Buildbarn action stuck in queue
The scheduler accepted the action but has not assigned it to an eligible worker. Queue growth is usually a matching or capacity signal, not an action-execution failure.
Common causes
- No workers match the action platform properties
- The matching size class has insufficient capacity
- Workers are disconnected or unhealthy
- A burst of long actions is consuming the available concurrency
What to check
- Compare action platform properties with registered worker platforms
- Inspect queue depth and oldest-operation age by platform queue
- Check worker registration, heartbeats, and active concurrency
- Separate sustained saturation from one malformed platform request
Primary sources
Use these references to confirm protocol and version-specific behavior.
Investigate with build-level evidence
Hermetiq correlates Bazel actions, cache behavior, Buildbarn infrastructure, and remote-execution timing so teams can move from a status code to the build and system behavior behind it.
Technical review: July 20, 2026 · Verify flags and behavior against the Bazel and Buildbarn versions deployed in your environment.