Management For Developing Applications in Docker

This library is intended to make it easier to develop applications when using docker. It allows you to set up initial docker configuration, and to execute commands inside the main docker container from the host machine. It aims to be similar to Fabric, but for local development with docker applications.

Getting Started

A typical setup looks something like this:

1. A docker-compose.yml (or a docker setup that has been created manually) with at least one "main" python container. For instance, if you are developing a web application, you might have a redis container, a database container, and a web container, and the web container is the one that contains your python code. You can also use custom @dm.command functions to set up your docker cluster without docker-compose, if you want.

2. A script that is the entrypoint for your management command. I typically use ./do in the project's root directory. It looks something like this (for a Django application, commands will be different depending on the language/framework you are using and your goals):

    #!/usr/bin/env python
   
    import os
   
    import dockerman as dm
   
    # enable buildkit
    os.environ["DOCKER_BUILDKIT"] = "1"
    os.environ["COMPOSE_DOCKER_CLI_BUILD"] = "1"
   
   
    @dm.command(passthrough=True)
    def bash(args):
        """Bash shell on the web container."""
        dm.crun("bash", args)
   
   
    @dm.command()
    def start(args):
        """Start all services."""
        dm.run("docker-compose up -d")
   
   
    @dm.command()
    def stop(args):
        """Stop all services."""
        dm.run("docker-compose stop")
   
   
    @dm.command()
    def dbshell(args):
        """Execute a database shell."""
        dm.crun("psql -U myuser mydatabase", container="database")
   
   
    @dm.command()
    def shell(args):
        """Open a django shell on the web container."""
        dm.crun("django-admin shell", args)
   
   
    @dm.command(passthrough=True)
    def manage(args):
        """Run a django management command."""
        dm.crun("django-admin", args)
   
   
    @dm.command(
        dm.option('--name', help='Container name'),
    )
    def reset_container(args):
        """Reset a container."""
        dm.run(f"docker-compose stop {args.name}")
        dm.run(f"docker-compose rm {args.name}")
        dm.run("docker-compose up -d")
   
   
    if __name__ == "__main__":
        dm.set_default_container("web")
        dm.main()

With this setup, you can run commands like ./do help, ./do shell, etc.

Concepts

dm.command

This is a decorator that turns a function into a command. The command will have the same name as the function it decorates, and the docstring will be the documentation that appears when you type ./do help or ./do help [command]. All underscores will be converted to hyphens in the resulting command name.

If you specify passthrough=True, all extra command line arguments will be passed to any dm.crun or dm.run statements executed within the function (this is the purpose of the command function receiving the args parameter, and passing that same args parameter to dm.crun and dm.run).

For example, if you'd like to run Django management commands in the web container:

@dm.command(passthrough=True)
def manage(args):
    """Run Django management commands."""
    dm.crun("django-admin", args)

Then when you run something like:

$ ./do manage makemigrations --name add_user_is_active_field accounts

The makemigrations --name add_user_is_active_field accounts will be passed through to django-admin on the container.

Default Commands

Another possible argument to @dm.command is default=True. This will cause the system to use this command for everything that doesn't match any other command. For instance, instead of defining a shell command for django-admin, you could do the following:

@dm.command(passthrough=True, default=True)
def manage(args):
    """Run Django management commands."""
    dm.crun("django-admin", args)

Then, if you type ./do shell and there is no matching shell command defined, it will act as though you typed ./do manage shell.

dm.run

This runs a command on the host. Things like dm.run('docker network add test') are typical.

dm.crun

This runs a command in a docker container. Passing container="web" will tell it to run on the "web" container. If you do not pass container, it will use the default container specified in dm.set_default_container.

dm.option

You can pass one or more dm.option arguments to the dm.command decorator. These will set up argument options for your command, using the argparse module. They are passed directly to parser.add_argument, so they have the same parameters.

An example:

@dm.command(@dm.option("--name", dest="name", help="Your name"))
def hello(args):
    print(f"Hello, {args.name}!")

dm.log, dm.info, dm.warning, dm.error

These are logging statements. Each one has it's own color indicative of the type of message you want to show. For example:

@dm.command(@dm.option("--name"))
def hello(args):
    if args.name.lower() in ("tyler", "steve", "james"):
        dm.error(f"Sorry, your name cannot be {args.name}. Get a new one.")
        sys.exit(1)
    print(f"Hello, {args.name}!")