Add README and script

1 files changed, 192 insertions, 0 deletions

diff --git a/rbuild.py b/rbuild.py
new file mode 100644
index 0000000..c39e33e
--- /dev/null
+++ b/rbuild.py
@@ -0,0 +1,192 @@
+#!/bin/env python3
+
+import argparse
+import hashlib
+import json
+import subprocess
+import tempfile
+import os
+import sys
+from datetime import datetime
+from typing import (
+	List,
+	Dict,
+	Any,
+	Optional,
+	Set,
+	Tuple
+)
+
+# Constants for labels
+CONFIG_HASH_LABEL = 'rbuild.config_sha256'
+BUILD_TIME_LABEL = 'rbuild.build_time'
+COMPOSE_NAME_LABEL = 'rbuild.compose_name'
+
+def parse_env_var_to_int(key: str, default: Optional[int] = None) -> int:
+	"""Parses an environment variable to an integer value."""
+	try:
+		timeout = os.getenv(key, default=default)
+		return int(timeout)
+	except (ValueError, TypeError):
+		raise ValueError(f'Failed to parse "{key}", should be a numeric time in seconds')
+
+def die(*kargs, exit_status : int = 1, **kwargs):
+	"""Kill the program with a custom message"""
+	print(*kargs, **kwargs, file=sys.stderr)
+	sys.exit(exit_status)
+
+def run_command(command: List[str]) -> str:
+	"""Runs a command and returns the stdout."""
+
+	command_str = ' '.join(command)
+	try:
+		result = subprocess.run(command, stdout=subprocess.PIPE, text=True, check=True)
+	except subprocess.CalledProcessError as e:
+		die(f'Failed to run command: "{command_str}", exited={e.returncode}')
+	except subprocess.TimeoutExpired:
+		die(f'Command timed out: "{command_str}"')
+	return result.stdout
+
+def is_image_expired(image: str, config_sha256: str, build_ttl: int) -> bool:
+	"""Checks if a docker image is expired."""
+	inspect_output = run_command(['docker', 'inspect', image])
+	labels = json.loads(inspect_output)[0]['Config']['Labels']
+
+	if labels.get('rbuild.config_sha256') != config_sha256:
+		return True
+
+	build_time = datetime.fromisoformat(labels.get('rbuild.build_time'))
+	delta = datetime.utcnow() - build_time
+
+	return delta.total_seconds() > build_ttl
+
+def remove_images(compose_name : str, operating_images : Set[str] = set()):
+	""" Remove images created by rbuild, provided operating_images it purges stale images"""
+	stale_images = []
+
+	image_list_output = run_command(['docker', 'image', 'list', '--format', 'json'])
+	for image_output in image_list_output.split('\n'):
+
+		if not image_output:
+			continue
+
+		img = json.loads(image_output)
+
+		image_inspect_output = run_command(['docker', 'inspect', img['ID']])
+
+		image_details = json.loads(image_inspect_output)[0]
+
+		labels = image_details['Config']['Labels']
+
+		image_name = labels.get('rbuild.compose_name') if labels else None
+
+		if image_name != compose_name or \
+			any((tag in operating_images for tag in image_details['RepoTags'])):
+			continue
+
+		stale_images.append(img['ID'])
+
+	if stale_images:
+		run_command(['docker', 'image', 'rm', *stale_images])
+
+def read_config(filename : str) -> Tuple[str, Dict]:
+	""" Read the config from disk """
+
+	config_output = run_command(['docker', 'compose', '-f', filename, 'config', '--format', 'json'])
+
+	config = json.loads(config_output)
+
+	return config_output, config
+
+def build_main(filename: str, force_rebuild=False) -> None:
+	config_output, config = read_config(filename)
+
+	config_sha256 = hashlib.sha256(config_output.encode()).hexdigest()
+
+	name = config.get('name')
+
+	# 2. Determine if working images are expired
+	ps_output = run_command(['docker', 'compose', '-f', filename, 'ps', '--all', '--format', 'json'])
+	containers = json.loads(ps_output)
+
+	any_expired = False
+
+	for container in containers:
+		image = container.get('Image')
+		if is_image_expired(image, config_sha256, BUILD_TTL):
+			any_expired = True
+			break
+
+	if not (force_rebuild or any_expired or len(containers) == 0):
+		exit(0)
+
+	# 3. Modify config
+	build_time = datetime.utcnow()
+	operating_images = set()
+	for service_name, service_data in config['services'].items():
+		labels = service_data.setdefault('build', {}).setdefault('labels', {})
+
+		labels['rbuild.config_sha256'] = config_sha256
+		labels['rbuild.build_time'] = build_time.isoformat()
+		labels['rbuild.compose_name'] = name
+
+		new_image = f'rbuild-{name}-{service_name}:{build_time.timestamp()}'
+		operating_images.add(new_image)
+		service_data['image'] = new_image
+
+	# 4. Save this config to a temporary JSON file
+	with tempfile.NamedTemporaryFile(mode='w+', suffix='.json') as temp_file:
+		json.dump(config, temp_file)
+
+		temp_file.flush()
+
+		# 5. Build and bring the dockerfile up
+		subprocess.run(['docker', 'compose', '-f', temp_file.name, 'build', '--no-cache', '--pull'], check=True)
+		subprocess.run([
+			'docker', 'compose', '-f', temp_file.name,
+			'up', '--remove-orphans', '--detach', f'--wait-timeout={UP_TIMEOUT_PERIOD}'
+		], check=True)
+
+	# 6. Get rid of stale images
+	remove_images(name, operating_images)
+
+def remove_main(filename : str) -> None:
+	""" Remove all images """
+
+	_, config = read_config(filename)
+	compose_name = config['name']
+	remove_images(compose_name)
+	sys.exit(0)
+
+if __name__ == '__main__':
+	BUILD_TTL = parse_env_var_to_int('BUILD_TTL', default=(24 * 60 * 60))
+	UP_TIMEOUT_PERIOD = parse_env_var_to_int('UP_TIMEOUT_PERIOD', default=60)
+
+	parser = argparse.ArgumentParser(description='Automatically rebuild a series of containers with docker compose.')
+
+	parser.add_argument('filename', type=str, help='The docker-compose file to use.')
+
+	parser.add_argument('--build-period', type=int, default=BUILD_TTL, help='Time images are allowed to live (in seconds.)')
+	parser.add_argument('--up-timeout-period', type=int, default=UP_TIMEOUT_PERIOD, help='Up timeout period in seconds.')
+	parser.add_argument('--force-rebuild', default=False, action='store_true', help='Force all containers to be rebuilt')
+
+	# Add remove-images to the mutually exclusive group
+	parser.add_argument('--remove-images', default=False, action='store_true', help='Remove all images')
+
+	try:
+		import argcomplete
+		argcomplete.autocomplete(parser)
+	except ImportError:
+		pass
+
+	args = parser.parse_args()
+
+	# Check for mutual exclusivity
+	if args.remove_images and args.force_rebuild:
+		die("Error: --remove-images cannot be used with --force-rebuild")
+
+	if args.remove_images:
+		remove_main(args.filename)
+
+	build_main(args.filename, force_rebuild=args.force_rebuild)
+