2 from invirt.common import *
5 from os.path import getmtime
6 from contextlib import closing
10 try: loader = yaml.CSafeLoader
11 except: loader = yaml.SafeLoader
13 src_path = '/etc/invirt/master.yaml'
14 src_dirpath = '/etc/invirt/conf.d'
15 cache_path = '/var/lib/invirt/cache.json'
16 lock_path = '/var/lib/invirt/cache.lock'
19 """Splice dict-tree d2 into d1. Return d1.
21 d2 may be None for an empty dict-tree, because yaml.load produces that.
24 >>> d = {'a': {'b': 1}, 'c': 2}
25 >>> augment(d, {'a': {'d': 3}})
26 {'a': {'b', 1, 'd': 3}, 'c': 2}
28 {'a': {'b', 1, 'd': 3}, 'c': 2}
33 if k in d1 and isinstance(d1[k], dict):
39 def run_parts_list(dirname):
40 """Reimplements Debian's run-parts --list.
42 One difference from run-parts's behavior: run-parts --list /foo/
43 will give output like /foo//bar, but run_parts_list('/foo/') gives
44 /foo/bar in deference to Python conventions.
46 Matches documented behavior of run-parts in debianutils v2.28.2, dated 2007.
49 lanana_re = re.compile('^[a-z0-9]+$')
50 lsb_re = re.compile('^_?([a-z0-9_.]+-)+[a-z0-9]+$')
51 deb_cron_re = re.compile('^[a-z0-9][a-z0-9-]*$')
52 for name in os.listdir(dirname):
53 if lanana_re.match(name) or lsb_re.match(name) or deb_cron_re.match(name):
54 yield os.path.join(dirname, name)
58 for name in run_parts_list(src_dirpath):
63 for filename in list_files():
64 with closing(open(filename)) as f:
65 augment(config, yaml.load(f, loader))
69 return max(max(getmtime(filename) for filename in list_files()),
70 getmtime(src_dirpath))
72 def load(force_refresh = False):
74 Try loading the configuration from the faster-to-load JSON cache at
75 cache_path. If it doesn't exist or is outdated, load the configuration
76 instead from the original YAML file at src_path and regenerate the cache.
77 I assume I have the permissions to write to the cache directory.
80 # Namespace container for state variables, so that they can be updated by
87 src_mtime = get_src_mtime()
88 try: cache_mtime = getmtime(cache_path)
89 except OSError: do_refresh = True
90 else: do_refresh = src_mtime + 1 >= cache_mtime
92 # We chose not to simply say
94 # do_refresh = src_mtime >= cache_time
96 # because between the getmtime(src_path) and the time the cache is
97 # rewritten, the master configuration may have been updated, so future
98 # checks here would find a cache with a newer mtime than the master
99 # (and thus treat the cache as containing the latest version of the
100 # master). The +1 means that for at least a full second following the
101 # update to the master, this function will refresh the cache, giving us
102 # 1 second to write the cache. Note that if it takes longer than 1
103 # second to write the cache, then this situation could still arise.
105 # The getmtime calls should logically be part of the same transaction
106 # as the rest of this function (cache read + conditional cache
107 # refresh), but to wrap everything in an flock would cause the
108 # following cache read to be less streamlined.
111 # Try reading from the cache first. This must be transactionally
112 # isolated from concurrent writes to prevent reading an incomplete
113 # (changing) version of the data (but the transaction can share the
114 # lock with other concurrent reads). This isolation is accomplished
115 # using an atomic filesystem rename in the refreshing stage.
117 with closing(open(cache_path)) as f:
118 ns.cfg = json.read(f.read())
119 except: do_refresh = True
122 # Atomically reload the source and regenerate the cache. The read and
123 # write must be a single transaction, or a stale version may be
124 # written (if another read/write of a more recent configuration
125 # is interleaved). The final atomic rename is to keep this
126 # transactionally isolated from the above cache read. If we fail to
127 # acquire the lock, just try to load the master configuration.
129 with lock_file(lock_path):
130 ns.cfg = load_master()
132 with closing(open(cache_path + '.tmp', 'w')) as f:
133 f.write(json.write(ns.cfg))
134 except: pass # silent failure
135 else: rename(cache_path + '.tmp', cache_path)
137 ns.cfg = load_master()
141 structs = dicts2struct(dicts, '')
142 safestructs = dicts2struct(dicts, '', '')