Do not reuse remote write requests in case of error

Author: alanprot

pkg/distributor/distributor.go

@@ -874,7 +874,12 @@ func (d *Distributor) send(ctx context.Context, ingester ring.InstanceDesc, time
 	req.Source = source
 
 	_, err = c.PushPreAlloc(ctx, req)
-	cortexpb.ReuseWriteRequest(req)
+
+	// We should not reuse the req in case of errors:
+	// See: https://github.com/grpc/grpc-go/issues/6355
+	if err == nil {
+		cortexpb.ReuseWriteRequest(req)
+	}
 
 	if len(metadata) > 0 {
 		d.ingesterAppends.WithLabelValues(ingester.Addr, typeMetadata).Inc()