Distributor: Loki API can receive gzipped JSON (#3291)

* Push API recognize HTTP header "Content-Encoding: gzip" and upload gzipped JSON

* Fix documentation mistake

docs/sources/api/_index.md

@@ -581,6 +581,8 @@ JSON post body can be sent in the following format:
 }
 ```
 
+You can set `Content-Encoding: gzip` request header and post gzipped JSON.
+
 > **NOTE**: logs sent to Loki for every stream must be in timestamp-ascending
 > order; logs with identical timestamps are only allowed if their content
 > differs. If a log line is received with a timestamp older than the most

pkg/distributor/http.go

@@ -1,6 +1,8 @@
 package distributor
 
 import (
+	"compress/gzip"
+	"fmt"
 	"math"
 	"net/http"
 	"time"
@@ -23,6 +25,7 @@ import (
 
 var (
 	contentType = http.CanonicalHeaderKey("Content-Type")
+	contentEnc  = http.CanonicalHeaderKey("Content-Encoding")
 
 	bytesIngested = promauto.NewCounterVec(prometheus.CounterOpts{
 		Namespace: "loki",
@@ -63,7 +66,24 @@ func (d *Distributor) PushHandler(w http.ResponseWriter, r *http.Request) {
 func ParseRequest(r *http.Request) (*logproto.PushRequest, error) {
 	userID, _ := user.ExtractOrgID(r.Context())
 	logger := util_log.WithContext(r.Context(), util_log.Logger)
-	body := lokiutil.NewSizeReader(r.Body)
+
+	var body lokiutil.SizeReader
+
+	contentEncoding := r.Header.Get(contentEnc)
+	switch contentEncoding {
+	case "":
+		body = lokiutil.NewSizeReader(r.Body)
+	case "gzip":
+		gzipReader, err := gzip.NewReader(r.Body)
+		if err != nil {
+			return nil, err
+		}
+		defer gzipReader.Close()
+		body = lokiutil.NewSizeReader(gzipReader)
+	default:
+		return nil, fmt.Errorf("Content-Encoding %q not supported", contentEncoding)
+	}
+
 	contentType := r.Header.Get(contentType)
 	var req logproto.PushRequest
 
@@ -97,6 +117,7 @@ func ParseRequest(r *http.Request) (*logproto.PushRequest, error) {
 			"msg", "push request parsed",
 			"path", r.URL.Path,
 			"contentType", contentType,
+			"contentEncoding", contentEncoding,
 			"bodySize", humanize.Bytes(uint64(body.Size())),
 			"streams", len(req.Streams),
 			"entries", totalEntries,