Adds --log_file flag.

- The flag allows to write logs to an specific file. Logs would
  continue to be written to standard error.

Author: ser-io

frontend/src/host_orchestrator/main.go

@@ -18,6 +18,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"net/http"
 	"net/http/httputil"
@@ -110,9 +111,20 @@ func main() {
 	abURL := flag.String("android_build_url", defaultAndroidBuildURL, "URL to an Android Build API.")
 	imRootDir := flag.String("cvd_artifacts_dir", defaultCVDArtifactsDir(), "Directory where cvd will download android build artifacts to.")
 	address := flag.String("listen_addr", DefaultListenAddress, "IP address to listen for requests.")
+	logFile := flag.String("log_file", "", "Path to file to write logs to.")
 
 	flag.Parse()
 
+	if *logFile != "" {
+		f, err := os.OpenFile(*logFile, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
+		if err != nil {
+			log.Fatalf("error opening log file %q: %v", *logFile, err)
+		}
+		defer f.Close()
+		w := io.MultiWriter(os.Stderr, f)
+		log.SetOutput(w)
+	}
+
 	if err := os.MkdirAll(*imRootDir, 0774); err != nil {
 		log.Fatalf("Unable to create artifacts directory: %v", err)
 	}