feat(logger): implement optional body logging

cmd/tfstated/main.go

@@ -51,7 +51,7 @@ func run(
 
 	httpServer := &http.Server{
 		Addr:    net.JoinHostPort(config.Host, config.Port),
-		Handler: logger.Middleware(mux),
+		Handler: logger.Middleware(mux, false),
 	}
 	go func() {
 		log.Printf("listening on %s\n", httpServer.Addr)

pkg/logger/body_writer.go

@@ -2,6 +2,7 @@ package logger
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
 	"net"
 	"net/http"
@@ -9,11 +10,20 @@ import (
 
 type bodyWriter struct {
 	http.ResponseWriter
-	status int
+	body    *bytes.Buffer
+	maxSize int
+	bytes   int
+	status  int
 }
 
-func newBodyWriter(writer http.ResponseWriter) *bodyWriter {
+func newBodyWriter(writer http.ResponseWriter, recordBody bool) *bodyWriter {
+	var body *bytes.Buffer
+	if recordBody {
+		body = bytes.NewBufferString("")
+	}
 	return &bodyWriter{
+		body:           body,
+		maxSize:        64000,
 		ResponseWriter: writer,
 		status:         http.StatusNotImplemented,
 	}
@@ -21,6 +31,15 @@ func newBodyWriter(writer http.ResponseWriter) *bodyWriter {
 
 // implements http.ResponseWriter
 func (w *bodyWriter) Write(b []byte) (int, error) {
+	if w.body != nil {
+		if w.body.Len()+len(b) > w.maxSize {
+			w.body.Write(b[:w.maxSize-w.body.Len()])
+		} else {
+			w.body.Write(b)
+		}
+	}
+
+	w.bytes += len(b)
 	return w.ResponseWriter.Write(b)
 }
 

pkg/logger/middleware.go

@@ -8,7 +8,7 @@ import (
 	"time"
 )
 
-func Middleware(next http.Handler) http.Handler {
+func Middleware(next http.Handler, recordBody bool) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method == "GET" && r.URL.Path == "/healthz" {
 			next.ServeHTTP(w, r)
@@ -29,7 +29,7 @@ func Middleware(next http.Handler) http.Handler {
 		path := r.URL.Path
 		query := r.URL.RawQuery
 
-		bw := newBodyWriter(w)
+		bw := newBodyWriter(w, recordBody)
 
 		next.ServeHTTP(bw, r)
 
@@ -45,8 +45,12 @@ func Middleware(next http.Handler) http.Handler {
 		responseAttributes := []slog.Attr{
 			slog.Time("time", end.UTC()),
 			slog.Duration("latency", end.Sub(start)),
+			slog.Int("length", bw.bytes),
 			slog.Int("status", bw.status),
 		}
+		if recordBody {
+			responseAttributes = append(responseAttributes, slog.String("body", bw.body.String()))
+		}
 		attributes := []slog.Attr{
 			{
 				Key:   "request",