Add filtered URL label to ws_connection_failover_count metrics (#684)

Author: cawthorne

src/metrics/index.ts

@@ -360,6 +360,6 @@ export const metrics = new Metrics(() => ({
   wsConnectionFailoverCount: new client.Gauge({
     name: 'ws_connection_failover_count',
     help: 'The number of consecutive unresponsive connection detections (no data for WS_SUBSCRIPTION_UNRESPONSIVE_TTL), used to trigger URL failover',
-    labelNames: ['transport_name'] as const,
+    labelNames: ['transport_name', 'url'] as const,
   }),
 }))

src/transports/websocket.ts

@@ -417,9 +417,12 @@ export class WebSocketTransport<
       logger.info(
         `The connection is unresponsive (last message ${timeSinceLastMessage}ms ago), incremented failover counter to ${this.streamHandlerInvocationsWithNoConnection}`,
       )
+      // Filter out query params from the URL to avoid leaking sensitive data
+      // and prevent metric cardinality explosion
+      const filteredUrl = this.currentUrl.split('?')[0]
       metrics
         .get('wsConnectionFailoverCount')
-        .labels({ transport_name: this.name })
+        .labels({ transport_name: this.name, url: filteredUrl })
         .set(this.streamHandlerInvocationsWithNoConnection)
     }