Re: overlay order important and not documented?

[Howard Chu <hyc@symas.com>]

Pierangelo Masarati wrote:
> Howard Chu wrote:
>
> > Not documented... The accesslog overlay serializes all write 
> > operations by taking a lock. This means only one write operation is 
> > allowed to progress at any time.
> >
> > The refint overlay creates multiple write operations from a single 
> > write operation. If the accesslog overlay has already locked the 
> > current operation, then yes, the refint overlay will deadlock at that 
> > point because its write operations still go through the entire overlay 
> > stack. I think the fix for this will be to change the refint overlay 
> > to bypass any overlays above it when performing its own writes.
>
> Wouldn't this prevent writes by refint from being logged by accesslog?

Yes, and that's probably the cleanest behavior. The overlay stack is 
only supposed to be executed completely for operations that came from 
the frontend. Any overlay on the stack should go through any other 
overlays below it, but not through any that are above it.

--
  -- Howard Chu
  Chief Architect, Symas Corp.  http://www.symas.com
  Director, Highland Sun        http://highlandsun.com/hyc
  Chief Architect, OpenLDAP     http://www.openldap.org/project/