在 AlertManager 报警通知中展示监控图表

原文档地址：https://mp.weixin.qq.com/s/Wcp7ltEbnHpUlbaF9JDgZg

去绘制渲染报警图表，然后上传到对象存储中保存起来，在钉钉中就可以直接展示了，Promoter 就是这个方案的一个实现，支持在消息通知中展示实时报警图表，效果图如下所示：

目前是将报警数据渲染成图片后上传到 S3 对象存储，所以需要配置一个对象存储（阿里云 OSS 也可以），此外消息通知展示样式支持模板定制，该功能参考自项目 https://github.dev/timonwong/prometheus-webhook-dingtalk。

模板

默认模板位于 template/default.tmpl，可以根据自己需求定制：

{{ define "__subject" }}[{{ .Status | toUpper }}{{ if eq .Status "firing" }}:{{ .Alerts.Firing | len }}{{ end }}] {{ .GroupLabels.SortedPairs.Values | join " " }} {{ if gt (len .CommonLabels) (len .GroupLabels) }}({{ with .CommonLabels.Remove .GroupLabels.Names }}{{ .Values | join " " }}{{ end }}){{ end }}{{ end }}
{{ define "__alertmanagerURL" }}{{ .ExternalURL }}/#/alerts?receiver={{ .Receiver }}{{ end }}

{{ define "default.__text_alert_list" }}{{ range . }}
### {{ .Annotations.summary }}

**详情:** {{ .Annotations.description }}

{{ range .Images }}
**条件:** `{{ .Title }}`
![]({{ .Url }})
{{- end }}

**标签:**
{{ range .Labels.SortedPairs }}{{ if and (ne (.Name) "severity") (ne (.Name) "summary") }}> - {{ .Name }}: {{ .Value | markdown | html }}
{{ end }}{{ end }}
{{ end }}{{ end }}

{{/* Default */}}
{{ define "default.title" }}{{ template "__subject" . }}{{ end }}
{{ define "default.content" }}
{{ if gt (len .Alerts.Firing) 0 -}}
#### **{{ .Alerts.Firing | len }} 条报警**
{{ template "default.__text_alert_list" .Alerts.Firing }}
{{ range .AtMobiles }}@{{ . }}{{ end }}
{{- end }}
{{ if gt (len .Alerts.Resolved) 0 -}}
#### **{{ .Alerts.Resolved | len }} 条报警恢复**
{{ template "default.__text_alert_list" .Alerts.Resolved }}
{{ range .AtMobiles }}@{{ . }}{{ end }}
{{- end }}
{{- end }}

部署

默认配置文件如下所示，放置在 /etc/promoter/config.yaml：

debug: true
http_port: 8080
timeout: 5s
prometheus_url: <prometheus_url>  # Prometheus 的地址
metric_resolution: 100

s3:
  access_key: <ak>
  secret_key: <sk>
  endpoint: oss-cn-beijing.aliyuncs.com
  region: cn-beijing
  bucket: <bucket>

dingtalk:
  url: https://oapi.dingtalk.com/robot/send?access_token=<token>
  secret: <SEC>  # secret for signature

可以直接使用 Docker 镜像 cnych/promoter:v0.1.1 部署，在 Kubernetes 中部署可以直接参考 deploy/kubernetes/promoter.yaml。

启动完成后在 AlertManager 配置中指定 Webhook 地址即可：

route:
  group_by: ['alertname', 'cluster']
  group_wait: 30s
  group_interval: 2m
  repeat_interval: 1h
  receiver: webhook

receivers:
- name: 'webhook'
  webhook_configs:
  - url: 'http://promoter.kube-mon.svc.cluster.local:8080/webhook'  # 配置 promoter 的 webhook 接口
    send_resolved: true

核心原理

该项目采用 golang 实现，Webhook 的实现很简单，这里的核心部分是如何渲染监控图表，核心方式是通过 Prometheus 的 API 接口来获取查询的指标数据：

func Metrics(server, query string, queryTime time.Time, duration, step time.Duration) (promModel.Matrix, error) {
 client, err := prometheus.NewClient(prometheus.Config{Address: server})
 if err != nil {
  return nil, fmt.Errorf("failed to create Prometheus client: %v", err)
 }

 api := prometheusApi.NewAPI(client)
 value, _, err := api.QueryRange(context.Background(), query, prometheusApi.Range{
  Start: queryTime.Add(-duration),
  End:   queryTime,
  Step:  duration / step,
 })
 if err != nil {
  return nil, fmt.Errorf("failed to query Prometheus: %v", err)
 }

 metrics, ok := value.(promModel.Matrix)
 if !ok {
  return nil, fmt.Errorf("unsupported result format: %s", value.Type().String())
 }

 return metrics, nil
}

然后将获取的指标绘制出来，图形绘制使用的 gonum.org/v1/plot 这个包来实现的：

func PlotMetric(metrics promModel.Matrix, level float64, direction string) (io.WriterTo, error) {
 p, err := plot.New()
 if err != nil {
  return nil, fmt.Errorf("failed to create new plot: %v", err)
 }

 textFont, err := vg.MakeFont("Helvetica", 3*vg.Millimeter)
 if err != nil {
  return nil, fmt.Errorf("failed to load font: %v", err)
 }

 evalTextFont, err := vg.MakeFont("Helvetica", 5*vg.Millimeter)
 if err != nil {
  return nil, fmt.Errorf("failed to load font: %v", err)
 }

 evalTextStyle := draw.TextStyle{
  Color:  color.NRGBA{A: 150},
  Font:   evalTextFont,
  XAlign: draw.XRight,
  YAlign: draw.YBottom,
 }

 p.X.Tick.Marker = plot.TimeTicks{Format: "15:04:05"}
 p.X.Tick.Label.Font = textFont
 p.Y.Tick.Label.Font = textFont
 p.Legend.Font = textFont
 p.Legend.Top = true
 p.Legend.YOffs = 15 * vg.Millimeter

 // Color palette for drawing lines
 paletteSize := 8
 palette, err := brewer.GetPalette(brewer.TypeAny, "Dark2", paletteSize)
 if err != nil {
  return nil, fmt.Errorf("failed to get color palette: %v", err)
 }
 colors := palette.Colors()

 var lastEvalValue float64

 for s, sample := range metrics {
  data := make(plotter.XYs, 0)
  for _, v := range sample.Values {
   fs := v.Value.String()
   if fs == "NaN" {
    _, err := drawLine(data, colors, s, paletteSize, p, metrics, sample)
    if err != nil {
     return nil, err
    }

    data = make(plotter.XYs, 0)
    continue
   }

   f, err := strconv.ParseFloat(fs, 64)
   if err != nil {
    return nil, fmt.Errorf("sample value not float: %s", v.Value.String())
   }
   data = append(data, plotter.XY{X: float64(v.Timestamp.Unix()), Y: f})
   lastEvalValue = f
  }

  _, err := drawLine(data, colors, s, paletteSize, p, metrics, sample)
  if err != nil {
   return nil, err
  }
 }

 var polygonPoints plotter.XYs

 if direction == "<" {
  polygonPoints = plotter.XYs{{X: p.X.Min, Y: level}, {X: p.X.Max, Y: level}, {X: p.X.Max, Y: p.Y.Min}, {X: p.X.Min, Y: p.Y.Min}}
 } else {
  polygonPoints = plotter.XYs{{X: p.X.Min, Y: level}, {X: p.X.Max, Y: level}, {X: p.X.Max, Y: p.Y.Max}, {X: p.X.Min, Y: p.Y.Max}}
 }

 poly, err := plotter.NewPolygon(polygonPoints)
 if err != nil {
  return nil, err
 }
 poly.Color = color.NRGBA{R: 255, A: 40}
 poly.LineStyle.Color = color.NRGBA{R: 0, A: 0}
 p.Add(poly)
 p.Add(plotter.NewGrid())

 // Draw plot in canvas with margin
 margin := 6 * vg.Millimeter
 width := 20 * vg.Centimeter
 height := 10 * vg.Centimeter
 c, err := draw.NewFormattedCanvas(width, height, "png")
 if err != nil {
  return nil, fmt.Errorf("failed to create canvas: %v", err)
 }

 cropedCanvas := draw.Crop(draw.New(c), margin, -margin, margin, -margin)
 p.Draw(cropedCanvas)

 // Draw last evaluated value
 evalText := fmt.Sprintf("latest evaluation: %.2f", lastEvalValue)

 plotterCanvas := p.DataCanvas(cropedCanvas)

 trX, trY := p.Transforms(&plotterCanvas)
 evalRectangle := evalTextStyle.Rectangle(evalText)

 points := []vg.Point{
  {X: trX(p.X.Max) + evalRectangle.Min.X - 8*vg.Millimeter, Y: trY(lastEvalValue) + evalRectangle.Min.Y - vg.Millimeter},
  {X: trX(p.X.Max) + evalRectangle.Min.X - 8*vg.Millimeter, Y: trY(lastEvalValue) + evalRectangle.Max.Y + vg.Millimeter},
  {X: trX(p.X.Max) + evalRectangle.Max.X - 6*vg.Millimeter, Y: trY(lastEvalValue) + evalRectangle.Max.Y + vg.Millimeter},
  {X: trX(p.X.Max) + evalRectangle.Max.X - 6*vg.Millimeter, Y: trY(lastEvalValue) + evalRectangle.Min.Y - vg.Millimeter},
 }
 plotterCanvas.FillPolygon(color.NRGBA{R: 255, G: 255, B: 255, A: 90}, points)
 plotterCanvas.FillText(evalTextStyle, vg.Point{X: trX(p.X.Max) - 6*vg.Millimeter, Y: trY(lastEvalValue)}, evalText)

 return c, nil
}

func drawLine(data plotter.XYs, colors []color.Color, s int, paletteSize int, p *plot.Plot, metrics promModel.Matrix, sample *promModel.SampleStream) (*plotter.Line, error) {
 var l *plotter.Line
 var err error
 if len(data) > 0 {
  l, err = plotter.NewLine(data)
  if err != nil {
   return &plotter.Line{}, fmt.Errorf("failed to create line: %v", err)
  }

  l.LineStyle.Width = vg.Points(1)
  l.LineStyle.Color = colors[s%paletteSize]

  p.Add(l)
  if len(metrics) > 1 {
   m := labelText.FindStringSubmatch(sample.Metric.String())
   if m != nil {
    p.Legend.Add(m[1], l)
   }
  }
 }

 return l, nil
}

更多实现细节可以前往项目 https://github.com/cnych/promoter 查看。