MySQL Bugs: #16243: support for one-instance startup exclusive lock

Bug #16243	support for one-instance startup exclusive lock
Submitted:	6 Jan 2006 3:50
Reporter:	xuefer tinys	Email Updates:
Status:	Open	Impact on me:	None
Category:	MySQL Server	Severity:	S4 (Feature request)
Version:	4.1	OS:	Linux (linux)
Assigned to:		CPU Architecture:	Any

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Description:
it's nice we have skip-external-locking. but there's 0.001% chance (by mistake, by bad init.d script) which lead to 50% data lost.
so why not make a one-instance exclusive locking which force mysql itself refuse to startup if a lock-file is locked, which mean a mysql is already started up, no matter it's working or freezed, in specified data-dir.
and tools such as myisamchk should check this lock to avoid "fixing" index by mistake

How to repeat:
1. start mysqld with skip-external-locking
2. run myisamchk on same data-dir

or
1. start mysqld with skip-external-locking
2. run mysqld again on same data-dir by mistake (u've lost pid file or just haven't killed all mysqld childs)

stupid but destroy data before you cry