\G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 127.0.0.1
                  Master_User: repuser
                  Master_Port: 3305
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000002
          Read_Master_Log_Pos: 426595
               Relay_Log_File: ip-172-31-17-228-relay-bin.000004
                Relay_Log_Pos: 19023
        Relay_Master_Log_File: mysql-bin.000002
             Slave_IO_Running: Yes
            Slave_SQL_Running: No
              Replicate_Do_DB:
          Replicate_Ignore_DB:
           Replicate_Do_Table:
       Replicate_Ignore_Table: (...)