tracking UnhandledPromiseRejection(s) (#3386)

docker/grafana/provisioning/dashboards/lodestar.json

@@ -2236,6 +2236,87 @@
             "align": false,
             "alignLevel": null
           }
+        },
+        {
+          "datasource": null,
+          "fieldConfig": {
+            "defaults": {
+              "color": {
+                "mode": "palette-classic"
+              },
+              "custom": {
+                "axisLabel": "",
+                "axisPlacement": "auto",
+                "barAlignment": 0,
+                "drawStyle": "line",
+                "fillOpacity": 0,
+                "gradientMode": "none",
+                "hideFrom": {
+                  "legend": false,
+                  "tooltip": false,
+                  "viz": false
+                },
+                "lineInterpolation": "linear",
+                "lineWidth": 1,
+                "pointSize": 5,
+                "scaleDistribution": {
+                  "type": "linear"
+                },
+                "showPoints": "auto",
+                "spanNulls": false,
+                "stacking": {
+                  "group": "A",
+                  "mode": "none"
+                },
+                "thresholdsStyle": {
+                  "mode": "off"
+                }
+              },
+              "mappings": [],
+              "thresholds": {
+                "mode": "absolute",
+                "steps": [
+                  {
+                    "color": "green",
+                    "value": null
+                  },
+                  {
+                    "color": "red",
+                    "value": 80
+                  }
+                ]
+              }
+            },
+            "overrides": []
+          },
+          "gridPos": {
+            "h": 8,
+            "w": 12,
+            "x": 0,
+            "y": 51
+          },
+          "id": 268,
+          "options": {
+            "legend": {
+              "calcs": [],
+              "displayMode": "list",
+              "placement": "bottom"
+            },
+            "tooltip": {
+              "mode": "single"
+            }
+          },
+          "targets": [
+            {
+              "exemplar": false,
+              "expr": "rate(unhandeled_promise_rejections[$__rate_interval])",
+              "interval": "",
+              "legendFormat": "Errors",
+              "refId": "A"
+            }
+          ],
+          "title": "UnhandledPromiseRejection rate",
+          "type": "timeseries"
         }
       ],
       "title": "VM Stats",

packages/lodestar/src/metrics/metrics.ts

@@ -33,6 +33,9 @@ export function createMetrics(
     const clockSlot = getCurrentSlot(config, genesisTime);
     validatorMonitor.scrapeMetrics(clockSlot);
   });
+  process.on("unhandledRejection", (_error) => {
+    lodestar.unhandeledPromiseRejections.inc();
+  });
 
   collectDefaultMetrics({
     register,

packages/lodestar/src/metrics/metrics/lodestar.ts

@@ -529,5 +529,9 @@ export function createLodestarMetrics(
       help: "regen function total errors",
       labelNames: ["entrypoint", "caller"],
     }),
+    unhandeledPromiseRejections: register.gauge({
+      name: "unhandeled_promise_rejections",
+      help: "UnhandeledPromiseRejection count",
+    }),
   };
 }