HTTP Request Sink Tool (#8689)

* request sink test

* append if not exist

tools/http-request-sink/main.go

@@ -0,0 +1,76 @@
+// Package main implements a simple, http-request-sink which writes
+// incoming http request bodies to an append-only text file at a specified directory.
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+
+	"github.com/prysmaticlabs/prysm/shared/params"
+)
+
+func main() {
+	port := flag.Int("port", 8080, "port to listen on")
+	writeDirPath := flag.String("write-dir", "", "directory to write an append-only file")
+	flag.Parse()
+	if *writeDirPath == "" {
+		log.Fatal("Needs a -write-dir path")
+	}
+
+	// If the file doesn't exist, create it, or append to the file.
+	f, err := os.OpenFile(
+		filepath.Join(*writeDirPath, "requests.log"),
+		os.O_APPEND|os.O_CREATE|os.O_RDWR,
+		params.BeaconIoConfig().ReadWritePermissions,
+	)
+	if err != nil {
+		log.Println(err)
+	}
+	defer func() {
+		if err = f.Close(); err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	http.HandleFunc("/", func(writer http.ResponseWriter, r *http.Request) {
+		reqContent := map[string]interface{}{}
+		if err = parseRequest(r, &reqContent); err != nil {
+			log.Println(err)
+		}
+		log.Printf("Capturing request from %s", r.RemoteAddr)
+		if err = captureRequest(f, reqContent); err != nil {
+			log.Println(err)
+		}
+	})
+	log.Printf("Listening on port %d", *port)
+	log.Fatal(http.ListenAndServe(":"+strconv.Itoa(*port), nil))
+}
+
+func captureRequest(f *os.File, m map[string]interface{}) error {
+	enc, err := json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	_, err = f.WriteString(fmt.Sprintf("%s\n", enc))
+	return err
+}
+
+func parseRequest(req *http.Request, unmarshalStruct interface{}) error {
+	body, err := ioutil.ReadAll(req.Body)
+	if err != nil {
+		return err
+	}
+	if err = req.Body.Close(); err != nil {
+		return err
+	}
+	req.Body = ioutil.NopCloser(bytes.NewBuffer(body))
+	return json.Unmarshal(body, unmarshalStruct)
+}