pull-images.py

#!/usr/bin/env python3
"""
Pull images for `docker-compose build` with ignore filter.

https://github.com/docker/compose/issues/6668

The code is placed into public domain.
"""

import argparse
from subprocess import run

# parsing yaml in sorted way
import oyaml as yaml


def get_image_heir(composefile, debug=print):
    debug('Parsing ' + composefile)
    pose = yaml.safe_load(open(composefile, 'r'))

    # pairs [level, image, locality]
    # level - hierarchy starting from 0 (like indentation)
    # image - image name to pull
    # locality - None, 'local', `remote` - tested during run
    imagestack = []
    images = []

    for key, val in pose['services'].items():
        # --- val format ---
        # app:
        #  image: registry.example.com/dev/backend_app:latest
        #  build:
        #    context: .
        #    dockerfile: ./srv/app/Dockerfile
        #    target: dev

        # service = key
        if 'build' not in val:
            continue
        dockerfile = val['build']['dockerfile']
        debug('Found Dockerfile: ' + dockerfile)
        # if 'target' in val['build']:
        #    target = val['build']['target']
        # else:
        #    target = None

        level = 0
        with open(dockerfile, 'r') as dockery:
            for line in dockery:
                if line.startswith('FROM'):
                    # FROM python
                    image = line.split()[1]
                    debug('  Found image: ' + image)
                    if image not in images:
                        images.append(image)
                        imagestack.append([level, image, None])
    return imagestack


def pull_images(imagestack, ignore=[], debug=print):
    for level, image, locality in imagestack:
        if image in ignore:
            debug('Ignoring ' + image)
        else:
            debug('Pulling ' + image)
            cmd = 'docker pull {}'.format(image)
            run(cmd, shell=True, check=True)


if __name__ == '__main__':
    desc = 'Pull images for `docker-compose build` with ignore filter.'
    parser = argparse.ArgumentParser(description=desc)
    parser.add_argument('composefile', metavar='<docker-compose.yml>',
                        help='docker-compose.yml with build sections')
    parser.add_argument('-i', '--ignore', metavar='image1,image2,...',
                        help='images to ignore while pulling')
    args = parser.parse_args()
    composefile = args.composefile
    ignore = [] if args.ignore is None else args.ignore.split(',')

    imagestack = get_image_heir(composefile)
    # for level, image, locality in imagestack:
    #    print("{}{} - {}".format(" "*level, image, locality))

    pull_images(imagestack, ignore=ignore)