[Linux-cluster] service startup order

[Budai Laszlo]

Hi Ralph,

thank you for your quick answer.
That Knowledge base article indeed presents that dependencies
possibility. Unfortunately I do not have the required version of
rgmanager :(

kind regards,
Laszlo

On 07/28/2011 10:34 AM, Ralph.Grothe at itdz-berlin.de wrote:
>  
>
>> -----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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>>>
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