-----Mike Spreitzer/Watson/IBM@IBMUS wrote: -----
>To: "OpenStack Development Mailing List \(not for usage questions\)"
><openstack-dev@lists.openstack.org>
>From: Mike Spreitzer/Watson/IBM@IBMUS
>Date: 10/30/2013 03:56PM
>Subject: Re: [openstack-dev] [Heat] Comments on Steve Baker's
>Proposal on HOT Software Config
>
>Lakshminaraya Renganarayana/Watson/IBM@IBMUS wrote on
>10/30/2013 03:35:32 PM:
>
>
>
>> Zane Bitter <zbit...@redhat.com> wrote on 10/29/2013 08:46:21
>AM:
>
>> ...
>
>> In this method
>
>> > (i.e. option (2) above) shouldn't we be building the dependency
>graph in
>
>> > Heat rather than running through them sequentially as specified
>by the
>
>> > user? In that case, we should use a dictionary not a list:
>
>> >
>
>> > app_server:
>
>> > type: OS::Nova::Server
>
>> > properties:
>
>> > components:
>
>> > install_user_profile:
>
>> > definition: InstallWasProfile
>
>> > params:
>
>> > user_id
>
>> > install_admin_profile:
>
>> > definition: InstallWasProfile
>
>> > params:
>
>> > admin_id
>
>>
>
>> I missed this implication of using a list! You are right, it should
>be
>
>> a dictionary and Heat would be building the dependence graph.
>
>
>
>Using a dictionary instead of a list can work, but
>I think we might be going overboard here. Do we expect the component
>invocations on a given VM instance to run concurrently? I think that
>has been dissed before. Chef users are happy to let a role be a list
>of recipes, not a DAG. A list is simple; is there an actual problem
>with it?
Yes, there was some agreement on component invocations on a given VM instance
being run sequentially. However, the issue here is slightly different. If, as a
design principle, Heat analyzes dependences between component invocations,
then it should do that irrespective of whether the component invocations are
on the same VM or from different VMs. Given this, a list of component invocations
would imply an ordering which is in addition to the ordering induced by dependences.
Whereas a dictionary would not impose any additional ordering.
Thanks,
LN
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