Docker Compose allows you to easily define and run multi-container applications. My team just 'inherited' a node.js with a PostgreSQL application. As this is not our main technology stack, debugging and running this through Docker Compose sounds like a perfect pit.
We already had a DOCKERFILE created for the Node.js app so the only thing left to do was create our Docker Compose file:
Nothing special. However, when we tried to start the containers through docker compose up, it failed with the following error message:
>docker compose up
[+] Building 0.0s (0/0)
listing workers for Build: failed to list workers: Unavailable: connection error: desc = "transport: Error while dialing unable to upgrade to h2c, received 404"
After some trial and error, we were able to pinpoint the issue to the 'build' part of the docker compose file:
services:
app:
build: .
If we replaced the build context by a pre-created image instead everything worked. In Docker Compose, the build context is a crucial concept that defines the directory or URL containing the Dockerfile and other necessary files for building a Docker image. The build context can be specified in two main ways: as a single string defining a context path (as we did in the example above) or as a detailed build definition.
By why do we get this error?
It seems somewhat related to BuildKit.
So what is BuildKit?
BuildKit is a feature included with the Docker daemon that simplifies the process of building and packaging container images. It provides new functionality and improves the builds' performance.
Unfortunately for an unknown reason it didn’t want to work in combination with Docker Compose. The way we fixed it for this scenario is by falling back to the legacy builder. This can be done by setting the DOCKER_BUILDKIT environment variable to 0 before running docker compose up:
>SET DOCKER_BUILDKIT=0
>docker compose up