[Openais] Proposed change to default nodeid generation

[Joel Becker]

On Wed, Aug 20, 2008 at 11:17:18AM -0700, Steven Dake wrote:
> On Wed, 2008-08-20 at 18:52 +0200, Andrew Beekhof wrote:
> We talked on irc and came to the conclusion that apparently it is
> impossible to fix the kernel issue with the assumption of 1^31 bits and
> it is impossible to fix the openais/corosync assumption of 1^32 bits
> nodeids.  

	Boy, are we awesome.

> Therefore a patch (with man page) of an api that gets the nodeids in 31
> bit fashion from cpg would be workable.
> 
> ie:
> 
> cpg_nodid_31bit_set(handle).
> 
> would be suitable if this would meet everyone's needs.

	Well, what happens with CLM?  Does it report the 32bit nodeid?
What about EVS?  Btw, it's interesting (though irrelevant) that EVS uses
'unsigned int' instead of uint32_t.  I think this is a little more core,
and I'd like to explore what we're really after.
	I don't think we should force all openais/corosync nodeids to
2^31 bits.  The protocol should stay 2^32 bits.  I don't think Andrew
was asking for this either.
	I think Andrew was just looking for a way to limit the
autogenerated node numbers, because his software uses the
autogeneration.  The cman stack never cares because it sets the nodeids
itself, which requires a configuration file and explicit nodeid
specification by the admin.
	So, first, Andrew, does pacemaker have a method for querying
membership and nodeids?  Forget ocfs2_controld/dlm_controld.  I just
write a random application, and I want it to use pacemaker.  Are there
functions for "what is my nodeid?" and "what nodeids exist in the
cluster?"?  What do those functions look like?  I'm assuming they work
in the absence of cpg, so it isn't just cpg here.
	Both Andrew and Steve, I'm assuming that pacemaker exists as a
kind of corosync plugin these days.  So it has some access to the config
space.  Now, the cman config plugin fills in the nodeids, whereas
pacemaker appears to get them from corosync's automatic method.  Is
there any way a plugin could have a hook from the autogeneration code?
That is, corosync determines it should be autogenerating a node number,
so it calls ->auto_node_num().  This defaults to the current IP address
method, but pacemaker could provide a new method that returns whatever
value it wants.  Internal to corosync and on the wire, it's still
stored/sent as uint32_t, just like cman's nodeids.

Joel

-- 

"The only way to get rid of a temptation is to yield to it."
         - Oscar Wilde 

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127