Include eventid in log lines when processing incoming federation transactions (#3959)

when processing incoming transactions, it can be hard to see what's going on,
because we process a bunch of stuff in parallel, and because we may end up
recursively working our way through a chain of three or four events.

This commit creates a way to use logcontexts to add the relevant event ids to
the log lines.

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/util/test_logcontext.py b/tests/util/test_logcontext.py
index 4633db77b3..8adaee3c8d 100644
--- a/tests/util/test_logcontext.py
+++ b/tests/util/test_logcontext.py
@@ -159,6 +159,11 @@ class LoggingContextTestCase(unittest.TestCase):
             self.assertEqual(r, "bum")
             self._check_test_key("one")
 
+    def test_nested_logging_context(self):
+        with LoggingContext(request="foo"):
+            nested_context = logcontext.nested_logging_context(suffix="bar")
+            self.assertEqual(nested_context.request, "foo-bar")
+
 
 # a function which returns a deferred which has been "called", but
 # which had a function which returned another incomplete deferred on