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Diffstat (limited to 'lib/thandy/lockfile/__init__.py')
| -rw-r--r-- | lib/thandy/lockfile/__init__.py | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/lib/thandy/lockfile/__init__.py b/lib/thandy/lockfile/__init__.py new file mode 100644 index 0000000..a167cd8 --- /dev/null +++ b/lib/thandy/lockfile/__init__.py @@ -0,0 +1,286 @@ + +""" +lockfile.py - Platform-independent advisory file locks. + +Requires Python 2.5 unless you apply 2.4.diff +Locking is done on a per-thread basis instead of a per-process basis. + +Usage: + +>>> lock = LockFile('somefile') +>>> try: +... lock.acquire() +... except AlreadyLocked: +... print 'somefile', 'is locked already.' +... except LockFailed: +... print 'somefile', 'can\\'t be locked.' +... else: +... print 'got lock' +got lock +>>> print lock.is_locked() +True +>>> lock.release() + +>>> lock = LockFile('somefile') +>>> print lock.is_locked() +False +>>> with lock: +... print lock.is_locked() +True +>>> print lock.is_locked() +False + +>>> lock = LockFile('somefile') +>>> # It is okay to lock twice from the same thread... +>>> with lock: +... lock.acquire() +... +>>> # Though no counter is kept, so you can't unlock multiple times... +>>> print lock.is_locked() +False + +Exceptions: + + Error - base class for other exceptions + LockError - base class for all locking exceptions + AlreadyLocked - Another thread or process already holds the lock + LockFailed - Lock failed for some other reason + UnlockError - base class for all unlocking exceptions + AlreadyUnlocked - File was not locked. + NotMyLock - File was locked but not by the current thread/process +""" + +import sys +import socket +import os +import threading +import time +import urllib +import warnings + +# Work with PEP8 and non-PEP8 versions of threading module. +if not hasattr(threading, "current_thread"): + threading.current_thread = threading.currentThread +if not hasattr(threading.Thread, "get_name"): + threading.Thread.get_name = threading.Thread.getName + +__all__ = ['Error', 'LockError', 'LockTimeout', 'AlreadyLocked', + 'LockFailed', 'UnlockError', 'NotLocked', 'NotMyLock', + 'LinkLockFile', 'MkdirLockFile', 'SQLiteLockFile', + 'LockBase'] + +class Error(Exception): + """ + Base class for other exceptions. + + >>> try: + ... raise Error + ... except Exception: + ... pass + """ + pass + +class LockError(Error): + """ + Base class for error arising from attempts to acquire the lock. + + >>> try: + ... raise LockError + ... except Error: + ... pass + """ + pass + +class LockTimeout(LockError): + """Raised when lock creation fails within a user-defined period of time. + + >>> try: + ... raise LockTimeout + ... except LockError: + ... pass + """ + pass + +class AlreadyLocked(LockError): + """Some other thread/process is locking the file. + + >>> try: + ... raise AlreadyLocked + ... except LockError: + ... pass + """ + pass + +class LockFailed(LockError): + """Lock file creation failed for some other reason. + + >>> try: + ... raise LockFailed + ... except LockError: + ... pass + """ + pass + +class UnlockError(Error): + """ + Base class for errors arising from attempts to release the lock. + + >>> try: + ... raise UnlockError + ... except Error: + ... pass + """ + pass + +class NotLocked(UnlockError): + """Raised when an attempt is made to unlock an unlocked file. + + >>> try: + ... raise NotLocked + ... except UnlockError: + ... pass + """ + pass + +class NotMyLock(UnlockError): + """Raised when an attempt is made to unlock a file someone else locked. + + >>> try: + ... raise NotMyLock + ... except UnlockError: + ... pass + """ + pass + +class LockBase: + """Base class for platform-specific lock classes.""" + def __init__(self, path, threaded=True): + """ + >>> lock = LockBase('somefile') + >>> lock = LockBase('somefile', threaded=False) + """ + self.path = path + self.lock_file = os.path.abspath(path) + ".lock" + self.hostname = socket.gethostname() + self.pid = os.getpid() + if threaded: + t = threading.current_thread() + # Thread objects in Python 2.4 and earlier do not have ident + # attrs. Worm around that. + ident = getattr(t, "ident", hash(t)) + self.tname = "-%x" % (ident & 0xffffffff) + else: + self.tname = "" + dirname = os.path.dirname(self.lock_file) + self.unique_name = os.path.join(dirname, + "%s%s.%s" % (self.hostname, + self.tname, + self.pid)) + + def acquire(self, timeout=None): + """ + Acquire the lock. + + * If timeout is omitted (or None), wait forever trying to lock the + file. + + * If timeout > 0, try to acquire the lock for that many seconds. If + the lock period expires and the file is still locked, raise + LockTimeout. + + * If timeout <= 0, raise AlreadyLocked immediately if the file is + already locked. + """ + raise NotImplemented("implement in subclass") + + def release(self): + """ + Release the lock. + + If the file is not locked, raise NotLocked. + """ + raise NotImplemented("implement in subclass") + + def is_locked(self): + """ + Tell whether or not the file is locked. + """ + raise NotImplemented("implement in subclass") + + def i_am_locking(self): + """ + Return True if this object is locking the file. + """ + raise NotImplemented("implement in subclass") + + def break_lock(self): + """ + Remove a lock. Useful if a locking thread failed to unlock. + """ + raise NotImplemented("implement in subclass") + + def __enter__(self): + """ + Context manager support. + """ + self.acquire() + return self + + def __exit__(self, *_exc): + """ + Context manager support. + """ + self.release() + +def _fl_helper(cls, mod, *args, **kwds): + warnings.warn("Import from %s module instead of lockfile package" % mod, + DeprecationWarning, stacklevel=2) + # This is a bit funky, but it's only for awhile. The way the unit tests + # are constructed this function winds up as an unbound method, so it + # actually takes three args, not two. We want to toss out self. + if not isinstance(args[0], str): + # We are testing, avoid the first arg + args = args[1:] + if len(args) == 1 and not kwds: + kwds["threaded"] = True + return cls(*args, **kwds) + +def LinkFileLock(*args, **kwds): + """Factory function provided for backwards compatibility. + + Do not use in new code. Instead, import LinkLockFile from the + lockfile.linklockfile module. + """ + import linklockfile + return _fl_helper(linklockfile.LinkLockFile, "lockfile.linklockfile", + *args, **kwds) + +def MkdirFileLock(*args, **kwds): + """Factory function provided for backwards compatibility. + + Do not use in new code. Instead, import MkdirLockFile from the + lockfile.mkdirlockfile module. + """ + import mkdirlockfile + return _fl_helper(mkdirlockfile.MkdirLockFile, "lockfile.mkdirlockfile", + *args, **kwds) + +def SQLiteFileLock(*args, **kwds): + """Factory function provided for backwards compatibility. + + Do not use in new code. Instead, import SQLiteLockFile from the + lockfile.mkdirlockfile module. + """ + import sqlitelockfile + return _fl_helper(sqlitelockfile.SQLiteLockFile, "lockfile.sqlitelockfile", + *args, **kwds) + +if hasattr(os, "link"): + import linklockfile as _llf + LockFile = _llf.LinkLockFile +else: + import mkdirlockfile as _mlf + LockFile = _mlf.MkdirLockFile + +FileLock = LockFile + |