Last few days one of our customers (one of the largest Ruby on Rails sites on the Net) was struggling to solve some really strange problem - once upon a time they were getting an error from ActiveRecord on their site:
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(ActiveRecord::StatementInvalid) "Mysql::Error: Lock wait timeout exceeded; try restarting transaction: UPDATE some_table..... |
They have innodb_lock_wait_timeout set to 20 seconds. After a few hours of looking for strange transactions we were decided to create s script to dump SHOW INNODB STATUS and SHOW FULL PROCESSLIST commands output to a file every 10 seconds to catch one of those moments when this error occurred.
Today we’ve got next error and started digging in our logs…
After a couple of hours of looking in logs, parsing binary logs from MySQL …
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