Dagger hangs with a BuildKit error: reset the engine container

TL;DR

Find the engine containers with docker container list filtered on the dagger-engine name prefix, then stop and remove them. Optionally run docker volume prune and docker system prune to clear container state, at the cost of a slow first run when the engine is re-provisioned.

Steps

1. Find the engine containers with docker container list filtered on the dagger-engine name prefix, then stop and remove them. Optionally run docker volume prune and docker system prune to clear container state, at the cost of a slow first run when the engine is re-provisioned. If you custom-provisioned the engine, adapt the container names to your setup. Re-run the function afterwards; the engine comes back clean.

When to use

You are seeing this: If you custom-provisioned the engine, adapt the container names to your setup. Use this skill when you run into "Dagger hangs with a BuildKit error: reset the engine container".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Source: Official Dagger troubleshooting docs: a Dagger Function may hang or become unresponsive, eventually failing with BuildKit errors like buildkit failed to respond or container state improper. The documented fix is to stop and remove the Dagger Engine container and optionally clear its state.

Verified resolution: Find the engine containers with docker container list filtered on the dagger-engine name prefix, then stop and remove them. Optionally run docker volume prune and docker system prune to clear container state, at the cost of a slow first run when the engine is re-provisioned. If you custom-provisioned the engine, adapt the container names to your setup. Re-run the function afterwards; the engine comes back clean.

Source URL: https://devel.docs.dagger.io/0.21/reference/troubleshooting/