[Pacemaker] Shouldn't colocation -inf: be mandatory?

[Vadym Chepkov]

On Jun 15, 2010, at 5:26 PM, Dejan Muhamedagic wrote:

> On Tue, Jun 15, 2010 at 04:44:31PM -0400, Vadym Chepkov wrote:
>> 
>> On Jun 15, 2010, at 3:55 PM, Dejan Muhamedagic wrote:
>> 
>>> On Tue, Jun 15, 2010 at 03:41:17PM -0400, Vadym Chepkov wrote:
>>>> 
>>>> On Jun 15, 2010, at 3:36 PM, Dejan Muhamedagic wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> On Tue, Jun 15, 2010 at 08:45:37AM -0400, Vadym Chepkov wrote:
>>>>>> 
>>>>>> On Jun 15, 2010, at 6:14 AM, Dejan Muhamedagic wrote:
>>>>>> 
>>>>>>> Hi,
>>>>>>> 
>>>>>>> On Tue, Jun 15, 2010 at 10:57:47AM +0200, Andrew Beekhof wrote:
>>>>>>>> On Tue, Jun 15, 2010 at 10:23 AM, Andreas Kurz <andreas.kurz at linbit.com> wrote:
>>>>>>>>> On Tuesday 15 June 2010 08:40:58 Andrew Beekhof wrote:
>>>>>>>>>> On Mon, Jun 14, 2010 at 4:22 PM, Vadym Chepkov <vchepkov at gmail.com> wrote:
>>>>>>>>>>> On Jun 7, 2010, at 8:04 AM, Vadym Chepkov wrote:
>>>>>>>>>>>> I filed bug 2435, glad to hear "it's not me"
>>>>>>>>>>> 
>>>>>>>>>>> Andrew closed this bug
>>>>>>>>>>> (http://developerbugs.linux-foundation.org/show_bug.cgi?id=2435) as
>>>>>>>>>>> resolved, but I respectfully disagree.
>>>>>>>>>>> 
>>>>>>>>>>> I will try to explain a problem again in this list.
>>>>>>>>>>> 
>>>>>>>>>>> lets assume you want to have several resources running on the same node.
>>>>>>>>>>> They are independent, so if one is going down, others shouldn't be
>>>>>>>>>>> stopped. You would do this by using a resource set, like this:
>>>>>>>>>>> 
>>>>>>>>>>> primitive dummy1 ocf:pacemaker:Dummy
>>>>>>>>>>> primitive dummy2 ocf:pacemaker:Dummy
>>>>>>>>>>> primitive dummy3 ocf:pacemaker:Dummy
>>>>>>>>>>> colocation together inf: ( dummy1 dummy2 dummy3 )
>>>>>>>>>>> 
>>>>>>>>>>> and I expect them to run on the same host, but they are not and I
>>>>>>>>>>> attached hb_report to the case to prove it.
>>>>>>>>>>> 
>>>>>>>>>>> Andrew closed it with the comment "Thats because you have
>>>>>>>>>>> sequential="false" for the colocation set." But sequential="false" means
>>>>>>>>>>> doesn't matter what order do they start.
>>>>>>>>>> 
>>>>>>>>>> No.  Thats not what it means.
>>>>>>>>>> And I believe I should know.
>>>>>>>>>> 
>>>>>>>>>> It means that the members of the set are NOT collocated with each
>>>>>>>>>> other, only with any preceding set.
>>>>>>>>> 
>>>>>>>>> Just for clarification:
>>>>>>>>> 
>>>>>>>>> colocation together inf: ( dummy1 dummy2 dummy3 ) dummy4
>>>>>>>>> 
>>>>>>>>> .... is a shortcut for:
>>>>>>>>> 
>>>>>>>>> colocation together1 inf: dummy4 dummy1
>>>>>>>>> colocation together1 inf: dummy4 dummy2
>>>>>>>>> colocation together1 inf: dummy4 dummy3
>>>>>>>>> 
>>>>>>>>> ... is that correct?
>>>>>>>> 
>>>>>>>> Only if sequential != false.
>>>>>>> 
>>>>>>> You wanted to say "sequential == false"?
>>>>>>> 
>>>>>>>> For some reason the shell appears to be setting that by default.
>>>>>>> 
>>>>>>> This is sequential == false:
>>>>>>> 
>>>>>>> colocation together inf: ( dummy1 dummy2 dummy3 ) dummy4
>>>>>>> 
>>>>>>> This is sequential == true:
>>>>>>> 
>>>>>>> colocation together inf: dummy1 dummy2 dummy3 dummy4
>>>>>>> 
>>>>>>> Thanks,
>>>>>>> 
>>>>>>> Dejan
>>>>>> 
>>>>>> 
>>>>>> I guess colocation syntax needs to be expanded to allow something like this
>>>>>> 
>>>>>> colocation only-one -inf: (dummy1 dummy2 sequential="true")
>>>>>> 
>>>>>> colocation together 5000: (dummy1 dummy2 sequential="true")
>>>>> 
>>>>> How's this different from a regular constraint?
>>>>> 
>>>> 
>>>> 
>>>> Because it does not create a resource set with two resources
>>>> and if you put it in parentheses, it creates set with sequential="false"
>>> 
>>> What I meant was what is the difference between these two:
>>> 
>>> <rsc_colocation id="c1" rsc="p1" score="500" with-rsc="p2"/>
>>> 
>>> <rsc_colocation id="c1" score="500">
>>> <resource_set id="c1-0">
>>> <resource_ref id="p1"/>
>>> <resource_ref id="p2"/>
>>> </resource_set>
>>> </rsc_colocation>
>>> 
>> 
>> I take it there is no difference for the positive score, 
>> it just looks like former looks like there is a dependency of p1 on p2.
>> 
>> But there is a definite difference with a negative score, 
>> 
>> if you have something like this
>> 
>> colocation only-one -inf: dummy1 dummy2
>> 
>> so you don't want to have them to run on the same host ever.
> 
>> and the host with dummy2 goes down.
>> Instead of just not starting dummy2 anywhere it will kill dummy1 too and start dummy2 on the surviving host.
>> That's an outage and not what I wanted to achieve.
> 
> Obviously that's not "ever", it's only if there's more than one
> node on which they can run. If you put
> 
> 	colocation only-one -10: dummy1 dummy2
> 
> instead, you should get what you wanted.
> 


That the issue, I need "ever", and that's what Andrew's patch is going to fix.

Vadym