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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
//go:build linux
package main
import (
"fmt"
"io"
"net/http"
"tailscale.com/client/local"
"tailscale.com/client/tailscale/apitype"
)
// metrics is a simple metrics HTTP server, if enabled it forwards requests to
// the tailscaled's LocalAPI usermetrics endpoint at /localapi/v0/usermetrics.
type metrics struct {
debugEndpoint string
lc *local.Client
}
func proxy(w http.ResponseWriter, r *http.Request, url string, do func(*http.Request) (*http.Response, error)) {
req, err := http.NewRequestWithContext(r.Context(), r.Method, url, r.Body)
if err != nil {
http.Error(w, fmt.Sprintf("failed to construct request: %s", err), http.StatusInternalServerError)
return
}
req.Header = r.Header.Clone()
resp, err := do(req)
if err != nil {
http.Error(w, fmt.Sprintf("failed to proxy request: %s", err), http.StatusInternalServerError)
return
}
defer resp.Body.Close()
for key, val := range resp.Header {
for _, v := range val {
w.Header().Add(key, v)
}
}
w.WriteHeader(resp.StatusCode)
if _, err := io.Copy(w, resp.Body); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
}
func (m *metrics) handleMetrics(w http.ResponseWriter, r *http.Request) {
localAPIURL := "http://" + apitype.LocalAPIHost + "/localapi/v0/usermetrics"
proxy(w, r, localAPIURL, m.lc.DoLocalRequest)
}
func (m *metrics) handleDebug(w http.ResponseWriter, r *http.Request) {
if m.debugEndpoint == "" {
http.Error(w, "debug endpoint not configured", http.StatusNotFound)
return
}
debugURL := "http://" + m.debugEndpoint + r.URL.Path
proxy(w, r, debugURL, http.DefaultClient.Do)
}
// registerMetricsHandlers registers a simple HTTP metrics handler at /metrics, forwarding
// requests to tailscaled's /localapi/v0/usermetrics API.
//
// In 1.78.x and 1.80.x, it also proxies debug paths to tailscaled's debug
// endpoint if configured to ease migration for a breaking change serving user
// metrics instead of debug metrics on the "metrics" port.
func registerMetricsHandlers(mux *http.ServeMux, lc *local.Client, debugAddrPort string) {
m := &metrics{
lc: lc,
debugEndpoint: debugAddrPort,
}
mux.HandleFunc("GET /metrics", m.handleMetrics)
mux.HandleFunc("/debug/", m.handleDebug) // TODO(tomhjp): Remove for 1.82.0 release.
}
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