Python script to build simple Docker images using GO binaries (located in $GOPATH/bin)

build-img.py

import argparse
import io
import os
import tarfile

import docker

parser = argparse.ArgumentParser()
parser.add_argument('app', help='GO app name (located in $GOPATH/bin/)')
parser.add_argument('tag', help='Docker image tag')
parser.add_argument('--save-ctx', help='save Docker build context', action='store_true')
args = parser.parse_args()

# check if the given app exists in $GOPATH/bin
gopath = os.getenv('GOPATH')
if (gopath is None):
    raise Exception('GOPATH not set')
app_path = os.path.join(gopath, 'bin', args.app)
if not os.path.exists(app_path):
    raise Exception(f'file {app_path} not found')

with io.BytesIO() as buff:
    # create tar.gz with context
    with tarfile.open(fileobj=buff, mode='w:gz') as ctx:
        # Dockerfile
        dockerfile = (f'''FROM buildpack-deps:jessie-curl
COPY {args.app} /usr/bin/
ENTRYPOINT ["/usr/bin/{args.app}"]''').encode("utf-8")
        df_info = tarfile.TarInfo('Dockerfile')
        df_info.size = len(dockerfile)
        ctx.addfile(df_info, io.BytesIO(dockerfile))
        # $GOPATH/bin/app
        ctx.add(app_path, arcname=args.app)
        ctx.close()

    # save context to <app>.tar.gz
    if args.save_ctx:
        with open(f'{args.app}.tar.gz', 'wb') as f:
            f.write(buff.getvalue())

    # build the image using buff as build context
    client = docker.from_env()
    client.images.pull('buildpack-deps', 'jessie-curl')
    buff.seek(0)
    img = client.images.build(fileobj=buff, tag=args.tag, custom_context=True, encoding='gzip')