[Linux-cluster] fence_ovh - Fence agent for OVH

[Adrian Gibanel]

  As requested by digimer in linux-ha irc channel here there is fence_ovh. It's not a priority that it's included by default in official distribution of cluster software but if you guide me on how to polish it I think I can improve it a lot more and make tests in real machines (as long as my machines are still test machines and not production ones). 

1) What is fence_ovh 

fence_ovh is a fence agent based on python for the big French datacentre provider OVH. You can get information about OVH on: http://www.ovh.co.uk/ . I also wanted to make clear that I'm not part of official OVH staff. 

2) Features 
The script has two main functions: 

* Reboot into rescue mode (action=off) 
* Reboot into the hard disk (action=on;action=reboot) 

3) Technical details 
So as you might deduce the classical fence mechanism which turns off the other node is not actually done by turning off the machine but by rebooting it into a rescue mode. 

Another particular thing to mention is that the script checks if the machine has rebooted ok into rescue mode thanks to an OVH API which reports the date when the server rebooted. By the way the OVH API is also used in the main function that consists in rebooting the machine into rescue mode. 

4) How to use it 

4.1) Make sure python-soappy package is installed (Debian/Ubuntu).
4.2) Save fence_ovh in /usr/sbin 
4.3) Run: ccs_update_schema so that new metadata is put into cluster.rng 
4.4) If needed validate your configuration: 
ccs_config_validate -v -f /etc/pve/cluster.conf.new 
4.5) Here's an example of how to use it in cluster.conf:

<?xml version="1.0"?>
<cluster name="ha-008-010" config_version="3">

<cman keyfile="/var/lib/pve-cluster/corosync.authkey" transport="udpu" two_node="1" expected_votes="1">
</cman>

<fencedevices>
        <fencedevice agent="fence_ovh" name="fence008" email="admin at domain.com" ipaddr="ns123456" login="ab12345-ovh" passwd="MYSECRET" />
        <fencedevice agent="fence_ovh" name="fence010" email="admin at domain.com" ipaddr="ns789012" login="ab12345-ovh" passwd="MYSECRET" />
</fencedevices>

<clusternodes>
<clusternode name="server008" nodeid="1" votes="1">
  <fence>
    <method name="1">
      <device name="fence008" action="off"/>
    </method>
  </fence>
</clusternode>
<clusternode name="server010" nodeid="2" votes="1">
  <fence>
    <method name="1">
      <device name="fence010" action="off"/>
    </method>
  </fence>
</clusternode>
</clusternodes>


</cluster>



Finally I attach to this email the first version of ovh_fence script. It can be improved a lot, I've just realised that I've left some mention an .ini file in the metadata that I had used previously to feed user / pass while now they are gathered from cluster.conf configuration directly as any fence agent.

The original thread from Proxmox forum from which I adapted original secofor script: http://forum.proxmox.com/threads/11066-Proxmox-HA-Cluster-at-OVH-Fencing?p=75152#post75152

P.S.: It was not easy to develop a fence agent because there's no documentation on it. I maybe arise another email in this same mailing list about this subject. 

-- 

-- 
Adrián Gibanel 
I.T. Manager 

+34 675 683 301 
www.btactic.com 



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