1 files changed, 10 insertions, 1 deletions
diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py
index ffdea0de8d..f4de6b9f54 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -108,7 +108,16 @@ class Measure:
     def __init__(self, clock, name):
         self.clock = clock
         self.name = name
-        parent_context = current_context()
+        curr_context = current_context()
+        if not curr_context:
+            logger.warning(
+                "Starting metrics collection %r from sentinel context: metrics will be lost",
+                name,
+            )
+            parent_context = None
+        else:
+            assert isinstance(curr_context, LoggingContext)
+            parent_context = curr_context
         self._logging_context = LoggingContext(
             "Measure[%s]" % (self.name,), parent_context
         )