I have deployed on prod 10+ java/js microservices in GKE, all is good, none use external volumes, its a simple process in pipeline of generating new image, pushing to container registry and when upgrading the app to new version, just deploy new deployment with the new image and pods using rolling update are upgraded.
My question is how would it look like with Common Lisp application ? The main benefit of the language is that the code can be changed in runtime. Should the config .lisp files be attached as ConfigMap? (update to ConfigMap still requires recreation of pods for the new ConfigMap changes to be applied) Or maybe as some volume? (but what about there being 10x pods of the same deployment? all read from the same volume? what if there are 50 pods or more (wont there be some problems?)) And should the deploy of new version of the application look like v1 and v2 (new pods) or do we use somehow the benefits of runtime changes (with solutions I mentioned above), and the pods version stays the same, while the new code is added via some external solution
I would probably generate an image with the compiled code, and possibly a post-dump image, then rely on Kubernetes to restart pods in your Deployment or StatefulSet in a sensible way. If necessary (and web-based), use Readiness checks to gate what pods will be receiving requests.
As an aside, the projected contents of a ConfigMap should show up in side the container, unless you have specified the filename(s) of the projected keys from the ConfigMap, so it should be possible to keep the source that way, then have either the code itself check for updates or have another mechanism to signal "time for a reload". But, unless you pair that with compilation, you would probably end up with interpreted code.