From 60adcbed919afd5c85442775eca822fec43d816d Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Tue, 31 Mar 2020 15:18:41 +0100
Subject: [PATCH] Fix "'NoneType' has no attribute start|stop" logcontext
 errors (#7181)

Fixes #7179.
---
 changelog.d/7181.misc      |  1 +
 synapse/http/site.py       | 13 ++++++-------
 synapse/logging/context.py |  5 +++++
 3 files changed, 12 insertions(+), 7 deletions(-)
 create mode 100644 changelog.d/7181.misc

diff --git a/changelog.d/7181.misc b/changelog.d/7181.misc
new file mode 100644
index 0000000000..731f4dcb52
--- /dev/null
+++ b/changelog.d/7181.misc
@@ -0,0 +1 @@
+Clean up some LoggingContext code.
diff --git a/synapse/http/site.py b/synapse/http/site.py
index e092193c9c..32feb0d968 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -193,6 +193,12 @@ class SynapseRequest(Request):
         self.finish_time = time.time()
         Request.connectionLost(self, reason)
 
+        if self.logcontext is None:
+            logger.info(
+                "Connection from %s lost before request headers were read", self.client
+            )
+            return
+
         # we only get here if the connection to the client drops before we send
         # the response.
         #
@@ -236,13 +242,6 @@ class SynapseRequest(Request):
     def _finished_processing(self):
         """Log the completion of this request and update the metrics
         """
-
-        if self.logcontext is None:
-            # this can happen if the connection closed before we read the
-            # headers (so render was never called). In that case we'll already
-            # have logged a warning, so just bail out.
-            return
-
         usage = self.logcontext.get_resource_usage()
 
         if self._processing_finished_time is None:
diff --git a/synapse/logging/context.py b/synapse/logging/context.py
index a8eafb1c7c..3254d6a8df 100644
--- a/synapse/logging/context.py
+++ b/synapse/logging/context.py
@@ -539,6 +539,11 @@ def set_current_context(context: LoggingContextOrSentinel) -> LoggingContextOrSe
     Returns:
         The context that was previously active
     """
+    # everything blows up if we allow current_context to be set to None, so sanity-check
+    # that now.
+    if context is None:
+        raise TypeError("'context' argument may not be None")
+
     current = current_context()
 
     if current is not context: