diff --git a/synapse/util/caches/deferred_cache.py b/synapse/util/caches/deferred_cache.py
index 601305487c..1adc92eb90 100644
--- a/synapse/util/caches/deferred_cache.py
+++ b/synapse/util/caches/deferred_cache.py
@@ -105,7 +105,7 @@ class DeferredCache(Generic[KT, VT]):
keylen=keylen,
cache_name=name,
cache_type=cache_type,
- size_callback=(lambda d: len(d)) if iterable else None,
+ size_callback=(lambda d: len(d) or 1) if iterable else None,
metrics_collection_callback=metrics_cb,
apply_cache_factor_from_config=apply_cache_factor_from_config,
) # type: LruCache[KT, VT]
diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py
index ffdea0de8d..24123d5cc4 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -108,7 +108,15 @@ 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 from sentinel context: metrics will be lost"
+ )
+ parent_context = None
+ else:
+ assert isinstance(curr_context, LoggingContext)
+ parent_context = curr_context
self._logging_context = LoggingContext(
"Measure[%s]" % (self.name,), parent_context
)
|
