[ClusterLabs] [rgmanager] Recovering a failed (but running) server in rgmanager

[Digimer]

On 19/09/16 03:07 PM, Digimer wrote:
> On 19/09/16 02:39 PM, Digimer wrote:
>> On 19/09/16 02:30 PM, Jan Pokorný wrote:
>>> On 18/09/16 15:37 -0400, Digimer wrote:
>>>>   If, for example, a server's definition file is corrupted while the
>>>> server is running, rgmanager will put the server into a 'failed' state.
>>>> That's fine and fair.
>>>
>>> Please, be more precise.  Is it "vm" resource agent that you are talking
>>> about, hence server is the particular virtual machine to be managed?
>>> Is the agent in the role of a service (defined at a top-level) or
>>> a standard resource (without special treatment, possibly with
>>> dependent services further in the group)?
>>
>> In 'clustat', vm:foo reports 'failed' after the vm.sh calls a status and
>> gets a bad return (because the foo.xml file was corrupted by creating a
>> typo that breaks the XML, as an example).
>>
>> I'm not sure if that answers your question, sorry.
>>
>>>>   The problem is that, once the file is fixed, there appears to be no
>>>> way to go failed -> started without disabling (and thus powering off)
>>>> the VM. This is troublesom because it forces an interruption when the
>>>> service could have been placed under resource management without a reboot.
>>>>
>>>>   For example, doing 'clusvcadm -e <server>' when the service was
>>>> 'disabled' (say because of a manual boot of the server), rgmanager
>>>> detects that the server is running fine and simply marks the server as
>>>> 'started'. Is there no way to do something similar to go 'failed' ->
>>>> 'started' without the 'disable' step?
>>>
>>> In case it's a VM as a service, this could possibly be "exploited"
>>> (never tested that, though):
>>>
>>> # MANWIDTH=72 man rgmanager | col -b \
>>>   | sed -n '/^VIRTUAL MACHINE/{:a;p;n;/^\s*$/d;ba}'
>>>> VIRTUAL MACHINE FEATURES
>>>>        Apart from what is noted in the VM resource agent, rgman-
>>>>        ager  provides  a  few  convenience features when dealing
>>>>        with virtual machines.
>>>>         * it will use live migration when transferring a virtual
>>>>         machine  to  a  more-preferred  host in the cluster as a
>>>>         consequence of failover domain operation
>>>>         * it will search the other instances of rgmanager in the
>>>>         cluster  in  the  case  that a user accidentally moves a
>>>>         virtual machine using other management tools
>>>>         * unlike services, adding a virtual  machine  to  rgman-
>>>>         ager’s  configuration will not cause the virtual machine
>>>>         to be restarted
>>>>         *  removing   a   virtual   machine   from   rgmanager’s
>>>>         configuration will leave the virtual machine running.
>>>
>>> (see the last two items).
>>
>> So a possible "recover" would be to remove the VM from rgmanager, then
>> add it back? I can see that working, but it seems heavy handed. :)
>>
>>>>   I tried freezing the service, no luck. I also tried coalescing via
>>>> '-c', but that didn't help either.
>>>
>>> Any path from "failed" in the resource (group) life-cycle goes either
>>> through "disabled" or "stopped" if I am not mistaken, so would rather
>>> experiment with adding a new service and dropping the old one per
>>> the above description as a possible workaround (perhaps in the reverse
>>> order so as to retain the same name for the service, indeed unless
>>> rgmanager would actively prevent that anyway -- no idea).
>>
>> This is my understanding as well, yes (that failed must go through
>> 'disabled' or 'stopped').
>>
>> I'll try the remove/re-add option and report back.
> 
> OK, didn't work.
> 
> I corrupted the XML definition to cause rgmanager to report it as
> 'failed', removed it from rgmanager (clustat no longer reported it at
> all), re-added it and when it came back, it was still listed as 'failed'.

Ha!

So, it was still flagged as 'failed', so I called '-d' to disable it
(after adding it back to rgmanager) and it went 'disabled' WITHOUT
stopping the server. When I called '-e' on node 2 (the server was on
node 1), it started on node 1 properly and returned to a 'started' state
without restarting.

I wonder if I could call disable directly from the other node...

-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?