[Pacemaker] Patch of fence agent fence_wti to support named port groups

[Thibaut Pouzet]

Hi,

There have been a lot of discussions lately regarding pacemaker's 
configuration to support multiple PDUs for fencing. These discussions 
apply to two possible setup:
* One node dually powered by two physically separated PDUs that are on 
two separated power supply circuits
* One node dually powered by one PDU that is itself powered by two 
separated power supply circuits

Pacemaker's configuration is to do "pdu1_portA_off, pdu2_portB_off, 
pdu1_portA_on,pdu2_portB_on". However, when this has to be done on one 
single PDU as in the second setup, pdu1 and pdu2 are the same device. 
This require to open/close four connexions in a row on the same 
hardware. This can work if telnet is used, but not if it is SSH that is 
used (at least with our PDUs).

We have relatively new WTI NPS-8HD20-2 and we could not make fencing 
work properly with this method on this hardware, and with secure="true". 
Since it is possible to configure named port groups on the PDUs, we 
decided to use them instead. Once the configuration done at the PDU 
level, all we have to do is to issue "/OFF fence_group_1" or "/ON 
fence_group_1", and then the device takes care itself to 
power-off/power-on all the power outlets associated with the named group.

NPS-8HD20-2
The fence agent fence_wti that is shipped with 
"fence-agents-3.1.5-25.el6_4.2.x86_64" on CentOS 6.4 cannot work with 
named port groups. It only works with single outlets. We have patched 
fence_wti in order to make it also work with named port groups, here is 
the diff file : http://pastebin.com/qUuFSSue .

Once you have patched fence_agent, you don't need four stonith primitive 
anymore, just one like the following :
primitive wti_fence01 stonith:fence_wti \
          params ipaddr="a.b.c.d" port="named_port_group" login="foo" 
passwd="bar" shell_timeout="60" login_timeout="60" 
pcmk_host_list="fence01" secure="true"

Hope this will be useful to someone someday.

Cheers,

Thibaut
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