[one-dev] Live migration / recovery - suggestions

[Gareth Bult]

Hey Guys, I've done a little work on the migration script - this is what I've done here .. 
- be nice if something similar could be implemented @ source .. ? 

1. ssh_exec_and_log (generic change - this could be useful elsewhere..) modify as follows; 


function ssh_exec_and_log 
{ 
message=$2 
cleanup=$3 # ++ 

EXEC_LOG_ERR=`$1 2>&1 1>/dev/null` 
EXEC_LOG_RC=$? 

if [ $EXEC_LOG_RC -ne 0 ]; then 
log_error "Command \"$1\" failed: $EXEC_LOG_ERR" 
if [ ! -z $cleanup ]; then # ++ 
$cleanup # ++ 
fi # ++ 


if [ -n "$2" ]; then 
error_message "$2" 
else 
error_message "Error executing $1: $EXEC_LOG_ERR" 
fi 
return $EXEC_LOG_RC 
fi 
} 
i.e. allow a third parameter which is a function to call if the exec fails. 

2. migrate (for my vdc code), add "CleanUp" as a last parameter on the exec_and_log on the last line 


ssh_exec_and_log "virsh --connect $LIBVIRT_URI migrate --live $deploy_id $QEMU_PROTOCOL://$dest_host/system" \ 
"Could not migrate $deploy_id to $dest_host" CleanUp 
3. Then add the following function to migrate; 


function CleanUp 
{ 
VDC=$(dirname $0)/../../../vdc-nebula 
if [ -d "${VDC}" ]; then 
${VDC}/remotes/tm/vdc/postmigrate_fail ${deploy_id} ${dest_host} 
fi 
} 

Cleanup could be extended for other storage options ... ?? 
I guess ideally you would pass the driver through and CleanUp would become completely generic and postmigrate_fail 
would become just another standard routine?? 


hth 
Gareth. 

-- 
	
Gareth Bult 
“The odds of hitting your target go up dramatically when you aim at it.” 
See the status of my current project at http://vdc-store.com 


----- Original Message -----

From: "Ruben S. Montero" <rsmontero at opennebula.org> 
To: "Gareth Bult" <gareth at linux.co.uk> 
Cc: dev at lists.opennebula.org 
Sent: Monday, 13 January, 2014 3:41:50 PM 
Subject: Re: [one-dev] Live migration / recovery 

Totally agree, in fact we've seen this in the past. 

This is fairly easy to add, one_vmm_exec.rb includes a pseudo-dsl to specify the actions, each action includes a fail action. Looking at the code we have also to roll-back the networking configuration on the target host. 

Added a new issue for this. In the meantime we can just use the previous workaround. 

http://dev.opennebula.org/issues/2633 



On Mon, Jan 13, 2014 at 2:59 PM, Gareth Bult < gareth at linux.co.uk > wrote: 



Ok, this almost seems too easy ... :) 

What I was trying to avoid was more tweaking of ON files when installing VDC. 

The issue I see is that each time someone upgraded ON, they will potentially have a chain of 
small patches to apply ... if I supply a few small patches based on "if <vdc installed> - do something extra" 
would you include these in the stock scripts?? 

Gareth. 

-- 
	
Gareth Bult 
“The odds of hitting your target go up dramatically when you aim at it.” 
See the status of my current project at http://vdc-store.com 



From: "Ruben S. Montero" < rsmontero at opennebula.org > 
To: "Gareth Bult" < gareth at linux.co.uk > 
Cc: dev at lists.opennebula.org 
Sent: Sunday, 12 January, 2014 10:36:30 PM 
Subject: Re: [one-dev] Live migration / recovery 

Hi Gareth 

As the migrate script can be easily updated we do not provide any hook for that. I'd go to kvm/migrate, and do a simple if [ $? ... after the virsh command to kill the cache on the target host. 

Cheers 

Ruben 


On Thu, Dec 19, 2013 at 12:54 PM, Gareth Bult < gareth at linux.co.uk > wrote: 

<blockquote>

Hi, 

I implemented live migration for the VDC driver a few weeks back and on the whole it seems to work 
quite well. The "premigrate" script creates a cache instance on the target server and puts the source 
cache into proxy mode, then the "postmigrate" script kills the original cache instance. 

Problem :: if the migration fails, I'm left with a running cache on both the source and target servers, with 
the source cache in proxy mode. I have a 1-line CLI command to revert the issue, but I need to hook into 
the system in order to call it. 

How to do I do this, I guess effectively I need something like "postmigrate_fail" .. ??? 

tia 
Gareth. 

-- 
	Gareth Bult 
“The odds of hitting your target go up dramatically when you aim at it.” 




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-- 
-- 
Ruben S. Montero, PhD 
Project co-Lead and Chief Architect 
OpenNebula - Flexible Enterprise Cloud Made Simple 
www.OpenNebula.org | rsmontero at opennebula.org | @OpenNebula 





</blockquote>




-- 
-- 
Ruben S. Montero, PhD 
Project co-Lead and Chief Architect 
OpenNebula - Flexible Enterprise Cloud Made Simple 
www.OpenNebula.org | rsmontero at opennebula.org | @OpenNebula 

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