My friend Ed’s capacity to automate stuff is quite awesome. Yesterday he automated a way of making our Continuous Integration system alert us when one of the agents went offline. This is already automated in our CI system, but it just wasn’t automated enough for Ed’s liking, so he wrote a script. His script will send us an email whenever an agent goes offline. I haven’t recieved any emails so far, so either the agents are all fine, or the script isn’t working – there’s no way to tell, so I expect Ed will automate a way of telling us whether the automated script has run successfully.

Then today, in the true spirit of “DevOps”, he tells me he has automated a way of reverting our CI agents to a snapshot and plugged it in to the CI system, for good measure. The CI agents are all VMs deployed by VMware, so Ed has used the PowerCLI plugin to do the automation.

Basically the script just iterates over a list of VMs which are in a particular resource pool, and reverts them all to a snaphot. Here’s the script itself:

connect-viserver myserver.mycompany.com -User username -Password secret

$vmcsv = import-csv $args[0]

ForEach($line in $vmcsv){
Get-VM $line.name | Get-Snapshot -Name $line.snap | Set-VM -VM $line.name -confirm:$false
Get-VM $line.name | Start-VM
}

disconnect-viserver -confirm:$false

import-csv looks something like this:

name, snap
linuxSvr1, snap1
xpSvr1, snap1
xpSvrIE7, snap1
w7SvrIE8, snap1
w7SvrIE9, snap1

Ed has added the execution of this script to our CI system, so any of the devs can revert their CI servers to a snapshot by simply pressing a button. They key thing here is to organise VMs into resource pools. We’ve got dedicated resource pools per dev team/project, so it’s safe enough to allow the devs to do this without running the risk of affecting anyone elses CI builds.

You can follow Ed on twitter (@ElMundio87) and check out his blog here: http://www.elmundio.net/blog/