Be able to correlate timeouts in reverse-proxy layer in front of Syna…

…pse (pull request ID from header)

Fix #13685

docs/usage/configuration/config_documentation.md

@@ -436,6 +436,12 @@ Sub-options for each listener include:
 * `x_forwarded`: Only valid for an 'http' listener. Set to true to use the X-Forwarded-For header as the client IP. Useful when Synapse is
  behind a reverse-proxy.
 
+* `request_id_header`: The header used as the basis for the request ID which
+ is used in logs and tracing to correlate requests. Useful when Synapse is
+ behind a reverse-proxy. For example, if you use Cloudflare in front of
+ Synapse, you can set this to `"cf-ray"` to match up requests even when the
+ Cloudflare layer times out before Synapse is done.
+
 * `resources`: Only valid for an 'http' listener. A list of resources to host
  on this port. Sub-options for each resource are:
 

synapse/config/server.py

@@ -206,6 +206,7 @@ class HttpListenerConfig:
  resources: List[HttpResourceConfig] = attr.Factory(list)
  additional_resources: Dict[str, dict] = attr.Factory(dict)
  tag: Optional[str] = None
+ request_id_header: Optional[str] = None
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -887,7 +888,7 @@ def read_gc_thresholds(
  )
 
 
-def parse_listener_def(num: int, listener: Any) -> ListenerConfig:
+def parse_listener_def(num: int, listener: JsonDict) -> ListenerConfig:
  """parse a listener config from the config file"""
  listener_type = listener["type"]
  # Raise a helpful error if direct TCP replication is still configured.
@@ -928,6 +929,7 @@ def parse_listener_def(num: int, listener: Any) -> ListenerConfig:
  resources=resources,
  additional_resources=listener.get("additional_resources", {}),
  tag=listener.get("tag"),
+ request_id_header=listener.get("request_id_header"),
  )
 
  return ListenerConfig(port, bind_addresses, listener_type, tls, http_config)

synapse/http/site.py

@@ -72,10 +72,12 @@ def __init__(
  site: "SynapseSite",
  *args: Any,
  max_request_body_size: int = 1024,
+ request_id_header: Optional[str],
  **kw: Any,
  ):
  super().__init__(channel, *args, **kw)
  self._max_request_body_size = max_request_body_size
+ self.request_id_header = request_id_header
  self.synapse_site = site
  self.reactor = site.reactor
  self._channel = channel # this is used by the tests
@@ -172,7 +174,13 @@ def set_opentracing_span(self, span: "opentracing.Span") -> None:
  self._opentracing_span = span
 
  def get_request_id(self) -> str:
- return "%s-%i" % (self.get_method(), self.request_seq)
+ if self.request_id_header:
+ request_id_value = self.getHeader(self.request_id_header)
+
+ if not request_id_value:
+ request_id_value = self.request_seq
+
+ return "%s-%i" % (self.get_method(), request_id_value)
 
  def get_redacted_uri(self) -> str:
  """Gets the redacted URI associated with the request (or placeholder if the URI
@@ -617,6 +625,7 @@ def request_factory(channel: HTTPChannel, queued: bool) -> Request:
  self,
  max_request_body_size=max_request_body_size,
  queued=queued,
+ request_id_header=config.http_options.request_id_header,
  )
 
  self.requestFactory = request_factory # type: ignore