Re: Getting around the single-threaded syncrepl model?

[Jerry <jerry@seibercom.net>]

On Mon, 23 Nov 2015 12:25:36 +0000 Howard Chu wrote:

> Bannister, Mark wrote:
> >>> --On Friday, November 20, 2015 6:31 PM +0000 Albert Braden
> >>> <abraden@about.com> wrote:  
> >>  
> >>> Hi Quanah,
> >>>
> >>> Are you sure your issues with syncrepl aren't specific to Zimbra? When
> >>> I ran the Zimbra at Homestead/Intuit we saw syncrepl issues, but I
> >>> have not seen those issues in non-Zimbra LDAP clusters.  
> >>
> >> Quite certain.  For one thing, I file very few syncrepl related ITSes,
> >> since I don't use it, but many are filed... For another, while I have
> >> encountered a very few issues with delta-syncrepl, the majority of
> >> issues I find w/ Zimbra and replication are related to syncrepl when it
> >> has to be used in an initial or fallback scenario.  
> >
> > What sort of issues?
> >  
> >> And here's some quick stats:
> >> $ grep syncrepl CHANGES  | grep -v delta | wc -l
> >> 76
> >>
> >> $ grep delta-syncrepl CHANGES  | wc -l
> >> 7
> >>
> >> Or syncrepl has had 10x times the issues.  
> >
> > Or syncrepl has 10x the users, more eyes spot more bugs, and is now more
> > stable because it has had more fixes? I'm just speculating here, but I
> > wouldn't be more confident in product Y because it is mentioned less in
> > the change log than product X.
> >
> > However, this is a tangent, and still does not help me with my original
> > question.  Correct me if I'm wrong, but delta-syncrepl is also going to
> > be running in a serial fashion on the master server, and so, if I'm
> > replicating out to hundreds of replicas, high network latency or timeouts
> > on a single replica would still have a big impact on my ability to
> > replicate everywhere within 5 minutes.
> >
> > Syncrepl/delta-syncrepl doesn't make a difference here.  Unless someone
> > has a better suggestion, as I don't suppose OpenLDAP is going to be fixed
> > to do this in parallel anytime soon, I will go ahead and launch multiple
> > replica processes on the master server as I proposed at the beginning of
> > the thread, and then balance the load across these processes to reduce
> > the impact of any one replica going slow.  
> 
> Certainly won't be changing in 2.4. Very likely to change in 2.5.
> 
> https://www.openldap.org/its/index.cgi/Incoming?id=8227
> 
> > (Or investigate other directory server products that can replicate in
> > parallel ...)  
> 
> Have fun investigating.

I don't know if this is of any use to anyone. There doesn't seem to be a whole
lot of information available.

<https://technet.microsoft.com/en-us/library/cc755994%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396>

-- 
Jerry