resolve-containers-from-compose.py
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	dereckson
	Apr 11 2022, 17:13

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roles/paas-docker/docker/files/resolve-containers-from-compose.py
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	#!/usr/bin/env python3

	# -------------------------------------------------------------
	# Resolve docker-compose containers names
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	# Project: Nasqueron
	# Description: Guess by naive heuristics the containers
	# run from a docker-compose YAML configuration.
	#
	# As Docker doesn't record any link between
	# a docker compose or stack information and the
	# running containers, the approach consist to
	# compare the containers names in a config file,
	# with the running containers on the machine.
	# License: BSD-2-Clause
	# -------------------------------------------------------------


	import subprocess
	import sys
	import yaml


	# -------------------------------------------------------------
	# Parse docker-compose.yml
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def parse_compose_config(config_path):
	with open(config_path) as fd:
	return yaml.safe_load(fd)


	def resolve_container_prefix(service, image):
	image_short = image.split("/")[1]
	return image_short + "_" + service + "_"


	def resolve_containers_prefix(compose_config):
	return [
	resolve_container_prefix(name, args["image"])
	for name, args in compose_config["services"].items()
	]


	# -------------------------------------------------------------
	# Interact with Docker CLI
	#
	# This avoid to have to deal with version conflicts with docker
	# Python libraries.
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def get_running_container_names():
	# TODO: avoid to invoke shell and spawn only the docker process
	process = subprocess.run(
	"docker ps \| awk 'NR!=1 {print $NF}'", capture_output=True, shell=True
	)

	if process.returncode != 0:
	raise RuntimeError("Can't get containers: " + process.stderr.decode().strip())

	return process.stdout.decode().strip().split("\n")


	# -------------------------------------------------------------
	# Cross config file and running Docker information
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def is_container_name_match(config_container, running_container):
	# The service web for the image acme/foo is foo_web_1:
	# <image name>_<service name>_<number>
	n = len(config_container)
	return (
	running_container.startswith(config_container)
	and running_container[n:].isnumeric()
	)


	def resolve_docker_compose_containers_name(config_path):
	config = parse_compose_config(config_path)

	config_containers = resolve_containers_prefix(config)
	running_containers = get_running_container_names()

	return [
	running_container
	for config_container in config_containers
	for running_container in running_containers
	if is_container_name_match(config_container, running_container)
	]


	# -------------------------------------------------------------
	# Application entry point
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def run(config_path):
	containers = resolve_docker_compose_containers_name(config_path)
	print(" ".join(containers))


	if __name__ == "__main__":
	argc = len(sys.argv)

	if argc < 2:
	print(f"Usage: {sys.argv[0]} <path to docker-compose.yml>", file=sys.stderr)
	sys.exit(1)

	run(sys.argv[1])

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