class PingPongServer(Observable):
PING_DELAY = Amount(1, Time.SECONDS)
def __init__(self, target_host, target_port, clock=time):
self._clock = clock
self._target = (target_host, target_port)
self._pings = AtomicGauge('pings')
self.metrics.register(self._pings)
def send_request(self, endpoint, message, ttl):
url_base = 'http://%s:%d' % self._target
try:
urllib2.urlopen('%s/%s/%s/%d' %
(url_base, endpoint, message, ttl)).read()
except Exception as e:
log.error('Failed to query %s: %s' % (url_base, e))
@HttpServer.route('/ping/:message')
@HttpServer.route('/ping/:message/:ttl')
def ping(self, message, ttl=60):
self._pings.increment()
log.info('Got ping (ttl=%s): %s' % (message, ttl))
ttl = int(ttl) - 1
if ttl > 0:
defer(partial(self.send_request, 'ping', message, ttl),
delay=self.PING_DELAY,
clock=self._clock)
class TwitterKazooClient(KazooClient, Observable):
@classmethod
def make(cls, *args, **kw):
# TODO(jcohen): Consider removing verbose option entirely in favor of just using loglevel.
verbose = kw.pop('verbose', False)
async = kw.pop('async', True)
if verbose:
loglevel = kw.pop('loglevel', logging.INFO)
else:
loglevel = kw.pop('loglevel', sys.maxsize)
logger = logging.getLogger('kazoo.devnull')
logger.setLevel(loglevel)
kw['logger'] = logger
zk = cls(*args, **kw)
if async:
zk.start_async()
zk.connecting.wait()
else:
zk.start()
return zk
def __init__(self, *args, **kw):
if 'connection_retry' not in kw:
# The default backoff delay limit in kazoo is 3600 seconds, which is generally
# too conservative for our use cases. If not supplied by the caller, provide
# a backoff that will truncate earlier.
kw['connection_retry'] = KazooRetry(
max_delay=DEFAULT_RETRY_MAX_DELAY_SECS, **DEFAULT_RETRY_DICT)
super(TwitterKazooClient, self).__init__(*args, **kw)
self.connecting = threading.Event()
self.__session_expirations = AtomicGauge('session_expirations')
self.__connection_losses = AtomicGauge('connection_losses')
self.__session_id = LambdaGauge('session_id', lambda: (self._session_id or 0))
self.metrics.register(self.__session_expirations)
self.metrics.register(self.__connection_losses)
self.metrics.register(self.__session_id)
self.add_listener(self._observable_listener)
def _observable_listener(self, state):
if state == KazooState.LOST:
self.__session_expirations.increment()
elif state == KazooState.SUSPENDED:
self.__connection_losses.increment()
def _session_callback(self, state):
rc = super(TwitterKazooClient, self)._session_callback(state)
if state == KeeperState.CONNECTING:
self.connecting.set()
return rc
@property
def live(self):
return self._live
class StatusStats(Observable):
def __init__(self):
self._count = AtomicGauge('count')
self._ns = AtomicGauge('total_ns')
self.metrics.register(self._count)
self.metrics.register(self._ns)
def increment(self, ns):
self._count.increment()
self._ns.add(ns)
class StatusStats(Observable):
def __init__(self):
self._count = AtomicGauge('count')
self._ns = AtomicGauge('total_ns')
self.metrics.register(self._count)
self.metrics.register(self._ns)
def increment(self, ns):
self._count.increment()
self._ns.add(ns)
class TwitterKazooClient(KazooClient, Observable):
@classmethod
def make(cls, *args, **kw):
verbose = kw.pop('verbose', False)
async = kw.pop('async', True)
if verbose is False:
kw['logger'] = logging.Logger('kazoo.devnull', level=sys.maxsize)
zk = cls(*args, **kw)
if async:
zk.start_async()
zk.connecting.wait()
else:
zk.start()
return zk
def __init__(self, *args, **kw):
super(TwitterKazooClient, self).__init__(*args, **kw)
self.connecting = threading.Event()
self.__session_expirations = AtomicGauge('session_expirations')
self.__connection_losses = AtomicGauge('connection_losses')
self.__session_id = LambdaGauge('session_id', lambda:
(self._session_id or 0))
self.metrics.register(self.__session_expirations)
self.metrics.register(self.__connection_losses)
self.metrics.register(self.__session_id)
self.add_listener(self._observable_listener)
def _observable_listener(self, state):
if state == KazooState.LOST:
self.__session_expirations.increment()
elif state == KazooState.SUSPENDED:
self.__connection_losses.increment()
def _session_callback(self, state):
rc = super(TwitterKazooClient, self)._session_callback(state)
if state == KeeperState.CONNECTING:
self.connecting.set()
return rc
@property
def live(self):
return self._live
class TwitterKazooClient(KazooClient, Observable):
@classmethod
def make(cls, *args, **kw):
verbose = kw.pop('verbose', False)
async = kw.pop('async', True)
if verbose is False:
kw['logger'] = logging.Logger('kazoo.devnull', level=sys.maxsize)
zk = cls(*args, **kw)
if async:
zk.start_async()
zk.connecting.wait()
else:
zk.start()
return zk
def __init__(self, *args, **kw):
super(TwitterKazooClient, self).__init__(*args, **kw)
self.connecting = threading.Event()
self.__session_expirations = AtomicGauge('session_expirations')
self.__connection_losses = AtomicGauge('connection_losses')
self.__session_id = LambdaGauge('session_id', lambda: (self._session_id or 0))
self.metrics.register(self.__session_expirations)
self.metrics.register(self.__connection_losses)
self.metrics.register(self.__session_id)
self.add_listener(self._observable_listener)
def _observable_listener(self, state):
if state == KazooState.LOST:
self.__session_expirations.increment()
elif state == KazooState.SUSPENDED:
self.__connection_losses.increment()
def _session_callback(self, state):
rc = super(TwitterKazooClient, self)._session_callback(state)
if state == KeeperState.CONNECTING:
self.connecting.set()
return rc
@property
def live(self):
return self._live
class PingPongServer(Observable):
PING_DELAY = Amount(1, Time.SECONDS)
def __init__(self, target_host, target_port, clock=time):
self._clock = clock
self._target = (target_host, target_port)
self._pings = AtomicGauge("pings")
self.metrics.register(self._pings)
def send_request(self, endpoint, message, ttl):
url_base = "http://%s:%d" % self._target
try:
urllib2.urlopen("%s/%s/%s/%d" % (url_base, endpoint, message, ttl)).read()
except Exception as e:
log.error("Failed to query %s: %s" % (url_base, e))
@HttpServer.route("/ping/:message")
@HttpServer.route("/ping/:message/:ttl")
def ping(self, message, ttl=60):
self._pings.increment()
log.info("Got ping (ttl=%s): %s" % (message, ttl))
ttl = int(ttl) - 1
if ttl > 0:
defer(partial(self.send_request, "ping", message, ttl), delay=self.PING_DELAY, clock=self._clock)
class ZooKeeper(object):
"""A convenience wrapper around the low-level ZooKeeper API.
Blocks until the initial connection is established, and proxies method calls
to the corresponding ZK functions, passing the handle.
Supports both synchronous and asynchronous APIs.
Syncronous API Notes:
Synchronous calls will block across connection loss or session
expiration until reconnected.
Asynchronous API Notes:
Asynchronous calls will queue up while the session/connection is
unhealthy and only be dispatched while zookeeper is healthy. It is
still possible for asynchronous calls to fail should the session be
severed after the call has been successfully dispatched. In other
words: don't assume your rc will always be zookeeper.OK.
Watches will behave as normal assuming successful dispatch. In general
when using this wrapper, you should retry your call if your watch is
fired with EXPIRED_SESSION_STATE and ignore anything else whose state is
not CONNECTED_STATE. This wrapper will never re-dispatch calls that
have been sent to zookeeper without error.
"""
class Error(Exception): pass
class ConnectionTimeout(Error): pass
class InvalidEnsemble(Error): pass
class Stopped(Error): pass
# White-list of methods that accept a ZK handle as their first argument
_ZK_SYNC_METHODS = frozenset([
'add_auth', 'close', 'create', 'delete', 'exists', 'get', 'get_acl',
'get_children', 'is_unrecoverable', 'recv_timeout', 'set', 'set2',
'set_acl', 'set_watcher', 'state',
])
_ZK_ASYNC_METHODS = frozenset([
'acreate', 'adelete', 'aexists', 'aget', 'aget_acl', 'aget_children', 'aset',
'aset_acl', 'async'
])
COMPLETION_RETRY = frozenset([
zookeeper.CONNECTIONLOSS,
zookeeper.OPERATIONTIMEOUT,
zookeeper.SESSIONEXPIRED,
zookeeper.CLOSING,
])
@classmethod
def expand_ensemble(cls, servers):
"""Expand comma-separated list of host:port to comma-separated, fully-resolved list of ip:port."""
server_ports = []
for server_port in servers.split(','):
server_split = server_port.split(':', 2)
if len(server_split) == 1:
server, port = server_split[0], cls.DEFAULT_PORT
else:
try:
server, port = server_split[0], int(server_split[1])
except ValueError:
raise cls.InvalidEnsemble('Invalid ensemble string: %s' % server_port)
try:
for ip in set(socket.gethostbyname_ex(server)[2]):
server_ports.append('%s:%s' % (ip, port))
except socket.gaierror:
raise cls.InvalidEnsemble('Could not resolve %s' % server)
return ','.join(server_ports)
DEFAULT_TIMEOUT_SECONDS = 30.0
DEFAULT_ENSEMBLE = 'localhost:2181'
DEFAULT_PORT = 2181
DEFAULT_ACL = ZooDefs.Acls.OPEN_ACL_UNSAFE
MAX_RECONNECTS = 1
# (is live?, is stopped?) => human readable status
STATUS_MATRIX = {
(True, True): 'WTF',
(True, False): 'OK',
(False, True): 'STOPPED',
(False, False): 'CONNECTING'
}
class Completion(object):
def __init__(self, zk, function, *args, **kw):
self._zk = zk
self._cid = random.randint(0, sys.maxint - 1)
self._logger = kw.pop('logger', log.debug)
@wraps(function)
def wrapper(zh):
return function(zh, *args, **kw)
self._fn = wrapper
self._logger('Created %s args:(%s) kw:{%s}' % (
self,
', '.join(map(repr, args)),
', '.join('%s: %r' % (key, val) for key, val in kw.items())))
def __str__(self):
return '%s(id:%s, zh:%s, %s)' % (
self.__class__.__name__, self._cid, self._zk._zh, self._fn.__name__)
def __call__(self):
try:
self._logger('%s start' % self)
result = self._fn(self._zk._zh)
self._logger('%s success' % self)
return result
except TypeError as e:
# Raced; zh now dead, so re-enqueue.
if self._zk._zh is not None:
raise
self._logger('%s raced, re-enqueueing' % self)
self._zk._add_completion(self._fn)
except (zookeeper.ConnectionLossException, zookeeper.InvalidStateException, SystemError) as e:
self._logger('%s excepted (%s), re-enqueueing' % (self, e))
self._zk._add_completion(self._fn)
return zookeeper.OK
# N.B.(wickman) This is code is theoretically racy. We cannot synchronize
# events across the zookeeper C event loop, however we do everything in
# our power to catch transitional latches. These are almost always
# exercised in tests and never in practice.
#
# TODO(wickman) ConnectionLoss probably does not encapsulate all the
# exception states that arise on connection loss and/or session
# expiration. However, we don't want to blanket catch ZooKeeperException
# because some things e.g. get() will raise NoNodeException. We should
# partition the exception space in two: behavioral exceptions and, well,
# exceptional exceptions.
class BlockingCompletion(Completion):
def __call__(self):
while True:
try:
self._logger('%s start' % self)
result = self._fn(self._zk._zh)
self._logger('%s success' % self)
return result
except (zookeeper.ConnectionLossException,
zookeeper.InvalidStateException,
TypeError) as e:
# TypeError because we raced on live latch from True=>False when _zh gets reinitialized.
if isinstance(e, TypeError) and self._zk._zh is not None:
self._logger('%s excepted, user error' % self)
raise
# We had the misfortune of the live latch being set but having a session event propagate
# before the BlockingCompletion could be executed.
while not self._zk._stopped.is_set():
self._logger('%s [live: %s] excepted on connection event: %s' % (
self, self._zk._live.is_set(), e))
self._zk._live.wait(timeout=0.1)
if self._zk._live.is_set():
break
if self._zk._stopped.is_set():
raise ZooKeeper.Stopped('ZooKeeper is stopped.')
except Exception as e:
self._logger('%s excepted unexpectedly: %s' % (self, e))
raise
def __init__(self,
servers=None,
timeout_secs=None,
watch=None,
max_reconnects=None,
authentication=None,
logger=log.debug):
"""Create new ZooKeeper object.
Blocks until ZK negotation completes, or the timeout expires. By default
only tries to connect once. Use a larger 'max_reconnects' if you want
to be resilient to things such as DNS outages/changes.
If watch is set to a function, it is called whenever the global
zookeeper watch is dispatched using the same function signature, with the
exception that this object is used in place of the zookeeper handle.
If authentication is set, it should be a tuple of (scheme, credentials),
for example, ('digest', 'username:password')
"""
default_ensemble = self.DEFAULT_ENSEMBLE
default_timeout = self.DEFAULT_TIMEOUT_SECONDS
default_reconnects = self.MAX_RECONNECTS
if WITH_APP:
options = app.get_options()
default_ensemble = options.twitter_common_zookeeper_ensemble
default_timeout = options.twitter_common_zookeeper_timeout
default_reconnects = options.twitter_common_zookeeper_reconnects
self._servers = servers or default_ensemble
self._timeout_secs = timeout_secs or default_timeout
self._init_count = 0
self._credentials = authentication
self._authenticated = threading.Event()
self._live = threading.Event()
self._stopped = threading.Event()
self._completions = Queue()
self._zh = None
self._watch = watch
self._logger = logger
self._max_reconnects = max_reconnects if max_reconnects is not None else default_reconnects
self._init_stats()
self.reconnect()
def __del__(self):
self._safe_close()
def _log(self, msg):
self._logger('[zh:%s] %s' % (self._zh, msg))
def _init_stats(self):
self._gauge_session_expirations = AtomicGauge('session-expirations')
self._gauge_connection_losses = AtomicGauge('connection-losses')
def session_id(self):
try:
session_id, _ = zookeeper.client_id(self._zh)
return session_id
except:
return None
@property
def session_expirations(self):
return self._gauge_session_expirations.read()
@property
def connection_losses(self):
return self._gauge_connection_losses.read()
@property
def live(self):
return self._live.is_set()
def stop(self):
"""Gracefully stop this Zookeeper session."""
self._log('Shutting down ZooKeeper')
self._stopped.set()
self._safe_close()
self._completions = Queue() # there is no .clear()
def restart(self):
"""Stop and restart this Zookeeper session. Unfinished completions will be retried
on reconnection."""
self._safe_close()
self._stopped.clear()
self.reconnect()
def _safe_close(self):
if self._zh is not None:
zh, self._zh = self._zh, None
try:
zookeeper.close(zh)
except zookeeper.ZooKeeperException:
# the session has been corrupted or otherwise disconnected
pass
self._live.clear()
def _add_completion(self, function, *args, **kw):
self._completions.put(self.Completion(self, function, logger=self._log, *args, **kw))
def _clear_completions(self):
while self._live.is_set():
try:
completion = self._completions.get_nowait()
completion()
self._completions.task_done()
except Empty:
return
def reconnect(self):
"""Attempt to reconnect to ZK."""
if self._stopped.is_set():
self._safe_close()
return
def safe_close(zh):
try:
zookeeper.close(zh)
except:
# TODO(wickman) When the SystemError bug is fixed in zkpython, narrow this except clause.
pass
def activate():
self._authenticated.set()
self._live.set()
def on_authentication(zh, rc):
if self._zh != zh:
safe_close(zh)
return
if rc == zookeeper.OK:
activate()
def maybe_authenticate():
if self._authenticated.is_set() or not self._credentials:
activate()
return
try:
scheme, credentials = self._credentials
zookeeper.add_auth(self._zh, scheme, credentials, on_authentication)
except zookeeper.ZooKeeperException as e:
self._logger('Failed to authenticate: %s' % e)
def connection_handler(handle, type, state, path):
if self._zh != handle:
safe_close(handle)
return
if self._stopped.is_set():
return
if self._watch:
self._watch(self, type, state, path)
if state == zookeeper.CONNECTED_STATE:
self._logger('Connection started, setting live.')
maybe_authenticate()
self._clear_completions()
elif state == zookeeper.EXPIRED_SESSION_STATE:
self._logger('Session lost, clearing live state.')
self._gauge_session_expirations.increment()
self._live.clear()
self._authenticated.clear()
self._zh = None
self._init_count = 0
self.reconnect()
else:
self._logger('Connection lost, clearing live state.')
self._gauge_connection_losses.increment()
self._live.clear()
# this closure is exposed for testing only -- in order to simulate session events.
self._handler = connection_handler
timeout_ms = int(self._timeout_secs * 1000)
while True:
self._safe_close()
servers = self.expand_ensemble(self._servers)
self._log('Connecting to ZK hosts at %s' % servers)
self._zh = zookeeper.init(servers, connection_handler, timeout_ms)
self._init_count += 1
self._live.wait(self._timeout_secs + 1)
if self._live.is_set():
break
elif self._max_reconnects > 0 and self._init_count >= self._max_reconnects:
self._safe_close()
raise ZooKeeper.ConnectionTimeout('Timed out waiting for ZK connection to %s' % servers)
self._log('Successfully connected to ZK at %s' % servers)
def _wrap_sync(self, function_name):
"""Wrap a zookeeper module function in an error-handling completion that injects the
current zookeeper handle as the first parameter."""
function = getattr(zookeeper, function_name)
@wraps(function)
def _curry(*args, **kwargs):
return self.BlockingCompletion(self, function, logger=self._log, *args, **kwargs)()
return _curry
def _wrap_async(self, function_name):
"""Wrap an asynchronous zookeeper module function in an error-handling
completion that injects the current zookeeper handle as the first
parameter and puts it on a completion queue if the current connection
state is unhealthy."""
function = getattr(zookeeper, function_name)
@wraps(function)
def _curry(*args, **kwargs):
completion = self.Completion(self, function, logger=self._log, *args, **kwargs)
if self._live.is_set():
return completion()
else:
# TODO(wickman) This is racy, should it go from not live => live
# prior to Queue.put. Two solutions: a periodic background thread
# that attempts to empty the completion queue, or use a mutex-protected
# container for self._live.
self._completions.put(self.Completion(self, function, logger=self._log, *args, **kwargs))
return zookeeper.OK # proxy OK.
return _curry
def safe_create(self, path, acl=DEFAULT_ACL):
child = '/'
for component in filter(None, path.split('/')):
child = posixpath.join(child, component)
try:
self.create(child, "", acl, 0)
except zookeeper.NodeExistsException:
continue
except zookeeper.NoAuthException:
if not self.exists(child):
raise
return child
def safe_delete(self, path):
try:
if not self.exists(path):
return True
for child in self.get_children(path):
if not self.safe_delete(posixpath.join(path, child)):
return False
self.delete(path)
except zookeeper.ZooKeeperException:
return False
return True
def __getattr__(self, function_name):
"""Proxy to underlying ZK functions."""
if function_name in ZooKeeper._ZK_SYNC_METHODS:
return self._wrap_sync(function_name)
elif function_name in ZooKeeper._ZK_ASYNC_METHODS:
return self._wrap_async(function_name)
else:
raise AttributeError('%r has no attribute %r' % (self, function_name))
def __str__(self):
return 'ZooKeeper(status=%s,queued=%d,servers=%r)' % (
self.STATUS_MATRIX[(self._live.is_set(), self._stopped.is_set())],
self._completions.qsize(), self._servers)
def __repr__(self):
return 'ZooKeeper(servers=%r)' % self._servers
class ZooKeeper(Observable):
"""A convenience wrapper around the low-level ZooKeeper API.
Blocks until the initial connection is established, and proxies method calls
to the corresponding ZK functions, passing the handle.
Supports both synchronous and asynchronous APIs.
Syncronous API Notes:
Synchronous calls will block across connection loss or session
expiration until reconnected.
Asynchronous API Notes:
Asynchronous calls will queue up while the session/connection is
unhealthy and only be dispatched while zookeeper is healthy. It is
still possible for asynchronous calls to fail should the session be
severed after the call has been successfully dispatched. In other
words: don't assume your rc will always be zookeeper.OK.
Watches will behave as normal assuming successful dispatch. In general
when using this wrapper, you should retry your call if your watch is
fired with EXPIRED_SESSION_STATE and ignore anything else whose state is
not CONNECTED_STATE. This wrapper will never re-dispatch calls that
have been sent to zookeeper without error.
"""
class Error(Exception):
pass
class ConnectionTimeout(Error):
pass
class InvalidEnsemble(Error):
pass
class Stopped(Error):
pass
# White-list of methods that accept a ZK handle as their first argument
_ZK_SYNC_METHODS = frozenset([
'add_auth',
'close',
'create',
'delete',
'exists',
'get',
'get_acl',
'get_children',
'is_unrecoverable',
'recv_timeout',
'set',
'set2',
'set_acl',
'set_watcher',
'state',
])
_ZK_ASYNC_METHODS = frozenset([
'acreate', 'adelete', 'aexists', 'aget', 'aget_acl', 'aget_children',
'aset', 'aset_acl', 'async'
])
COMPLETION_RETRY = frozenset([
zookeeper.CONNECTIONLOSS,
zookeeper.OPERATIONTIMEOUT,
zookeeper.SESSIONEXPIRED,
zookeeper.CLOSING,
])
@classmethod
def expand_ensemble(cls, servers):
"""Expand comma-separated list of host:port to comma-separated, fully-resolved list of ip:port."""
server_ports = []
for server_port in servers.split(','):
server_split = server_port.split(':', 2)
if len(server_split) == 1:
server, port = server_split[0], cls.DEFAULT_PORT
else:
try:
server, port = server_split[0], int(server_split[1])
except ValueError:
raise cls.InvalidEnsemble('Invalid ensemble string: %s' %
server_port)
try:
for ip in socket.gethostbyname_ex(server)[2]:
server_ports.append('%s:%s' % (ip, port))
except socket.gaierror:
raise cls.InvalidEnsemble('Could not resolve %s' % server)
return ','.join(server_ports)
DEFAULT_TIMEOUT_SECONDS = 30.0
DEFAULT_ENSEMBLE = 'localhost:2181'
DEFAULT_PORT = 2181
DEFAULT_ACL = ZooDefs.Acls.OPEN_ACL_UNSAFE
MAX_RECONNECTS = 1
# (is live?, is stopped?) => human readable status
STATUS_MATRIX = {
(True, True): 'WTF',
(True, False): 'OK',
(False, True): 'STOPPED',
(False, False): 'CONNECTING'
}
class Completion(object):
def __init__(self, zk, function, *args, **kw):
self._zk = zk
self._cid = random.randint(0, sys.maxint - 1)
self._logger = kw.pop('logger', log.debug)
@wraps(function)
def wrapper(zh):
return function(zh, *args, **kw)
self._fn = wrapper
self._logger('Created %s args:(%s) kw:{%s}' % (self, ', '.join(
map(repr, args)), ', '.join('%s: %r' % (key, val)
for key, val in kw.items())))
def __str__(self):
return '%s(id:%s, zh:%s, %s)' % (self.__class__.__name__,
self._cid, self._zk._zh,
self._fn.__name__)
def __call__(self):
try:
self._logger('%s start' % self)
result = self._fn(self._zk._zh)
self._logger('%s success' % self)
return result
except TypeError as e:
# Raced; zh now dead, so re-enqueue.
if self._zk._zh is not None:
raise
self._logger('%s raced, re-enqueueing' % self)
self._zk._add_completion(self._fn)
except (zookeeper.ConnectionLossException,
zookeeper.InvalidStateException,
zookeeper.SessionExpiredException, SystemError) as e:
self._logger('%s excepted (%s), re-enqueueing' % (self, e))
self._zk._add_completion(self._fn)
return zookeeper.OK
# N.B.(wickman) This is code is theoretically racy. We cannot synchronize
# events across the zookeeper C event loop, however we do everything in
# our power to catch transitional latches. These are almost always
# exercised in tests and never in practice.
#
# TODO(wickman) ConnectionLoss probably does not encapsulate all the
# exception states that arise on connection loss and/or session
# expiration. However, we don't want to blanket catch ZooKeeperException
# because some things e.g. get() will raise NoNodeException. We should
# partition the exception space in two: behavioral exceptions and, well,
# exceptional exceptions.
class BlockingCompletion(Completion):
def __call__(self):
while True:
try:
self._logger('%s start' % self)
result = self._fn(self._zk._zh)
self._logger('%s success' % self)
return result
except (zookeeper.ConnectionLossException,
zookeeper.InvalidStateException,
zookeeper.SessionExpiredException, TypeError) as e:
# TypeError because we raced on live latch from True=>False when _zh gets reinitialized.
if isinstance(e, TypeError) and self._zk._zh is not None:
self._logger('%s excepted, user error' % self)
raise
# We had the misfortune of the live latch being set but having a session event propagate
# before the BlockingCompletion could be executed.
while not self._zk._stopped.is_set():
self._logger(
'%s [live: %s] excepted on connection event: %s' %
(self, self._zk._live.is_set(), e))
self._zk._live.wait(timeout=0.1)
if self._zk._live.is_set():
break
if self._zk._stopped.is_set():
raise ZooKeeper.Stopped('ZooKeeper is stopped.')
except Exception as e:
self._logger('%s excepted unexpectedly: %s' % (self, e))
raise
def __init__(self,
servers=None,
timeout_secs=None,
watch=None,
max_reconnects=None,
authentication=None,
logger=log.debug):
"""Create new ZooKeeper object.
Blocks until ZK negotation completes, or the timeout expires. By default
only tries to connect once. Use a larger 'max_reconnects' if you want
to be resilient to things such as DNS outages/changes.
If watch is set to a function, it is called whenever the global
zookeeper watch is dispatched using the same function signature, with the
exception that this object is used in place of the zookeeper handle.
If authentication is set, it should be a tuple of (scheme, credentials),
for example, ('digest', 'username:password')
"""
default_ensemble = self.DEFAULT_ENSEMBLE
default_timeout = self.DEFAULT_TIMEOUT_SECONDS
default_reconnects = self.MAX_RECONNECTS
if WITH_APP:
options = app.get_options()
default_ensemble = options.twitter_common_zookeeper_ensemble
default_timeout = options.twitter_common_zookeeper_timeout
default_reconnects = options.twitter_common_zookeeper_reconnects
self._servers = servers or default_ensemble
self._timeout_secs = timeout_secs or default_timeout
self._init_count = 0
self._credentials = authentication
self._authenticated = threading.Event()
self._live = threading.Event()
self._stopped = threading.Event()
self._completions = Queue()
self._zh = None
self._watch = watch
self._logger = logger
self._max_reconnects = max_reconnects if max_reconnects is not None else default_reconnects
self._init_metrics()
self.reconnect()
def __del__(self):
self._safe_close()
def _log(self, msg):
self._logger('[zh:%s] %s' % (self._zh, msg))
def _init_metrics(self):
self._session_expirations = AtomicGauge('session_expirations')
self._connection_losses = AtomicGauge('connection_losses')
self.metrics.register(self._session_expirations)
self.metrics.register(self._connection_losses)
self.metrics.register(
LambdaGauge('session_id', lambda: self.session_id))
self.metrics.register(
LambdaGauge('live', lambda: int(self._live.is_set())))
@property
def session_id(self):
try:
session_id, _ = zookeeper.client_id(self._zh)
return session_id
except:
return None
@property
def session_expirations(self):
return self._session_expirations.read()
@property
def connection_losses(self):
return self._connection_losses.read()
@property
def live(self):
return self._live
def stop(self):
"""Gracefully stop this Zookeeper session."""
self._log('Shutting down ZooKeeper')
self._stopped.set()
self._safe_close()
self._completions = Queue() # there is no .clear()
def restart(self):
"""Stop and restart this Zookeeper session. Unfinished completions will be retried
on reconnection."""
self._safe_close()
self._stopped.clear()
self.reconnect()
def _safe_close(self):
if self._zh is not None:
zh, self._zh = self._zh, None
try:
zookeeper.close(zh)
except zookeeper.ZooKeeperException:
# the session has been corrupted or otherwise disconnected
pass
self._live.clear()
def _add_completion(self, function, *args, **kw):
self._completions.put(
self.Completion(self, function, logger=self._log, *args, **kw))
def _clear_completions(self):
while self._live.is_set():
try:
completion = self._completions.get_nowait()
completion()
self._completions.task_done()
except Empty:
return
def reconnect(self):
"""Attempt to reconnect to ZK."""
if self._stopped.is_set():
self._safe_close()
return
def safe_close(zh):
try:
zookeeper.close(zh)
except:
# TODO(wickman) When the SystemError bug is fixed in zkpython, narrow this except clause.
pass
def activate():
self._authenticated.set()
self._live.set()
def on_authentication(zh, rc):
if self._zh != zh:
safe_close(zh)
return
if rc == zookeeper.OK:
activate()
def maybe_authenticate():
if self._authenticated.is_set() or not self._credentials:
activate()
return
try:
scheme, credentials = self._credentials
zookeeper.add_auth(self._zh, scheme, credentials,
on_authentication)
except zookeeper.ZooKeeperException as e:
self._logger('Failed to authenticate: %s' % e)
def connection_handler(handle, type, state, path):
if self._zh != handle:
safe_close(handle)
return
if self._stopped.is_set():
return
if self._watch:
self._watch(self, type, state, path)
if state == zookeeper.CONNECTED_STATE:
self._logger('Connection started, setting live.')
maybe_authenticate()
self._clear_completions()
elif state == zookeeper.EXPIRED_SESSION_STATE:
self._logger('Session lost, clearing live state.')
self._session_expirations.increment()
self._live.clear()
self._authenticated.clear()
self._zh = None
self._init_count = 0
self.reconnect()
else:
self._logger('Connection lost, clearing live state.')
self._connection_losses.increment()
self._live.clear()
# this closure is exposed for testing only -- in order to simulate session events.
self._handler = connection_handler
timeout_ms = int(self._timeout_secs * 1000)
while True:
self._safe_close()
servers = self.expand_ensemble(self._servers)
self._log('Connecting to ZK hosts at %s' % servers)
self._zh = zookeeper.init(servers, connection_handler, timeout_ms)
self._init_count += 1
self._live.wait(self._timeout_secs + 1)
if self._live.is_set():
break
elif self._max_reconnects > 0 and self._init_count >= self._max_reconnects:
self._safe_close()
raise ZooKeeper.ConnectionTimeout(
'Timed out waiting for ZK connection to %s' % servers)
self._log('Successfully connected to ZK at %s' % servers)
def _wrap_sync(self, function_name):
"""Wrap a zookeeper module function in an error-handling completion that injects the
current zookeeper handle as the first parameter."""
function = getattr(zookeeper, function_name)
@wraps(function)
def _curry(*args, **kwargs):
return self.BlockingCompletion(self,
function,
logger=self._log,
*args,
**kwargs)()
return _curry
def _wrap_async(self, function_name):
"""Wrap an asynchronous zookeeper module function in an error-handling
completion that injects the current zookeeper handle as the first
parameter and puts it on a completion queue if the current connection
state is unhealthy."""
function = getattr(zookeeper, function_name)
@wraps(function)
def _curry(*args, **kwargs):
completion = self.Completion(self,
function,
logger=self._log,
*args,
**kwargs)
if self._live.is_set():
return completion()
else:
# TODO(wickman) This is racy, should it go from not live => live
# prior to Queue.put. Two solutions: a periodic background thread
# that attempts to empty the completion queue, or use a mutex-protected
# container for self._live.
self._completions.put(
self.Completion(self,
function,
logger=self._log,
*args,
**kwargs))
return zookeeper.OK # proxy OK.
return _curry
def safe_create(self, path, acl=DEFAULT_ACL):
child = '/'
for component in filter(None, path.split('/')):
child = posixpath.join(child, component)
try:
self.create(child, "", acl, 0)
except zookeeper.NodeExistsException:
continue
except zookeeper.NoAuthException:
if not self.exists(child):
raise
return child
def safe_delete(self, path):
try:
if not self.exists(path):
return True
for child in self.get_children(path):
if not self.safe_delete(posixpath.join(path, child)):
return False
self.delete(path)
except zookeeper.ZooKeeperException:
return False
return True
def __getattr__(self, function_name):
"""Proxy to underlying ZK functions."""
if function_name in ZooKeeper._ZK_SYNC_METHODS:
return self._wrap_sync(function_name)
elif function_name in ZooKeeper._ZK_ASYNC_METHODS:
return self._wrap_async(function_name)
else:
raise AttributeError('%r has no attribute %r' %
(self, function_name))
def __str__(self):
return 'ZooKeeper(status=%s,queued=%d,servers=%r)' % (
self.STATUS_MATRIX[(self._live.is_set(), self._stopped.is_set())],
self._completions.qsize(), self._servers)
def __repr__(self):
return 'ZooKeeper(servers=%r)' % self._servers