[Linux-cluster] service startup order

[Ralph.Grothe at itdz-berlin.de]

> -----Original Message-----
> From: linux-cluster-bounces at redhat.com 
> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Budai
Laszlo
> Sent: Thursday, July 28, 2011 9:06 AM
> To: linux-cluster at redhat.com
> Subject: Re: [Linux-cluster] service startup order
> 
> @Ralph: could you please provide me some references where 
> have you found
> those attributes of the service tag (depend, depend_mode) and 
> for the RM
> tag (central_processing)? Thank you.

Even Digimer is metioning this attribute in her excellent wiki

http://wiki.alteeve.com/index.php/RHCS_v2_cluster.conf#central_pr
ocessing


If you have a login account at RHN you may find this article in
their knowledge base

https://access.redhat.com/kb/docs/DOC-26981


Apart from that the only text where this attrib was used that I
have come across so far was an RH doc treating deployment of SAP
on RHCS
But it only appears there in a sample config snippet without
further explanation.
I guess that they needed to activate it because they were using
the RHCS event processing interface?

http://www.redhat.com/f/pdf/ha-sap-v1-6-4.pdf

> 
> Kind regards,
> Laszlo
> 
> 
> On 07/28/2011 09:24 AM, Ralph.Grothe at itdz-berlin.de wrote:
> > Hi Digimer, hi Lazlo,
> >
> > sorry, for intruding your thread but this is something that I
am
> > also interested in and which I haven't fully fathomed yet.
> >
> >> -----Original Message-----
> >> From: linux-cluster-bounces at redhat.com 
> >> [mailto:linux-cluster-bounces at redhat.com] On Behalf Of
Digimer
> >> Sent: Thursday, July 28, 2011 2:51 AM
> >> To: linux clustering
> >> Subject: Re: [Linux-cluster] service startup order
> >>
> >> Parallel services will be started simultaneously. Services 
> >> configured as
> >> service trees will start in the order that they are defined 
> >> (and stopped
> >> in reverse order).
> >>
> >> This covers the start order well:
> >> - https://fedorahosted.org/cluster/wiki/ResourceTrees
> >>
> > The referred to wiki article only seems to treat
> > starting/stopping order and hierarchy (parent-child vs.
sibling)
> > of resources within one service aka resource group.
> > That sounds pretty clear.
> > But what about ordering and possible dependencies between
> > separate services?
> >
> > You mentioned service trees. You didn't actually mean
resource
> > trees?
> > If however your wording was deliberate (what I assume) I
wonder
> > if one can nest service tag blocks as one can nest resource
tags
> > within a single service block to express dependencies or
> > hierarchy and hence starting order between and of services?
> > Because all the sample configuration snippets I have seen so
far
> > in various docs lack such nesting of services.
> >
> > The reason that interests me is because I have such a case
where
> > a customer requires such a dependency between two distinct
> > services that during normal operation (i.e. no node has left
the
> > cluster) are hosted on different nodes.
> > I told them, from what I have perceived of HA clustering and
RHCS
> > in particular so far, that if they wish to express such an
> > interdependency that they would have to put all resources
which
> > are now split up in two services, in a nested manner that
would
> > map the intended hierarchy, in a single service.
> >
> > Because they insisted on their layout I searched a little and
> > discovered the, in the official RHCS Admin doc not mentioned,
> > service tag attributes "depend" and "depend_mode".
> >
> > However, their usage at first seemed pretty useless because
the
> > clusterware seemed to completely ignore them and start/stop
> > services in sometimes unpredictable ways and even restarted
them
> > at random.
> > Until I, more by accident, discovered that additionally the
"rm"
> > tag's attribute "central_processing" needed to be defined and
> > assigned to "1" or "true" for this feature to work
approximately.
> > I say apprimately here because we still have issues with this
> > cluster that require futher testing.
> > I hardly dare mentioning, that unfortunately this system
already
> > went into production, now of course lacking any HA,
> > why we had to defer further testing.
> >
> >
> > Regards
> > Ralph
> >
> >  
> >
> > --
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> > Linux-cluster at redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-cluster
> >
> 
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