In my mind zero-downtime deployment is the gold standard of deployment. Octopus should support this model to the fullest. Given proper tooling (in Octopus) this is very easy to accomplish for customers.

I think most ASP.NET apps should be deployed in the following way:

1. Put the app behind a load balancer such as ARR (built-in and free)
2. For each new deployment create a fresh IIS site
3. Configure the site
4. Request a configurable set of important URLs to start the site and warmup caches
5. Validate, that those URLs return 200 and contain a given check string (a smoke test)
6. If all is OK, switch the HTTP route to the new site
7. After a few minutes the old app is drained. No more requests are in-flight
8. After 20min IIS automatically shuts down the now idle old worker process but it stays functional

It should be possible to easily switch back to old versions. A history of N (= 10?) old fully functioning versions should be kept.

We accomplish: Zero-downtime deployments. Not even app startup time. Safe deployments because the stage site was smoke tested. Ability to rollback instantly. Those are very valuable.

Manually configuring a Blue/Green system is not enough. It should be integrated into Octopus and require minimal developer expertise. I want you to build and support this. I don't want to be able to make mistakes (for example by letting the B/G configuration diverge or by deploying to the wrong slot).

It should not be necessary to write significant amounts of own scripting code to accomplish things. Scrips are often broken and error cases are not well-tested. Building as much of this as possible into Octopus removes sources of errors and gives confidence. Confidence in deployments is very valuable to customers.

If Octopus can support this model with minimal developer effort and with a high degree of confidence then this is clearly the new gold standard of deploying in .NET. There would be no reason not to do this. Using Octopus becomes a no-brainer.

In fact it is hard to find an automated solution for Blue/Green style deployment right now. It has not been productized yet. That's what's prompting this feature request.