diff --git a/synapse/logging/_structured.py b/synapse/logging/_structured.py
new file mode 100644
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--- /dev/null
+++ b/synapse/logging/_structured.py
@@ -0,0 +1,374 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+import logging
+import os.path
+import sys
+import typing
+import warnings
+
+import attr
+from constantly import NamedConstant, Names, ValueConstant, Values
+from zope.interface import implementer
+
+from twisted.logger import (
+ FileLogObserver,
+ FilteringLogObserver,
+ ILogObserver,
+ LogBeginner,
+ Logger,
+ LogLevel,
+ LogLevelFilterPredicate,
+ LogPublisher,
+ eventAsText,
+ globalLogBeginner,
+ jsonFileLogObserver,
+)
+
+from synapse.config._base import ConfigError
+from synapse.logging._terse_json import (
+ TerseJSONToConsoleLogObserver,
+ TerseJSONToTCPLogObserver,
+)
+from synapse.logging.context import LoggingContext
+
+
+def stdlib_log_level_to_twisted(level: str) -> LogLevel:
+ """
+ Convert a stdlib log level to Twisted's log level.
+ """
+ lvl = level.lower().replace("warning", "warn")
+ return LogLevel.levelWithName(lvl)
+
+
+@attr.s
+@implementer(ILogObserver)
+class LogContextObserver(object):
+ """
+ An ILogObserver which adds Synapse-specific log context information.
+
+ Attributes:
+ observer (ILogObserver): The target parent observer.
+ """
+
+ observer = attr.ib()
+
+ def __call__(self, event: dict) -> None:
+ """
+ Consume a log event and emit it to the parent observer after filtering
+ and adding log context information.
+
+ Args:
+ event (dict)
+ """
+ # Filter out some useless events that Twisted outputs
+ if "log_text" in event:
+ if event["log_text"].startswith("DNSDatagramProtocol starting on "):
+ return
+
+ if event["log_text"].startswith("(UDP Port "):
+ return
+
+ if event["log_text"].startswith("Timing out client") or event[
+ "log_format"
+ ].startswith("Timing out client"):
+ return
+
+ context = LoggingContext.current_context()
+
+ # Copy the context information to the log event.
+ if context is not None:
+ context.copy_to_twisted_log_entry(event)
+ else:
+ # If there's no logging context, not even the root one, we might be
+ # starting up or it might be from non-Synapse code. Log it as if it
+ # came from the root logger.
+ event["request"] = None
+ event["scope"] = None
+
+ self.observer(event)
+
+
+class PythonStdlibToTwistedLogger(logging.Handler):
+ """
+ Transform a Python stdlib log message into a Twisted one.
+ """
+
+ def __init__(self, observer, *args, **kwargs):
+ """
+ Args:
+ observer (ILogObserver): A Twisted logging observer.
+ *args, **kwargs: Args/kwargs to be passed to logging.Handler.
+ """
+ self.observer = observer
+ super().__init__(*args, **kwargs)
+
+ def emit(self, record: logging.LogRecord) -> None:
+ """
+ Emit a record to Twisted's observer.
+
+ Args:
+ record (logging.LogRecord)
+ """
+
+ self.observer(
+ {
+ "log_time": record.created,
+ "log_text": record.getMessage(),
+ "log_format": "{log_text}",
+ "log_namespace": record.name,
+ "log_level": stdlib_log_level_to_twisted(record.levelname),
+ }
+ )
+
+
+def SynapseFileLogObserver(outFile: typing.io.TextIO) -> FileLogObserver:
+ """
+ A log observer that formats events like the traditional log formatter and
+ sends them to `outFile`.
+
+ Args:
+ outFile (file object): The file object to write to.
+ """
+
+ def formatEvent(_event: dict) -> str:
+ event = dict(_event)
+ event["log_level"] = event["log_level"].name.upper()
+ event["log_format"] = "- {log_namespace} - {log_level} - {request} - " + (
+ event.get("log_format", "{log_text}") or "{log_text}"
+ )
+ return eventAsText(event, includeSystem=False) + "\n"
+
+ return FileLogObserver(outFile, formatEvent)
+
+
+class DrainType(Names):
+ CONSOLE = NamedConstant()
+ CONSOLE_JSON = NamedConstant()
+ CONSOLE_JSON_TERSE = NamedConstant()
+ FILE = NamedConstant()
+ FILE_JSON = NamedConstant()
+ NETWORK_JSON_TERSE = NamedConstant()
+
+
+class OutputPipeType(Values):
+ stdout = ValueConstant(sys.__stdout__)
+ stderr = ValueConstant(sys.__stderr__)
+
+
+@attr.s
+class DrainConfiguration(object):
+ name = attr.ib()
+ type = attr.ib()
+ location = attr.ib()
+ options = attr.ib(default=None)
+
+
+@attr.s
+class NetworkJSONTerseOptions(object):
+ maximum_buffer = attr.ib(type=int)
+
+
+DEFAULT_LOGGERS = {"synapse": {"level": "INFO"}}
+
+
+def parse_drain_configs(
+ drains: dict
+) -> typing.Generator[DrainConfiguration, None, None]:
+ """
+ Parse the drain configurations.
+
+ Args:
+ drains (dict): A list of drain configurations.
+
+ Yields:
+ DrainConfiguration instances.
+
+ Raises:
+ ConfigError: If any of the drain configuration items are invalid.
+ """
+ for name, config in drains.items():
+ if "type" not in config:
+ raise ConfigError("Logging drains require a 'type' key.")
+
+ try:
+ logging_type = DrainType.lookupByName(config["type"].upper())
+ except ValueError:
+ raise ConfigError(
+ "%s is not a known logging drain type." % (config["type"],)
+ )
+
+ if logging_type in [
+ DrainType.CONSOLE,
+ DrainType.CONSOLE_JSON,
+ DrainType.CONSOLE_JSON_TERSE,
+ ]:
+ location = config.get("location")
+ if location is None or location not in ["stdout", "stderr"]:
+ raise ConfigError(
+ (
+ "The %s drain needs the 'location' key set to "
+ "either 'stdout' or 'stderr'."
+ )
+ % (logging_type,)
+ )
+
+ pipe = OutputPipeType.lookupByName(location).value
+
+ yield DrainConfiguration(name=name, type=logging_type, location=pipe)
+
+ elif logging_type in [DrainType.FILE, DrainType.FILE_JSON]:
+ if "location" not in config:
+ raise ConfigError(
+ "The %s drain needs the 'location' key set." % (logging_type,)
+ )
+
+ location = config.get("location")
+ if os.path.abspath(location) != location:
+ raise ConfigError(
+ "File paths need to be absolute, '%s' is a relative path"
+ % (location,)
+ )
+ yield DrainConfiguration(name=name, type=logging_type, location=location)
+
+ elif logging_type in [DrainType.NETWORK_JSON_TERSE]:
+ host = config.get("host")
+ port = config.get("port")
+ maximum_buffer = config.get("maximum_buffer", 1000)
+ yield DrainConfiguration(
+ name=name,
+ type=logging_type,
+ location=(host, port),
+ options=NetworkJSONTerseOptions(maximum_buffer=maximum_buffer),
+ )
+
+ else:
+ raise ConfigError(
+ "The %s drain type is currently not implemented."
+ % (config["type"].upper(),)
+ )
+
+
+def setup_structured_logging(
+ hs,
+ config,
+ log_config: dict,
+ logBeginner: LogBeginner = globalLogBeginner,
+ redirect_stdlib_logging: bool = True,
+) -> LogPublisher:
+ """
+ Set up Twisted's structured logging system.
+
+ Args:
+ hs: The homeserver to use.
+ config (HomeserverConfig): The configuration of the Synapse homeserver.
+ log_config (dict): The log configuration to use.
+ """
+ if config.no_redirect_stdio:
+ raise ConfigError(
+ "no_redirect_stdio cannot be defined using structured logging."
+ )
+
+ logger = Logger()
+
+ if "drains" not in log_config:
+ raise ConfigError("The logging configuration requires a list of drains.")
+
+ observers = []
+
+ for observer in parse_drain_configs(log_config["drains"]):
+ # Pipe drains
+ if observer.type == DrainType.CONSOLE:
+ logger.debug(
+ "Starting up the {name} console logger drain", name=observer.name
+ )
+ observers.append(SynapseFileLogObserver(observer.location))
+ elif observer.type == DrainType.CONSOLE_JSON:
+ logger.debug(
+ "Starting up the {name} JSON console logger drain", name=observer.name
+ )
+ observers.append(jsonFileLogObserver(observer.location))
+ elif observer.type == DrainType.CONSOLE_JSON_TERSE:
+ logger.debug(
+ "Starting up the {name} terse JSON console logger drain",
+ name=observer.name,
+ )
+ observers.append(
+ TerseJSONToConsoleLogObserver(observer.location, metadata={})
+ )
+
+ # File drains
+ elif observer.type == DrainType.FILE:
+ logger.debug("Starting up the {name} file logger drain", name=observer.name)
+ log_file = open(observer.location, "at", buffering=1, encoding="utf8")
+ observers.append(SynapseFileLogObserver(log_file))
+ elif observer.type == DrainType.FILE_JSON:
+ logger.debug(
+ "Starting up the {name} JSON file logger drain", name=observer.name
+ )
+ log_file = open(observer.location, "at", buffering=1, encoding="utf8")
+ observers.append(jsonFileLogObserver(log_file))
+
+ elif observer.type == DrainType.NETWORK_JSON_TERSE:
+ metadata = {"server_name": hs.config.server_name}
+ log_observer = TerseJSONToTCPLogObserver(
+ hs=hs,
+ host=observer.location[0],
+ port=observer.location[1],
+ metadata=metadata,
+ maximum_buffer=observer.options.maximum_buffer,
+ )
+ log_observer.start()
+ observers.append(log_observer)
+ else:
+ # We should never get here, but, just in case, throw an error.
+ raise ConfigError("%s drain type cannot be configured" % (observer.type,))
+
+ publisher = LogPublisher(*observers)
+ log_filter = LogLevelFilterPredicate()
+
+ for namespace, namespace_config in log_config.get(
+ "loggers", DEFAULT_LOGGERS
+ ).items():
+ # Set the log level for twisted.logger.Logger namespaces
+ log_filter.setLogLevelForNamespace(
+ namespace,
+ stdlib_log_level_to_twisted(namespace_config.get("level", "INFO")),
+ )
+
+ # Also set the log levels for the stdlib logger namespaces, to prevent
+ # them getting to PythonStdlibToTwistedLogger and having to be formatted
+ if "level" in namespace_config:
+ logging.getLogger(namespace).setLevel(namespace_config.get("level"))
+
+ f = FilteringLogObserver(publisher, [log_filter])
+ lco = LogContextObserver(f)
+
+ if redirect_stdlib_logging:
+ stuff_into_twisted = PythonStdlibToTwistedLogger(lco)
+ stdliblogger = logging.getLogger()
+ stdliblogger.addHandler(stuff_into_twisted)
+
+ # Always redirect standard I/O, otherwise other logging outputs might miss
+ # it.
+ logBeginner.beginLoggingTo([lco], redirectStandardIO=True)
+
+ return publisher
+
+
+def reload_structured_logging(*args, log_config=None) -> None:
+ warnings.warn(
+ "Currently the structured logging system can not be reloaded, doing nothing"
+ )
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