diff options
Diffstat (limited to 'oslo_db/api.py')
| -rw-r--r-- | oslo_db/api.py | 41 |
1 files changed, 34 insertions, 7 deletions
diff --git a/oslo_db/api.py b/oslo_db/api.py index 62cf889..7f92756 100644 --- a/oslo_db/api.py +++ b/oslo_db/api.py @@ -24,6 +24,7 @@ API methods. """ import logging +import random import threading import time @@ -103,15 +104,21 @@ class wrap_db_retry(object): :param exception_checker: checks if an exception should trigger a retry :type exception_checker: callable + + :param jitter: determine increase retry interval use jitter or not, jitter + is always interpreted as True for a DBDeadlockError + :type jitter: bool """ def __init__(self, retry_interval=1, max_retries=20, inc_retry_interval=True, max_retry_interval=10, retry_on_disconnect=False, retry_on_deadlock=False, - exception_checker=lambda exc: False): + exception_checker=lambda exc: False, + jitter=False): super(wrap_db_retry, self).__init__() + self.jitter = jitter self.db_error = (exception.RetryRequest, ) # default is that we re-raise anything unexpected self.exception_checker = exception_checker @@ -127,7 +134,7 @@ class wrap_db_retry(object): def __call__(self, f): @six.wraps(f) def wrapper(*args, **kwargs): - next_interval = self.retry_interval + sleep_time = next_interval = self.retry_interval remaining = self.max_retries while True: @@ -150,12 +157,20 @@ class wrap_db_retry(object): # NOTE(vsergeyev): We are using patched time module, so # this effectively yields the execution # context to another green thread. - time.sleep(next_interval) + time.sleep(sleep_time) if self.inc_retry_interval: - next_interval = min( - next_interval * 2, - self.max_retry_interval - ) + # NOTE(jiangyikun): In order to minimize the chance of + # regenerating a deadlock and reduce the average sleep + # time, we are using jitter by default when the + # deadlock is detected. With the jitter, + # sleep_time = [0, next_interval), otherwise, without + # the jitter, sleep_time = next_interval. + if isinstance(e, exception.DBDeadlock): + jitter = True + else: + jitter = self.jitter + sleep_time, next_interval = self._get_inc_interval( + next_interval, jitter) remaining -= 1 return wrapper @@ -170,6 +185,18 @@ class wrap_db_retry(object): return True return self.exception_checker(exc) + def _get_inc_interval(self, n, jitter): + # NOTE(jiangyikun): The "n" help us to record the 2 ** retry_times. + # The "sleep_time" means the real time to sleep: + # - Without jitter: sleep_time = 2 ** retry_times = n + # - With jitter: sleep_time = [0, 2 ** retry_times) < n + n = n * 2 + if jitter: + sleep_time = random.uniform(0, n) + else: + sleep_time = n + return min(sleep_time, self.max_retry_interval), n + class DBAPI(object): """Initialize the chosen DB API backend. |