Add minimum total connection threshold for active ratio alerts

Introduced `ALERT_ACTIVE_CONNECTION_RATIO_MIN_TOTAL_CONNECTIONS` to reduce false positives by requiring a minimum number of total connections before evaluating the active connection ratio. Updated the logic and description in relevant files for clarity and configurability.

.env.example

@@ -42,6 +42,9 @@ ENCRYPTION_KEY=REPLACE_WITH_FERNET_KEY
 CORS_ORIGINS=http://localhost:5173,http://localhost:8080
 # Target polling interval in seconds.
 POLL_INTERVAL_SECONDS=30
+# Active Connection Ratio alert is only evaluated when total sessions
+# are at least this number (reduces false positives on low-traffic DBs).
+ALERT_ACTIVE_CONNECTION_RATIO_MIN_TOTAL_CONNECTIONS=5
 # Initial admin bootstrap user (created on first startup if not present).
 INIT_ADMIN_EMAIL=admin@example.com
 INIT_ADMIN_PASSWORD=ChangeMe123!

backend/app/core/config.py

@@ -25,6 +25,7 @@ class Settings(BaseSettings):
     encryption_key: str
     cors_origins: str = "http://localhost:5173"
     poll_interval_seconds: int = 30
+    alert_active_connection_ratio_min_total_connections: int = 5
     init_admin_email: str = "admin@example.com"
     init_admin_password: str = "ChangeMe123!"
 

backend/app/services/alerts.py

@@ -268,7 +268,11 @@ async def _build_standard_rules(db: AsyncSession, target: Target) -> tuple[list[
     slowest_query_total = await _latest_query_snapshot_max(db, target.id, "total_time")
 
     active_ratio = None
-    if active_connections is not None and total_connections and total_connections > 0:
+    if (
+        active_connections is not None
+        and total_connections is not None
+        and total_connections >= settings.alert_active_connection_ratio_min_total_connections
+    ):
         active_ratio = active_connections / total_connections
 
     rollback_ratio_15m, tx_total_15m = await _rollback_ratio_recent(
@@ -280,7 +284,10 @@ async def _build_standard_rules(db: AsyncSession, target: Target) -> tuple[list[
             _RuleInput(
                 key="active_connections_ratio",
                 name="Active Connection Ratio",
-                description="Share of active sessions over total sessions.",
+                description=(
+                    "Share of active sessions over total sessions. "
+                    f"Only evaluated when total sessions >= {settings.alert_active_connection_ratio_min_total_connections}."
+                ),
                 category="capacity",
                 value=active_ratio,
                 warning_threshold=0.70,