[ClusterLabs] pcs stonith update <id> <args> problems

[Tomas Jelinek]

Dne 16. 07. 21 v 16:30 Digimer napsal(a):
> On 2021-07-16 9:26 a.m., Tomas Jelinek wrote:
>> Dne 16. 07. 21 v 6:35 Andrei Borzenkov napsal(a):
>>> On 16.07.2021 01:02, Digimer wrote:
>>>> Hi all,
>>>>
>>>>     I've got a predicament... I want to update a stonith resource to
>>>> remove an argument. Specifically, when resource move nodes, I want to
>>>> change the stonith delay to favour the new host. This involves adding
>>>> the 'delay="x"' argument to one stonith resource, and removing it from
>>>> the other;
>>>>
>>>> Example;
>>>>
>>>> ====
>>>> # pcs cluster cib | grep -B7 -A7 '"delay"'
>>>>         <primitive class="stonith" id="ipmilan_node1"
>>>> type="fence_ipmilan">
>>>>           <instance_attributes id="ipmilan_node1-instance_attributes">
>>>>             <nvpair id="ipmilan_node1-instance_attributes-ipaddr"
>>>> name="ipaddr" value="10.201.17.1"/>
>>>>             <nvpair id="ipmilan_node1-instance_attributes-password"
>>>> name="password" value="xxx"/>
>>>>             <nvpair id="ipmilan_node1-instance_attributes-pcmk_host_list"
>>>> name="pcmk_host_list" value="an-a02n01"/>
>>>>             <nvpair id="ipmilan_node1-instance_attributes-username"
>>>> name="username" value="admin"/>
>>>>             <nvpair id="ipmilan_node1-instance_attributes-delay"
>>>> name="delay" value="15"/>
>>>>           </instance_attributes>
>>>>           <operations>
>>>>             <op id="ipmilan_node1-monitor-interval-60" interval="60"
>>>> name="monitor"/>
>>>>           </operations>
>>>>         </primitive>
>>>> ====
>>>>
>>>> Here, the stonith resource 'ipmilan_node1' has the delay="15".
>>>>
>>>> If I run:
>>>>
>>>> ====
>>>> # pcs stonith update ipmilan_node1 fence_ipmilan ipaddr="10.201.17.1"
>>>> password="xxx" username="admin"; echo $?
>>>> 0
>>>> ====
>>>>
>>>> I see nothing happen in journald, and the delay argument remains in the
>>>> 'pcs cluster cib' output. If, however, I do;
>>>>
>>>> ====
>>>> # /usr/sbin/pcs stonith update ipmilan_node1 fence_ipmilan
>>>> ipaddr="10.201.17.1" password="xxx" username="admin" delay="0"; echo $?
>>>> 0
>>>> ====
>>>>
>>>> I can see in journald that the CIB was updated and can confirm in 'pcs
>>>> cluster cib' that the 'delay' value becomes '0'. So it seems that, if an
>>>> argument previously existed and is NOT specified in an update, it is not
>>>> removed.
>>>>
>>>> Is this intentional for some reason? If so, how would I remove the delay
>>>> attribute?
>>
>> Yes, this is intentional. As far as I remember, update commands in pcs
>> have always worked this way:
>> * do not change attributes not specified in the command
>> * if an attribute is specified with an empty value, remove the attribute
>> from cluster configuration
>> * else set specified value of the specified attribute in cluster
>> configuration
>>
>> This means you only need to specify attributes you want to change. You
>> don't need to bother with attributes you want to keep unchanged.
>>
>> If you want to delete the delay attribute, you can do it like this:
>> pcs stonith update ipmilan_node1 delay=
>> This will remove delay and keep all the other attributes unchanged.
>>
>> I'm not sure why this principle is not documented in pcs man page. We
>> can fix that, though.
>>
>> Note that specifying a stonith agent in the update command does nothing
>> (which is expected) and is silently ignored by pcs (which is a bug).
>>
>> Regards,
>> Tomas
> 
> Ah, thank you (and as Andrei)!
> 
> Is this behaviour not documented in 'pcs stonith help' -> update? Or was
> I blind and missed it?
> 

I think this isn't documented anywhere in pcs. It may be described in 
Clusters from Scratch or a similar document. I think I've read it 
somewhere, but I'm not sure where it was.

Anyway, I put it on our todo list to get it explained in pcs help and 
man page.


Thanks,
Tomas