Troubleshooting Kubernetes Sessions in Posit Workbench: stdin errors within pod

Issue

When attempting to Kubernetes sessions on Posit Workbench hosted within a VM, you may notice sessions get stuck in a "starting" state. Although the sessions appear as running in the details view, they fail to fully initialize due to websocket connection issues between the Kubernetes Launcher plugin and the Kubernetes API.

The logs will populate with the following error:

ERROR Could not write stdin for pod: session-<sessionID>-<User>---rstudio-pro-<SessionType>; LOGGED FROM: rstudio::job_launcher::impls::kubernetes::KubernetesApi::writeStdinToPod

Description

The root cause of this issue is that the Kubernetes Launcher plugin cannot establish websocket connections to the Kubernetes API to write stdin. This typically occurs on the Kubernetes environment, and we would recommend reaching out to your Kubernetes administrators to review your Kubernetes configuration.

Solution

1. Verify that the launcher.kubernetes.conf file exists and is properly configured according to the documentation.
2. For troubleshooting:
   • Temporarily disable SSL for accessing the Kubernetes API if it's enabled
   • Perform a traffic capture from the Kubernetes plugin to the Kubernetes API node while launching a session
   • Enable additional Kubernetes API logging on your Kubernetes vendor (if AKS/EKS) to identify potential traffic blocks
3. Check network policies and firewall rules to ensure websocket traffic is allowed between the Launcher node and the Kubernetes API endpoint

If you're still having issues, you can reach out to Support by opening a ticket here.