Can a ReplicaSet be configured to allow in progress updates to complete?


I currently have a kubernetes setup where we are running a decoupled drupal/gatsby app. The drupal acts as a content repository that gatsby pulls from when building. Drupal is also configured through a custom module to connect to the k8s api and patch the deployment gatsby runs under. Gatsby doesn't run persistently, instead this deployment uses gatsby as an init container to build the site so that it can then be served by a nginx container. By patching the deployment(modifying a label) a new replicaset is created which forces a new gatsby build, ultimately replacing the old build.

This seems to work well and I'm reasonably happy with it except for one aspect. There is currently an issue with the default scaling behaviour of replica sets when it comes to multiple subsequent content edits. When you make a subsequent content edit within drupal it will still contact the k8s api and patch the deployment. This results in a new replicaset being created, the original replicaset being left as is, the previous replicaset being scaled down and any pods that are currently being created(gatsby building) are killed. I can see why this is probably desirable in most situations but for me this increases the amount of time that it takes for you to be able to see these changes on the site. If multiple people are using drupal at the same time making edits this will be compounded and could become problematic.

Ideally I would like the containers that are currently building to be able to complete and for those replicasets to finish scaling up, queuing another replicaset to be created once this is completed. This would allow any updates in the first build to be deployed asap, whilst queueing up another build immediately after to include any subsequent content, and this could continue for as long as the load is there to require it and no longer. Is there any way to accomplish this?

-- Nick Dancer

1 Answer


It is the regular behavior of Kubernetes. When you update a Deployment it creates new ReplicaSet and respectively a Pod according to new settings. Kubernetes keeps some old ReplicatSets in case of possible roll-backs.

If I understand your question correctly. You cannot change this behavior, so you need to do something with architecture of your application.

-- Artem Golenyaev
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