docker-paas-list-containers.py
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	#!/usr/bin/env python3

	# -------------------------------------------------------------
	# Docker PaaS - List of containers
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	# Project: Nasqueron
	# Description: Resolve the dependencies between containers
	# into a graph, and use topological sorting
	# to offer an order of containers.
	#
	# This can be used to run every container in
	# the right order to avoid any link issue.
	#
	# License: BSD-2-Clause
	# -------------------------------------------------------------


	from graphlib import TopologicalSorter
	import subprocess
	import sys
	import yaml


	PAAS_METADATA_PATH = "/srv/paas"
	CONTAINER_DELIMITERS = [":"]


	# -------------------------------------------------------------
	# Resolve dependencies
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def solve_containers_order(containers, dependencies):
	graph = {}

	for service, instances in containers.items():
	if service not in dependencies:
	graph \|= {instance: [] for instance in instances}
	continue

	rules = dependencies[service]
	for instance, args in instances.items():
	graph[instance] = solve_dependencies(containers, rules, instance, args)

	return list(TopologicalSorter(graph).static_order())


	def solve_dependencies(containers, rules, instance, args):
	other_instances = []

	if "depends_of_containers" in rules:
	other_instances += [
	get_value(args, container_key)
	for container_key in rules["depends_of_containers"]
	]

	if "depends_of_services" in rules:
	if "network" not in args:
	print(
	f"[WARN] Can't resolve depends_of_services rule for instance {instance} as no network is specified.",
	file=sys.stderr,
	)
	return other_instances

	for service in rules["depends_of_services"]:
	for other_instance, other_args in containers[service].items():
	if "network" not in other_args:
	# For example, pixelfed_redis isn't on a network
	continue

	if args["network"] == other_args["network"]:
	other_instances.append(other_instance)

	return other_instances


	# -------------------------------------------------------------
	# Helper methods to get and clean container values
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def clean_value(container):
	for delimiter in CONTAINER_DELIMITERS:
	pos = container.find(delimiter)
	if pos > -1:
	container = container[:pos]

	return container


	def get_value(args, key):
	if "." in key:
	pos = key.find(".")
	return get_value(args[key[:pos]], key[pos + 1 :])

	try:
	return clean_value(args[key])
	except KeyError:
	print(f"[FATAL] No {key} in {args}", file=sys.stderr)
	sys.exit(1)


	# -------------------------------------------------------------
	# Helper methods to query Salt pillar
	# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


	def query_pillar(key):
	cmd = ["sudo", "salt-call", "pillar.get", key, "--out", "yaml"]
	process = subprocess.run(cmd, capture_output=True)

	if process.returncode != 0:
	raise RuntimeError("Can't query Salt: " + process.stderr)

	return yaml.safe_load(process.stdout)["local"]


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


	def run():
	try:
	containers = query_pillar("docker_containers")
	dependencies = query_pillar("docker_containers_dependencies")
	except RuntimeError as e:
	print(e, file=sys.stderr)
	sys.exit(2)

	for container in solve_containers_order(containers, dependencies):
	print(container)


	if __name__ == "__main__":
	run()

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	Mar 27 2023, 19:42

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