diff options
| -rw-r--r-- | nova/tests/test_misc.py | 34 | ||||
| -rw-r--r-- | nova/utils.py | 67 |
2 files changed, 92 insertions, 9 deletions
diff --git a/nova/tests/test_misc.py b/nova/tests/test_misc.py index 1fbaf304f..961499a60 100644 --- a/nova/tests/test_misc.py +++ b/nova/tests/test_misc.py @@ -16,8 +16,12 @@ import errno import os +import random import select +from eventlet import greenpool +from eventlet import greenthread + from nova import test from nova.utils import parse_mailmap, str_dict_replace, synchronized @@ -72,11 +76,37 @@ class LockTestCase(test.TestCase): self.assertEquals(foo.__name__, 'foo', "Wrapped function's name " "got mangled") - def test_synchronized(self): + def test_synchronized_internally(self): + """We can lock across multiple green threads""" + seen_threads = list() + @synchronized('testlock', external=False) + def f(id): + for x in range(10): + seen_threads.append(id) + greenthread.sleep(0) + + threads = [] + pool = greenpool.GreenPool(10) + for i in range(10): + threads.append(pool.spawn(f, i)) + + for thread in threads: + thread.wait() + + self.assertEquals(len(seen_threads), 100) + # Looking at the seen threads, split it into chunks of 10, and verify + # that the last 9 match the first in each chunk. + for i in range(10): + for j in range(9): + self.assertEquals(seen_threads[i*10], seen_threads[i*10+1+j]) + + + def test_synchronized_externally(self): + """We can lock across multiple processes""" rpipe1, wpipe1 = os.pipe() rpipe2, wpipe2 = os.pipe() - @synchronized('testlock') + @synchronized('testlock', external=True) def f(rpipe, wpipe): try: os.write(wpipe, "foo") diff --git a/nova/utils.py b/nova/utils.py index 499af2039..8936614cc 100644 --- a/nova/utils.py +++ b/nova/utils.py @@ -41,6 +41,7 @@ from xml.sax import saxutils from eventlet import event from eventlet import greenthread +from eventlet import semaphore from eventlet.green import subprocess None from nova import exception @@ -531,17 +532,69 @@ def loads(s): return json.loads(s) -def synchronized(name): +_semaphores_semaphore = semaphore.Semaphore() +_semaphores = {} + + +class _NoopContextManager(object): + def __enter__(self): + pass + + def __exit__(self, exc_type, exc_val, exc_tb): + pass + + +def synchronized(name, external=False): + """Synchronization decorator + + Decorating a method like so: + @synchronized('mylock') + def foo(self, *args): + ... + + ensures that only one thread will execute the bar method at a time. + + Different methods can share the same lock: + @synchronized('mylock') + def foo(self, *args): + ... + + @synchronized('mylock') + def bar(self, *args): + ... + + This way only one of either foo or bar can be executing at a time. + + The external keyword argument denotes whether this lock should work across + multiple processes. This means that if two different workers both run a + a method decorated with @synchronized('mylock', external=True), only one + of them will execute at a time. + """ + def wrap(f): @functools.wraps(f) def inner(*args, **kwargs): - LOG.debug(_("Attempting to grab %(lock)s for method " - "%(method)s..." % {"lock": name, + with _semaphores_semaphore: + if name not in _semaphores: + _semaphores[name] = semaphore.Semaphore() + sem = _semaphores[name] + LOG.debug(_('Attempting to grab semaphore "%(lock)s" for method ' + '"%(method)s"...' % {"lock": name, "method": f.__name__})) - lock = lockfile.FileLock(os.path.join(FLAGS.lock_path, - 'nova-%s.lock' % name)) - with lock: - return f(*args, **kwargs) + with sem: + if external: + LOG.debug(_('Attempting to grab file lock "%(lock)s" for ' + 'method "%(method)s"...' % + {"lock": name, "method": f.__name__})) + lock_file_path = os.path.join(FLAGS.lock_path, + 'nova-%s.lock' % name) + lock = lockfile.FileLock(lock_file_path) + else: + lock = _NoopContextManager() + + with lock: + return f(*args, **kwargs) + return inner return wrap |