rebar3_docker

A simple rebar plugin to build docker containers out of an Erlang release.

Build

$ rebar3 compile

Use

Add the plugin to your rebar config:

{plugins, [
    rebar3_docker
]}.

Add docker the configuration as needed to your rebar config:

{docker, [
    % The tag to be used to publish the docker image.
    % If not specified, uses "locale/release_name".
    {tag, "local/somename"},
    % The version of the erlang docker image.
    % If not specified, uses "25.3.2.2"
    {erlang_version, "25.3.2.2"},
    % If you need to further customize the building environment,
    % this option overrides the official erlang image with anything you want.
    % in this case the erlang_version option is ignored 
    % Must still be an alpine based image and contain OTP + Rebar3!
    % {builder_image, "your-repo/your-image:tag"},
    % The name of the application release.
    % If not specified use the first release name found in the relx config.
    {appname, "appname"},
    % The extra packages to install in the building docker layer.
    {build_packages, [            % 
        make,
        gcc,
        "libc-dev",
        "libbsd-dev"
    ]},
    % The git url to be rewritten. Used to access private repository.
    {git_url_rewrites, [
        {"https://github.com/", "git@github.com:"}
    ]},
    % The extra runtime package to install in the final docker image.
    {runtime_packages, []},
    % The ports to be exposed by the docker image.
    {ports, [
        {8888, tcp}
    ]},
    % The docker image environment.
    {env, [
        {'COOKIE', "dummy"},
        {'LOGGER_LEVEL', debug}
    ]},
    % The target platform for the build output
    % You can specify multiple platform if your docker configuration allows it
    % If not specified, then the flag isn't used when building the docker image
    {platform, ["linux/arm64"]}
]}

Be sure to configure a relx release and then just call the plugin build command:

$ rebar3 docker build

Example of a minimal working configuration for a release using port 1234, and defining logging and cookie environment variables:

{plugins, [
    {rebar3_docker, {git, "https://github.com/stritzinger/rebar3_docker.git",
                     {tag, "0.1.0"}}}
]}.
{deps, []}.
{docker, [
    {ports, [{1234, tcp}]},
    {env, [
        {'COOKIE', "dummy"},
        {'LOGGER_LEVEL', debug}
    ]}
]}.
{relx, [
    {release, {myapp, "1.0.0"}, [myapp, sasl]},
    {include_src, false},
    {include_erts, true}
]}.

STARTING A CONTAINER

When the image as been build you can create a container and start it with:

docker create --name myapp local/myapp
docker start myapp

Or run it interactively in console mode:

docker run --rm -it local/myapp console

If your application export some ports, you will need to explicitly publish it with the docker argument -p 1234:1234.

DEBUGGING

When running the build command, the docker configuration is saved in:

_build/[PROFILE]/container/Dockerfile

TODO

Add support for multiple profiles.