Skip invalid metrics for StaticPool

Author: dan-fernandes

tiled/server/metrics.py

@@ -6,7 +6,7 @@
 
 from prometheus_client import Counter, Gauge, Histogram
 from sqlalchemy import event
-from sqlalchemy.pool import QueuePool
+from sqlalchemy.pool import QueuePool, StaticPool
 
 REQUEST_DURATION = Histogram(
     "tiled_request_duration_seconds",
@@ -220,6 +220,10 @@ def on_checkout(dbapi_connection, connection_record, connection_proxy):
         DB_POOL_CHECKEDOUT.labels(name).inc()
         DB_POOL_CHECKOUTS_TOTAL.labels(name).inc()
 
+        # Skip for single-connection database:
+        if isinstance(pool, StaticPool):
+            return
+
         # First overflow: we just used the very first overflow slot
         if pool.overflow() == 1:
             DB_POOL_FIRST_OVERFLOW_TOTAL.labels(name).inc()