On Nov 13, 2007, at 10:17 AM, Cousin Marc wrote:
Le Monday 12 November 2007 17:41:18, vous avez écrit :
On Nov 12, 2007, at 5:13 PM, Cousin Marc wrote:
Le Monday 12 November 2007 16:13:45 Andrew Beekhof, vous avez
écrit :
On Nov 12, 2007, at 2:29 PM, Cousin Marc wrote:
Hi,
I'm trying to figure out the actual behaviour of heartbeat (I'm
using
2.1.2+hg.11310.702e4f418ca8-2, as provided for debian sid)
I'm sorry if it's a bit long and complicated, don't hesitate to
ask
me to
clarify some parts ...
I've detailed the steps I'm following, as I've found several
docs in
the wiki
contradicting each other.
I'm trying for my tests to build a 3 node cluster (drbdtest1, 2
and
3), with 2
nodes hosting a drbd device, and one resource group having to be
collocated
with the master drbd resource.
First, I create a drbd resource ...
No problem here. Without constraints, it's running anywhere.
I'm adding a location constraint telling heartbeat not to run on
drbdtest3 ...
cibadmin -o constraints -C -X '
<rsc_location id="place_r0" rsc="cloner0">
<rule id="prefered_place_r0" score="-INFINITY">
<expression attribute="#uname" id="colocr0_1"
operation="eq"
value="drbdtest3"/>
</rule>'
that will work, but you're better off with a rsc_colcation
constraint
(also set the score=-INFINITY)
It's OK, now it's not running on the third node. It's activating a
master on
drbdtest1.
Then I create my resource group ('applisr0'), with no constraints
for now.
It's OK, but of course, with no constraints, it's not running
where
it should.
In fact, it's running on the third node.
Then I put a constraint telling it not to run on a stopped node.
cibadmin -o constraints -C -X '<rsc_colocation
id="r0_et_applis_stopped"
from="applisr0" to="cloner0" to_role="stopped" score="-INFINITY"/>
It's not working. The group is still trying to start on the third
node.
Instead of a double negative, just go with a positive:
cibadmin -o constraints -C -X '<rsc_colocation id="r0_et_applis"
from="applisr0" to="cloner0" score="INFINITY"/>
I've tried a lot of other configurations. I think that 'stopped'
is
not
working...
The most obvious way to verify it is this :
if I replace the previous constraint with :
cibadmin -o constraints -U -X '<rsc_colocation
id="r0_et_applis_stopped"
from="applisr0" to="cloner0" to_role="stopped" score="+INFINITY"/
>'
the resource isn't running anywhere. I think it means that every
node is
considered to be in the stopped role.
I can make it work this way :
cibadmin -o constraints -C -X '<rsc_colocation
id="r0_et_applis_master"
from="applisr0" to="cloner0" to_role="master" score="+INFINITY"/>'
So, to sum it up, it seems to me that the stopped role is seen as
true on
every node...
Am I right ?
For clones, this may be correct.
Most people find the regular way sufficient but there's no argument
that the double negative should also work.
If you'd like to log a bug in bugzilla I will make sure it gets
fixed.
Okay, but I still don't get it completely :
<rsc_colocation id="r0_et_applis_stopped" from="applisr0"
to="cloner0"
to_role="stopped" score="-INFINITY"/>
And
<rsc_colocation id="r0_et_applis_master" from="applisr0"
to="cloner0"
to_role="master" score="+INFINITY"/>'
I didn't include to_role="master" in the inverse constraint
So I get it even less :)
Doesn't it mean that we would just tell heartbeat that we want to
start
applisr0 anywhere where cloner0 is started ?
yes, that's what
<rsc_colocation id="r0_et_applis_stopped" from="applisr0" to="cloner0"
to_role="stopped" score="-INFINITY"/>
does too.
so i assumed thats what you wanted.
I want it to applisr0 run anywhere where cloner0 is master.
then you only need the second one
<rsc_colocation id="r0_et_applis_master" from="applisr0" to="cloner0"
to_role="master" score="+INFINITY"/>'
The idea behind what I was doing was that I would put -INFINITY
anywhere I
wouldn't want applisr0 to run (stopped and slave), and a small score
(something like 100) where I would rather have it to run (my
preferred node
for applisr0).
sure, in theory that should also work (though you've demonstrated that
it doesn't and i need to fix that)
If I put +INFINITY as a score for colocation, wouldn't hearbeat
consider that
as long as cloner0 and applisr0 are at the same place, the score is
+INFINITY, wherever it can make both of them run ?
no, your +100 preference would still take effect... it would determine
which clone instance we decided to colocate it with
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