I am trying to implement a simple advisory locking system for my application. It is trying to mimic the functionality of a legacy inhouse database application, and the mysql GET_LOCK or LOCK TABLE does not seem sufficient for our purposes, as our application requires tables to be locked/unlocked, and for multiple locks to be active at any time. (The GET_LOCK unlocks any previous locks before locking any new ones, which really screws with our code :-) ).
Anyway, My locking table will have the following format (or similiar), CREATE TABLE mylocks ( lockname char(20) not null, pid int not null, status int not null, PRIMARY KEY (lockname) ); When our application needs to "lock" a table, it will populate a row with the status set to "1" and the pid set to the thread connection id. When our application sees that a lockname is "locked", it needs to also verify that the connection id is still valid. (i.e. that the process did not crash with "locks" active). This is the bit that has stumped me. I originally was just going to do a "show processlist", but I've just read in the manual that this does not necessarily show all processes (depending on the current users grant table). My questions: 1. Is there any way to check the "pid" (connection id) to see if it is still alive? (I dont want any information about it, just whether it's still connected). 2. has anyone already implemented such an advisory locking system? (rather than reinventing the wheel). 3. Is what I am trying to do just plain dumb! Many regards, Ian Collins. System Manager KIWIPLAN NZ Ltd. --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
