Pod.exec stdin never closes

[jacobtomlinson]

Which project are you reporting a bug for?

kr8s

What happened?

When writing to stdin with Pod.exec(..., stdin=...) the stream is never closed. This means if the process being executed is waiting for the stdin file to be closed it will hang forever.

import kr8s, sys
pod = kr8s.objects.Pod.get("my-pod")
pod.exec(["cat"], stdin="hello", stdout=sys.stdout.buffer)
# I would expect `hello` to be printed to stdout but it just hangs forever

This seems to be a limitation of the websocket API in Kubernetes and is being tracked in kubernetes/kubernetes#89899. There is a KEP which should handle fixing this in a future release of Kubernetes kubernetes/enhancements#4016.

[jacobtomlinson]

It looks like this has been resolved upstream via the V5 RemoteCommand protocol added in kubernetes/kubernetes#119157. This will be included in Kubernetes v1.29.

Once this release is out we need to retest this and make any appropriate changes. We may also need to add a check so that if the user tries to pass stdin on a cluster that is <1.29 they get a warning or error.

To close stdin we will need to send the channel ID (0) to the close channel 255.

[jacobtomlinson]

Support for 1.29 just landed in #257 so we are no longer blocked in updating to the V5 RemoteCommand protocol.

We will need to decide what happens when folks are on older Kubernetes versions, maybe a warning or exception if they try and use stdin?