指標與監控

公開應用程式指標讓你可以在正式環境中監控請求速率、延遲時間、錯誤率和資源使用情況。Prometheus 是與 Go 應用程式搭配使用最常見的監控系統。

使用 gin-contrib/openmetrics

gin-contrib/openmetrics 中介軟體提供了開箱即用的 Prometheus 指標端點：

go get github.com/gin-contrib/openmetrics

package main

import (
  "github.com/gin-contrib/openmetrics"
  "github.com/gin-gonic/gin"
)

func main() {
  r := gin.Default()

  // Expose /metrics endpoint for Prometheus scraping
  r.Use(openmetrics.NewOpenMetrics("myapp", openmetrics.WithExpose()))

  r.GET("/ping", func(c *gin.Context) {
    c.JSON(200, gin.H{"message": "pong"})
  })

  r.Run(":8080")
}

自訂 Prometheus 指標

如需更多控制，可以直接使用 prometheus/client_golang 函式庫：

package main

import (
  "strconv"
  "time"

  "github.com/gin-gonic/gin"
  "github.com/prometheus/client_golang/prometheus"
  "github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
  httpRequestsTotal = prometheus.NewCounterVec(
    prometheus.CounterOpts{
      Name: "http_requests_total",
      Help: "Total number of HTTP requests",
    },
    []string{"method", "path", "status"},
  )

  httpRequestDuration = prometheus.NewHistogramVec(
    prometheus.HistogramOpts{
      Name:    "http_request_duration_seconds",
      Help:    "HTTP request duration in seconds",
      Buckets: prometheus.DefBuckets,
    },
    []string{"method", "path"},
  )
)

func init() {
  prometheus.MustRegister(httpRequestsTotal)
  prometheus.MustRegister(httpRequestDuration)
}

func MetricsMiddleware() gin.HandlerFunc {
  return func(c *gin.Context) {
    start := time.Now()

    c.Next()

    duration := time.Since(start).Seconds()
    status := strconv.Itoa(c.Writer.Status())

    httpRequestsTotal.WithLabelValues(c.Request.Method, c.FullPath(), status).Inc()
    httpRequestDuration.WithLabelValues(c.Request.Method, c.FullPath()).Observe(duration)
  }
}

func main() {
  r := gin.Default()
  r.Use(MetricsMiddleware())

  // Expose metrics endpoint (separate from application routes)
  r.GET("/metrics", gin.WrapH(promhttp.Handler()))

  r.GET("/ping", func(c *gin.Context) {
    c.JSON(200, gin.H{"message": "pong"})
  })

  r.Run(":8080")
}

需要監控的關鍵指標

對於正式環境的 Gin 應用程式，追蹤以下指標：

指標	類型	用途
`http_requests_total`	Counter	按方法、路徑、狀態碼統計的請求總數
`http_request_duration_seconds`	Histogram	請求延遲分布
`http_requests_in_flight`	Gauge	目前正在處理的請求數
`http_response_size_bytes`	Histogram	回應主體大小

在獨立連接埠上提供指標

在正式環境中，在獨立的連接埠上提供指標以保持其內部存取：

package main

import (
  "net/http"

  "github.com/gin-gonic/gin"
  "github.com/prometheus/client_golang/prometheus/promhttp"
)

func main() {
  // Application server
  app := gin.Default()
  app.GET("/ping", func(c *gin.Context) {
    c.JSON(200, gin.H{"message": "pong"})
  })

  // Metrics server on a separate port
  go func() {
    metrics := http.NewServeMux()
    metrics.Handle("/metrics", promhttp.Handler())
    http.ListenAndServe(":9090", metrics)
  }()

  app.Run(":8080")
}

這樣你就可以將 8080 連接埠公開暴露，同時讓 9090 連接埠保持在基礎設施內部。

Prometheus 抓取配置

將你的應用程式新增到 Prometheus 配置中：

scrape_configs:
  - job_name: "gin-app"
    scrape_interval: 15s
    static_configs:
      - targets: ["localhost:9090"]

測試

# Generate some traffic
curl http://localhost:8080/ping

# Check metrics
curl http://localhost:9090/metrics

你應該會看到類似以下的輸出：

# HELP http_requests_total Total number of HTTP requests
# TYPE http_requests_total counter
http_requests_total{method="GET",path="/ping",status="200"} 1

# HELP http_request_duration_seconds HTTP request duration in seconds
# TYPE http_request_duration_seconds histogram
http_request_duration_seconds_bucket{method="GET",path="/ping",le="0.005"} 1
...