[Pacemaker] custom resource-agent

[David Lang]

On Tue, 1 Oct 2013, Dejan Muhamedagic wrote:

> On Tue, Oct 01, 2013 at 07:22:20AM -0700, David Lang wrote:
>> On Tue, 1 Oct 2013, Dejan Muhamedagic wrote:
>>
>>> Hi David,
>>>
>>> On Mon, Sep 30, 2013 at 12:41:23PM -0700, David Lang wrote:
>>>> On Mon, 30 Sep 2013, David Lang wrote:
>>>>
>>>>> On Mon, 30 Sep 2013, Michael Schwartzkopff wrote:
>>>>>
>>>>>> Am Montag, 30. September 2013, 21:12:56 schrieb Peter Romfeld:
>>>>>>> I am working in AWS i cant just use a VIP i need to use a floating
>>>>>>> secondary IP which i reassign through script, i want to let pacemaker
>>>>>>> handle the reassignment...
>>>>>>
>>>>>> Please explain the difference of a VIP and a "secondary IP" in
>>>>>> your opinion.
>>>>>
>>>>> with AWS you need to inform amazon of the change, not just change
>>>>> the IP on the local box, that requires much more work than a
>>>>> simple local VIP
>>>>
>>>> being more detailed, instead of just
>>>> ifconfig eth0:0 $vip
>>>> you have to do something like
>>>>
>>>> /opt/aws/bin/ec2-assign-private-ip-addresses -n $ENI_ID --secondary-private-ip-address $VIP --allow-reassignment --region $REGION
>>>
>>> We may consider adding such an option to IPaddr2. Has anybody
>>> ever tried that?
>>>
>>>> pingresult=`ping -c 1 -W 1 $VIP | grep time= | wc -l`
>>>> if [ "$pingresult" == "0" ]; then
>>>>  echo `date` "-- Restarting network"
>>>>  /sbin/service network restart > /dev/null 2>&1
>>>
>>> That may break the cluster communication, which may lead to split
>>> brain, etc. Is that really the only way?
>>
>> It's not the only way, but you do have the problem that the call to
>> aws management interface is asynchronous, you don't know when it's
>> going to complete, and until it does, the IP doesn't actually work.
>
> Wouldn't it be then safer to wait until it starts working, i.e.
> to monitor in a loop?

that's exactly what the snippet of code above is for, to detect when the other 
box no longer has the address.

David Lang