[Linux-HA] ipfail in V2

Alan Robertson alanr at unix.sh
Thu Oct 20 09:30:50 MDT 2005


Andrew Beekhof wrote:
> On 10/20/05, Alan Robertson <alanr at unix.sh> wrote:
>>Andrew Beekhof wrote:
>>>On 10/20/05, Lars Marowsky-Bree <lmb at suse.de> wrote:
>>>>On 2005-10-20T13:22:30, Simon Rowe <srowe at cambridgebroadband.com> wrote:
>>>>
>>>>>>(OK, or wait for someone on the linux-ha team to write it.)
>>>>>I don't have the time for either. I'll have to dump V2 and see if V1
>>>>>provides sufficient working functionality.
>>>>I suppose this being Open Source, you could find a developer who'd take
>>>>a bribe and implement this feature for you for less than you'd have paid
>>>>for a single node license of a commercial clustering product...
>>>While in principle I personally would never take bribes, in practice I
>>>have no principles :-)
>>>
>>>With what we have now in CVS, we can get a reasonably close
>>>approximation of ipfail.
>>>You wont get true damping - so some ping-pong'ing of resources may still occur.
>>>It may also be not as efficient as we'd like it to be.
>>>
>>>lmb: random thought... if the "ipfail RA" checked the values on the
>>>other nodes before it updated the CIB, then we could avoid dipping
>>>into the PE.  the check would be trivial, just specify a different
>>Writing the code to do this is not trivial...
>>
>>
>>Let's see ... you need to write a join protocol, and then you need to
>>exchange votes with everyone else, and...
>>
>>Right now, they have NO communication with other nodes at all.
> 
> you dont need any of that.  query the CIB:
> 
> crm_attribute -G -U some_host -n the_attribute -t nodes

How does this help with hysteresis?

You need to know the value they have of the attribute _before they 
update it_.  Because, once they update it, boom, you're off on a 
reconfigure-the-cluster mission.  It's too late then.



-- 
     Alan Robertson <alanr at unix.sh>

"Openness is the foundation and preservative of friendship...  Let me 
claim from you at all times your undisguised opinions." - William 
Wilberforce



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