package main
import (
"fmt"
"log"
"net"
"net/http"
"net/http/pprof"
"time"
)
// startDebug serves Go's runtime profiles (heap, goroutines, CPU) on
// addr, for an operator on the machine to read with `go tool pprof`.
// It is off unless addr is set, and refuses any address that is not
// loopback: a profile shows request paths, repository names and
// whatever else is in memory, so it is never put where the proxy in
// front could reach it. Its own mux, never http.DefaultServeMux.
func startDebug(addr string) error {
if addr == "" {
return nil
}
host, _, err := net.SplitHostPort(addr)
if err != nil {
return fmt.Errorf("debug address %q: %w", addr, err)
}
if ip := net.ParseIP(host); host != "localhost" && (ip == nil || !ip.IsLoopback()) {
return fmt.Errorf("debug address %q is not loopback: profiles show what is in memory, so they are served on this machine only", addr)
}
mux := http.NewServeMux()
mux.HandleFunc("/debug/pprof/", pprof.Index)
mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
ln, err := net.Listen("tcp", addr)
if err != nil {
return fmt.Errorf("debug address %q: %w", addr, err)
}
srv := &http.Server{Handler: mux, ReadHeaderTimeout: 10 * time.Second}
go func() {
if err := srv.Serve(ln); err != nil && err != http.ErrServerClosed {
log.Printf("debug: profiles stopped: %v", err)
}
}()
log.Printf("debug: runtime profiles on %s", ln.Addr())
return nil
}