Add Labels limit exceeded panel to dashboard (#1076)

New panel supposed to display events when VM drops extra label
on exceeding `maxLabelsPerTimeseries` limit.

dashboards/victoriametrics.json

@@ -50,7 +50,7 @@
   "gnetId": null,
   "graphTooltip": 0,
   "id": null,
-  "iteration": 1606684714463,
+  "iteration": 1613595700130,
   "links": [
     {
       "icon": "doc",
@@ -2264,7 +2264,7 @@
           "fillGradient": 0,
           "gridPos": {
             "h": 8,
-            "w": 24,
+            "w": 12,
             "x": 0,
             "y": 11
           },
@@ -2339,6 +2339,105 @@
             "align": false,
             "alignLevel": null
           }
+        },
+        {
+          "aliasColors": {},
+          "bars": false,
+          "dashLength": 10,
+          "dashes": false,
+          "datasource": "$ds",
+          "description": "VictoriaMetrics limits the number of labels per each metric with `-maxLabelsPerTimeseries` command-line flag.\n\nThis prevents from ingesting metrics with too many labels. The value of `maxLabelsPerTimeseries` must be adjusted for your workload.\n\nWhen limit is exceeded (graph is > 0) - extra labels are dropped, which could result in unexpected identical time series.",
+          "fieldConfig": {
+            "defaults": {
+              "custom": {},
+              "links": []
+            },
+            "overrides": []
+          },
+          "fill": 1,
+          "fillGradient": 0,
+          "gridPos": {
+            "h": 8,
+            "w": 12,
+            "x": 12,
+            "y": 11
+          },
+          "hiddenSeries": false,
+          "id": 116,
+          "legend": {
+            "avg": false,
+            "current": false,
+            "max": false,
+            "min": false,
+            "show": false,
+            "total": false,
+            "values": false
+          },
+          "lines": true,
+          "linewidth": 1,
+          "links": [],
+          "nullPointMode": "null",
+          "percentage": false,
+          "pluginVersion": "7.1.1",
+          "pointradius": 2,
+          "points": false,
+          "renderer": "flot",
+          "seriesOverrides": [],
+          "spaceLength": 10,
+          "stack": false,
+          "steppedLine": false,
+          "targets": [
+            {
+              "expr": "sum(increase(vm_metrics_with_dropped_labels_total{job=\"$job_insert\", instance=~\"$instance\"}[5m]))",
+              "format": "time_series",
+              "hide": false,
+              "interval": "",
+              "intervalFactor": 1,
+              "legendFormat": "metrics with dropped labels",
+              "refId": "A"
+            }
+          ],
+          "thresholds": [],
+          "timeFrom": null,
+          "timeRegions": [],
+          "timeShift": null,
+          "title": "Labels limit exceeded ($instance)",
+          "tooltip": {
+            "shared": true,
+            "sort": 0,
+            "value_type": "individual"
+          },
+          "type": "graph",
+          "xaxis": {
+            "buckets": null,
+            "mode": "time",
+            "name": null,
+            "show": true,
+            "values": []
+          },
+          "yaxes": [
+            {
+              "decimals": 2,
+              "format": "percentunit",
+              "label": null,
+              "logBase": 1,
+              "max": null,
+              "min": "0",
+              "show": true
+            },
+            {
+              "format": "short",
+              "label": null,
+              "logBase": 1,
+              "max": null,
+              "min": "0",
+              "show": true
+            }
+          ],
+          "yaxis": {
+            "align": false,
+            "alignLevel": null
+          }
         }
       ],
       "title": "Troubleshooting",