openstack/swift
Code Issues Proposed changes

Merge "Add a Timeout when getting Memcache connections"

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Jenkins 2013-10-09 07:48:38 +00:00 committed by Gerrit Code Review
commit db89ff9b2e
2 changed files with 80 additions and 17 deletions
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35
swift/common/memcached.py
View File

@ -60,6 +60,7 @@ from swift.common.utils import json
DEFAULT_MEMCACHED_PORT = 11211
CONN_TIMEOUT = 0.3
POOL_TIMEOUT = 1.0 # WAG
IO_TIMEOUT = 2.0
PICKLE_FLAG = 1
JSON_FLAG = 2
@ -94,6 +95,10 @@ class MemcacheConnectionError(Exception):
pass
class MemcachePoolTimeout(Timeout):
pass
class MemcacheConnPool(Pool):
"""Connection pool for Memcache Connections"""
@ -128,8 +133,8 @@ class MemcacheRing(object):
"""
def __init__(self, servers, connect_timeout=CONN_TIMEOUT,
io_timeout=IO_TIMEOUT, tries=TRY_COUNT,
allow_pickle=False, allow_unpickle=False,
io_timeout=IO_TIMEOUT, pool_timeout=POOL_TIMEOUT,
tries=TRY_COUNT, allow_pickle=False, allow_unpickle=False,
max_conns=2):
self._ring = {}
self._errors = dict(((serv, []) for serv in servers))
@ -145,11 +150,12 @@ class MemcacheRing(object):
for server in servers))
self._connect_timeout = connect_timeout
self._io_timeout = io_timeout
self._pool_timeout = pool_timeout
self._allow_pickle = allow_pickle
self._allow_unpickle = allow_unpickle or allow_pickle
def _exception_occurred(self, server, e, action='talking',
sock=None, fp=None):
sock=None, fp=None, got_connection=True):
if isinstance(e, Timeout):
logging.error(_("Timeout %(action)s to memcached: %(server)s"),
{'action': action, 'server': server})
@ -168,9 +174,10 @@ class MemcacheRing(object):
del sock
except Exception:
pass
# We need to return something to the pool
# A new connection will be created the next time it is retreived
self._return_conn(server, None, None)
if got_connection:
# We need to return something to the pool
# A new connection will be created the next time it is retreived
self._return_conn(server, None, None)
now = time.time()
self._errors[server].append(time.time())
if len(self._errors[server]) > ERROR_LIMIT_COUNT:
@ -197,17 +204,13 @@ class MemcacheRing(object):
continue
sock = None
try:
# NOTE: We do NOT place a Timeout over the MemcacheConnPool's
# get() method. The MemcacheConnPool's create() method already
# places a timeout around the connect() system call, which we
# catch below. It is possible for the underlying Queue of the
# MemcacheConnPool to be contended such that this greenlet is
# waiting for one or more connections to be freed up. If there
# is a particularly slow memcache server causing that problme,
# then the IO_TIMEOUT will catch that behavior, so we do not
# have to place a Timeout here.
fp, sock = self._client_cache[server].get()
with MemcachePoolTimeout(self._pool_timeout):
fp, sock = self._client_cache[server].get()
yield server, fp, sock
except MemcachePoolTimeout as e:
self._exception_occurred(
server, e, action='getting a connection',
got_connection=False)
except (Exception, Timeout) as e:
# Typically a Timeout exception caught here is the one raised
# by the create() method of this server's MemcacheConnPool

62
test/unit/common/test_memcached.py
View File

@ -17,6 +17,7 @@
"""Tests for swift.common.utils"""
from __future__ import with_statement
from collections import defaultdict
import logging
import socket
import time
@ -27,7 +28,7 @@ from eventlet import GreenPool, sleep, Queue
from eventlet.pools import Pool
from swift.common import memcached
from mock import patch
from mock import patch, MagicMock
from test.unit import NullLoggingHandler
@ -407,6 +408,65 @@ class TestMemcached(unittest.TestCase):
connections.get_nowait()
self.assertTrue(connections.empty())
def test_connection_pool_timeout(self):
orig_conn_pool = memcached.MemcacheConnPool
try:
connections = defaultdict(Queue)
pending = defaultdict(int)
served = defaultdict(int)
class MockConnectionPool(orig_conn_pool):
def get(self):
pending[self.server] += 1
conn = connections[self.server].get()
pending[self.server] -= 1
return conn
def put(self, *args, **kwargs):
connections[self.server].put(*args, **kwargs)
served[self.server] += 1
memcached.MemcacheConnPool = MockConnectionPool
memcache_client = memcached.MemcacheRing(['1.2.3.4:11211',
'1.2.3.5:11211'],
io_timeout=0.5,
pool_timeout=0.1)
p = GreenPool()
for i in range(10):
p.spawn(memcache_client.set, 'key', 'value')
# let everyone block
sleep(0)
self.assertEqual(pending['1.2.3.5:11211'], 10)
# hand out a couple slow connection
mock_conn = MagicMock(), MagicMock()
mock_conn[1].sendall = lambda x: sleep(0.2)
connections['1.2.3.5:11211'].put(mock_conn)
connections['1.2.3.5:11211'].put(mock_conn)
# so far so good, everyone is still waiting
sleep(0)
self.assertEqual(pending['1.2.3.5:11211'], 8)
self.assertEqual(len(memcache_client._errors['1.2.3.5:11211']), 0)
# but they won't wait longer than pool_timeout
mock_conn = MagicMock(), MagicMock()
connections['1.2.3.4:11211'].put(mock_conn)
connections['1.2.3.4:11211'].put(mock_conn)
p.waitall()
self.assertEqual(len(memcache_client._errors['1.2.3.5:11211']), 8)
self.assertEqual(served['1.2.3.5:11211'], 2)
self.assertEqual(len(memcache_client._errors['1.2.3.4:11211']), 0)
self.assertEqual(served['1.2.3.4:11211'], 8)
# and we never got more put in that we gave out
self.assertEqual(connections['1.2.3.5:11211'].qsize(), 2)
self.assertEqual(connections['1.2.3.4:11211'].qsize(), 2)
finally:
memcached.MemcacheConnPool = orig_conn_pool
if __name__ == '__main__':
unittest.main()