Re: slapcat hangs v2.2.24

[Howard Chu <hyc@symas.com>]

Curt Blank wrote:

> Thank you, that explanation helps. There are probably a lot of stale 
> locks in there now because I have aborted slapcat a number of times now.
>
> Let me ask this, would doing a db_verify also clear this up? The 
> reason I ask is that last week when I was having this problem after a 
> test slapadd load I did a db_verify and after that slapcat seems to 
> have then worked every time.

I trust you've actually read the db_verify documentation:
http://www.sleepycat.com/docs/utility/db_verify.html

Note that the db_verify utility operates on individual database files, 
it doesn't do anything to the database environment. And it explicitly 
does nothing related to locks, so I would expect it won't affect the 
situation. The only thing that cleans up a stale environment is to 
perform a recovery.

> Howard Chu wrote:
>
> > Curt Blank wrote:
> >
> > > Thanks, I'll give that a shot when I can schedule an outage, 
> > > hopefully overnight tonight.
> > >
> > > Further info: This is a new ldap server just bought online with 
> > > v2.2.24, as such is was loaded from scratch using ldapadd without 
> > > any errors. Then immediately after starting slapd this slapcat 
> > > problem was there, so I'm just curious as to what the db_recovery is 
> > > expected to do? I would think the db would be pristine from just 
> > > being loaded.
> >
> >
> >
> > Generally it is safe to use slapcat and slapd simultaneously when 
> > using back-bdb and back-hdb, but if slapd is busy doing database 
> > updates, it will have outstanding locks that may impede slapcat's 
> > progress. (And vice versa, slapcat only obtains read locks but it may 
> > temporarily prevent slapd from obtaining a write lock that it needs.)
> >
> > If you see a hang like this when slapd is not running that generally 
> > means there are stale locks leftover in the database environment from 
> > an abnormal termination of some previous run. Also note that in the 
> > current version, interrupting slapcat before it completes will also 
> > leave stale locks in the database. That is what db_recover will clear 
> > up.
> >
> > In the next release (2.3.xx) we have added automatic detection of 
> > abnormal shutdowns, which will make all recovery fully automated, and 
> > this kind of situation should never arise any more.


--
 -- Howard Chu
 Chief Architect, Symas Corp.       Director, Highland Sun
 http://www.symas.com               http://highlandsun.com/hyc
 Symas: Premier OpenSource Development and Support