Changeset 793 for trunk/packages/sipb-xen-base/files/usr/share
- Timestamp:
- Jul 30, 2008, 9:50:42 PM (16 years ago)
- Location:
- trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt
- Files:
-
- 2 edited
Legend:
- Unmodified
- Added
- Removed
-
trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt/common.py
r790 r793 40 40 return wrapper 41 41 42 def with_lock_file(path ):42 def with_lock_file(path, exclusive = True): 43 43 """ 44 44 Context manager for lock files. Example: … … 54 54 @with_closing(file(path, 'w')) 55 55 def g(f): 56 flock(f, LOCK_EX) 56 if exclusive: locktype = LOCK_EX 57 else: locktype = LOCK_SH 58 flock(f, locktype) 57 59 try: return func() 58 60 finally: flock(f, LOCK_UN) -
trunk/packages/sipb-xen-base/files/usr/share/python-support/sipb-xen-base/invirt/config.py
r792 r793 5 5 default_src_path = '/etc/invirt/master.yaml' 6 6 default_cache_path = '/var/lib/invirt/cache.json' 7 lock_file = '/var/lib/invirt/cache.lock' 7 8 8 9 def load(src_path = default_src_path, … … 15 16 I assume I have the permissions to write to the cache directory. 16 17 """ 18 # Namespace container for various state variables, so that they can be 19 # updated by closures. 20 ns = struct() 21 17 22 if force_refresh: 18 do_refresh = True23 ns.do_refresh = True 19 24 else: 20 25 src_mtime = getmtime(src_path) 21 try: cache_mtime = getmtime(cache_path)22 except OSError: do_refresh= True23 else: do_refresh= src_mtime > cache_mtime26 try: cache_mtime = getmtime(cache_path) 27 except OSError: ns.do_refresh = True 28 else: ns.do_refresh = src_mtime > cache_mtime 24 29 25 if not do_refresh: 26 # try reading from the cache first 27 try: cfg = with_closing(file(cache_path))(lambda f: json.read(f.read())) 28 except: do_refresh = True 30 if not ns.do_refresh: 31 # Try reading from the cache first. This must be transactionally 32 # isolated from concurrent writes to prevent reading an incomplete 33 # (changing) version of the data (but the transaction can share the 34 # lock with other concurrent reads). 35 @with_lock_file(lock_file, False) 36 def read_cache(): 37 try: ns.cfg = with_closing(file(cache_path))(lambda f: json.read(f.read())) 38 except: ns.do_refresh = True 29 39 30 if do_refresh:40 if ns.do_refresh: 31 41 # Atomically reload the source and regenerate the cache. The read and 32 42 # write must be a single transaction, or a stale version may be 33 43 # written. 34 @with_lock_file( '/var/lib/invirt/cache.lock')35 def cfg():44 @with_lock_file(lock_file) 45 def refresh_cache(): 36 46 import yaml 37 47 try: default_loader = yaml.CSafeLoader 38 48 except: default_loader = yaml.SafeLoader 39 cfg = with_closing(file(src_path))(lambda f: yaml.load(f, default_loader))40 try: with_closing(file(cache_path, 'w'))(lambda f: f.write(json.write( cfg)))49 ns.cfg = with_closing(file(src_path))(lambda f: yaml.load(f, default_loader)) 50 try: with_closing(file(cache_path, 'w'))(lambda f: f.write(json.write(ns.cfg))) 41 51 except: pass # silent failure 42 return cfg 43 return cfg 52 return ns.cfg 44 53 45 54 dicts = load()
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