/usr/lib/python2.7/dist-packages/pymongo/topology.py is in python-pymongo 3.4.0-1.
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#
# 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.
"""Internal class to monitor a topology of one or more servers."""
import os
import random
import threading
import warnings
import weakref
from bson.py3compat import itervalues, PY3
if PY3:
import queue as Queue
else:
import Queue
from pymongo import common
from pymongo import periodic_executor
from pymongo.pool import PoolOptions
from pymongo.topology_description import (updated_topology_description,
TOPOLOGY_TYPE,
TopologyDescription)
from pymongo.errors import ServerSelectionTimeoutError
from pymongo.monotonic import time as _time
from pymongo.server import Server
from pymongo.server_selectors import (any_server_selector,
arbiter_server_selector,
secondary_server_selector,
writable_server_selector,
Selection)
def process_events_queue(queue_ref):
q = queue_ref()
if not q:
return False # Cancel PeriodicExecutor.
while True:
try:
event = q.get_nowait()
except Queue.Empty:
break
else:
fn, args = event
fn(*args)
return True # Continue PeriodicExecutor.
class Topology(object):
"""Monitor a topology of one or more servers."""
def __init__(self, topology_settings):
self._topology_id = topology_settings._topology_id
self._listeners = topology_settings._pool_options.event_listeners
pub = self._listeners is not None
self._publish_server = pub and self._listeners.enabled_for_server
self._publish_tp = pub and self._listeners.enabled_for_topology
# Create events queue if there are publishers.
self._events = None
self._events_thread = None
if self._publish_server or self._publish_tp:
self._events = Queue.Queue(maxsize=100)
if self._publish_tp:
self._events.put((self._listeners.publish_topology_opened,
(self._topology_id,)))
self._settings = topology_settings
topology_description = TopologyDescription(
topology_settings.get_topology_type(),
topology_settings.get_server_descriptions(),
topology_settings.replica_set_name,
None,
None,
topology_settings)
self._description = topology_description
if self._publish_tp:
initial_td = TopologyDescription(TOPOLOGY_TYPE.Unknown, {}, None,
None, None, self._settings)
self._events.put((
self._listeners.publish_topology_description_changed,
(initial_td, self._description, self._topology_id)))
for seed in topology_settings.seeds:
if self._publish_server:
self._events.put((self._listeners.publish_server_opened,
(seed, self._topology_id)))
# Store the seed list to help diagnose errors in _error_message().
self._seed_addresses = list(topology_description.server_descriptions())
self._opened = False
self._lock = threading.Lock()
self._condition = self._settings.condition_class(self._lock)
self._servers = {}
self._pid = None
if self._publish_server or self._publish_tp:
def target():
return process_events_queue(weak)
executor = periodic_executor.PeriodicExecutor(
interval=common.EVENTS_QUEUE_FREQUENCY,
min_interval=0.5,
target=target,
name="pymongo_events_thread")
# We strongly reference the executor and it weakly references
# the queue via this closure. When the topology is freed, stop
# the executor soon.
weak = weakref.ref(self._events)
self.__events_executor = executor
executor.open()
def open(self):
"""Start monitoring, or restart after a fork.
No effect if called multiple times.
.. warning:: Topology is shared among multiple threads and is protected
by mutual exclusion. Using Topology from a process other than the one
that initialized it will emit a warning and may result in deadlock. To
prevent this from happening, MongoClient must be created after any
forking OR MongoClient must be started with connect=False.
"""
if self._pid is None:
self._pid = os.getpid()
else:
if os.getpid() != self._pid:
warnings.warn(
"MongoClient opened before fork. Create MongoClient "
"with connect=False, or create client after forking. "
"See PyMongo's documentation for details: http://api."
"mongodb.org/python/current/faq.html#pymongo-fork-safe>")
with self._lock:
self._ensure_opened()
def select_servers(self,
selector,
server_selection_timeout=None,
address=None):
"""Return a list of Servers matching selector, or time out.
:Parameters:
- `selector`: function that takes a list of Servers and returns
a subset of them.
- `server_selection_timeout` (optional): maximum seconds to wait.
If not provided, the default value common.SERVER_SELECTION_TIMEOUT
is used.
- `address`: optional server address to select.
Calls self.open() if needed.
Raises exc:`ServerSelectionTimeoutError` after
`server_selection_timeout` if no matching servers are found.
"""
if server_selection_timeout is None:
server_timeout = self._settings.server_selection_timeout
else:
server_timeout = server_selection_timeout
with self._lock:
self._description.check_compatible()
now = _time()
end_time = now + server_timeout
server_descriptions = self._description.apply_selector(
selector, address)
while not server_descriptions:
# No suitable servers.
if server_timeout == 0 or now > end_time:
raise ServerSelectionTimeoutError(
self._error_message(selector))
self._ensure_opened()
self._request_check_all()
# Release the lock and wait for the topology description to
# change, or for a timeout. We won't miss any changes that
# came after our most recent apply_selector call, since we've
# held the lock until now.
self._condition.wait(common.MIN_HEARTBEAT_INTERVAL)
self._description.check_compatible()
now = _time()
server_descriptions = self._description.apply_selector(
selector, address)
return [self.get_server_by_address(sd.address)
for sd in server_descriptions]
def select_server(self,
selector,
server_selection_timeout=None,
address=None):
"""Like select_servers, but choose a random server if several match."""
return random.choice(self.select_servers(selector,
server_selection_timeout,
address))
def select_server_by_address(self, address,
server_selection_timeout=None):
"""Return a Server for "address", reconnecting if necessary.
If the server's type is not known, request an immediate check of all
servers. Time out after "server_selection_timeout" if the server
cannot be reached.
:Parameters:
- `address`: A (host, port) pair.
- `server_selection_timeout` (optional): maximum seconds to wait.
If not provided, the default value
common.SERVER_SELECTION_TIMEOUT is used.
Calls self.open() if needed.
Raises exc:`ServerSelectionTimeoutError` after
`server_selection_timeout` if no matching servers are found.
"""
return self.select_server(any_server_selector,
server_selection_timeout,
address)
def on_change(self, server_description):
"""Process a new ServerDescription after an ismaster call completes."""
# We do no I/O holding the lock.
with self._lock:
# Any monitored server was definitely in the topology description
# once. Check if it's still in the description or if some state-
# change removed it. E.g., we got a host list from the primary
# that didn't include this server.
if self._description.has_server(server_description.address):
td_old = self._description
if self._publish_server:
old_server_description = td_old._server_descriptions[
server_description.address]
self._events.put((
self._listeners.publish_server_description_changed,
(old_server_description, server_description,
server_description.address, self._topology_id)))
self._description = updated_topology_description(
self._description, server_description)
self._update_servers()
if self._publish_tp:
self._events.put((
self._listeners.publish_topology_description_changed,
(td_old, self._description, self._topology_id)))
# Wake waiters in select_servers().
self._condition.notify_all()
def get_server_by_address(self, address):
"""Get a Server or None.
Returns the current version of the server immediately, even if it's
Unknown or absent from the topology. Only use this in unittests.
In driver code, use select_server_by_address, since then you're
assured a recent view of the server's type and wire protocol version.
"""
return self._servers.get(address)
def has_server(self, address):
return address in self._servers
def get_primary(self):
"""Return primary's address or None."""
# Implemented here in Topology instead of MongoClient, so it can lock.
with self._lock:
topology_type = self._description.topology_type
if topology_type != TOPOLOGY_TYPE.ReplicaSetWithPrimary:
return None
return writable_server_selector(self._new_selection())[0].address
def _get_replica_set_members(self, selector):
"""Return set of replica set member addresses."""
# Implemented here in Topology instead of MongoClient, so it can lock.
with self._lock:
topology_type = self._description.topology_type
if topology_type not in (TOPOLOGY_TYPE.ReplicaSetWithPrimary,
TOPOLOGY_TYPE.ReplicaSetNoPrimary):
return set()
return set([sd.address for sd in selector(self._new_selection())])
def get_secondaries(self):
"""Return set of secondary addresses."""
return self._get_replica_set_members(secondary_server_selector)
def get_arbiters(self):
"""Return set of arbiter addresses."""
return self._get_replica_set_members(arbiter_server_selector)
def request_check_all(self, wait_time=5):
"""Wake all monitors, wait for at least one to check its server."""
with self._lock:
self._request_check_all()
self._condition.wait(wait_time)
def reset_pool(self, address):
with self._lock:
server = self._servers.get(address)
if server:
server.pool.reset()
def reset_server(self, address):
"""Clear our pool for a server and mark it Unknown.
Do *not* request an immediate check.
"""
with self._lock:
self._reset_server(address)
def reset_server_and_request_check(self, address):
"""Clear our pool for a server, mark it Unknown, and check it soon."""
with self._lock:
self._reset_server(address)
self._request_check(address)
def update_pool(self):
# Remove any stale sockets and add new sockets if pool is too small.
with self._lock:
for server in self._servers.values():
server._pool.remove_stale_sockets()
def close(self):
"""Clear pools and terminate monitors. Topology reopens on demand."""
with self._lock:
for server in self._servers.values():
server.close()
# Mark all servers Unknown.
self._description = self._description.reset()
self._update_servers()
# Publish only after releasing the lock.
if self._publish_tp:
self._events.put((self._listeners.publish_topology_closed,
(self._topology_id,)))
if self._publish_server or self._publish_tp:
self.__events_executor.close()
@property
def description(self):
return self._description
def _new_selection(self):
"""A Selection object, initially including all known servers.
Hold the lock when calling this.
"""
return Selection.from_topology_description(self._description)
def _ensure_opened(self):
"""Start monitors, or restart after a fork.
Hold the lock when calling this.
"""
if not self._opened:
self._opened = True
self._update_servers()
# Start or restart the events publishing thread.
if self._publish_tp or self._publish_server:
self.__events_executor.open()
else:
# Restart monitors if we forked since previous call.
for server in itervalues(self._servers):
server.open()
def _reset_server(self, address):
"""Clear our pool for a server and mark it Unknown.
Hold the lock when calling this. Does *not* request an immediate check.
"""
server = self._servers.get(address)
# "server" is None if another thread removed it from the topology.
if server:
server.reset()
# Mark this server Unknown.
self._description = self._description.reset_server(address)
self._update_servers()
def _request_check(self, address):
"""Wake one monitor. Hold the lock when calling this."""
server = self._servers.get(address)
# "server" is None if another thread removed it from the topology.
if server:
server.request_check()
def _request_check_all(self):
"""Wake all monitors. Hold the lock when calling this."""
for server in self._servers.values():
server.request_check()
def _update_servers(self):
"""Sync our Servers from TopologyDescription.server_descriptions.
Hold the lock while calling this.
"""
for address, sd in self._description.server_descriptions().items():
if address not in self._servers:
monitor = self._settings.monitor_class(
server_description=sd,
topology=self,
pool=self._create_pool_for_monitor(address),
topology_settings=self._settings)
weak = None
if self._publish_server:
weak = weakref.ref(self._events)
server = Server(
server_description=sd,
pool=self._create_pool_for_server(address),
monitor=monitor,
topology_id=self._topology_id,
listeners=self._listeners,
events=weak)
self._servers[address] = server
server.open()
else:
self._servers[address].description = sd
for address, server in list(self._servers.items()):
if not self._description.has_server(address):
server.close()
self._servers.pop(address)
def _create_pool_for_server(self, address):
return self._settings.pool_class(address, self._settings.pool_options)
def _create_pool_for_monitor(self, address):
options = self._settings.pool_options
# According to the Server Discovery And Monitoring Spec, monitors use
# connect_timeout for both connect_timeout and socket_timeout. The
# pool only has one socket so maxPoolSize and so on aren't needed.
monitor_pool_options = PoolOptions(
connect_timeout=options.connect_timeout,
socket_timeout=options.connect_timeout,
ssl_context=options.ssl_context,
ssl_match_hostname=options.ssl_match_hostname,
socket_keepalive=True,
event_listeners=options.event_listeners,
appname=options.appname)
return self._settings.pool_class(address, monitor_pool_options,
handshake=False)
def _error_message(self, selector):
"""Format an error message if server selection fails.
Hold the lock when calling this.
"""
is_replica_set = self._description.topology_type in (
TOPOLOGY_TYPE.ReplicaSetWithPrimary,
TOPOLOGY_TYPE.ReplicaSetNoPrimary)
if is_replica_set:
server_plural = 'replica set members'
elif self._description.topology_type == TOPOLOGY_TYPE.Sharded:
server_plural = 'mongoses'
else:
server_plural = 'servers'
if self._description.known_servers:
# We've connected, but no servers match the selector.
if selector is writable_server_selector:
if is_replica_set:
return 'No primary available for writes'
else:
return 'No %s available for writes' % server_plural
else:
return 'No %s match selector "%s"' % (server_plural, selector)
else:
addresses = list(self._description.server_descriptions())
servers = list(self._description.server_descriptions().values())
if not servers:
if is_replica_set:
# We removed all servers because of the wrong setName?
return 'No %s available for replica set name "%s"' % (
server_plural, self._settings.replica_set_name)
else:
return 'No %s available' % server_plural
# 1 or more servers, all Unknown. Are they unknown for one reason?
error = servers[0].error
same = all(server.error == error for server in servers[1:])
if same:
if error is None:
# We're still discovering.
return 'No %s found yet' % server_plural
if (is_replica_set and not
set(addresses).intersection(self._seed_addresses)):
# We replaced our seeds with new hosts but can't reach any.
return (
'Could not reach any servers in %s. Replica set is'
' configured with internal hostnames or IPs?' %
addresses)
return str(error)
else:
return ','.join(str(server.error) for server in servers
if server.error)
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