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![Erik Johnston](/assets/img/avatar_default.png)
If the client failed to process incoming commands during the initial set up of the replication connection it would immediately disconnect and reconnect, resulting in a tightloop. This can happen, for example, when subscribing to a stream that has a row that is too long in the backlog. The fix here is to not consider the connection successfully set up until the client has succesfully subscribed and caught up with the streams. This ensures that the retry logic timers aren't reset until then, meaning that if an error does happen during start up the client will continue backing off before retrying again.
239 lines
8.5 KiB
Python
239 lines
8.5 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2017 Vector Creations Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""A replication client for use by synapse workers.
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"""
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import logging
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from twisted.internet import defer
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from twisted.internet.protocol import ReconnectingClientFactory
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from .commands import (
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FederationAckCommand,
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InvalidateCacheCommand,
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RemovePusherCommand,
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UserIpCommand,
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UserSyncCommand,
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)
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from .protocol import ClientReplicationStreamProtocol
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logger = logging.getLogger(__name__)
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class ReplicationClientFactory(ReconnectingClientFactory):
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"""Factory for building connections to the master. Will reconnect if the
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connection is lost.
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Accepts a handler that will be called when new data is available or data
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is required.
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"""
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maxDelay = 5 # Try at least once every N seconds
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def __init__(self, hs, client_name, handler):
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self.client_name = client_name
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self.handler = handler
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self.server_name = hs.config.server_name
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self._clock = hs.get_clock() # As self.clock is defined in super class
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hs.get_reactor().addSystemEventTrigger("before", "shutdown", self.stopTrying)
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def startedConnecting(self, connector):
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logger.info("Connecting to replication: %r", connector.getDestination())
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def buildProtocol(self, addr):
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logger.info("Connected to replication: %r", addr)
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return ClientReplicationStreamProtocol(
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self.client_name, self.server_name, self._clock, self.handler
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)
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def clientConnectionLost(self, connector, reason):
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logger.error("Lost replication conn: %r", reason)
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ReconnectingClientFactory.clientConnectionLost(self, connector, reason)
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def clientConnectionFailed(self, connector, reason):
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logger.error("Failed to connect to replication: %r", reason)
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ReconnectingClientFactory.clientConnectionFailed(
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self, connector, reason
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)
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class ReplicationClientHandler(object):
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"""A base handler that can be passed to the ReplicationClientFactory.
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By default proxies incoming replication data to the SlaveStore.
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"""
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def __init__(self, store):
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self.store = store
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# The current connection. None if we are currently (re)connecting
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self.connection = None
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# Any pending commands to be sent once a new connection has been
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# established
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self.pending_commands = []
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# Map from string -> deferred, to wake up when receiveing a SYNC with
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# the given string.
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# Used for tests.
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self.awaiting_syncs = {}
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# Set of stream names that have been subscribe to, but haven't yet
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# caught up with. This is used to track when the client has been fully
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# connected to the remote.
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self.streams_connecting = None
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# The factory used to create connections.
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self.factory = None
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def start_replication(self, hs):
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"""Helper method to start a replication connection to the remote server
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using TCP.
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"""
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client_name = hs.config.worker_name
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self.factory = ReplicationClientFactory(hs, client_name, self)
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host = hs.config.worker_replication_host
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port = hs.config.worker_replication_port
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hs.get_reactor().connectTCP(host, port, self.factory)
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def on_rdata(self, stream_name, token, rows):
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"""Called when we get new replication data. By default this just pokes
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the slave store.
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Can be overriden in subclasses to handle more.
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"""
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logger.debug("Received rdata %s -> %s", stream_name, token)
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return self.store.process_replication_rows(stream_name, token, rows)
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def on_position(self, stream_name, token):
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"""Called when we get new position data. By default this just pokes
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the slave store.
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Can be overriden in subclasses to handle more.
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"""
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# When we get a `POSITION` command it means we've finished getting
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# missing updates for the given stream, and are now up to date.
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self.streams_connecting.discard(stream_name)
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if not self.streams_connecting:
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self.finished_connecting()
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return self.store.process_replication_rows(stream_name, token, [])
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def on_sync(self, data):
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"""When we received a SYNC we wake up any deferreds that were waiting
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for the sync with the given data.
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Used by tests.
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"""
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d = self.awaiting_syncs.pop(data, None)
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if d:
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d.callback(data)
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def get_streams_to_replicate(self):
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"""Called when a new connection has been established and we need to
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subscribe to streams.
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Returns a dictionary of stream name to token.
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"""
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args = self.store.stream_positions()
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user_account_data = args.pop("user_account_data", None)
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room_account_data = args.pop("room_account_data", None)
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if user_account_data:
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args["account_data"] = user_account_data
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elif room_account_data:
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args["account_data"] = room_account_data
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# Record which streams we're in the process of subscribing to
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self.streams_connecting = set(args.keys())
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return args
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def get_currently_syncing_users(self):
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"""Get the list of currently syncing users (if any). This is called
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when a connection has been established and we need to send the
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currently syncing users. (Overriden by the synchrotron's only)
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"""
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return []
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def send_command(self, cmd):
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"""Send a command to master (when we get establish a connection if we
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don't have one already.)
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"""
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if self.connection:
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self.connection.send_command(cmd)
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else:
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logger.warn("Queuing command as not connected: %r", cmd.NAME)
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self.pending_commands.append(cmd)
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def send_federation_ack(self, token):
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"""Ack data for the federation stream. This allows the master to drop
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data stored purely in memory.
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"""
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self.send_command(FederationAckCommand(token))
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def send_user_sync(self, user_id, is_syncing, last_sync_ms):
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"""Poke the master that a user has started/stopped syncing.
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"""
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self.send_command(UserSyncCommand(user_id, is_syncing, last_sync_ms))
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def send_remove_pusher(self, app_id, push_key, user_id):
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"""Poke the master to remove a pusher for a user
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"""
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cmd = RemovePusherCommand(app_id, push_key, user_id)
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self.send_command(cmd)
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def send_invalidate_cache(self, cache_func, keys):
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"""Poke the master to invalidate a cache.
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"""
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cmd = InvalidateCacheCommand(cache_func.__name__, keys)
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self.send_command(cmd)
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def send_user_ip(self, user_id, access_token, ip, user_agent, device_id, last_seen):
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"""Tell the master that the user made a request.
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"""
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cmd = UserIpCommand(user_id, access_token, ip, user_agent, device_id, last_seen)
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self.send_command(cmd)
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def await_sync(self, data):
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"""Returns a deferred that is resolved when we receive a SYNC command
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with given data.
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[Not currently] used by tests.
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"""
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return self.awaiting_syncs.setdefault(data, defer.Deferred())
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def update_connection(self, connection):
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"""Called when a connection has been established (or lost with None).
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"""
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self.connection = connection
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if connection:
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for cmd in self.pending_commands:
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connection.send_command(cmd)
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self.pending_commands = []
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# This will happen if we don't actually subscribe to any streams
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if not self.streams_connecting:
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self.finished_connecting()
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def finished_connecting(self):
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"""Called when we have successfully subscribed and caught up to all
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streams we're interested in.
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"""
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logger.info("Finished connecting to server")
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# We don't reset the delay any earlier as otherwise if there is a
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# problem during start up we'll end up tight looping connecting to the
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# server.
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self.factory.resetDelay()
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