chore: [release-3.0.x] fix: codec not initialized in downstream rou…

…ndtripper (#12879)

Co-authored-by: Kaviraj Kanagaraj <kavirajkanagaraj@gmail.com>

pkg/lokifrontend/frontend/config.go

@@ -43,7 +43,7 @@ func InitFrontend(cfg CombinedFrontendConfig, ring ring.ReadRing, limits v1.Limi
 	switch {
 	case cfg.DownstreamURL != "":
 		// If the user has specified a downstream Prometheus, then we should use that.
-		rt, err := NewDownstreamRoundTripper(cfg.DownstreamURL, http.DefaultTransport)
+		rt, err := NewDownstreamRoundTripper(cfg.DownstreamURL, http.DefaultTransport, codec)
 		return rt, nil, nil, err
 	case cfg.FrontendV2.SchedulerAddress != "" || ring != nil:
 		// If query-scheduler address is configured, use Frontend.

pkg/lokifrontend/frontend/downstream_roundtripper.go

@@ -20,13 +20,13 @@ type downstreamRoundTripper struct {
 	codec         queryrangebase.Codec
 }
 
-func NewDownstreamRoundTripper(downstreamURL string, transport http.RoundTripper) (queryrangebase.Handler, error) {
+func NewDownstreamRoundTripper(downstreamURL string, transport http.RoundTripper, codec queryrangebase.Codec) (queryrangebase.Handler, error) {
 	u, err := url.Parse(downstreamURL)
 	if err != nil {
 		return nil, err
 	}
 
-	return &downstreamRoundTripper{downstreamURL: u, transport: transport}, nil
+	return &downstreamRoundTripper{downstreamURL: u, transport: transport, codec: codec}, nil
 }
 
 func (d downstreamRoundTripper) Do(ctx context.Context, req queryrangebase.Request) (queryrangebase.Response, error) {