From: James [mailto:[EMAIL PROTECTED] > I am interested in setting up 3 read only slaves and one > write master. I am thinking of implementing this because > one server is slower than 3 ;-). But anyway, I have read > all the docs and I am fairly sure how I want do this and > keep the sanity checking in the loop. What I am > considering doing is checking (in intervals) the binlog > positions between the slave and the master. I am worried > about this being out of synch, for just about every 3 > reads, there is a write. I am looking to see if this is > a good idea, and what others comments/suggestions are.
It all depends on how much traffic your db server is getting and how quickly you want to be notified if replication is behind or a slave thread died. Your idea of checking the binlog position between the slave(s) and master at an interval is a good one, though you run the risk of getting it at "the wrong time," such as when a rather large update is being made, and being notified with a false positive. I have a very similar setup -- one master, two slaves. What I did was set up a Perl script to run in the cron every 5 minutes. It logs into each slave and performs a SHOW SLAVE STATUS. From this it looks at the Slave_IO_Running and Slave_SQL_Running columns to determine that the slave thread is still operating. If either is 'no' it pages me with the 'Last_error' column. This may not be optimal, as you sound as though you want to see if/when replication is out of sync and not just completely dead. I'd say give it a shot checking the binlog positions. If you find yourself getting a lot of false positives, try having the check script sleep for N seconds and check again to be sure of itself before notifying you, just to see if it needs to catch up. HTH! -- Mike Johnson Web Developer Smarter Living, Inc. phone (617) 886-5539 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
