From a483e08ffa7536e18a89b2cc5da2de1070e65d78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9A=D0=B8=D1=80=D0=B8=D0=BB=D0=BB=20=D0=93=D0=BE=D1=80?=
 =?UTF-8?q?=D0=B1=D1=83=D0=BD=D0=BE=D0=B2?= <kirya_gorbunov_2015@mail.ru>
Date: Mon, 11 Mar 2024 12:31:19 +0300
Subject: [PATCH] add gzip rsp #153 (#182)
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1. Give a descriptive title to your PR.
2. Provide a description of your changes.
3. Make sure you have some relevant tests.
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Co-authored-by: Gorbunov Kirill Andreevich <kgorbunov@mtsbank.ru>
Reviewed-on: https://git.unistack.org/unistack-org/micro-server-http/pulls/182
Co-authored-by: Кирилл Горбунов <kirya_gorbunov_2015@mail.ru>
Co-committed-by: Кирилл Горбунов <kirya_gorbunov_2015@mail.ru>
---
 handler/meter/meter.go | 65 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 4 deletions(-)

diff --git a/handler/meter/meter.go b/handler/meter/meter.go
index cd31576..037fdc7 100644
--- a/handler/meter/meter.go
+++ b/handler/meter/meter.go
@@ -2,14 +2,37 @@ package meter // import "go.unistack.org/micro-server-http/v4/handler/meter"
 
 import (
 	"bytes"
+	"compress/gzip"
 	"context"
+	"io"
+	"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 (
+	contentEncodingHeader = "Content-Encoding"
+	acceptEncodingHeader  = "Accept-Encoding"
+)
+
+var gzipPool = sync.Pool{
+	New: func() interface{} {
+		return gzip.NewWriter(nil)
+	},
+}
+
+var bufPool = sync.Pool{
+	New: func() interface{} {
+		return bytes.NewBuffer(nil)
+	},
+}
+
 // guard to fail early
 var _ MeterServiceServer = (*Handler)(nil)
 
@@ -57,12 +80,46 @@ func NewHandler(opts ...Option) *Handler {
 }
 
 func (h *Handler) Metrics(ctx context.Context, req *codecpb.Frame, rsp *codecpb.Frame) error {
-	buf := bytes.NewBuffer(nil)
-	if err := h.opts.Meter.Write(buf, h.opts.MeterOptions...); err != nil {
-		return errors.InternalServerError(h.opts.Name, "%v", err)
+	log, ok := logger.FromContext(ctx)
+	if !ok {
+		log = logger.DefaultLogger()
+	}
+
+	buf := bufPool.Get().(*bytes.Buffer)
+	defer bufPool.Put(buf)
+	buf.Reset()
+
+	w := io.Writer(buf)
+
+	if md, ok := metadata.FromContext(ctx); gzipAccepted(md) && ok {
+		md.Set(contentEncodingHeader, "gzip")
+		gz := gzipPool.Get().(*gzip.Writer)
+		defer gzipPool.Put(gz)
+
+		gz.Reset(w)
+		defer gz.Close()
+
+		w = gz
+	}
+
+	if err := h.opts.Meter.Write(w, h.opts.MeterOptions...); err != nil {
+		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
+	}
+	if strings.Contains(a, "gzip") {
+		return true
+	}
+	return false
+}