fetch_or_build.py

import time
import sys
import os
import dateutil.parser
from docker import Client

"""
Helper script to determine if you should rebuild the image or use the upstream image
using the modification timestamp of the Dockerfile.

Requires that you first pull down the image from upstream.

Returns either 'build_image' or 'upstream_image'

Usage: fetch_or_build.py JohnDoe/SuperImage Dockerfile
"""

cli = Client(base_url='unix://var/run/docker.sock')

if len(sys.argv) < 2:
    print 'Usage: fetch_or_build.py JohnDoe/SuperImage Dockerfile'
    sys.exit(1)
else:
    IMAGE = sys.argv[1]
    IMAGEFILE = sys.argv[2]


def get_image_timestamp(image):
    """
    Returns UNIX timestamp of image file
    """
    get_image = None

    try:
        get_image = cli.inspect_image(image)
    except:
        print 'Image not found. Exiting.'
        return False

    dt = get_image.get('Created', False)
    if dt:
        parsed_date = dateutil.parser.parse(dt)
        return time.mktime(parsed_date.timetuple())
    else:
        return False


def get_imagefile_timestamp(imagefile):
    if os.path.isfile(imagefile):
        return os.stat(IMAGEFILE).st_mtime
    else:
        return False


def __main__():
    image_ts = get_image_timestamp(IMAGE)
    imagefile_ts = get_imagefile_timestamp(IMAGEFILE)

    if imagefile_ts > image_ts:
        print 'build_image'
    else:
        print 'upstream_image'


__main__()