# Copyright (C) The Arvados Authors. All rights reserved.
#
# SPDX-License-Identifier: Apache-2.0
+"""Follow events on an Arvados cluster
-from __future__ import absolute_import
-from future import standard_library
-standard_library.install_aliases()
-from builtins import str
-from builtins import object
-import arvados
-from . import config
-from . import errors
-from .retry import RetryLoop
+This module provides different ways to get notified about events that happen
+on an Arvados cluster. You indicate which events you want updates about, and
+provide a function that is called any time one of those events is received
+from the server.
-import logging
+`subscribe` is the main entry point. It helps you construct one of the two
+API-compatible client classes: `EventClient` (which uses WebSockets) or
+`PollClient` (which periodically queries the logs list methods).
+"""
+
+import enum
import json
-import _thread
-import threading
-import time
+import logging
import os
import re
import ssl
-from ws4py.client.threadedclient import WebSocketClient
+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 WSMethod(enum.Enum):
+ """Arvados WebSocket methods
-class _EventClient(WebSocketClient):
- def __init__(self, url, filters, on_event, last_log_id, on_closed):
- ssl_options = {'ca_certs': arvados.util.ca_certs_path()}
- if config.flag_is_true('ARVADOS_API_HOST_INSECURE'):
- ssl_options['cert_reqs'] = ssl.CERT_NONE
- else:
- ssl_options['cert_reqs'] = ssl.CERT_REQUIRED
+ 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
- # Warning: If the host part of url resolves to both IPv6 and
- # IPv4 addresses (common with "localhost"), only one of them
- # will be attempted -- and it might not be the right one. See
- # ws4py's WebSocketBaseClient.__init__.
- super(_EventClient, self).__init__(url, ssl_options=ssl_options)
- self.filters = filters
- self.on_event = on_event
+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._closing_lock = threading.RLock()
- self._closing = False
- self._closed = threading.Event()
- self.on_closed = on_closed
+ 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 opened(self):
- for f in self.filters:
- self.subscribe(f, self.last_log_id)
+ 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 closed(self, code, reason=None):
- self._closed.set()
- self.on_closed()
+ def close(self, code: int=1000, reason: str='', timeout: float=0) -> None:
+ """Close the WebSocket connection and stop processing events
- def received_message(self, m):
- with self._closing_lock:
- if not self._closing:
- self.on_event(json.loads(str(m)))
+ Arguments:
- def close(self, code=1000, reason='', timeout=0):
- """Close event client and optionally wait for it to finish.
+ * code: int --- The WebSocket close code sent to the server when
+ disconnecting. Default 1000.
- :timeout: is the number of seconds to wait for ws4py to
- indicate that the connection has closed.
+ * reason: str --- The WebSocket close reason sent to the server when
+ disconnecting. Default is an empty string.
+
+ * timeout: float --- How long to wait for the WebSocket server to
+ acknowledge the disconnection, in seconds. Default 0, which means
+ no timeout.
"""
- super(_EventClient, self).close(code, reason)
- with self._closing_lock:
- # make sure we don't process any more messages.
- self._closing = True
- # wait for ws4py to tell us the connection is closed.
- self._closed.wait(timeout=timeout)
+ self.is_closed.set()
+ self._client.close_timeout = timeout or None
+ self._client.close(code, reason)
- def subscribe(self, f, last_log_id=None):
- m = {"method": "subscribe", "filters": f}
- if last_log_id is not None:
- m["last_log_id"] = last_log_id
- self.send(json.dumps(m))
+ def run_forever(self) -> None:
+ """Run the WebSocket client indefinitely
- def unsubscribe(self, f):
- self.send(json.dumps({"method": "unsubscribe", "filters": f}))
+ 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
-class EventClient(object):
- def __init__(self, url, filters, on_event_cb, last_log_id):
- self.url = url
- if filters:
- self.filters = [filters]
- else:
- self.filters = [[]]
- self.on_event_cb = on_event_cb
- self.last_log_id = last_log_id
- self.is_closed = threading.Event()
- self._setup_event_client()
+ Arguments:
- def _setup_event_client(self):
- self.ec = _EventClient(self.url, self.filters, self.on_event,
- self.last_log_id, self.on_closed)
- self.ec.daemon = True
- try:
- self.ec.connect()
- except Exception:
- self.ec.close_connection()
- raise
+ * f: arvados.events.Filter | None --- One filter to subscribe to
+ events for.
- def subscribe(self, f, last_log_id=None):
- self.filters.append(f)
- self.ec.subscribe(f, last_log_id)
+ * 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):
- del self.filters[self.filters.index(f)]
- self.ec.unsubscribe(f)
+ def unsubscribe(self, f: Filter) -> None:
+ """Unsubscribe from an event stream
- def close(self, code=1000, reason='', timeout=0):
- self.is_closed.set()
- self.ec.close(code, reason, timeout)
+ 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:
+ _logger.error("EventClient thread could not contact websocket server.")
+ self.is_closed.set()
+ _thread.interrupt_main()
- def on_event(self, m):
- if m.get('id') != None:
- self.last_log_id = m.get('id')
+ def on_event(self, m: Dict[str, Any]) -> None:
+ """Handle an event from the WebSocket server
+
+ 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.
+
+ Arguments:
+
+ * m: Dict[str, Any] --- The event object, deserialized from JSON.
+ """
+ try:
+ self.last_log_id = m['id']
+ except KeyError:
+ pass
try:
self.on_event_cb(m)
- except Exception as e:
+ except Exception:
_logger.exception("Unexpected exception from event callback.")
_thread.interrupt_main()
- def on_closed(self):
- if not self.is_closed.is_set():
- _logger.warning("Unexpected close. Reconnecting.")
- for tries_left in RetryLoop(num_retries=25, backoff_start=.1, max_wait=15):
- try:
- self._setup_event_client()
- _logger.warning("Reconnect successful.")
- break
- except Exception as e:
- _logger.warning("Error '%s' during websocket reconnect.", e)
- if tries_left == 0:
- _logger.exception("EventClient thread could not contact websocket server.")
- self.is_closed.set()
- _thread.interrupt_main()
- return
+ def run(self) -> None:
+ """Run the client loop
- def run_forever(self):
- # Have to poll here to let KeyboardInterrupt get raised.
- while not self.is_closed.wait(1):
- pass
+ 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()
class PollClient(threading.Thread):
- def __init__(self, api, filters, on_event, poll_time, last_log_id):
+ """Follow Arvados events via polling logs
+
+ PollClient follows events on Arvados cluster by periodically running
+ logs list API calls. Users can select the events they want to follow and
+ run their own callback function on each.
+ """
+ def __init__(
+ self,
+ api: 'arvados.api_resources.ArvadosAPIClient',
+ filters: Optional[Filter],
+ on_event: EventCallback,
+ poll_time: float=15,
+ last_log_id: Optional[int]=None,
+ ) -> None:
+ """Initialize a polling client
+
+ Constructor arguments:
+
+ * api: arvados.api_resources.ArvadosAPIClient --- The Arvados API
+ client used to query logs. It will be used in a separate thread,
+ so if it is not an instance of `arvados.safeapi.ThreadSafeApiCache`
+ it should not be reused after the thread is started.
+
+ * 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: arvados.events.EventCallback --- When the client
+ receives an event from the WebSocket server, it calls this
+ function with the event object.
+
+ * poll_time: float --- The number of seconds to wait between querying
+ logs. Default 15.
+
+ * last_log_id: int | None --- If specified, queries will include a
+ filter for logs with an `id` at least this value.
+ """
super(PollClient, self).__init__()
self.api = api
if filters:
self._closing = threading.Event()
self._closing_lock = threading.RLock()
- def run(self):
if self.last_log_id != None:
# Caller supplied the last-seen event ID from a previous
- # connection
- skip_old_events = [["id", ">", str(self.last_log_id)]]
+ # connection.
+ self._skip_old_events = [["id", ">", str(self.last_log_id)]]
else:
# We need to do a reverse-order query to find the most
- # recent event ID (see "if not skip_old_events" below).
- skip_old_events = False
+ # recent event ID (see "if not self._skip_old_events"
+ # in run()).
+ self._skip_old_events = False
+
+ def run(self):
+ """Run the client loop
+ This method runs in a separate thread to poll and process events
+ from the server.
+ """
self.on_event({'status': 200})
while not self._closing.is_set():
for f in self.filters:
for tries_left in RetryLoop(num_retries=25, backoff_start=.1, max_wait=self.poll_time):
try:
- if not skip_old_events:
+ 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
# filter on that same cutoff time, or
# (once we see our first matching event)
# the ID of the last-seen event.
- skip_old_events = [[
+ #
+ # 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",
items = self.api.logs().list(
order="id desc",
limit=1,
- filters=f+skip_old_events).execute()
+ filters=f+filter_by_time).execute()
if items["items"]:
- skip_old_events = [
+ 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
# order.
items = self.api.logs().list(
order="id asc",
- filters=f+skip_old_events).execute()
+ filters=f+self._skip_old_events).execute()
break
except errors.ApiError as error:
pass
_thread.interrupt_main()
return
for i in items["items"]:
- skip_old_events = [["id", ">", str(i["id"])]]
+ self._skip_old_events = [["id", ">", str(i["id"])]]
with self._closing_lock:
if self._closing.is_set():
return
self._closing.wait(self.poll_time)
def run_forever(self):
+ """Run the polling 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, 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 close(self, code: Optional[int]=None, reason: Optional[str]=None, timeout: float=0) -> None:
+ """Stop polling and processing events
- If an :on_event: handler is running in a different thread,
- first wait (indefinitely) for it to return.
+ Arguments:
- After closing, wait up to :timeout: seconds for the thread to
- finish the poll request in progress (if any).
+ * code: Optional[int] --- Ignored; this argument exists for API
+ compatibility with `EventClient.close`.
- :code: and :reason: are ignored. They are present for
- interface compatibility with EventClient.
- """
+ * reason: Optional[str] --- Ignored; this argument exists for API
+ compatibility with `EventClient.close`.
+ * timeout: float --- How long to wait for the client thread to finish
+ processing events. Default 0, which means no timeout.
+ """
with self._closing_lock:
self._closing.set()
try:
# to do so raises the same exception."
pass
- def subscribe(self, f):
+ 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.
+
+ * last_log_id: Optional[int] --- Ignored; this argument exists for
+ API compatibility with `EventClient.subscribe`.
+ """
self.on_event({'status': 200})
self.filters.append(f)
def unsubscribe(self, f):
+ """Unsubscribe from an event stream
+
+ Arguments:
+
+ * f: arvados.events.Filter | None --- One event filter to stop
+ receiving events for.
+ """
del self.filters[self.filters.index(f)]
else:
return client
-
-def subscribe(api, filters, on_event, poll_fallback=15, last_log_id=None):
+def subscribe(
+ api: 'arvados.api_resources.ArvadosAPIClient',
+ filters: Optional[Filter],
+ on_event: EventCallback,
+ poll_fallback: float=15,
+ last_log_id: Optional[int]=None,
+) -> Union[EventClient, PollClient]:
+ """Start a thread to monitor events
+
+ This method tries to construct an `EventClient` to process Arvados
+ events via WebSockets. If that fails, or the
+ `ARVADOS_DISABLE_WEBSOCKETS` flag is set in user configuration, it falls
+ back to constructing a `PollClient` to process the events via API
+ polling.
+
+ Arguments:
+
+ * api: arvados.api_resources.ArvadosAPIClient --- The Arvados API
+ client used to query logs. It may be used in a separate thread,
+ so if it is not an instance of `arvados.safeapi.ThreadSafeApiCache`
+ it should not be reused after this method returns.
+
+ * filters: arvados.events.Filter | None --- One event filter to
+ subscribe to after initializing the client. If not specified, the
+ client will subscribe to all events.
+
+ * on_event: arvados.events.EventCallback --- When the client receives an
+ event, it calls this function with the event object.
+
+ * poll_time: float --- The number of seconds to wait between querying
+ logs. If 0, this function will refuse to construct a `PollClient`.
+ Default 15.
+
+ * last_log_id: int | None --- If specified, start processing events with
+ at least this `id` value.
"""
- :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)
projects / arvados.git / blobdiff