feat: optionally enable pprof endpoint in extproc (#1395)

**Description**

This optionally enables pprof endpoint in order to troubleshoot and
debug the running application easily, including lock contentions.

---------

Signed-off-by: Takeshi Yoneda <[email protected]>

Author: mathetake

cmd/extproc/main.go

@@ -7,7 +7,10 @@ package main
 
 import (
 	"context"
+	"errors"
 	"log"
+	"net/http"
+	"net/http/pprof"
 	"os"
 	"os/signal"
 	"syscall"
@@ -17,6 +20,27 @@ import (
 )
 
 func main() {
+	// Run the pprof server if the DISABLE_PPROF environment variable is not set.
+	//
+	// Enabling the pprof server by default helps with debugging performance issues in production.
+	// The impact should be negligible when the actual pprof endpoints are not being accessed.
+	if _, ok := os.LookupEnv("DISABLE_PPROF"); !ok {
+		go func() {
+			const pprofPort = "6060" // The same default port as in th Go pprof documentation.
+			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)
+			server := &http.Server{Addr: ":" + pprofPort, Handler: mux, ReadHeaderTimeout: 5 * time.Second}
+			log.Printf("starting pprof server on port %s", pprofPort)
+			if err := server.ListenAndServe(); err != nil && errors.Is(err, http.ErrServerClosed) {
+				log.Printf("pprof server stopped: %v", err)
+			}
+		}()
+	}
+
 	ctx, cancel := context.WithCancel(context.Background())
 	signalsChan := make(chan os.Signal, 1)
 	signal.Notify(signalsChan, syscall.SIGINT, syscall.SIGTERM)

manifests/charts/ai-gateway-helm/values.yaml

@@ -32,6 +32,10 @@ extProc:
   ##     value: "ai-gateway-extproc"
   ##   - name: OTEL_TRACES_EXPORTER
   ##     value: "otlp"
+  ##   # This disables pprof endpoint at "localhost:6060/debug/pprof" that can be accessed via port-forwarding for profiling.
+  ##   # Enabled by default for troubleshooting purposes given the impact is negligible when not in use.
+  ##   - name: DISABLE_PPROF
+  ##     value: "true"
   ##
   extraEnvVars: []