+++ /dev/null
-import json
-from invirt.common import *
-from os.path import getmtime
-
-default_src_path = '/etc/invirt/master.yaml'
-default_cache_path = '/var/lib/invirt/cache.json'
-lock_file = '/var/lib/invirt/cache.lock'
-
-def load(src_path = default_src_path,
- cache_path = default_cache_path,
- force_refresh = False):
- """
- Try loading the configuration from the faster-to-load JSON cache at
- cache_path. If it doesn't exist or is outdated, load the configuration
- instead from the original YAML file at src_path and regenerate the cache.
- I assume I have the permissions to write to the cache directory.
- """
- # Namespace container for various state variables, so that they can be
- # updated by closures.
- ns = struct()
-
- if force_refresh:
- ns.do_refresh = True
- else:
- src_mtime = getmtime(src_path)
- try: cache_mtime = getmtime(cache_path)
- except OSError: ns.do_refresh = True
- else: ns.do_refresh = src_mtime > cache_mtime
-
- if not ns.do_refresh:
- # Try reading from the cache first. This must be transactionally
- # isolated from concurrent writes to prevent reading an incomplete
- # (changing) version of the data (but the transaction can share the
- # lock with other concurrent reads).
- @with_lock_file(lock_file, False)
- def read_cache():
- try: ns.cfg = with_closing(file(cache_path)) (
- lambda f: json.read(f.read()))
- except: ns.do_refresh = True
-
- if ns.do_refresh:
- # Atomically reload the source and regenerate the cache. The read and
- # write must be a single transaction, or a stale version may be
- # written.
- @with_lock_file(lock_file)
- def refresh_cache():
- import yaml
- ns.cfg = with_closing(file(src_path)) (
- lambda f: yaml.load(f, yaml.CSafeLoader))
- try: with_closing(file(cache_path, 'w')) (
- lambda f: f.write(json.write(ns.cfg)))
- except: pass # silent failure
- return ns.cfg
-
-dicts = load()
-structs = dicts2struct(dicts)
-
-# vim:et:sw=4:ts=4