Support for Docker contexts, or a Docker socket in an alternative location

[breun]

Description

I'm using Colima to run Docker containers on macOS and pulling and running images via the docker CLI tool works just fine. Colima created and activated a Docker context with a socket in $HOME/.colima/default/docker.sock:

❯ docker context ls
NAME              DESCRIPTION                               DOCKER ENDPOINT                                       KUBERNETES ENDPOINT                ORCHESTRATOR
colima *          colima                                    unix:///Users/nbreunese/.colima/default/docker.sock                                      
default           Current DOCKER_HOST based configuration   unix:///var/run/docker.sock                           https://35.204.107.135 (default)   swarm
rancher-desktop   Rancher Desktop moby context              unix:///Users/nbreunese/.rd/docker.sock

It seems that docker-maven-plugin does not find or use this Docker context, because when I run a Maven project which uses docker-maven-plugin I get the following error:

No <dockerHost> given, no DOCKER_HOST environment variable, no read/writable '/var/run/docker.sock' or '//./pipe/docker_engine' and no external provider like Docker machine configured

According to the Global Configuration section in the documentation, docker-maven-plugin checks /var/run/docker.sock on macOS, but I don't see mention of support for Docker contexts. Does docker-maven-plugin support Docker contexts? If not, could this be added? If it does, it does not seem to work for me. In that case, is there a way to specify a local Docker socket via the DOCKER_HOST environment variable?

Info

• docker-maven-plugin version : 0.40.1
• Maven version (mvn -v) : 3.8.6

• Docker version :

❯ docker version
Client:
 Version:           20.10.14
 API version:       1.41
 Go version:        go1.18.1
 Git commit:        0a7772e
 Built:             Tue May 03 01:09:34 2022
 OS/Arch:           darwin/amd64
 Context:           colima
 Experimental:      true

Server:
 Engine:
  Version:          20.10.11
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.16.15
  Git commit:       847da184ad5048b27f5bdf9d53d070f731b43180
  Built:            Wed Apr 13 23:41:08 2022
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          v1.5.8
  GitCommit:        1e5ef943eb76627a6d3b6de8cd1ef6537f393a71
 runc:
  Version:          1.0.0-rc95
  GitCommit:        b9ee9c6314599f1b4a7f497e1f1f856fe433d3b7
 docker-init:
  Version:          0.19.0
  GitCommit: 

• If it's a bug, how to reproduce : Run Colima and then a Maven build with docker-maven-plugin
• If it's a feature request, what is your use case : Using docker-maven-plugin that works with Colima (and other tools that don't put the Docker socket at /var/run/docker.sock.
• Sample project : Any project that uses docker-maven-plugin

[rhuss]

You are correct, dmp doesn't support Docker contexts, but does it work if you set the environment variable DOCKER_HOST to "unix:///Users/nbreunese/.colima/default/docker.sock" (or alternatively the <dockerHost> plugin configuration variable) ?

[breun]

Setting DOCKER_HOST like that indeed works, thanks! It would still be nice if docker-maven-plugin would add support for Docker contexts, but I can use this as a workaround for now.