Nodejs / Nuxt 3 Paketo Buildpacks: Container start 'failed to launch: determine start command: when there is no default process a command is required'

Question

I have a Nuxt / Vue.js based app (example code here), where I already used Cloud Native Buildpacks to build a container for the Server Side Rendering mode. I'm in the process of migrating to Nuxt 3.x / Vue.js 3.x and updated my Paketo build to a newer builder image accordingly:

pack build ghcr.io/jonashackt/microservice-ui-nuxt-js:latest \
              --builder paketobuildpacks/builder-jammy-base \
              --path .

Sadly when I try to run the container after a successful build using the following command (for how to generally build and run a Nuxt-based container with Cloud Native Buildpacks see this answer):

docker run --rm -i --tty --env "HOST=0.0.0.0" -p 3000:3000 ghcr.io/jonashackt/microservice-ui-nuxt-js

I get the following error:

ERROR: failed to launch: determine start command: when there is no default process a command is required

How can I build a container that runs out-of-the-box or - if thats not possible - override the entrypoint or something?

Answer 1

As taken from this post running Nuxt 3 in Docker takes the following ENTRYPOINT configuration: ENTRYPOINT ["node", ".output/server/index.mjs"]. Thus it should be easy to override this at the docker run command. But luckily I stumbled upon the depts of the Paketo node.js docs, where it is described how to specify a custom entrypoint right at the Paketo build time!

We need to leverage the --env parameter BP_LAUNCHPOINT here. My working pack build command then looks like this:

pack build ghcr.io/jonashackt/microservice-ui-nuxt-js:latest \
          --builder paketobuildpacks/builder-jammy-base \
          --env BP_LAUNCHPOINT=".output/server/index.mjs" \
          --path . 

With that solution the correct entrypoint is baked into the image and we don't need to bother with it at runtime. Thus the docker run command stays the same:

docker run --rm -i --tty --env "HOST=0.0.0.0" -p 3000:3000 ghcr.io/jonashackt/microservice-ui-nuxt-js