contrib/mixin/mixin.libsonnet: Add dashboard for peer round trip time

This helps users debug firing alerts.

contrib/mixin/mixin.libsonnet

@@ -1230,6 +1230,115 @@
                 },
               ],
             },
+            {
+              aliasColors: {},
+              bars: false,
+              dashLength: 10,
+              dashes: false,
+              datasource: '$datasource',
+              decimals: 0,
+              editable: true,
+              'error': false,
+              fieldConfig: {
+                defaults: {
+                  custom: {},
+                },
+                overrides: [],
+              },
+              fill: 0,
+              fillGradient: 0,
+              gridPos: {
+                h: 7,
+                w: 12,
+                x: 0,
+                y: 28,
+              },
+              hiddenSeries: false,
+              id: 42,
+              isNew: true,
+              legend: {
+                alignAsTable: false,
+                avg: false,
+                current: false,
+                max: false,
+                min: false,
+                rightSide: false,
+                show: false,
+                total: false,
+                values: false,
+              },
+              lines: true,
+              linewidth: 2,
+              links: [],
+              nullPointMode: 'connected',
+              options: {
+                alertThreshold: true,
+              },
+              percentage: false,
+              pluginVersion: '7.4.3',
+              pointradius: 5,
+              points: false,
+              renderer: 'flot',
+              seriesOverrides: [],
+              spaceLength: 10,
+              stack: false,
+              steppedLine: false,
+              targets: [
+                {
+                  expr: 'histogram_quantile(0.99, sum by (instance, le) (rate(etcd_network_peer_round_trip_time_seconds_bucket{%s="$cluster"}[5m])))' % $._config.clusterLabel,
+                  interval: '',
+                  intervalFactor: 2,
+                  legendFormat: '{{instance}} Peer round trip time',
+                  metric: 'etcd_network_peer_round_trip_time_seconds_bucket',
+                  refId: 'A',
+                  step: 2,
+                },
+              ],
+              thresholds: [],
+              timeFrom: null,
+              timeRegions: [],
+              timeShift: null,
+              title: 'Peer round trip time',
+              tooltip: {
+                msResolution: false,
+                shared: true,
+                sort: 0,
+                value_type: 'individual',
+              },
+              type: 'graph',
+              xaxis: {
+                buckets: null,
+                mode: 'time',
+                name: null,
+                show: true,
+                values: [],
+              },
+              yaxes: [
+                {
+                  '$$hashKey': 'object:925',
+                  decimals: null,
+                  format: 's',
+                  label: null,
+                  logBase: 1,
+                  max: null,
+                  min: null,
+                  show: true,
+                },
+                {
+                  '$$hashKey': 'object:926',
+                  format: 'short',
+                  label: null,
+                  logBase: 1,
+                  max: null,
+                  min: null,
+                  show: true,
+                },
+              ],
+              yaxis: {
+                align: false,
+                alignLevel: null,
+              },
+            },
           ],
           title: 'New row',
         },