ginuerzh
785d52da31
Allow browser-based dashboards (e.g. Flutter web apps) to access the metrics endpoint by setting Access-Control-Allow-Origin: * and handling OPTIONS preflight requests.
124 lines
2.7 KiB
Go
124 lines
2.7 KiB
Go
package service
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import (
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"net"
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"net/http"
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"sync"
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"github.com/go-gost/core/auth"
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"github.com/go-gost/core/service"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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)
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const (
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// DefaultPath is the default HTTP path for the metrics endpoint.
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DefaultPath = "/metrics"
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)
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type options struct {
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path string
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auther auth.Authenticator
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}
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// Option configures the metrics service.
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type Option func(*options)
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// PathOption sets the HTTP path for the metrics endpoint.
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func PathOption(path string) Option {
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return func(o *options) {
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o.path = path
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}
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}
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// AutherOption sets the authenticator for the metrics endpoint.
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func AutherOption(auther auth.Authenticator) Option {
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return func(o *options) {
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o.auther = auther
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}
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}
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type metricService struct {
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s *http.Server
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ln net.Listener
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cclose chan struct{}
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closeOnce sync.Once
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closeErr error
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}
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// NewService creates a metrics Service that exposes Prometheus metrics over HTTP.
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func NewService(network, addr string, opts ...Option) (service.Service, error) {
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if network == "" {
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network = "tcp"
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}
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ln, err := net.Listen(network, addr)
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if err != nil {
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return nil, err
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}
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var options options
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for _, opt := range opts {
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opt(&options)
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}
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if options.path == "" {
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options.path = DefaultPath
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}
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mux := http.NewServeMux()
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mux.Handle(options.path, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// CORS headers for browser-based access (e.g. Flutter dashboard)
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w.Header().Set("Access-Control-Allow-Origin", "*")
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w.Header().Set("Access-Control-Allow-Methods", "GET, OPTIONS")
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w.Header().Set("Access-Control-Allow-Headers", "*")
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if r.Method == http.MethodOptions {
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w.WriteHeader(http.StatusNoContent)
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return
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}
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if options.auther != nil {
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u, p, _ := r.BasicAuth()
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if _, ok := options.auther.Authenticate(r.Context(), u, p, auth.WithService("@metrics")); !ok {
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w.WriteHeader(http.StatusUnauthorized)
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return
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}
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}
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promhttp.Handler().ServeHTTP(w, r)
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}))
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return &metricService{
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s: &http.Server{
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Handler: mux,
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},
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ln: ln,
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cclose: make(chan struct{}),
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}, nil
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}
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// Serve starts the metrics HTTP server and blocks until the listener is closed.
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func (s *metricService) Serve() error {
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return s.s.Serve(s.ln)
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}
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// Addr returns the network address the metrics server is listening on.
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func (s *metricService) Addr() net.Addr {
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return s.ln.Addr()
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}
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// Close stops the metrics HTTP server. It is safe to call multiple times.
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func (s *metricService) Close() error {
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s.closeOnce.Do(func() {
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close(s.cclose)
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s.closeErr = s.s.Close()
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})
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return s.closeErr
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}
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// IsClosed reports whether the metrics service has been closed.
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func (s *metricService) IsClosed() bool {
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select {
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case <-s.cclose:
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return true
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default:
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return false
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}
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}
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