[ClusterLabs] related to fencing in general , docker containers

[Andrei Borzenkov]

On 19.06.2022 18:24, Sridhar K wrote:
> Team,
> 
> Trying to test docker resource agent , getting below error , any issues
> w.r.t below command ?
> 
> [root at 5e8851dac338 /]# pcs resource create test_docker2
> ocf:heartbeat:docker image=nginx reuse=true  op monitor interval=30s
> 
> Docker container nginx is running
> [root at 5e8851dac338 /]# docker ps
> CONTAINER ID   IMAGE     COMMAND                  CREATED         STATUS
>       PORTS                NAMES
> 3adb20c8a3fc   nginx     "/docker-entrypoint.…"   2 minutes ago   Up 2
> minutes   0.0.0.0:80->80/tcp   mynginx1
> [
> 
> pcs status command :
> Failed Resource action
> * test_docker2_stop_0 on 450196e74dc0 'unknown error' (1): call=42,
> status=complete, exitreason='Docker service is in error state while
> checking for test_docker2, based on image, nginx: Client: Docker Engine -
> Community',

This error is string is returned by resource agent when "docker version"
returns 1.

>     last-rc-change='Sun Jun 19 20:51:58 2022', queued=0ms, exec=97ms
> 
> regards
> Sridhar
> 
> 
> 
> 
> 
> 
> On Sun, 19 Jun 2022 at 15:40, Sridhar K <sriatk at gmail.com> wrote:
> 
>> Thank you Ken,Andrei for the response
>>
>> As of now, I have completed the below  (below is for POC purpose) Ideally
>> there will be 3 VM's and each VM will have one docker container
>> [pacemaker + corosync + sqlServer] same network
>> 1.Created a docker image with [pacemaker + corosync + sqlServer]
>> 2. Created a docker network and brought up 3 containers of the above image
>> which are part of the created network
>> 3. Created  a pacemaker cluster out of 3 containers
>> 4. Create AG group of sqlserver
>> 5. Tested failover of Sqlserver , by making a container(i,e pcs cluster
>> standby container id) to standby , failover was working.
>>
>> All above was in a VM , now need to think w.r.t fencing
>> As the pacemaker is running within the docker container anything w.r.t
>> fencing may not help
>> next was checking, how about doing something w.r.t fencing at VM level so
>> that fencing can kill/restart the docker container as required.
>>
>> considering 3 VMs
>> If 1 VM itself goes down , SqlServer will be still up as two VM's are fine
>> and within them, docker containers (pacemaker + corosync + sqlServer) are
>> running
>> If 2 VM goes down , then SqlServer will not be available.
>>
>>
>> Related to Bundles
>> I tried, and got an error posted the same  in the forum, also in Bundles
>> required number of replicas will be spawned, How can I configure out of 3
>> replicas which will be my master Sqlserver and the rest will be replicas
>>
>>
>> Hi Ken,
>> will check this, if am able to fence docker containers(pacemaker +
>> corosync + sqlServer), it should be of some help, and will check how to
>> handle VM failures
>>
>> You
>>> will probably need one fencing agent for each physical host where
>>> docker
>>> is running and map cluster nodes (containers) to the correct agent
>>> (i.e.
>>> physical host).
>>
>> Regards
>> Sridhar
>>
>>
>>
>>
>> On Fri, 17 Jun 2022 at 20:29, Andrei Borzenkov <arvidjaar at gmail.com>
>> wrote:
>>
>>> On 17.06.2022 16:53, Sridhar K wrote:
>>>> Hi Team,
>>>>
>>>> Please share any pointers, references, example usage's w.r.t fencing in
>>>> general and its use w.r.t docker containers.
>>>>
>>>> referring as of now
>>>> https://clusterlabs.org/pacemaker/doc/crm_fencing.html
>>>>
>>>> need to check the feasibility of fencing w.r.t docker containers
>>>>
>>>
>>> There is fence_docker, you will need to configure docker on each
>>> physical host to accept remote connections from each cluster node. You
>>> will probably need one fencing agent for each physical host where docker
>>> is running and map cluster nodes (containers) to the correct agent (i.e.
>>> physical host).
>>>
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>>
> 
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