Comments on Script To Check If MySQL Master Master Replication Is Working Correctly

    there are 2 parameter we need to watch and make sure that replication is running, 1 is Slave IO (the replication engine) and another is Slave SQL,

the Slave IO can  unable to run when we enter the wrong master/ slave paramater like replication user, etc...

 and Slave SQL can unable to run when some sql syntax is replicated to slave but found an error like duplicated key...

 the slave IO still running but when slave sql stopped, your slave will no longer have the same data with your master anymore...

 so you should add another parameter to check Slave_SQL_Running running or not

 best regards

Hi,

 the basic ideas of the script are right. But the implementation is not. The script is only complaining if the string "Slave_IO_Running: No" is matched in the output. That means we're not checking if the Slave is running correctly but rather checking if the Slave is explicitly not running. Any other error message, like password wrong or database not running would be ignored by this script.

 This script should check for Slave_IO_Running: Yes. and only if the is output is present, no notification is send. Additionally it should check for the Replication SQL as well as mentioned in the comment before.

 

I just ran into the situation described by the previous comments - the slave IO was running but the slave SQL was not. To fix, I simply changed the script to grep for the string "Slave_.*_Running: No".

Here is a script that improves upon this:

1) Checks for Slave_IO_Running Yes and Slave_SQL_Running Yes

2) Checks for Crashed MySQL Tables

3)  Ties in to Monit for alerting

http://www.widwad.com/content/automated-monitoring-of-mysql-replication-using-monit-how-i-did-it

(It also provides a link back to this article)

Personally, I would not create a text file to capture this, I would just use a variable and then check that variable ... the message doesn't need to include this grep, and if it does, just use the variable.

For example:

how_slave_status=$(( echo "show slave status \G;" ) | mysql -u root 2>&1 | grep "Slave_IO_Running")