legitimator-daemon

#!/usr/bin/python3 -tt

# Twisted hosts our website and helps with async tasks.
# The application threads are structured in the following way:
#
#  reactor
#   `-- manager (1 thread)
#   `-- workers (2 threads)
#   `-- website (4 threads)
#
from twisted.internet import reactor
from twisted.web.wsgi import WSGIResource
from twisted.web.server import Site
from twisted.python.threadpool import ThreadPool
from twisted.python import log

# Data are accessed through SQLSoup, using SQLAlchemy.
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy import create_engine
from sqlsoup import SQLSoup

# Command line arguments follow the GNU conventions.
from getopt import gnu_getopt
from sys import argv, stderr

# Configuration is stored in a simple ini file.
from configparser import ConfigParser

# Import all the application handles.
from legitimator import make_site, Manager, AccessModel


if __name__ == '__main__':
    def do_start(config):
        # Start Twisted logging to console.
        log.startLogging(stderr)

        # Read database configuration options.
        db_url = config.get('database', 'url')

        # Read website configuration options.
        http_debug = config.getboolean('http', 'debug', fallback=False)
        http_host = config.get('http', 'host', fallback='localhost')
        http_port = config.getint('http', 'port', fallback=5000)
        http_pool = config.getint('http', 'pool_size', fallback=4)

        # Read role mappings.
        access_model = AccessModel(config.items('access'))

        # Default to much saner database query defaults and always
        # commit and/or flush statements explicitly.
        factory = sessionmaker(autocommit=False, autoflush=False)

        # Prepare database connection with table reflection.
        engine = create_engine(db_url)
        session = scoped_session(sessionmaker(autocommit=False, autoflush=False))
        db = SQLSoup(engine, session=session)

        # Extract manager options, sans the pool_size we handle here.
        manager_opts = dict(config.items('manager'))
        manager_pool = int(manager_opts.pop('pool_size', 2))

        # Set the correct thread pool size for the manager.
        reactor.suggestThreadPoolSize(manager_pool)

        # Prepare the manager that runs in an exclusive thread.
        manager = Manager(db, **manager_opts)

        # Prepare the website that will get exposed to the users.
        site = make_site(db, manager, access_model, debug=http_debug)

        # Prepare WSGI site with a separate thread pool.
        pool = ThreadPool(http_pool, http_pool, 'http')
        site = Site(WSGIResource(reactor, pool, site))
        pool.start()

        # Bind the website to it's address.
        reactor.listenTCP(http_port, site, interface=http_host)

        # Run the Twisted reactor until the user terminates us.
        reactor.run()

        # Kill the HTTP ThreadPool.
        pool.stop()


    def do_help(*args, **kwargs):
        print('Usage: legitimator-daemon [--config=/etc/ntk/legitimator.ini]')
        print('Runs the legitimator-daemon with given configuration.')
        print('')
        print('OPTIONS:')
        print('  --help, -h          Display this help.')
        print('  --version, -V       Display version info.')
        print('')
        print('  --config, -c file   Load alternative configuration file.')

    def do_version(*args, **kwargs):
        print('legitimator (NTK) 1')

    # Parse command line arguments.
    opts, args = gnu_getopt(argv, 'hVc:', ['help', 'version', 'config='])

    action = do_start
    config_path = '/etc/ntk/legitimator.ini'

    for k, v in opts:
        if k in ('--help', '-h'):
            action = do_help
        elif k in ('--version', '-V'):
            action = do_version
        elif k in ('--config', '-c'):
            config_path = v

    # Load the configuration from file.
    if action not in (do_help, do_version):
        config = ConfigParser()
        config.read(config_path)

    # Perform the selected action.
    action(config=config)

# vim:set sw=4 ts=4 et:
# -*- coding: utf-8 -*-