75 lines
2.0 KiB
Go
75 lines
2.0 KiB
Go
package metrics
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import (
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"context"
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_ "embed"
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"fmt"
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"net"
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"net/http"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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"git.warky.dev/wdevs/pgsql-broker/pkg/broker/adapter"
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)
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//go:embed page.html
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var dashboardHTML []byte
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// Server is the embedded HTTP server exposing /metrics (standard Prometheus
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// exposition format) and / (a single-page HTML dashboard that polls
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// /metrics).
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type Server struct {
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httpServer *http.Server
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listener net.Listener
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logger adapter.Logger
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}
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// NewServer builds a Server bound to addr (e.g. "127.0.0.1:9469"). Binding
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// happens immediately so a port conflict is reported to the caller rather
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// than surfacing later in a background goroutine.
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func NewServer(m *Metrics, addr string, logger adapter.Logger) (*Server, error) {
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listener, err := net.Listen("tcp", addr)
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if err != nil {
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return nil, fmt.Errorf("failed to bind metrics server to %s: %w", addr, err)
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}
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mux := http.NewServeMux()
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mux.Handle("/metrics", promhttp.HandlerFor(m.Registry, promhttp.HandlerOpts{}))
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mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
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if r.URL.Path != "/" {
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http.NotFound(w, r)
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return
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}
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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_, _ = w.Write(dashboardHTML)
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})
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return &Server{
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httpServer: &http.Server{Handler: mux},
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listener: listener,
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logger: logger.With("component", "metrics-server"),
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}, nil
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}
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// Addr returns the actual bound address (useful when addr was given with a
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// ":0" port).
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func (s *Server) Addr() string {
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return s.listener.Addr().String()
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}
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// Start serves in the background. It returns immediately; Serve errors
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// (other than a clean Shutdown) are logged.
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func (s *Server) Start() {
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s.logger.Info("metrics server listening", "addr", s.Addr())
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go func() {
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if err := s.httpServer.Serve(s.listener); err != nil && err != http.ErrServerClosed {
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s.logger.Error("metrics server stopped unexpectedly", "error", err)
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}
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}()
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}
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// Stop gracefully shuts down the server.
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func (s *Server) Stop(ctx context.Context) error {
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return s.httpServer.Shutdown(ctx)
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}
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