@Marvin in prefect 2 on k8s, what will happen to a flow run, if the prefect server went down and up again after a few seconds?

When running a flow in Prefect 2.x on Kubernetes, if the Prefect server goes down and comes back online after a few seconds, the behavior generally depends on how Prefect is set up and how long the server downtime lasts. Typically, Prefect has been designed with resiliency in mind for such situations: 1. Short Downtime: For brief interruptions, like a few seconds, your flow runs may not be noticeably affected, especially if they are executing in Kubernetes pods. Kubernetes often manages the lifecycle of its pods independently of the Prefect server. The server handles orchestration, metadata storage, and scheduling, while the execution can continue uninterrupted in Kubernetes. 2. Flow Continuation: Prefect agents, which are responsible for kicking off flow runs, will continue to operate even if the server is temporarily unavailable. Once the server is back online, it can resume operation and pick up where it left off. 3. Resiliency and QoS of Agents: If the Prefect agent is running locally on Kubernetes, it can automatically reconcile the current state and update the server with the run status once connectivity is restored. Therefore, if the downtime is brief and non-disruptive to the running pods, the flows should continue running as expected, with any needed updates relayed once connectivity is re-established. For more detailed information, you can refer to the Prefect Kubernetes guide: Running Flows with Kubernetes. It seems there were no specific issues reported in the Prefect GitHub repository regarding server downtime affecting Kubernetes flows. So, it appears to be a generally stable setup for handling short-term server interruptions.

@Marvin in my case, the flow run is stuck in running status although there is no pod anymore. Can it be related to the server downtime?

A flow run being stuck in the "running" status without any active pods could indeed be related to server downtime or other interruptions. When the Prefect server experiences downtime, it might lose the current state or not receive updates about the status changes of pods, especially if those updates happen in its absence. Here are some common causes and solutions: 1. State Update Missing: If the flow run state transition to "completed," "failed," or another terminal state didn't reach the server before it went down, the run could be stuck in "running." You might need to manually update the state through the Prefect UI or CLI. 2. Flow Execution Mismatch: It's possible that the flow completed execution, but the Prefect server didn't capture this change due to downtime. Verifying the logs or execution details can provide insights into what occurred before the server went down. 3. Error in Communication: In Kubernetes, if there's a disruption in the communication between the Prefect Kubernetes agent and the server, this might result in state inconsistency. Restarting the agent can sometimes reconcile these inconsistencies once the server is back up. Unfortunately, I couldn't find specific issues related to "flow stuck running with no pod" in the Prefect GitHub repository, but these are some general areas to investigate based on typical behavior. You might also want to check out the Prefect Community Forum for other user experiences or report the issue if it persists. For further exploration, here's a link to Prefect's Kubernetes guide where you can review the best practices and troubleshooting steps: Running Flows with Kubernetes.