[Bug] Synchronous blocking in _wait_for_sandbox_ready crashes single-worker uvicorn server

[Yuyz0112]

Describe the bug

When creating a sandbox via POST /v1/sandboxes, the server synchronously blocks the asyncio event loop in _wait_for_sandbox_ready, causing liveness probe failures and pod restarts.

Root Cause

1. time.sleep() instead of await asyncio.sleep() in kubernetes_service.py line 185 — when the workload is not yet visible in the K8s API, the code hits time.sleep(poll_interval_seconds) which blocks the entire event loop. Line 212 in the same method correctly uses await asyncio.sleep().

2. Synchronous K8s client calls — get_workload(), get_status(), create_workload() all use the synchronous kubernetes Python client. Each API call blocks the event loop for the duration of the network round-trip.

3. Single uvicorn worker — cli.py calls uvicorn.run() without a workers parameter, defaulting to 1 process with 1 event loop.

Combined, a single POST /v1/sandboxes request can block the event loop for up to 60 seconds (sandbox_create_timeout_seconds). During this time, all other requests — including /health liveness probes — are unserviceable. Kubernetes kills the pod after enough missed probes.

To Reproduce

1. Deploy OpenSandbox server on Kubernetes with default Helm values (single replica, default liveness probe)
2. Create a sandbox with an image that hasn't been pulled yet on the target node
3. Observe server logs: sandbox stays Pending for the full 60s timeout
4. Observe pod restarts due to liveness probe failure

Suggested Fix

• Immediate: Replace time.sleep() on line 185 with await asyncio.sleep().
• Proper: Wrap synchronous K8s client calls in asyncio.loop.run_in_executor(), or switch to an async K8s client.

Environment

• OpenSandbox Server: v0.1.4 (Helm chart 0.1.0)
• Kubernetes: v1.28.15
• Runtime: containerd 1.6.36

[Pangjiping]

You could upgrade opensandbox-server to latest (0.1.9). This issue is fixed by #489

Release notes reference: https://github.com/alibaba/OpenSandbox/releases/tag/server%2Fv0.1.8