chore: more realtime data (#23010)

posthog/session_recordings/realtime_snapshots.py

@@ -3,7 +3,7 @@
 from typing import Optional
 
 import structlog
-from prometheus_client import Counter
+from prometheus_client import Counter, Histogram
 
 from posthog import settings
 from posthog.redis import get_client
@@ -23,6 +23,12 @@
     labelnames=["attempt_count"],
 )
 
+REALTIME_SUBSCRIPTIONS_DATA_LENGTH = Histogram(
+    "realtime_snapshots_data_length",
+    "The length of the data received from the realtime channel. It's ok for this to be zero _some times_ an increase in the rate of zero indicates a possible issue.",
+    labelnames=["attempt_count"],
+)
+
 
 SUBSCRIPTION_CHANNEL = "@posthog/replay/realtime-subscriptions"
 
@@ -91,6 +97,7 @@ def get_realtime_snapshots(team_id: str, session_id: str, attempt_count=0) -> Op
                     snapshots.append(line.decode("utf8"))
 
             REALTIME_SUBSCRIPTIONS_LOADED_COUNTER.labels(attempt_count=attempt_count).inc()
+            REALTIME_SUBSCRIPTIONS_DATA_LENGTH.labels(attempt_count=attempt_count).observe(len(snapshots))
             return snapshots
 
         return None