On 3/20/07, Doug Knight <[EMAIL PROTECTED]> wrote:
Hi Alan,
I've had some time to try to implement the OCF script for the PostgreSQL
WAL file forwarding configuration, and I still am having some issues. The
main issue is how do I set up an OCF script that allows the process to run
on both servers, one process in a "starting" mode ingesting transferred WAL
files, the other in an "accessible" mode allowing database access and
forwarding WAL files to the standby (right now the different states are
determined within the OCF script by looking for the existence of a
recovery.conf file, which indicates the "starting", standby side)? What I'm
trying to figure out is how to tell HA that it needs to start the standby
process and monitor it.
I've started looking at the multi-state configurations, but the
documentation isn't completely clear. Can you expand on it? I'd like
something similar to the answers you gave for the monitor, stop, and start
functions (when do they/can they get invoked, on which node, etc). One
specific area of the multi-state config I have a question about is how to
tell HA which server has the master role when first starting up the
resource. Any additional info would be great.
have a look at the drbd and Stateful agents:
http://hg.beekhof.net/lha/crm-dev/file/be220f2e9b40/resources/OCF/Stateful.in
but first read:
http://linux-ha.org/v2/Concepts/MultiState
in particular, section 6.1
Thanks,
Doug
On Wed, 2007-03-14 at 19:59 -0600, Alan Robertson wrote:
Doug Knight wrote:
> Yes, Thanks Alan. Let me digest it, and walk through my OCF script. I'll
> see if I have any other questions after that.
>
> Thanks for getting back to me.
>
> Doug
>
> On Wed, 2007-03-14 at 11:41 -0600, Alan Robertson wrote:
>> Doug Knight wrote:
>> > Hi All,
>> > I currently am running a two node cluster (host1 and host2) with
version
>> > 2.0.8. I have a resource defined with a place constraint of "#uname eq
>> > host1", so that it will start on host1 (using an OCF RA script,
>> > including all of the required methods). The resource itself has
>> > target_role set to "stopped".
>> >
>> > Question 1: Is the monitor method called regularly on both nodes to
make
>> > sure the resource is not running?
>>
>> No. It is called on every node when we first start up (we call it a
>> probe operation). If you ask us to, we will run it periodically to
>> ensure that a running copy continues to run.
>>
>> You can also manually request to run this initial probe again to catch
>> errors made by system administrators (but I don't know of anyone who
>> does that).
>>
>>
>> > Next, I change the target_role to "started" (i.e. I use the GUI and
>> > click the start button).
>> [Better yet, use the "outline" start button]
>>
>> > Question 2: What is the order of OCF methods called to bring up the
>> > resource? Is Monitor called before Start on host1? Does Stop and/or
>> > Monitor ever get called on host2?
>>
>> Monitor gets called when we first start up on every node.
>> It also get called repeatedly on any node that we think is running it --
>> if you ask us to monitor the resource.
>>
>> > Resource is up and running on host1, and I decide to move the resource
>> > to host2. I click the constraint and change it to "#uname eq host2".
The
>> > resource stops on host1 and starts on host2.
>> >
>> > Question 3: Same idea, what are the sequence of method calls to migrate
>> > the resource from host1 to host2?
>>
>> In the past...
>> monitor every resource on every node once to see what's already
>> running
>> start on "some node"
>> monitor periodically on "some node" (if requested)
>>
>> Request to move resource arrives...
>> stop monitoring on "some node" (if it had been requested)
>> stop resource on "some node"
>> start resource on "some other" node
>> monitor periodically on "some other node" (if requested)
>>
>> > I'm trying to thoroughly understand the sequence of events that occurs
>> > for each phase in support of the Postgres WAL file forwarding
>> > configuration I posted last week ("[Linux-HA] Two node cluster with
>> > Postgres in WAL file fwding mode", started March 1).
Let me offer this caveat:
Monitor might be called at any time.
Stop should work at any time,
and succeed harmlessly if it's already stopped.
Start should work at any time,
and succeed harmlessly if it's already started.
http://www.linux-ha.org/OCFResourceAgent gives more
details.
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_______________________________________________________
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Home Page: http://linux-ha.org/
