openstack/swift
Code Issues Proposed changes

memcache: Make error-limiting values configurable

Browse Source 
Previously these were all hardcoded; let operators tweak them as needed.
Significantly, this also allows operators to disable error-limiting
entirely, which may be a useful protection in case proxies are
configured with a single memcached server.

Use error_suppression_limit and error_suppression_interval to mirror the
option names used by the proxy-server to ratelimit backend Swift
servers.

Co-Authored-By: Alistair Coles <alistairncoles@gmail.com>
Change-Id: Ife005cb8545dd966d7b0e34e5496a0354c003881
This commit is contained in:
Tim Burke 2020-11-02 15:27:16 -08:00 committed by Tim Burke
parent c75e23e81f
commit aff65242ff
6 changed files with 186 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
etc/memcache.conf-sample
View File

@ -26,3 +26,11 @@
# tries = 3
# Timeout for read and writes
# io_timeout = 2.0
#
# How long without an error before a server's error count is reset. This will
# also be how long before a server is reenabled after suppression is triggered.
# Set to 0 to disable error-limiting.
# error_suppression_interval = 60.0
#
# How many errors can accumulate before a server is temporarily ignored.
# error_suppression_limit = 10

9
etc/proxy-server.conf-sample
View File

@ -160,6 +160,7 @@ use = egg:swift#proxy
#
# How long without an error before a node's error count is reset. This will
# also be how long before a node is reenabled after suppression is triggered.
# Set to 0 to disable error-limiting.
# error_suppression_interval = 60
#
# How many errors can accumulate before a node is temporarily ignored.
@ -693,6 +694,14 @@ use = egg:swift#memcache
# Sets the maximum number of connections to each memcached server per worker
# memcache_max_connections = 2
#
# How long without an error before a server's error count is reset. This will
# also be how long before a server is reenabled after suppression is triggered.
# Set to 0 to disable error-limiting.
# error_suppression_interval = 60.0
#
# How many errors can accumulate before a server is temporarily ignored.
# error_suppression_limit = 10
#
# More options documented in memcache.conf-sample
[filter:ratelimit]

25
swift/common/memcached.py
View File

@ -72,8 +72,7 @@ TRY_COUNT = 3
# if ERROR_LIMIT_COUNT errors occur in ERROR_LIMIT_TIME seconds, the server
# will be considered failed for ERROR_LIMIT_DURATION seconds.
ERROR_LIMIT_COUNT = 10
ERROR_LIMIT_TIME = 60
ERROR_LIMIT_DURATION = 60
ERROR_LIMIT_TIME = ERROR_LIMIT_DURATION = 60
def md5hash(key):
@ -160,10 +159,16 @@ class MemcacheRing(object):
def __init__(self, servers, connect_timeout=CONN_TIMEOUT,
io_timeout=IO_TIMEOUT, pool_timeout=POOL_TIMEOUT,
tries=TRY_COUNT, allow_pickle=False, allow_unpickle=False,
max_conns=2, logger=None):
max_conns=2, logger=None,
error_limit_count=ERROR_LIMIT_COUNT,
error_limit_time=ERROR_LIMIT_TIME,
error_limit_duration=ERROR_LIMIT_DURATION):
self._ring = {}
self._errors = dict(((serv, []) for serv in servers))
self._error_limited = dict(((serv, 0) for serv in servers))
self._error_limit_count = error_limit_count
self._error_limit_time = error_limit_time
self._error_limit_duration = error_limit_duration
for server in sorted(servers):
for i in range(NODE_WEIGHT):
self._ring[md5hash('%s-%s' % (server, i))] = server
@ -211,13 +216,17 @@ class MemcacheRing(object):
# We need to return something to the pool
# A new connection will be created the next time it is retrieved
self._return_conn(server, None, None)
if self._error_limit_time <= 0 or self._error_limit_duration <= 0:
return
now = time.time()
self._errors[server].append(time.time())
if len(self._errors[server]) > ERROR_LIMIT_COUNT:
self._errors[server].append(now)
if len(self._errors[server]) > self._error_limit_count:
self._errors[server] = [err for err in self._errors[server]
if err > now - ERROR_LIMIT_TIME]
if len(self._errors[server]) > ERROR_LIMIT_COUNT:
self._error_limited[server] = now + ERROR_LIMIT_DURATION
if err > now - self._error_limit_time]
if len(self._errors[server]) > self._error_limit_count:
self._error_limited[server] = now + self._error_limit_duration
self.logger.error('Error limiting server %s', server)
def _get_conns(self, key):

14
swift/common/middleware/memcache.py
View File

@ -17,8 +17,9 @@ import os
from six.moves.configparser import ConfigParser, NoSectionError, NoOptionError
from swift.common.memcached import (MemcacheRing, CONN_TIMEOUT, POOL_TIMEOUT,
IO_TIMEOUT, TRY_COUNT)
from swift.common.memcached import (
MemcacheRing, CONN_TIMEOUT, POOL_TIMEOUT, IO_TIMEOUT, TRY_COUNT,
ERROR_LIMIT_COUNT, ERROR_LIMIT_TIME)
from swift.common.utils import get_logger
@ -86,6 +87,10 @@ class MemcacheMiddleware(object):
'pool_timeout', POOL_TIMEOUT))
tries = int(memcache_options.get('tries', TRY_COUNT))
io_timeout = float(memcache_options.get('io_timeout', IO_TIMEOUT))
error_suppression_interval = float(memcache_options.get(
'error_suppression_interval', ERROR_LIMIT_TIME))
error_suppression_limit = float(memcache_options.get(
'error_suppression_limit', ERROR_LIMIT_COUNT))
if not self.memcache_servers:
self.memcache_servers = '127.0.0.1:11211'
@ -105,7 +110,10 @@ class MemcacheMiddleware(object):
allow_pickle=(serialization_format == 0),
allow_unpickle=(serialization_format <= 1),
max_conns=max_conns,
logger=self.logger)
logger=self.logger,
error_limit_count=error_suppression_limit,
error_limit_time=error_suppression_interval,
error_limit_duration=error_suppression_interval)
def __call__(self, env, start_response):
env['swift.cache'] = self.memcache

18
test/unit/common/middleware/test_memcache.py
View File

@ -160,6 +160,16 @@ class TestCacheMiddleware(unittest.TestCase):
self.assertEqual(
app.memcache._client_cache['6.7.8.9:10'].max_size, 5)
def test_conf_inline_ratelimiting(self):
with mock.patch.object(memcache, 'ConfigParser', get_config_parser()):
app = memcache.MemcacheMiddleware(
FakeApp(),
{'error_suppression_limit': '5',
'error_suppression_interval': '2.5'})
self.assertEqual(app.memcache._error_limit_count, 5)
self.assertEqual(app.memcache._error_limit_time, 2.5)
self.assertEqual(app.memcache._error_limit_duration, 2.5)
def test_conf_extra_no_section(self):
with mock.patch.object(memcache, 'ConfigParser',
get_config_parser(section='foobar')):
@ -336,6 +346,9 @@ class TestCacheMiddleware(unittest.TestCase):
# tries is limited to server count
self.assertEqual(memcache_ring._tries, 4)
self.assertEqual(memcache_ring._io_timeout, 1.0)
self.assertEqual(memcache_ring._error_limit_count, 10)
self.assertEqual(memcache_ring._error_limit_time, 60)
self.assertEqual(memcache_ring._error_limit_duration, 60)
@with_tempdir
def test_real_memcache_config(self, tempdir):
@ -363,6 +376,8 @@ class TestCacheMiddleware(unittest.TestCase):
10.0.0.4:11211
connect_timeout = 0.5
io_timeout = 1.0
error_suppression_limit = 0
error_suppression_interval = 1.5
"""
memcache_config_path = os.path.join(tempdir, 'memcache.conf')
with open(memcache_config_path, 'w') as f:
@ -376,6 +391,9 @@ class TestCacheMiddleware(unittest.TestCase):
self.assertEqual(memcache_ring._tries, 3)
# memcache conf options are defaults
self.assertEqual(memcache_ring._io_timeout, 1.0)
self.assertEqual(memcache_ring._error_limit_count, 0)
self.assertEqual(memcache_ring._error_limit_time, 1.5)
self.assertEqual(memcache_ring._error_limit_duration, 1.5)
if __name__ == '__main__':

129
test/unit/common/test_memcached.py
View File

@ -50,19 +50,23 @@ class MockedMemcachePool(memcached.MemcacheConnPool):
class ExplodingMockMemcached(object):
should_explode = True
exploded = False
def sendall(self, string):
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
if self.should_explode:
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
def readline(self):
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
if self.should_explode:
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
def read(self, size):
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
if self.should_explode:
self.exploded = True
raise socket.error(errno.EPIPE, os.strerror(errno.EPIPE))
def close(self):
pass
@ -512,6 +516,119 @@ class TestMemcached(unittest.TestCase):
self.assertEqual(memcache_client._client_cache['1.2.3.5:11211'].mocks,
[])
def test_error_limiting(self):
memcache_client = memcached.MemcacheRing(
['1.2.3.4:11211', '1.2.3.5:11211'], logger=self.logger)
mock1 = ExplodingMockMemcached()
mock2 = ExplodingMockMemcached()
mock2.should_explode = False
memcache_client._client_cache['1.2.3.4:11211'] = MockedMemcachePool(
[(mock2, mock2)] * 12)
memcache_client._client_cache['1.2.3.5:11211'] = MockedMemcachePool(
[(mock1, mock1)] * 12)
for _ in range(12):
memcache_client.set('some_key', [1, 2, 3])
# twelfth one skips .5 because of error limiting and goes straight
# to .4
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.5:11211: '
'[Errno 32] Broken pipe',
] * 11 + [
'Error limiting server 1.2.3.5:11211'
])
self.logger.clear()
mock2.should_explode = True
for _ in range(12):
memcache_client.set('some_key', [1, 2, 3])
# as we keep going, eventually .4 gets error limited, too
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.4:11211: '
'[Errno 32] Broken pipe',
] * 11 + [
'Error limiting server 1.2.3.4:11211'
])
self.logger.clear()
# continued requests just keep bypassing memcache
for _ in range(12):
memcache_client.set('some_key', [1, 2, 3])
self.assertEqual(self.logger.get_lines_for_level('error'), [])
# and get()s are all a "cache miss"
self.assertIsNone(memcache_client.get('some_key'))
self.assertEqual(self.logger.get_lines_for_level('error'), [])
def test_error_disabled(self):
memcache_client = memcached.MemcacheRing(
['1.2.3.4:11211'], logger=self.logger, error_limit_time=0)
mock1 = ExplodingMockMemcached()
memcache_client._client_cache['1.2.3.4:11211'] = MockedMemcachePool(
[(mock1, mock1)] * 20)
for _ in range(20):
memcache_client.set('some_key', [1, 2, 3])
# twelfth one skips .5 because of error limiting and goes straight
# to .4
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.4:11211: '
'[Errno 32] Broken pipe',
] * 20)
def test_error_limiting_custom_config(self):
def do_calls(time_step, num_calls, **memcache_kwargs):
self.logger.clear()
memcache_client = memcached.MemcacheRing(
['1.2.3.5:11211'], logger=self.logger,
**memcache_kwargs)
mock1 = ExplodingMockMemcached()
memcache_client._client_cache['1.2.3.5:11211'] = \
MockedMemcachePool([(mock1, mock1)] * num_calls)
for n in range(num_calls):
with mock.patch.object(memcached.time, 'time',
return_value=time_step * n):
memcache_client.set('some_key', [1, 2, 3])
# with default error_limit_time of 60, one call per 5 secs, twelfth one
# triggers error limit
do_calls(5, 12)
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.5:11211: '
'[Errno 32] Broken pipe',
] * 11 + [
'Error limiting server 1.2.3.5:11211'
])
# with default error_limit_time of 60, one call per 6 secs, error limit
# is not triggered
do_calls(6, 20)
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.5:11211: '
'[Errno 32] Broken pipe',
] * 20)
# with error_limit_time of 66, one call per 6 secs, twelfth one
# triggers error limit
do_calls(6, 12, error_limit_time=66)
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.5:11211: '
'[Errno 32] Broken pipe',
] * 11 + [
'Error limiting server 1.2.3.5:11211'
])
# with error_limit_time of 70, one call per 6 secs, error_limit_count
# of 11, 13th call triggers error limit
do_calls(6, 13, error_limit_time=70, error_limit_count=11)
self.assertEqual(self.logger.get_lines_for_level('error'), [
'Error talking to memcached: 1.2.3.5:11211: '
'[Errno 32] Broken pipe',
] * 12 + [
'Error limiting server 1.2.3.5:11211'
])
def test_delete(self):
memcache_client = memcached.MemcacheRing(['1.2.3.4:11211'],
logger=self.logger)