[Linux-HA] resource group design question

[Andrew Beekhof]

On 10/5/07, Daniel X Moore <dxm at sgi.com> wrote:
> Andrew Beekhof wrote:
> >> We have resource groups that contain multiple resources that sometimes
> >> need to be handled individually, and sometimes as a group.
> >>
> >> When starting or stopping a resource group, we want to be able to
> >> perform the start/stop operation on all the members at the same time (ie
> >> not stop a, stop b, stop c ... but stop a,b&c together.
> >
> > as in you dont want to issue 3 commands or you want the stopping to
> > occur in parallel?
>
> Not sequentially or parallel, but in one invocation... eg, don't run:
>
>         OCF_RESKEY_who=a plugin start
>         OCF_RESKEY_who=b plugin start
>         OCF_RESKEY_who=c plugin start
>
> but something like:
>
>         OCF_RESKEY_who="a b c" plugin start

you can write an agent that does this if you want, but i still don't
understand why since you can start/stop a group with one command.

i guess you could even OCF_RESKEY_who a reload-able parameter so that
if its value changes it would be up to the RA if it wanted to do a
full restart.

but i'm just taking shots in the dark here as I dont really understand
what it is you're trying to achieve

> > if the latter, can they start in parallel too?
> >
> > if so, maybe you just need to set ordered=false for the group...
>
> parallel would make life more difficult. But maybe something like
> aggregated=true, if such a thing existed.

it might, but i dont know what you mean by it

>
> >
> >> When adding a member to a group, we want to be able to start the
> >> individual member
> >
> > it you add it to the end, this is possible
> >
> >> and be able to synchronize with the completion of the
> >> removal.
> >>
> >> When removing a member, we want to be able to remove just that member
> >> and be able to synchronize with the completion of the removal.
> >
> > not sure i understand what you mean by "synchronize" in this context
>
> we need to be able to remove the member (ie stop it), and know when it
> has stopped (if the resource wasn't running, the member would be
> considered to have "stopped").

sounds a bit like notifications, but i dont recall if they work for groups

>
> >
> >> We also want to be able to update (reload) a set of members.
> >>
> >> So far, I have two approaches:
> >>
> >>         - have a single resource with a list of members.
> >>         - have a resource group with a individual resources for members
> >>
> >> The first approach makes it easy to deal with all members together, the
> >> second with individual members.
> >>
> >> Can anyone suggest a way to get a combination of these behaviours?
>
>
> --
> -------------------------------------------------------------------
>   Daniel Moore                              dxm at sgi.com
>   Engineering Manager: AppMan + HA          Phone:  +61-3-9963-1957
>   SGI Australian Software Group             Mobile: +61-4-1360-4720
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