Re: mod_dav_fs locking / Re: apr_dbm and concurrency

On Thu, Nov 23, 2023 at 05:42:10PM +0000, Emmanuel Dreyfus wrote:
> On Thu, Nov 23, 2023 at 05:36:06PM +0000, Joe Orton wrote:
> > 3) in the mean time I worked up a PR for mod_dav_fs which adds a global 
> > mutex around the dbm lockdb use. This passes my stress tests for the 
> > first time.
> 
> How concurent is the stress test? 

I've been testing with 20 concurrent clients on an 8 core machine.

> In the past, I have been badly hurt by a few WebDAV clients proactively 
> exploring the filesystem using locksdiscovery. That compeltely killed the 
> service. I introduced the DavLockDiscovery directive to work it around.

This is a good point. Was the load in that case PRPOFIND/depth:infinity 
do you know or "just" depth:1? A global lock like in my PR would make 
the PROPFIND load even worse, since the lock is held for the duration of 
the response and there are no concurrent read-only locks.

It might be necessary to disable lock discovery by default then, I don't 
know if any clients rely on or expose that but it's only a "MAY" that 
lock discvovery is possible in RFC4918. I suspect the lock recovery 
mechanism for most users & clients is to delete the lockdb.

Regards, Joe