-from ws4py.client.threadedclient import WebSocketClient
-import threading
+# Copyright (C) The Arvados Authors. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import enum
import json
+import logging
import os
-import time
-import ssl
import re
-import config
-import logging
-import arvados
+import ssl
+import sys
+import _thread
+import threading
+import time
+
+import websockets.exceptions as ws_exc
+import websockets.sync.client as ws_client
+
+from . import config
+from . import errors
+from . import util
+from .retry import RetryLoop
+from ._version import __version__
+
+from typing import (
+ Any,
+ Callable,
+ Dict,
+ Iterable,
+ List,
+ Optional,
+ Union,
+)
+
+EventCallback = Callable[[Dict[str, Any]], object]
+"""Type signature for an event handler callback"""
+FilterCondition = List[Union[None, str, 'Filter']]
+"""Type signature for a single filter condition"""
+Filter = List[FilterCondition]
+"""Type signature for an entire filter"""
_logger = logging.getLogger('arvados.events')
-class EventClient(WebSocketClient):
- def __init__(self, url, filters, on_event):
- ssl_options = None
- if re.match(r'(?i)^(true|1|yes)$',
- config.get('ARVADOS_API_HOST_INSECURE', 'no')):
- ssl_options={'cert_reqs': ssl.CERT_NONE}
+class WSMethod(enum.Enum):
+ """Arvados WebSocket methods
+
+ This enum represents valid values for the `method` field in messages
+ sent to an Arvados WebSocket server.
+ """
+ SUBSCRIBE = 'subscribe'
+ SUB = SUBSCRIBE
+ UNSUBSCRIBE = 'unsubscribe'
+ UNSUB = UNSUBSCRIBE
+
+
+class EventClient(threading.Thread):
+ """Follow Arvados events via WebSocket
+
+ EventClient follows events on Arvados cluster published by the WebSocket
+ server. Users can select the events they want to follow and run their own
+ callback function on each.
+ """
+ _USER_AGENT = 'Python/{}.{}.{} arvados.events/{}'.format(
+ *sys.version_info[:3],
+ __version__,
+ )
+
+ def __init__(
+ self,
+ url: str,
+ filters: Optional[Filter],
+ on_event_cb: EventCallback,
+ last_log_id: Optional[int]=None,
+ *,
+ insecure: Optional[bool]=None,
+ ) -> None:
+ """Initialize a WebSocket client
+
+ Constructor arguments:
+
+ * url: str --- The `wss` URL for an Arvados WebSocket server.
+
+ * filters: arvados.events.Filter | None --- One event filter to
+ subscribe to after connecting to the WebSocket server. If not
+ specified, the client will subscribe to all events.
+
+ * on_event_cb: arvados.events.EventCallback --- When the client
+ receives an event from the WebSocket server, it calls this
+ function with the event object.
+
+ * last_log_id: int | None --- If specified, this will be used as the
+ value for the `last_log_id` field in subscribe messages sent by
+ the client.
+
+ Constructor keyword arguments:
+
+ * insecure: bool | None --- If `True`, the client will not check the
+ validity of the server's TLS certificate. If not specified, uses
+ the value from the user's `ARVADOS_API_HOST_INSECURE` setting.
+ """
+ self.url = url
+ self.filters = [filters or []]
+ self.on_event_cb = on_event_cb
+ self.last_log_id = last_log_id
+ self.is_closed = threading.Event()
+ self._ssl_ctx = ssl.create_default_context(
+ purpose=ssl.Purpose.SERVER_AUTH,
+ cafile=util.ca_certs_path(),
+ )
+ if insecure is None:
+ insecure = config.flag_is_true('ARVADOS_API_HOST_INSECURE')
+ if insecure:
+ self._ssl_ctx.check_hostname = False
+ self._ssl_ctx.verify_mode = ssl.CERT_NONE
+ self._subscribe_lock = threading.Lock()
+ self._connect()
+ super().__init__(daemon=True)
+ self.start()
+
+ def _connect(self) -> None:
+ # There are no locks protecting this method. After the thread starts,
+ # it should only be called from inside.
+ self._client = ws_client.connect(
+ self.url,
+ logger=_logger,
+ ssl_context=self._ssl_ctx,
+ user_agent_header=self._USER_AGENT,
+ )
+ self._client_ok = True
+
+ def _subscribe(self, f: Filter, last_log_id: Optional[int]) -> None:
+ extra = {}
+ if last_log_id is not None:
+ extra['last_log_id'] = last_log_id
+ return self._update_sub(WSMethod.SUBSCRIBE, f, **extra)
+
+ def _update_sub(self, method: WSMethod, f: Filter, **extra: Any) -> None:
+ msg = json.dumps({
+ 'method': method.value,
+ 'filters': f,
+ **extra,
+ })
+ self._client.send(msg)
+
+ def close(self, code: int=1000, reason: str='', timeout: float=0) -> None:
+ """Close the WebSocket connection and stop processing events
+
+ Arguments:
+
+ * code: int --- The WebSocket close code sent to the server when
+ disconnecting. Default 1000.
+
+ * reason: str --- The WebSocket close reason sent to the server when
+ disconnecting. Default is the empty string.
+
+ * timeout: float --- How long to wait for the WebSocket server to
+ acknowledge the disconnection, in seconds. Default 0, which means
+ no timeout.
+ """
+ self.is_closed.set()
+ self._client.close_timeout = timeout or None
+ self._client.close(code, reason)
+
+ def run_forever(self) -> None:
+ """Run the WebSocket client indefinitely
+
+ This method blocks until the `close` method is called (e.g., from
+ another thread) or the client permanently loses its connection.
+ """
+ # Have to poll here to let KeyboardInterrupt get raised.
+ while not self.is_closed.wait(1):
+ pass
+
+ def subscribe(self, f: Filter, last_log_id: Optional[int]=None) -> None:
+ """Subscribe to another set of events from the server
+
+ Arguments:
+
+ * f: arvados.events.Filter | None --- One filter to subscribe to
+ events for.
+
+ * last_log_id: int | None --- If specified, request events starting
+ from this id. If not specified, the server will only send events
+ that occur after processing the subscription.
+ """
+ with self._subscribe_lock:
+ self._subscribe(f, last_log_id)
+ self.filters.append(f)
+
+ def unsubscribe(self, f: Filter) -> None:
+ """Unsubscribe from an event stream
+
+ Arguments:
+
+ * f: arvados.events.Filter | None --- One event filter to stop
+ receiving events for.
+ """
+ with self._subscribe_lock:
+ try:
+ index = self.filters.index(f)
+ except ValueError:
+ raise ValueError(f"filter not subscribed: {f!r}") from None
+ self._update_sub(WSMethod.UNSUBSCRIBE, f)
+ del self.filters[index]
+
+ def on_closed(self) -> None:
+ """Handle disconnection from the WebSocket server
+
+ This method is called when the client loses its connection from
+ receiving events. This implementation tries to establish a new
+ connection if it was not closed client-side.
+ """
+ if self.is_closed.is_set():
+ return
+ _logger.warning("Unexpected close. Reconnecting.")
+ for _ in RetryLoop(num_retries=25, backoff_start=.1, max_wait=15):
+ try:
+ self._connect()
+ except Exception as e:
+ _logger.warning("Error '%s' during websocket reconnect.", e)
+ else:
+ _logger.warning("Reconnect successful.")
+ break
else:
- ssl_options={'cert_reqs': ssl.CERT_REQUIRED}
- super(EventClient, self).__init__(url, ssl_options=ssl_options)
- self.filters = filters
- self.on_event = on_event
+ _logger.error("EventClient thread could not contact websocket server.")
+ self.is_closed.set()
+ _thread.interrupt_main()
- def opened(self):
- self.subscribe(self.filters)
+ def on_event(self, m: Dict[str, Any]) -> None:
+ """Handle an event from the WebSocket server
- def received_message(self, m):
- self.on_event(json.loads(str(m)))
+ This method is called whenever the client receives an event from the
+ server. This implementation records the `id` field internally, then
+ calls the callback function provided at initialization time.
- def close_connection(self):
+ Arguments:
+
+ * m: Dict[str, Any] --- The event object, deserialized from JSON.
+ """
try:
- self.sock.shutdown(socket.SHUT_RDWR)
- self.sock.close()
- except:
+ self.last_log_id = m['id']
+ except KeyError:
pass
+ try:
+ self.on_event_cb(m)
+ except Exception:
+ _logger.exception("Unexpected exception from event callback.")
+ _thread.interrupt_main()
- def subscribe(self, filters, last_log_id=None):
- m = {"method": "subscribe", "filters": filters}
- if last_log_id is not None:
- m["last_log_id"] = last_log_id
- self.send(json.dumps(m))
+ def run(self) -> None:
+ """Run the client loop
+
+ This method runs in a separate thread to receive and process events
+ from the server.
+ """
+ self.setName(f'ArvadosWebsockets-{self.ident}')
+ while self._client_ok and not self.is_closed.is_set():
+ try:
+ with self._subscribe_lock:
+ for f in self.filters:
+ self._subscribe(f, self.last_log_id)
+ for msg_s in self._client:
+ if not self.is_closed.is_set():
+ msg = json.loads(msg_s)
+ self.on_event(msg)
+ except ws_exc.ConnectionClosed:
+ self._client_ok = False
+ self.on_closed()
- def unsubscribe(self, filters):
- self.send(json.dumps({"method": "unsubscribe", "filters": filters}))
class PollClient(threading.Thread):
- def __init__(self, api, filters, on_event, poll_time):
+ def __init__(self, api, filters, on_event, poll_time, last_log_id):
super(PollClient, self).__init__()
self.api = api
if filters:
self.filters = [filters]
else:
- self.filters = []
+ self.filters = [[]]
self.on_event = on_event
self.poll_time = poll_time
- self.stop = threading.Event()
+ self.daemon = True
+ self.last_log_id = last_log_id
+ self._closing = threading.Event()
+ self._closing_lock = threading.RLock()
- def run(self):
- items = self.api.logs().list(limit=1, order="id desc", filters=self.filters[0]).execute()['items']
- if len(items) > 0:
- self.id = items[0]["id"]
+ if self.last_log_id != None:
+ # Caller supplied the last-seen event ID from a previous
+ # connection.
+ self._skip_old_events = [["id", ">", str(self.last_log_id)]]
else:
- self.id = 0
+ # We need to do a reverse-order query to find the most
+ # recent event ID (see "if not self._skip_old_events"
+ # in run()).
+ self._skip_old_events = False
+ def run(self):
self.on_event({'status': 200})
- while not self.stop.isSet():
- max_id = self.id
+ while not self._closing.is_set():
+ moreitems = False
for f in self.filters:
- items = self.api.logs().list(order="id asc", filters=f+[["id", ">", str(self.id)]]).execute()['items']
- for i in items:
- if i['id'] > max_id:
- max_id = i['id']
- self.on_event(i)
- self.id = max_id
- self.stop.wait(self.poll_time)
-
- def close(self):
- self.stop.set()
- self.join()
-
- def subscribe(self, filters):
- self.on_event({'status': 200})
- self.filters.append(filters)
+ for tries_left in RetryLoop(num_retries=25, backoff_start=.1, max_wait=self.poll_time):
+ try:
+ if not self._skip_old_events:
+ # If the caller didn't provide a known
+ # recent ID, our first request will ask
+ # for the single most recent event from
+ # the last 2 hours (the time restriction
+ # avoids doing an expensive database
+ # query, and leaves a big enough margin to
+ # account for clock skew). If we do find a
+ # recent event, we remember its ID but
+ # then discard it (we are supposed to be
+ # returning new/current events, not old
+ # ones).
+ #
+ # Subsequent requests will get multiple
+ # events in chronological order, and
+ # filter on that same cutoff time, or
+ # (once we see our first matching event)
+ # the ID of the last-seen event.
+ #
+ # Note: self._skip_old_events must not be
+ # set until the threshold is decided.
+ # Otherwise, tests will be unreliable.
+ filter_by_time = [[
+ "created_at", ">=",
+ time.strftime(
+ "%Y-%m-%dT%H:%M:%SZ",
+ time.gmtime(time.time()-7200))]]
+ items = self.api.logs().list(
+ order="id desc",
+ limit=1,
+ filters=f+filter_by_time).execute()
+ if items["items"]:
+ self._skip_old_events = [
+ ["id", ">", str(items["items"][0]["id"])]]
+ items = {
+ "items": [],
+ "items_available": 0,
+ }
+ else:
+ # No recent events. We can keep using
+ # the same timestamp threshold until
+ # we receive our first new event.
+ self._skip_old_events = filter_by_time
+ else:
+ # In this case, either we know the most
+ # recent matching ID, or we know there
+ # were no matching events in the 2-hour
+ # window before subscribing. Either way we
+ # can safely ask for events in ascending
+ # order.
+ items = self.api.logs().list(
+ order="id asc",
+ filters=f+self._skip_old_events).execute()
+ break
+ except errors.ApiError as error:
+ pass
+ else:
+ tries_left = 0
+ break
+ if tries_left == 0:
+ _logger.exception("PollClient thread could not contact API server.")
+ with self._closing_lock:
+ self._closing.set()
+ _thread.interrupt_main()
+ return
+ for i in items["items"]:
+ self._skip_old_events = [["id", ">", str(i["id"])]]
+ with self._closing_lock:
+ if self._closing.is_set():
+ return
+ try:
+ self.on_event(i)
+ except Exception as e:
+ _logger.exception("Unexpected exception from event callback.")
+ _thread.interrupt_main()
+ if items["items_available"] > len(items["items"]):
+ moreitems = True
+ if not moreitems:
+ self._closing.wait(self.poll_time)
+
+ def run_forever(self):
+ # Have to poll here, otherwise KeyboardInterrupt will never get processed.
+ while not self._closing.is_set():
+ self._closing.wait(1)
+
+ def close(self, code=None, reason=None, timeout=0):
+ """Close poll client and optionally wait for it to finish.
- def unsubscribe(self, filters):
- del self.filters[self.filters.index(filters)]
+ If an :on_event: handler is running in a different thread,
+ first wait (indefinitely) for it to return.
+ After closing, wait up to :timeout: seconds for the thread to
+ finish the poll request in progress (if any).
-def subscribe(api, filters, on_event, poll_fallback=15):
- '''
- api: Must be a newly created from arvados.api(cache=False), not shared with the caller, as it may be used by a background thread.
- filters: Initial subscription filters.
- on_event: The callback when a message is received
- poll_fallback: If websockets are not available, fall back to polling every N seconds. If poll_fallback=False, this will return None if websockets are not available.
- '''
- ws = None
- if 'websocketUrl' in api._rootDesc:
+ :code: and :reason: are ignored. They are present for
+ interface compatibility with EventClient.
+ """
+
+ with self._closing_lock:
+ self._closing.set()
try:
- url = "{}?api_token={}".format(api._rootDesc['websocketUrl'], api.api_token)
- ws = EventClient(url, filters, on_event)
- ws.connect()
- return ws
- except Exception as e:
- _logger.warn("Got exception %s trying to connect to websockets at %s" % (e, api._rootDesc['websocketUrl']))
- if ws:
- ws.close_connection()
- if poll_fallback:
- _logger.warn("Websockets not available, falling back to log table polling")
- p = PollClient(api, filters, on_event, poll_fallback)
- p.start()
- return p
+ self.join(timeout=timeout)
+ except RuntimeError:
+ # "join() raises a RuntimeError if an attempt is made to join the
+ # current thread as that would cause a deadlock. It is also an
+ # error to join() a thread before it has been started and attempts
+ # to do so raises the same exception."
+ pass
+
+ def subscribe(self, f):
+ self.on_event({'status': 200})
+ self.filters.append(f)
+
+ def unsubscribe(self, f):
+ del self.filters[self.filters.index(f)]
+
+
+def _subscribe_websocket(api, filters, on_event, last_log_id=None):
+ endpoint = api._rootDesc.get('websocketUrl', None)
+ if not endpoint:
+ raise errors.FeatureNotEnabledError(
+ "Server does not advertise a websocket endpoint")
+ uri_with_token = "{}?api_token={}".format(endpoint, api.api_token)
+ try:
+ client = EventClient(uri_with_token, filters, on_event, last_log_id)
+ except Exception:
+ _logger.warning("Failed to connect to websockets on %s" % endpoint)
+ raise
else:
- _logger.error("Websockets not available")
- return None
+ return client
+
+
+def subscribe(api, filters, on_event, poll_fallback=15, last_log_id=None):
+ """
+ :api:
+ a client object retrieved from arvados.api(). The caller should not use this client object for anything else after calling subscribe().
+ :filters:
+ Initial subscription filters.
+ :on_event:
+ The callback when a message is received.
+ :poll_fallback:
+ If websockets are not available, fall back to polling every N seconds. If poll_fallback=False, this will return None if websockets are not available.
+ :last_log_id:
+ Log rows that are newer than the log id
+ """
+
+ if not poll_fallback:
+ return _subscribe_websocket(api, filters, on_event, last_log_id)
+
+ try:
+ if not config.flag_is_true('ARVADOS_DISABLE_WEBSOCKETS'):
+ return _subscribe_websocket(api, filters, on_event, last_log_id)
+ else:
+ _logger.info("Using polling because ARVADOS_DISABLE_WEBSOCKETS is true")
+ except Exception as e:
+ _logger.warning("Falling back to polling after websocket error: %s" % e)
+ p = PollClient(api, filters, on_event, poll_fallback, last_log_id)
+ p.start()
+ return p