• 在 Go kit 中集成 Prometheus 进行 API 监控可以帮助开发人员更好地了解系统的性能和行为，提高系统的可观察性和可靠性。下面是一个简单的示例，演示如何在 Go kit 中集成 Prometheus 进行 API 监控：

  package main
  
  import (
  	"net/http"
  
  	"github.com/go-kit/kit/log"
  	"github.com/go-kit/kit/metrics/prometheus"
  	"github.com/go-kit/kit/metrics/provider"
  	"github.com/go-kit/kit/transport"
  	httptransport "github.com/go-kit/kit/transport/http"
  	"github.com/prometheus/client_golang/prometheus/promhttp"
  )
  
  func main() {
  	// 创建 Prometheus 监控器
  	fieldKeys := []string{"method", "error"}
  	requestCount := prometheus.NewCounterFrom(provider.NewProvider(), prometheus.CounterOpts{
  		Namespace: "my_api",
  		Name:      "request_count",
  		Help:      "Number of requests received.",
  	}, fieldKeys)
  	requestLatency := prometheus.NewSummaryFrom(provider.NewProvider(), prometheus.SummaryOpts{
  		Namespace: "my_api",
  		Name:      "request_latency",
  		Help:      "Total duration of requests in microseconds.",
  	}, fieldKeys)
  
  	// 创建 endpoint
  	helloEndpoint := func() string {
  		return "Hello, World!"
  	}
  	helloEndpoint = transport.NewServer(
  		helloEndpoint,
  		func(ctx context.Context, r *http.Request) (interface{}, error) {
  			return nil, nil
  		},
  		func(ctx context.Context, w http.ResponseWriter, response interface{}) error {
  			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  			fmt.Fprint(w, response.(string))
  			return nil
  		},
  		transport.ServerErrorLogger(log.NewNopLogger()),
  		transport.ServerErrorEncoder(errorEncoder),
  		transport.ServerBefore(prometheus.HTTPToContext()),
  	).Endpoint()
  
  	// 创建 HTTP server
  	r := mux.NewRouter()
  	r.Handle("/hello", httptransport.NewServer(
  		helloEndpoint,
  		httpDecodeRequest,
  		httpEncodeResponse,
  		httptransport.ServerBefore(prometheus.HTTPToContext()),
  		httptransport.ServerErrorLogger(log.NewNopLogger()),
  		httptransport.ServerErrorEncoder(errorEncoder),
  		httptransport.ServerBefore(prometheus.HTTPToContext()),
  	)).Methods("GET")
  	r.Handle("/metrics", promhttp.Handler())
  
  	fmt.Println("listening on :8080...")
  	http.ListenAndServe(":8080", r)
  }
  
  func httpDecodeRequest(_ context.Context, r *http.Request) (interface{}, error) {
  	return nil, nil
  }
  
  func httpEncodeResponse(_ context.Context, w http.ResponseWriter, response interface{}) error {
  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  	fmt.Fprint(w, response.(string))
  	return nil
  }
  
  func errorEncoder(_ context.Context, err error, w http.ResponseWriter) {
  	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
  	w.WriteHeader(http.StatusBadRequest)
  	fmt.Fprint(w, err.Error())
  }