HaProxy backend (or frontend/servers)  
Show backend stats
This Dashboard shows backend stats. 
You can use templating to choose one/multiple backend (singlestats works only with one). 
You can easily change backend to /frontend|server/ by editing query and replace backend with another one. 

Open issues or give feedback at : https://github.com/tcheronneau/grafana_dashboard
{
  "__inputs": [
    {
      "name": "DS_PROMETHEUS",
      "label": "Prometheus",
      "description": "v1.2.1",
      "type": "datasource",
      "pluginId": "prometheus",
      "pluginName": "Prometheus"
    }
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      "name": "Singlestat",
      "version": ""
    },
    {
      "type": "panel",
      "id": "graph",
      "name": "Graph",
      "version": ""
    },
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      "id": "grafana",
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      "id": "prometheus",
      "name": "Prometheus",
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    }
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  "title": "HaProxy backend (or frontend/servers)  ",
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  "hideControls": false,
  "sharedCrosshair": false,
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          },
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              "expr": "rate(haproxy_backend_bytes_in_total{backend=~\"$backend\"}[5m])",
              "interval": "",
              "intervalFactor": 2,
              "legendFormat": "",
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            }
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            "full": true,
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          },
          "targets": [
            {
              "expr": "rate(haproxy_backend_connections_total{backend=\"$backend\"}[10m])",
              "intervalFactor": 2,
              "metric": "haproxy_backend_connections_total",
              "refId": "A",
              "step": 60
            }
          ],
          "thresholds": "",
          "title": "Current connection",
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          },
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            {
              "expr": "rate(haproxy_backend_bytes_out_total{backend=\"$backend\"}[5m])",
              "intervalFactor": 2,
              "metric": "haproxy_backend_bytes_out_total",
              "refId": "A",
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            }
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          "thresholds": "",
          "title": "Bytes OUT",
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              "value": "null"
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    },
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      "collapse": false,
      "editable": true,
      "height": "250px",
      "panels": [
        {
          "aliasColors": {},
          "bars": false,
          "datasource": "${DS_PROMETHEUS}",
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          "fill": 1,
          "grid": {
            "threshold1": null,
            "threshold1Color": "rgba(216, 200, 27, 0.27)",
            "threshold2": null,
            "threshold2Color": "rgba(234, 112, 112, 0.22)"
          },
          "id": 2,
          "isNew": true,
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          },
          "lines": true,
          "linewidth": 2,
          "links": [],
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          "pointradius": 5,
          "points": false,
          "renderer": "flot",
          "seriesOverrides": [],
          "span": 12,
          "stack": false,
          "steppedLine": false,
          "targets": [
            {
              "expr": "sum(rate(haproxy_backend_http_responses_total{backend=~\"$backend\"}[10m])) by (backend, code)",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }} : {{ code }}",
              "refId": "A",
              "step": 2
            }
          ],
          "timeFrom": null,
          "timeShift": null,
          "title": "Haproxy $backend return code",
          "tooltip": {
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            "shared": true,
            "sort": 0,
            "value_type": "cumulative"
          },
          "type": "graph",
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          },
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        {
          "aliasColors": {},
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          },
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          "renderer": "flot",
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          "stack": false,
          "steppedLine": false,
          "targets": [
            {
              "expr": "haproxy_backend_current_session_rate{backend=~\"$backend\"}",
              "hide": false,
              "interval": "",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }}",
              "metric": "haproxy_backend_current_session_rate",
              "refId": "A",
              "step": 2
            }
          ],
          "timeFrom": null,
          "timeShift": null,
          "title": "Current $backend sessions",
          "tooltip": {
            "msResolution": false,
            "shared": true,
            "sort": 0,
            "value_type": "cumulative"
          },
          "type": "graph",
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          },
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            },
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              "format": "short",
              "label": null,
              "logBase": 1,
              "max": null,
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              "show": true
            }
          ]
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      ],
      "title": "New row"
    },
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      "collapse": false,
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      "height": "250px",
      "panels": [
        {
          "aliasColors": {},
          "bars": false,
          "datasource": "${DS_PROMETHEUS}",
          "editable": true,
          "error": false,
          "fill": 1,
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          "renderer": "flot",
          "seriesOverrides": [],
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          "stack": false,
          "steppedLine": false,
          "targets": [
            {
              "expr": "haproxy_backend_up{backend=~\"$backend\"}",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }}",
              "metric": "haproxy_backend_up",
              "refId": "A",
              "step": 2
            },
            {
              "expr": "haproxy_backend_weight{backend=~\"$backend\"}",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }}",
              "metric": "haproxy_backend_weight",
              "refId": "B",
              "step": 2
            }
          ],
          "timeFrom": null,
          "timeShift": null,
          "title": "$backend status and Weight",
          "tooltip": {
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            "shared": true,
            "sort": 0,
            "value_type": "cumulative"
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              "format": "short",
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            },
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              "max": null,
              "min": null,
              "show": true
            }
          ]
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      ],
      "title": "New row"
    },
    {
      "collapse": false,
      "editable": true,
      "height": "250px",
      "panels": [
        {
          "aliasColors": {},
          "bars": false,
          "datasource": "${DS_PROMETHEUS}",
          "editable": true,
          "error": false,
          "fill": 2,
          "grid": {
            "threshold1": null,
            "threshold1Color": "rgba(216, 200, 27, 0.27)",
            "threshold2": null,
            "threshold2Color": "rgba(234, 112, 112, 0.22)"
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          "isNew": true,
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            "max": false,
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          },
          "lines": true,
          "linewidth": 1,
          "links": [],
          "nullPointMode": "connected",
          "percentage": false,
          "pointradius": 5,
          "points": false,
          "renderer": "flot",
          "seriesOverrides": [
            {
              "alias": "/[a-z]* OUT/",
              "transform": "negative-Y"
            }
          ],
          "span": 12,
          "stack": false,
          "steppedLine": false,
          "targets": [
            {
              "expr": "rate(haproxy_backend_bytes_in_total{backend=~\"$backend\"}[10m])",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }} IN",
              "metric": "haproxy_backend_bytes_in_total",
              "refId": "A",
              "step": 2
            },
            {
              "expr": "rate(haproxy_backend_bytes_out_total{backend=~\"$backend\"}[10m])",
              "intervalFactor": 2,
              "legendFormat": "{{ backend }} OUT",
              "refId": "B",
              "step": 2
            }
          ],
          "timeFrom": null,
          "timeShift": null,
          "title": "Bytes IN/OUT",
          "tooltip": {
            "msResolution": false,
            "shared": true,
            "sort": 0,
            "value_type": "cumulative"
          },
          "type": "graph",
          "xaxis": {
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          },
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              "format": "bytes",
              "label": null,
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              "min": null,
              "show": true
            },
            {
              "format": "short",
              "label": null,
              "logBase": 1,
              "max": null,
              "min": null,
              "show": true
            }
          ]
        }
      ],
      "title": "New row"
    }
  ],
  "time": {
    "from": "now-1h",
    "to": "now"
  },
  "timepicker": {
    "refresh_intervals": [
      "5s",
      "10s",
      "30s",
      "1m",
      "5m",
      "15m",
      "30m",
      "1h",
      "2h",
      "1d"
    ],
    "time_options": [
      "5m",
      "15m",
      "1h",
      "6h",
      "12h",
      "24h",
      "2d",
      "7d",
      "30d"
    ]
  },
  "templating": {
    "list": [
      {
        "current": {},
        "datasource": "${DS_PROMETHEUS}",
        "hide": 0,
        "includeAll": true,
        "multi": true,
        "name": "backend",
        "options": [],
        "query": "label_values(backend)",
        "refresh": 1,
        "regex": ".*",
        "type": "query"
      }
    ]
  },
  "annotations": {
    "list": []
  },
  "schemaVersion": 12,
  "version": 88,
  "links": [],
  "gnetId": 789,
  "description": "Show backend stats"
}