From bee12a2f9cb94a7a451ab01e69a18deaffbe3b81 Mon Sep 17 00:00:00 2001
From: Gorbunov Kirill Andreevich <kgorbunov@mtsbank.ru>
Date: Mon, 11 Mar 2024 00:06:45 +0300
Subject: [PATCH] add gzip rsp #153

---
 handler/meter/meter.go | 53 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/handler/meter/meter.go b/handler/meter/meter.go
index cd31576..25a14de 100644
--- a/handler/meter/meter.go
+++ b/handler/meter/meter.go
@@ -2,14 +2,31 @@ package meter // import "go.unistack.org/micro-server-http/v4/handler/meter"
 
 import (
 	"bytes"
+	"compress/gzip"
 	"context"
+	"strings"
+	"sync"
 
 	codecpb "go.unistack.org/micro-proto/v4/codec"
 	"go.unistack.org/micro/v4/errors"
+	"go.unistack.org/micro/v4/logger"
+	"go.unistack.org/micro/v4/metadata"
 	"go.unistack.org/micro/v4/meter"
-	options "go.unistack.org/micro/v4/options"
+	"go.unistack.org/micro/v4/options"
 )
 
+const (
+	contentTypeHeader     = "Content-Type"
+	contentEncodingHeader = "Content-Encoding"
+	acceptEncodingHeader  = "Accept-Encoding"
+)
+
+var gzipPool = sync.Pool{
+	New: func() interface{} {
+		return gzip.NewWriter(nil)
+	},
+}
+
 // guard to fail early
 var _ MeterServiceServer = (*Handler)(nil)
 
@@ -57,12 +74,44 @@ func NewHandler(opts ...Option) *Handler {
 }
 
 func (h *Handler) Metrics(ctx context.Context, req *codecpb.Frame, rsp *codecpb.Frame) error {
+	log := logger.DefaultLogger()
 	buf := bytes.NewBuffer(nil)
+
+	if md, ok := metadata.FromContext(ctx); gzipAccepted(md) && ok {
+		md.Set(contentEncodingHeader, "gzip")
+		gz := gzipPool.Get().(*gzip.Writer)
+		defer gzipPool.Put(gz)
+
+		gz.Reset(buf)
+		defer gz.Close()
+
+		zw := gzip.NewWriter(buf)
+		defer zw.Close()
+		*zw = *gz
+	}
+
 	if err := h.opts.Meter.Write(buf, h.opts.MeterOptions...); err != nil {
-		return errors.InternalServerError(h.opts.Name, "%v", err)
+		log.Error(ctx, errors.InternalServerError(h.opts.Name, "%v", err))
+		return nil
 	}
 
 	rsp.Data = buf.Bytes()
 
 	return nil
 }
+
+// gzipAccepted returns whether the client will accept gzip-encoded content.
+func gzipAccepted(md metadata.Metadata) bool {
+	a, ok := md.Get(acceptEncodingHeader)
+	if !ok {
+		return false
+	}
+	parts := strings.Split(a, ",")
+	for _, part := range parts {
+		part = strings.TrimSpace(part)
+		if part == "gzip" || strings.HasPrefix(part, "gzip;") {
+			return true
+		}
+	}
+	return false
+}