# Copyright 2017 Vector Creations Ltd # # 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. """This module contains the implementation of both the client and server protocols. The basic structure of the protocol is line based, where the initial word of each line specifies the command. The rest of the line is parsed based on the command. For example, the `RDATA` command is defined as:: RDATA (Note that `` may contains spaces, but cannot contain newlines.) Blank lines are ignored. # Example An example iteraction is shown below. Each line is prefixed with '>' or '<' to indicate which side is sending, these are *not* included on the wire:: * connection established * > SERVER localhost:8823 > PING 1490197665618 < NAME synapse.app.appservice < PING 1490197665618 < REPLICATE > POSITION events 1 > POSITION backfill 1 > POSITION caches 1 > RDATA caches 2 ["get_user_by_id",["@01register-user:localhost:8823"],1490197670513] > RDATA events 14 ["ev", ["$149019767112vOHxz:localhost:8823", "!AFDCvgApUmpdfVjIXm:localhost:8823","m.room.guest_access","",null]] < PING 1490197675618 > ERROR server stopping * connection closed by server * """ import fcntl import logging import struct from inspect import isawaitable from typing import TYPE_CHECKING, List, Optional from prometheus_client import Counter from zope.interface import Interface, implementer from twisted.internet import task from twisted.internet.tcp import Connection from twisted.protocols.basic import LineOnlyReceiver from twisted.python.failure import Failure from synapse.logging.context import PreserveLoggingContext from synapse.metrics import LaterGauge from synapse.metrics.background_process_metrics import ( BackgroundProcessLoggingContext, run_as_background_process, ) from synapse.replication.tcp.commands import ( VALID_CLIENT_COMMANDS, VALID_SERVER_COMMANDS, Command, ErrorCommand, NameCommand, PingCommand, ReplicateCommand, ServerCommand, parse_command_from_line, ) from synapse.types import Collection from synapse.util import Clock from synapse.util.stringutils import random_string if TYPE_CHECKING: from synapse.replication.tcp.handler import ReplicationCommandHandler from synapse.server import HomeServer connection_close_counter = Counter( "synapse_replication_tcp_protocol_close_reason", "", ["reason_type"] ) tcp_inbound_commands_counter = Counter( "synapse_replication_tcp_protocol_inbound_commands", "Number of commands received from replication, by command and name of process connected to", ["command", "name"], ) tcp_outbound_commands_counter = Counter( "synapse_replication_tcp_protocol_outbound_commands", "Number of commands sent to replication, by command and name of process connected to", ["command", "name"], ) # A list of all connected protocols. This allows us to send metrics about the # connections. connected_connections = [] # type: List[BaseReplicationStreamProtocol] logger = logging.getLogger(__name__) PING_TIME = 5000 PING_TIMEOUT_MULTIPLIER = 5 PING_TIMEOUT_MS = PING_TIME * PING_TIMEOUT_MULTIPLIER class ConnectionStates: CONNECTING = "connecting" ESTABLISHED = "established" PAUSED = "paused" CLOSED = "closed" class IReplicationConnection(Interface): """An interface for replication connections.""" def send_command(cmd: Command): """Send the command down the connection""" @implementer(IReplicationConnection) class BaseReplicationStreamProtocol(LineOnlyReceiver): """Base replication protocol shared between client and server. Reads lines (ignoring blank ones) and parses them into command classes, asserting that they are valid for the given direction, i.e. server commands are only sent by the server. On receiving a new command it calls `on_` with the parsed command before delegating to `ReplicationCommandHandler.on_`. `ReplicationCommandHandler.on_` can optionally return a coroutine; if so, that will get run as a background process. It also sends `PING` periodically, and correctly times out remote connections (if they send a `PING` command) """ # The transport is going to be an ITCPTransport, but that doesn't have the # (un)registerProducer methods, those are only on the implementation. transport = None # type: Connection delimiter = b"\n" # Valid commands we expect to receive VALID_INBOUND_COMMANDS = [] # type: Collection[str] # Valid commands we can send VALID_OUTBOUND_COMMANDS = [] # type: Collection[str] max_line_buffer = 10000 def __init__(self, clock: Clock, handler: "ReplicationCommandHandler"): self.clock = clock self.command_handler = handler self.last_received_command = self.clock.time_msec() self.last_sent_command = 0 # When we requested the connection be closed self.time_we_closed = None # type: Optional[int] self.received_ping = False # Have we received a ping from the other side self.state = ConnectionStates.CONNECTING self.name = "anon" # The name sent by a client. self.conn_id = random_string(5) # To dedupe in case of name clashes. # List of pending commands to send once we've established the connection self.pending_commands = [] # type: List[Command] # The LoopingCall for sending pings. self._send_ping_loop = None # type: Optional[task.LoopingCall] # a logcontext which we use for processing incoming commands. We declare it as a # background process so that the CPU stats get reported to prometheus. self._logging_context = BackgroundProcessLoggingContext( "replication-conn-%s" % (self.conn_id,) ) def connectionMade(self): logger.info("[%s] Connection established", self.id()) self.state = ConnectionStates.ESTABLISHED connected_connections.append(self) # Register connection for metrics assert self.transport is not None self.transport.registerProducer(self, True) # For the *Producing callbacks self._send_pending_commands() # Starts sending pings self._send_ping_loop = self.clock.looping_call(self.send_ping, 5000) # Always send the initial PING so that the other side knows that they # can time us out. self.send_command(PingCommand(self.clock.time_msec())) self.command_handler.new_connection(self) def send_ping(self): """Periodically sends a ping and checks if we should close the connection due to the other side timing out. """ now = self.clock.time_msec() if self.time_we_closed: if now - self.time_we_closed > PING_TIMEOUT_MS: logger.info( "[%s] Failed to close connection gracefully, aborting", self.id() ) assert self.transport is not None self.transport.abortConnection() else: if now - self.last_sent_command >= PING_TIME: self.send_command(PingCommand(now)) if ( self.received_ping and now - self.last_received_command > PING_TIMEOUT_MS ): logger.info( "[%s] Connection hasn't received command in %r ms. Closing.", self.id(), now - self.last_received_command, ) self.send_error("ping timeout") def lineReceived(self, line: bytes): """Called when we've received a line""" with PreserveLoggingContext(self._logging_context): self._parse_and_dispatch_line(line) def _parse_and_dispatch_line(self, line: bytes): if line.strip() == "": # Ignore blank lines return linestr = line.decode("utf-8") try: cmd = parse_command_from_line(linestr) except Exception as e: logger.exception("[%s] failed to parse line: %r", self.id(), linestr) self.send_error("failed to parse line: %r (%r):" % (e, linestr)) return if cmd.NAME not in self.VALID_INBOUND_COMMANDS: logger.error("[%s] invalid command %s", self.id(), cmd.NAME) self.send_error("invalid command: %s", cmd.NAME) return self.last_received_command = self.clock.time_msec() tcp_inbound_commands_counter.labels(cmd.NAME, self.name).inc() self.handle_command(cmd) def handle_command(self, cmd: Command) -> None: """Handle a command we have received over the replication stream. First calls `self.on_` if it exists, then calls `self.command_handler.on_` if it exists (which can optionally return an Awaitable). This allows for protocol level handling of commands (e.g. PINGs), before delegating to the handler. Args: cmd: received command """ handled = False # First call any command handlers on this instance. These are for TCP # specific handling. cmd_func = getattr(self, "on_%s" % (cmd.NAME,), None) if cmd_func: cmd_func(cmd) handled = True # Then call out to the handler. cmd_func = getattr(self.command_handler, "on_%s" % (cmd.NAME,), None) if cmd_func: res = cmd_func(self, cmd) # the handler might be a coroutine: fire it off as a background process # if so. if isawaitable(res): run_as_background_process( "replication-" + cmd.get_logcontext_id(), lambda: res ) handled = True if not handled: logger.warning("Unhandled command: %r", cmd) def close(self): logger.warning("[%s] Closing connection", self.id()) self.time_we_closed = self.clock.time_msec() assert self.transport is not None self.transport.loseConnection() self.on_connection_closed() def send_error(self, error_string, *args): """Send an error to remote and close the connection.""" self.send_command(ErrorCommand(error_string % args)) self.close() def send_command(self, cmd, do_buffer=True): """Send a command if connection has been established. Args: cmd (Command) do_buffer (bool): Whether to buffer the message or always attempt to send the command. This is mostly used to send an error message if we're about to close the connection due our buffers becoming full. """ if self.state == ConnectionStates.CLOSED: logger.debug("[%s] Not sending, connection closed", self.id()) return if do_buffer and self.state != ConnectionStates.ESTABLISHED: self._queue_command(cmd) return tcp_outbound_commands_counter.labels(cmd.NAME, self.name).inc() string = "%s %s" % (cmd.NAME, cmd.to_line()) if "\n" in string: raise Exception("Unexpected newline in command: %r", string) encoded_string = string.encode("utf-8") if len(encoded_string) > self.MAX_LENGTH: raise Exception( "Failed to send command %s as too long (%d > %d)" % (cmd.NAME, len(encoded_string), self.MAX_LENGTH) ) self.sendLine(encoded_string) self.last_sent_command = self.clock.time_msec() def _queue_command(self, cmd): """Queue the command until the connection is ready to write to again.""" logger.debug("[%s] Queueing as conn %r, cmd: %r", self.id(), self.state, cmd) self.pending_commands.append(cmd) if len(self.pending_commands) > self.max_line_buffer: # The other side is failing to keep up and out buffers are becoming # full, so lets close the connection. # XXX: should we squawk more loudly? logger.error("[%s] Remote failed to keep up", self.id()) self.send_command(ErrorCommand("Failed to keep up"), do_buffer=False) self.close() def _send_pending_commands(self): """Send any queued commandes""" pending = self.pending_commands self.pending_commands = [] for cmd in pending: self.send_command(cmd) def on_PING(self, line): self.received_ping = True def on_ERROR(self, cmd): logger.error("[%s] Remote reported error: %r", self.id(), cmd.data) def pauseProducing(self): """This is called when both the kernel send buffer and the twisted tcp connection send buffers have become full. We don't actually have any control over those sizes, so we buffer some commands ourselves before knifing the connection due to the remote failing to keep up. """ logger.info("[%s] Pause producing", self.id()) self.state = ConnectionStates.PAUSED def resumeProducing(self): """The remote has caught up after we started buffering!""" logger.info("[%s] Resume producing", self.id()) self.state = ConnectionStates.ESTABLISHED self._send_pending_commands() def stopProducing(self): """We're never going to send any more data (normally because either we or the remote has closed the connection) """ logger.info("[%s] Stop producing", self.id()) self.on_connection_closed() def connectionLost(self, reason): logger.info("[%s] Replication connection closed: %r", self.id(), reason) if isinstance(reason, Failure): assert reason.type is not None connection_close_counter.labels(reason.type.__name__).inc() else: connection_close_counter.labels(reason.__class__.__name__).inc() try: # Remove us from list of connections to be monitored connected_connections.remove(self) except ValueError: pass # Stop the looping call sending pings. if self._send_ping_loop and self._send_ping_loop.running: self._send_ping_loop.stop() self.on_connection_closed() def on_connection_closed(self): logger.info("[%s] Connection was closed", self.id()) self.state = ConnectionStates.CLOSED self.pending_commands = [] self.command_handler.lost_connection(self) if self.transport: self.transport.unregisterProducer() # mark the logging context as finished self._logging_context.__exit__(None, None, None) def __str__(self): addr = None if self.transport: addr = str(self.transport.getPeer()) return "ReplicationConnection" % ( self.name, self.conn_id, addr, ) def id(self): return "%s-%s" % (self.name, self.conn_id) def lineLengthExceeded(self, line): """Called when we receive a line that is above the maximum line length""" self.send_error("Line length exceeded") class ServerReplicationStreamProtocol(BaseReplicationStreamProtocol): VALID_INBOUND_COMMANDS = VALID_CLIENT_COMMANDS VALID_OUTBOUND_COMMANDS = VALID_SERVER_COMMANDS def __init__( self, server_name: str, clock: Clock, handler: "ReplicationCommandHandler" ): super().__init__(clock, handler) self.server_name = server_name def connectionMade(self): self.send_command(ServerCommand(self.server_name)) super().connectionMade() def on_NAME(self, cmd): logger.info("[%s] Renamed to %r", self.id(), cmd.data) self.name = cmd.data class ClientReplicationStreamProtocol(BaseReplicationStreamProtocol): VALID_INBOUND_COMMANDS = VALID_SERVER_COMMANDS VALID_OUTBOUND_COMMANDS = VALID_CLIENT_COMMANDS def __init__( self, hs: "HomeServer", client_name: str, server_name: str, clock: Clock, command_handler: "ReplicationCommandHandler", ): super().__init__(clock, command_handler) self.client_name = client_name self.server_name = server_name def connectionMade(self): self.send_command(NameCommand(self.client_name)) super().connectionMade() # Once we've connected subscribe to the necessary streams self.replicate() def on_SERVER(self, cmd): if cmd.data != self.server_name: logger.error("[%s] Connected to wrong remote: %r", self.id(), cmd.data) self.send_error("Wrong remote") def replicate(self): """Send the subscription request to the server""" logger.info("[%s] Subscribing to replication streams", self.id()) self.send_command(ReplicateCommand()) # The following simply registers metrics for the replication connections pending_commands = LaterGauge( "synapse_replication_tcp_protocol_pending_commands", "", ["name"], lambda: {(p.name,): len(p.pending_commands) for p in connected_connections}, ) def transport_buffer_size(protocol): if protocol.transport: size = len(protocol.transport.dataBuffer) + protocol.transport._tempDataLen return size return 0 transport_send_buffer = LaterGauge( "synapse_replication_tcp_protocol_transport_send_buffer", "", ["name"], lambda: {(p.name,): transport_buffer_size(p) for p in connected_connections}, ) def transport_kernel_read_buffer_size(protocol, read=True): SIOCINQ = 0x541B SIOCOUTQ = 0x5411 if protocol.transport: fileno = protocol.transport.getHandle().fileno() if read: op = SIOCINQ else: op = SIOCOUTQ size = struct.unpack("I", fcntl.ioctl(fileno, op, b"\0\0\0\0"))[0] return size return 0 tcp_transport_kernel_send_buffer = LaterGauge( "synapse_replication_tcp_protocol_transport_kernel_send_buffer", "", ["name"], lambda: { (p.name,): transport_kernel_read_buffer_size(p, False) for p in connected_connections }, ) tcp_transport_kernel_read_buffer = LaterGauge( "synapse_replication_tcp_protocol_transport_kernel_read_buffer", "", ["name"], lambda: { (p.name,): transport_kernel_read_buffer_size(p, True) for p in connected_connections }, )