Re: Read-only lock on RPM db

[Jeff Johnson <jbj redhat com>]

On Tue, Aug 24, 2004 at 02:49:11PM -0700, Shawn Weber wrote:
> We have an automated third-party tool that builds a tree of code, called
> CruiseControl which some of you might be familiar with.   Occasionally,
> an automated build will fail when trying to acquire a read-only lock on
> the rpm database.
> 

Probably because another process has an exclusive fcntl lock.

> The error message itself looks something like this in the logs:
> 
> error: cannot get shared lock on /var/lib/rpm/Packages
> error: cannot open Packages index using db3 - Operation not permitted
> (1)

Hmmm, this smells like rpm-4.0.4 or earlier. That the case?

> 
> The main problem is that this error confuses a developer, since the
> error message that our automated build system (CruiseControl) returns is
> rather cryptic and the detailed build log must usually be inspected to
> determine that this is the root cause of the problem.
> 
> Does anyone know what can be done to alleviate this error from
> occasionally occuring, such as explicitly locking and unlocking the db?
> 

The solution will be to participate in the locking scheme that
rpm uses, basically shared/exclusive fcntl locks on /var/lib/rpm/Packages.

The first step, however, is gonna be to understand what process
has the exclusive lock, as you will not be able to get a shared
lock until the exclusive lock is relinquished.

Alternatively, use Berkeley DB concurrent access locks, been in "production"
rpm since rpm-4.1 (currently rpm-4.3.2 something) several years now, and
(mostly) avoids fcntl locks entirely.

73 de Jeff

-- 
Jeff Johnson	ARS N3NPQ
jbj@redhat.com (jbj@jbj.org)
Chapel Hill, NC