1 from __future__ import with_statement
4 from invirt.common import *
7 from os.path import getmtime
8 from contextlib import closing
12 try: loader = yaml.CSafeLoader
13 except: loader = yaml.SafeLoader
15 src_path = '/etc/invirt/master.yaml'
16 src_dirpath = '/etc/invirt/conf.d'
17 cache_path = '/var/lib/invirt/cache.json'
18 lock_path = '/var/lib/invirt/cache.lock'
21 """Splice dict-tree d2 into d1. Return d1.
23 d2 may be None for an empty dict-tree, because yaml.load produces that.
26 >>> d = {'a': {'b': 1}, 'c': 2}
27 >>> augment(d, {'a': {'d': 3}})
28 {'a': {'b', 1, 'd': 3}, 'c': 2}
30 {'a': {'b', 1, 'd': 3}, 'c': 2}
35 if k in d1 and isinstance(d1[k], dict):
41 def run_parts_list(dirname):
42 """Reimplements Debian's run-parts --list.
44 One difference from run-parts's behavior: run-parts --list /foo/
45 will give output like /foo//bar, but run_parts_list('/foo/') gives
46 /foo/bar in deference to Python conventions.
48 Matches documented behavior of run-parts in debianutils v2.28.2, dated 2007.
51 lanana_re = re.compile('^[a-z0-9]+$')
52 lsb_re = re.compile('^_?([a-z0-9_.]+-)+[a-z0-9]+$')
53 deb_cron_re = re.compile('^[a-z0-9][a-z0-9-]*$')
54 for name in os.listdir(dirname):
55 if lanana_re.match(name) or lsb_re.match(name) or deb_cron_re.match(name):
56 yield os.path.join(dirname, name)
60 for name in run_parts_list(src_dirpath):
65 for filename in list_files():
66 with closing(file(filename)) as f:
67 augment(config, yaml.load(f, loader))
71 return max(max(getmtime(filename) for filename in list_files()),
72 getmtime(src_dirpath))
74 def load(force_refresh = False):
76 Try loading the configuration from the faster-to-load JSON cache at
77 cache_path. If it doesn't exist or is outdated, load the configuration
78 instead from the original YAML file at src_path and regenerate the cache.
79 I assume I have the permissions to write to the cache directory.
82 # Namespace container for state variables, so that they can be updated by
89 src_mtime = get_src_mtime()
90 try: cache_mtime = getmtime(cache_path)
91 except OSError: do_refresh = True
92 else: do_refresh = src_mtime + 1 >= cache_mtime
94 # We chose not to simply say
96 # do_refresh = src_mtime >= cache_time
98 # because between the getmtime(src_path) and the time the cache is
99 # rewritten, the master configuration may have been updated, so future
100 # checks here would find a cache with a newer mtime than the master
101 # (and thus treat the cache as containing the latest version of the
102 # master). The +1 means that for at least a full second following the
103 # update to the master, this function will refresh the cache, giving us
104 # 1 second to write the cache. Note that if it takes longer than 1
105 # second to write the cache, then this situation could still arise.
107 # The getmtime calls should logically be part of the same transaction
108 # as the rest of this function (cache read + conditional cache
109 # refresh), but to wrap everything in an flock would cause the
110 # following cache read to be less streamlined.
113 # Try reading from the cache first. This must be transactionally
114 # isolated from concurrent writes to prevent reading an incomplete
115 # (changing) version of the data (but the transaction can share the
116 # lock with other concurrent reads). This isolation is accomplished
117 # using an atomic filesystem rename in the refreshing stage.
119 with closing(file(cache_path)) as f:
120 ns.cfg = json.read(f.read())
121 except: do_refresh = True
124 # Atomically reload the source and regenerate the cache. The read and
125 # write must be a single transaction, or a stale version may be
126 # written (if another read/write of a more recent configuration
127 # is interleaved). The final atomic rename is to keep this
128 # transactionally isolated from the above cache read. If we fail to
129 # acquire the lock, just try to load the master configuration.
131 with lock_file(lock_path):
132 ns.cfg = load_master()
134 with closing(file(cache_path + '.tmp', 'w')) as f:
135 f.write(json.write(ns.cfg))
136 except: pass # silent failure
137 else: rename(cache_path + '.tmp', cache_path)
139 ns.cfg = load_master()
143 structs = dicts2struct(dicts)