Slow configuration changes in WebRoles and WorkerRoles - RoleEnvironment.Changing

Question

We've been suffering for quite some time with what I think is really slow times to apply simple appsetting changes to our deployments. Let me describe our two deployments:
Deployment 1: 1 WebRole, generally two small instances. Changing an appsetting usually takes a tad under 2 minutes to complete.
Deployment 2: 1 WebRole and 3 WorkerRoles, generally two small instances for each role. Changing an appsetting usually takes just about 5 minutes to complete.
This just seems way too long. It's an appsetting after all. So today I started digging in to the RoleEnvironment.Changing event, thinking maybe my roles were being restarted for a simple appsetting change. On each of these roles I implemented a changing
event handler that looks exactly like this:
public void RoleChanging(object sender, RoleEnvironmentChangingEventArgs e)
if (e.Changes.Any(change => change is RoleEnvironmentTopologyChange))
e.Cancel = true;  // restart instance on topology change
else
e.Cancel = false;  // avoid restarting the instance for a setting change
Then in the OnStart() method I hook it up like so:
RoleEnvironment.Changing += RoleChanging;
After deploying old code without this to Prod slot and this new code to Staging slot and making an appsetting change on both there is essentially no difference in timing. So a few questions:
1) Have I misinterpreted how the Changing event works?
2) Is it normal to expect it to take 5 minutes for an appsetting change when I have 4 roles each with two instances? Am I fighting a battle that cannot be won?
Any insight is much appreciated...

Answer 1

Hi,
The code looks fine. To check whether the role still gets shutdown or not, you can handle the role's Stopping event, and write some messages to, say, table storage. Then if you see the message in table storage, it means the role has been restarted. Also please
try to write some messages in the Changing event to check whether your event handler is called.
Best Regards,
Ming Xu
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