We are facing some strange problem here. Sometimes, mysql is performing a very simple queries.
A good example is e.g. (from slow query log)
User@Host: user[user] @ [62.x.x.x]
Query_time: 14 Lock_time: 0 Rows_sent: 1 Rows_examined: 0
So it looks like all queries are collescted, like they are waiting for something, and then all of them are performed, the same moment.
All tables are MyISAM. When looking on those “hanging” processes with mysql processlist, their status is NULL.
Sometimes I could notice that with those NULL process one or two others are on status UPDATE or SENDING DATA status. Although tables involved in working queries are not the one related to NULL processes.(And even unix_timestamp() is hanging).
What I also understood from mysql docs is that NULL status is not possible for any long period.
Please, any advice would be welcome, because I totally stuck overhere
Problem is noticed on 5.0.18 and 5.0.27 both.