[justinsaccount]

Ok, great... I have a bunch of simple projects like that, one web instance running on a single host.

How do I safely upgrade it without downtime? Ensuring that the new version starts up properly and can receive traffic before sending it requests and stopping the old one?

With k8s: kubectl set image deployment/my-deployment mycontainer=myimage:1.9.1 (or just use kubectl apply -f)

With your nginx config: ????

[falcolas]

That moves the goalposts a bit. We've gone from a simple service to a fleet of highly available services on multiple hosts with zero downtime requirements.

At which point, sure, use Kubernetes.

[justinsaccount]

No.. I didn't move the goalposts at all.

Still A single service on a single machine, how do I safely upgrade it?

A rolling deployment in k8s does work the same way on a single host with minikube as it does on a 1000 node cluster, but I'm still just asking about the single host case.

[wgjordan]

> Still A single service on a single machine, how do I safely upgrade it?

Depending on your OS-package's provided init script (here Ubuntu), it's as simple as `service nginx reload`, (`service nginx upgrade` if upgrading nginx itself).

Or skip the init script entirely with `/usr/sbin/nginx -s reload`.

[justinsaccount]

I am asking how one would safely upgrade the service that nginx is proxying to, not how to restart nginx.

[icedchai]

You could do "blue-green" deployments with port numbers... service rev A is on port 1001, service rev B is on port 1002... deploy new rev... change nginx config to point to 1002... roll back, you repoint to 1001...

[justinsaccount]

So I need to write some code to keep track of which of A or B is running, then something else to template out a nginx configuration to switch between the two. Then I need to figure out how to upgrade the inactive one, test it, flip the port over in nginx, and flip it back if it breaks.

Or

kubectl apply -f app.yaml

Which is less complex?

[Aeolun]

sudo apt-get upgrade?

Lets not make it more difficult than it has to be.

[justinsaccount]

The new version fails to restart properly. Your site is now down. You upgraded the package so now you no longer have the old version on disk and can't easily start the previous version.

Let's not pretend that blindly upgrading a package is the same thing as safely rolling out the new version of a service.