Re: Segfault in slapd 2.4.8 - syncrepl and glue (ITS#5430)

[hyc@symas.com]

Duncan Gibb wrote:
> Howard Chu wrote:
> HYC>  Most notably, in template 1, you explicitly configured
> HYC>  syncprov on top of glue instead of taking the default
> HYC>  behavior of syncprov under glue.  As documented in
> HYC>  slapd.conf(5), you should only do that when you want a
> HYC>  single syncprov overlay to be master of the entire tree.
> HYC>  In this case, you clearly want syncprov to only master
> HYC>  one portion of the tree, with the subordinate being
> HYC>  taken care of by its own syncprov overlay.
>
> That's a legacy of several previous iterations of the real project.
> Ideally each box would have at most two backends - one holding
> everything for which it's a consumer, and on the relevant machines a
> second backend holding the data for which it's master, then glue, then a
> single syncprov making the whole tree available.  My colleague who
> implemented the first iteration did it that way and it should have
> worked, but the syncprov-glue interactions in 2.3.x were such that that
> resulted in sections of the tree not replicating and/or disappearing in
> various ill-defined situations.

The whole-tree approach may have some snags.
   1) it's intended to work with a single syncprov over the entire glued tree
   2) it requires a unique serverID for each master
   3) it probably won't work to start from a completely empty DB - the root 
entry needs to exist on each server.

-- 
   -- 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/