[Pacemaker] Enable remote monitoring

[Andrew Beekhof]

On Thu, Nov 8, 2012 at 5:24 PM, Gao,Yan <ygao at suse.com> wrote:
> Hi Andrew,
>
> On 11/08/12 13:09, Andrew Beekhof wrote:
>> On Tue, Nov 6, 2012 at 10:30 PM, Gao,Yan <ygao at suse.com> wrote:
>>> Hi,
>>>
>>> Currently, we can manage VMs via the VM agents. But the services running
>>> within VMs are not very easy to be monitored. If we could use
>>> nagios/icinga probes from the host to the guest, that would allow us to
>>> achieve this.
>>>
>>> Lars, Dejan and I have been discussing on this for some time. There have
>>> been quite some thoughts on how to implement it. Now we are inclined to
>>> a proposal from Lars. Please let me introduce the idea here, and see
>>> what you think about it.
>>>
>>> First, we could add a resource agent class. The RAs belonging to this
>>> class wrap around nagois/icinga probes. They can be configured as
>>> special monitor operations for the VMs. The behaviors should be like:
>>>
>>> 1. The special monitor operations start working after the VMs and the
>>> services inside are started.
>>>
>>> 2. Any failure of the monitor operations is treated as the failure of
>>> the VM, which triggers the recovery of the VM.
>>>
>>> Let me show a example:
>>>
>>> primitive db-vm ocf:heartbeat:VirtualDomain \
>>>         params config="db-vm" hypervisor="xen:///" \
>>>         ip="192.168.1.122" \
>>>         op monitor nagios:ftp interval="30s" params user="test"
>>>
>>> The "nagios:ftp" specifies which monitor agent is used to monitor the
>>> VM.  It's an optional attributes group expressing "class/provider/type"
>>> of the monitor agent, which defaults to "ocf:heartbeat:VirtualDomain"
>>> for this VM (if so, the monitor would be a normal one like we usually
>>> configure). We can add more monitors like "nagios:www" type and so on.
>>
>> What do you propose the XML should look like?
> Should be like:
> ...
> <op id="vm-monitor-30" name="monitor" class="nagios" type="ftp"
> interval="30s" ignore-first-failures="true">
>   <instance_attributes id="vm-monitor-30-params">
>     <nvpair id="vm-monitor-30-params" name="user" value="test">
>   </instance_attributes>
> </op>
> ...
>
>>
>>> We can specify particular "params" for a monitor. And the "ip" is
>>> actually not a useful parameter for the VirtualDomain, we put it there
>>> for its monitor operations to inherit, so that we don't have to specify
>>> for each monitor respectively.
>>
>> You plan to add 'ip' to the VirtualDomain metadata?
> It should be in the metatdata of nagios:ftp and also other monitor
> agents. We'd like parameters inheritance to avoid configuration repetition.

That sounds overly complex (you now need to do two metadata lookups to
determine the parameter lists).  I think I'd prefer to avoid that if
possible.

>
>>
>>>
>>>
>>> Other issues:
>>> - As we can see, there's some time window between when the VM is
>>> started, but prior to the monitored service starting. A solution is
>>> adding a "first-failure" flag for the monitor operation, which could
>>> allow us to ignore the *first* failures of a monitor until it has
>>> returned healthy once, unless the time is out. Ideally, it could be
>>> handled in LRM.
>>
>> What happens if there is never a first success?
>> The cluster will never find out.
> It'll reach the timeout and return.

Which timeout? Not the one in <op...> since the whole operation might
repeat many times over before succeeding.

> We should give a reasonable monitor
> timeout I think.
>
>>
>>>
>>> - A limitation is we would have to specify different monitor interval
>>> values for the services within a VM. Probably we could fix it in some
>>> way finally.
>>>
>>>
>>> Anyway, this's the most straightforward solution we can think of so far
>>> (Please correct me if I'm missing anything). It's open for discussion.
>>> Any comments and suggestions are welcome and appreciated.
>>
>> Doesn't look too bad.  Some finer points to discuss but I'm sure we
>> can reach agreement.
> Nice, thanks!
>
> Regards,
>   Gao,Yan
> --
> Gao,Yan <ygao at suse.com>
> Software Engineer
> China Server Team, SUSE.
>
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