c7f938ceaa
There are cases where we want to catch and retry some additional exceptions and treat them as RetryRequests depending on method that is being excecuted (e.g. StaleDataError or ObjectDeletedError). This patch changes the wrap_db_retry decorator to take an extra parameter that is a list of additional exception classes that will be caught and treated as a RetryRequest. Change-Id: I6c61b1d2f0331cac31dfde0afa523e44d470b83f
287 lines
10 KiB
Python
287 lines
10 KiB
Python
# Copyright (c) 2013 Rackspace Hosting
|
|
# All Rights Reserved.
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
# not use this file except in compliance with the License. You may obtain
|
|
# a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
# License for the specific language governing permissions and limitations
|
|
# under the License.
|
|
|
|
"""
|
|
=================================
|
|
Multiple DB API backend support.
|
|
=================================
|
|
|
|
A DB backend module should implement a method named 'get_backend' which
|
|
takes no arguments. The method can return any object that implements DB
|
|
API methods.
|
|
"""
|
|
|
|
import logging
|
|
import threading
|
|
import time
|
|
|
|
from oslo_utils import excutils
|
|
from oslo_utils import importutils
|
|
import six
|
|
|
|
from oslo_db._i18n import _LE
|
|
from oslo_db import exception
|
|
from oslo_db import options
|
|
|
|
|
|
LOG = logging.getLogger(__name__)
|
|
|
|
|
|
def safe_for_db_retry(f):
|
|
"""Indicate api method as safe for re-connection to database.
|
|
|
|
Database connection retries will be enabled for the decorated api method.
|
|
Database connection failure can have many causes, which can be temporary.
|
|
In such cases retry may increase the likelihood of connection.
|
|
|
|
Usage::
|
|
|
|
@safe_for_db_retry
|
|
def api_method(self):
|
|
self.engine.connect()
|
|
|
|
|
|
:param f: database api method.
|
|
:type f: function.
|
|
"""
|
|
f.__dict__['enable_retry_on_disconnect'] = True
|
|
return f
|
|
|
|
|
|
def retry_on_deadlock(f):
|
|
"""Retry a DB API call if Deadlock was received.
|
|
|
|
wrap_db_entry will be applied to all db.api functions marked with this
|
|
decorator.
|
|
"""
|
|
f.__dict__['enable_retry_on_deadlock'] = True
|
|
return f
|
|
|
|
|
|
def retry_on_request(f):
|
|
"""Retry a DB API call if RetryRequest exception was received.
|
|
|
|
wrap_db_entry will be applied to all db.api functions marked with this
|
|
decorator.
|
|
"""
|
|
f.__dict__['enable_retry_on_request'] = True
|
|
return f
|
|
|
|
|
|
class wrap_db_retry(object):
|
|
"""Retry db.api methods, if db_error raised
|
|
|
|
Retry decorated db.api methods. This decorator catches db_error and retries
|
|
function in a loop until it succeeds, or until maximum retries count
|
|
will be reached.
|
|
|
|
Keyword arguments:
|
|
|
|
:param retry_interval: seconds between transaction retries
|
|
:type retry_interval: int
|
|
|
|
:param max_retries: max number of retries before an error is raised
|
|
:type max_retries: int
|
|
|
|
:param inc_retry_interval: determine increase retry interval or not
|
|
:type inc_retry_interval: bool
|
|
|
|
:param max_retry_interval: max interval value between retries
|
|
:type max_retry_interval: int
|
|
|
|
:param exception_checker: checks if an exception should trigger a retry
|
|
:type exception_checker: callable
|
|
"""
|
|
|
|
def __init__(self, retry_interval=0, max_retries=0, inc_retry_interval=0,
|
|
max_retry_interval=0, retry_on_disconnect=False,
|
|
retry_on_deadlock=False, retry_on_request=False,
|
|
exception_checker=lambda exc: False):
|
|
super(wrap_db_retry, self).__init__()
|
|
|
|
self.db_error = ()
|
|
# default is that we re-raise anything unexpected
|
|
self.exception_checker = exception_checker
|
|
if retry_on_disconnect:
|
|
self.db_error += (exception.DBConnectionError, )
|
|
if retry_on_deadlock:
|
|
self.db_error += (exception.DBDeadlock, )
|
|
if retry_on_request:
|
|
self.db_error += (exception.RetryRequest, )
|
|
self.retry_interval = retry_interval
|
|
self.max_retries = max_retries
|
|
self.inc_retry_interval = inc_retry_interval
|
|
self.max_retry_interval = max_retry_interval
|
|
|
|
def __call__(self, f):
|
|
@six.wraps(f)
|
|
def wrapper(*args, **kwargs):
|
|
next_interval = self.retry_interval
|
|
remaining = self.max_retries
|
|
|
|
while True:
|
|
try:
|
|
return f(*args, **kwargs)
|
|
except Exception as e:
|
|
with excutils.save_and_reraise_exception() as ectxt:
|
|
if remaining > 0:
|
|
ectxt.reraise = not self._is_exception_expected(e)
|
|
else:
|
|
LOG.exception(_LE('DB exceeded retry limit.'))
|
|
# if it's a RetryRequest, we need to unpack it
|
|
if isinstance(e, exception.RetryRequest):
|
|
ectxt.type_ = type(e.inner_exc)
|
|
ectxt.value = e.inner_exc
|
|
# NOTE(vsergeyev): We are using patched time module, so
|
|
# this effectively yields the execution
|
|
# context to another green thread.
|
|
time.sleep(next_interval)
|
|
if self.inc_retry_interval:
|
|
next_interval = min(
|
|
next_interval * 2,
|
|
self.max_retry_interval
|
|
)
|
|
remaining -= 1
|
|
|
|
return wrapper
|
|
|
|
def _is_exception_expected(self, exc):
|
|
if isinstance(exc, self.db_error):
|
|
# RetryRequest is application-initated exception
|
|
# and not an error condition in case retries are
|
|
# not exceeded
|
|
if not isinstance(exc, exception.RetryRequest):
|
|
LOG.exception(_LE('DB error.'))
|
|
return True
|
|
return self.exception_checker(exc)
|
|
|
|
|
|
class DBAPI(object):
|
|
"""Initialize the chosen DB API backend.
|
|
|
|
After initialization API methods is available as normal attributes of
|
|
``DBAPI`` subclass. Database API methods are supposed to be called as
|
|
DBAPI instance methods.
|
|
|
|
:param backend_name: name of the backend to load
|
|
:type backend_name: str
|
|
|
|
:param backend_mapping: backend name -> module/class to load mapping
|
|
:type backend_mapping: dict
|
|
:default backend_mapping: None
|
|
|
|
:param lazy: load the DB backend lazily on the first DB API method call
|
|
:type lazy: bool
|
|
:default lazy: False
|
|
|
|
:keyword use_db_reconnect: retry DB transactions on disconnect or not
|
|
:type use_db_reconnect: bool
|
|
|
|
:keyword retry_interval: seconds between transaction retries
|
|
:type retry_interval: int
|
|
|
|
:keyword inc_retry_interval: increase retry interval or not
|
|
:type inc_retry_interval: bool
|
|
|
|
:keyword max_retry_interval: max interval value between retries
|
|
:type max_retry_interval: int
|
|
|
|
:keyword max_retries: max number of retries before an error is raised
|
|
:type max_retries: int
|
|
"""
|
|
|
|
def __init__(self, backend_name, backend_mapping=None, lazy=False,
|
|
**kwargs):
|
|
|
|
self._backend = None
|
|
self._backend_name = backend_name
|
|
self._backend_mapping = backend_mapping or {}
|
|
self._lock = threading.Lock()
|
|
|
|
if not lazy:
|
|
self._load_backend()
|
|
|
|
self.use_db_reconnect = kwargs.get('use_db_reconnect', False)
|
|
self.retry_interval = kwargs.get('retry_interval', 1)
|
|
self.inc_retry_interval = kwargs.get('inc_retry_interval', True)
|
|
self.max_retry_interval = kwargs.get('max_retry_interval', 10)
|
|
self.max_retries = kwargs.get('max_retries', 20)
|
|
|
|
def _load_backend(self):
|
|
with self._lock:
|
|
if not self._backend:
|
|
# Import the untranslated name if we don't have a mapping
|
|
backend_path = self._backend_mapping.get(self._backend_name,
|
|
self._backend_name)
|
|
LOG.debug('Loading backend %(name)r from %(path)r',
|
|
{'name': self._backend_name,
|
|
'path': backend_path})
|
|
backend_mod = importutils.import_module(backend_path)
|
|
self._backend = backend_mod.get_backend()
|
|
|
|
def __getattr__(self, key):
|
|
if not self._backend:
|
|
self._load_backend()
|
|
|
|
attr = getattr(self._backend, key)
|
|
if not hasattr(attr, '__call__'):
|
|
return attr
|
|
# NOTE(vsergeyev): If `use_db_reconnect` option is set to True, retry
|
|
# DB API methods, decorated with @safe_for_db_retry
|
|
# on disconnect.
|
|
retry_on_disconnect = self.use_db_reconnect and attr.__dict__.get(
|
|
'enable_retry_on_disconnect', False)
|
|
retry_on_deadlock = attr.__dict__.get('enable_retry_on_deadlock',
|
|
False)
|
|
retry_on_request = attr.__dict__.get('enable_retry_on_request', False)
|
|
|
|
if retry_on_disconnect or retry_on_deadlock or retry_on_request:
|
|
attr = wrap_db_retry(
|
|
retry_interval=self.retry_interval,
|
|
max_retries=self.max_retries,
|
|
inc_retry_interval=self.inc_retry_interval,
|
|
max_retry_interval=self.max_retry_interval,
|
|
retry_on_disconnect=retry_on_disconnect,
|
|
retry_on_deadlock=retry_on_deadlock,
|
|
retry_on_request=retry_on_request)(attr)
|
|
|
|
return attr
|
|
|
|
@classmethod
|
|
def from_config(cls, conf, backend_mapping=None, lazy=False):
|
|
"""Initialize DBAPI instance given a config instance.
|
|
|
|
:param conf: oslo.config config instance
|
|
:type conf: oslo.config.cfg.ConfigOpts
|
|
|
|
:param backend_mapping: backend name -> module/class to load mapping
|
|
:type backend_mapping: dict
|
|
|
|
:param lazy: load the DB backend lazily on the first DB API method call
|
|
:type lazy: bool
|
|
|
|
"""
|
|
|
|
conf.register_opts(options.database_opts, 'database')
|
|
|
|
return cls(backend_name=conf.database.backend,
|
|
backend_mapping=backend_mapping,
|
|
lazy=lazy,
|
|
use_db_reconnect=conf.database.use_db_reconnect,
|
|
retry_interval=conf.database.db_retry_interval,
|
|
inc_retry_interval=conf.database.db_inc_retry_interval,
|
|
max_retry_interval=conf.database.db_max_retry_interval,
|
|
max_retries=conf.database.db_max_retries)
|