pantsbuild / example-docker

An example repository to demonstrate Docker support in Pants

example-docker

An example repository to demonstrate Pantsbuild's experimental Docker support.

See pantsbuild.org for much more detailed documentation.

This is only one possible way of laying out your project with Pantsbuild. See pantsbuild.org/docs/source-roots#examples for some other example layouts.

Note: Pantsbuild and Pants will be used interchangebly, they refer to the same thing, the Pants Build System.

Running Pantsbuild

You run Pants goals using the pants launcher binary, which will bootstrap the version of Pants configured for this repo if necessary.

See here for how to install the pants binary.

Use pants --version to see the version of Pants configured for the repo (which you can also find in pants.toml).

Goals

Pants commands are called goals. You can get a list of goals with

pants help goals

Most goals take arguments to run on. To run on a single directory, use the directory name with : at the end. To recursively run on a directory and all its subdirectories, add :: to the end.

For example:

pants lint src/python/hello_world: src/docker::

You can run on all changed files:

pants --changed-since=HEAD lint

You can run on all changed files, and any of their "dependees":

pants --changed-since=HEAD --changed-dependees=transitive test

Example Goals

Try these out in this repo!

Run a Docker image

pants run src/docker/hello_world:python
pants run src/docker/hello_world:shell

List targets

pants list ::  # All targets.
pants list 'src/**/*.py'  # Just targets containing Python code.

Run linters, formatters and fixers

pants fix lint ::  # First format and fix, then lint all sources.

Count lines of code

pants count-loc '**/*'

Dynamic image tag

The documentation for dynamic image tagging has an example implementation here showcasing how it works.

DYNAMIC_TAG=$(date +%Y.%m.%d) pants package src/docker/dynamic_tags

10:47:43.89 [INFO] Completed: Building docker image dynamic_tags:1.0-2022.03.15
10:47:43.89 [INFO] Built docker image: dynamic_tags:1.0-2022.03.15
Docker image ID: sha256:8f6922aec0de7c147862672fa2cef4bd72f51e02b5a06089b0383355410b79f2

DYNAMIC_TAG=$(date +%Y.%m.%d) pants run src/docker/dynamic_tags
10:47:43.89 [INFO] Completed: Building docker image dynamic_tags:1.0-2022.03.15
  ____
| demo |
  ====
    \
     \
       ^__^
       (oo)\_______
       (__)\       )\/\
           ||----w |
           ||     ||

example-docker's Issues

Container not re-used on code change

I have been trying this example and wanted to check whether hot code reloading also works when running the Docker container with pants. What I noticed is, that on every code change a new container is run. For a lot of code changes, this would spin up a lot of containers. Am I missing something to be configured?