[Linux-cluster] rgmanager "depend" tag on RHEL4

[Mark Hlawatschek]

On Friday 27 July 2007 15:45:19 Lon Hohberger wrote:
> On Wed, Jul 25, 2007 at 08:50:17PM +0200, Mark Hlawatschek wrote:
> > > > I'd like to use the "depend" feature of rgmanager on RHEL4. Is there
> > > > a way to do this. E.g. would it be possible to run the cvs HEAD
> > > > version of rgmanager on a RHEL4.5 cluster infrastructure ?
> > >
> > > It doesn't build on RHEL4 right now; there's no equivalent to
> > > 'cman_get_fenceinfo()'.
> > >
> > > If you #if 0 out the 'node_fenced()' body and return 1, it builds.  I
> > > don't know if it will run... but it builds ;)
> > >
> > > It doesn't appear there's an equivalent function; so to implement it,
> > > one would have to perhaps parse /proc/cluster/services or something
> > > like that...
> >
> > What does the prototype of cman_get_fenceinfo() look like ? What is it
> > meant to do ?
>
> It gets the time the node was last fenced from CMAN.  When a node
> rejoins the cluster, this information is cleared.
>
> So, what rgmanager does is effectively:
>   nodeX died
>   does nodeX have fencing configured?
>     yes
>       wait for node X to be fenced or rejoin the cluster
>     no
>       continue
>
> > Is there another way to get the "depend" feature back-ported ?
>
> I think there's already a feature request open about it, by you?
Yes, there are two feature requests open that address service dependencies
247980 - RFE: (strong and weak) service dependencies
247772 - RFE: One service following another
>
> Implementation-wise, in RHEL5, there's an event queue for service state
> changes, and a function which broadcasts starts/stops
> (broadcast_event()).  The difference is that in RHEL5, you can multicast
> to all rgmanagers w/ one call - whereas on RHEL4, you have to open a
> connection to each and send the message individually.
>
> So, basically, it involves porting the event queue code and implementing
> broadcast_event().
OK, how much effort - in your opinion - would it be to port/implement these 
features ?
Is there a task scheduled to do these things ? 

Thanks,

Mark

-- 
Gruss / Regards,

Dipl.-Ing. Mark Hlawatschek
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