Bug 2074413: Thanos Querier high CPU and memory usage till OOM

This cherry-picks upstream patch that fixes the bug

Query: Fix (*exemplarsStream).receive/(*metricMetadataStream).receive/(*targetsStreamStream).receive
  infinite loop when target response Unimplemented error (thanos-io#4676) (thanos-io#4681)

See:
  - thanos-io#4676 (comment)
  - thanos-io#4681

Signed-off-by: hanjm <hanjinming@outlook.com>
(cherry picked from commit 2d4d140)

Signed-off-by: Sunil Thaha <3005132+sthaha@users.noreply.github.com>

pkg/exemplars/proxy.go

@@ -191,8 +191,8 @@ func (stream *exemplarsStream) receive(ctx context.Context) error {
 			if err := stream.server.Send(exemplarspb.NewWarningExemplarsResponse(err)); err != nil {
 				return errors.Wrapf(err, "sending exemplars error to server %v", stream.server)
 			}
-
-			continue
+			// Not an error if response strategy is warning.
+			return nil
 		}
 
 		if w := exemplar.GetWarning(); w != "" {

pkg/metadata/proxy.go

@@ -135,7 +135,8 @@ func (stream *metricMetadataStream) receive(ctx context.Context) error {
 				return errors.Wrapf(err, "sending metadata error to server %v", stream.server)
 			}
 
-			continue
+			// Not an error if response strategy is warning.
+			return nil
 		}
 
 		if w := resp.GetWarning(); w != "" {

pkg/targets/proxy.go

@@ -119,8 +119,8 @@ func (stream *targetsStream) receive(ctx context.Context) error {
 			if err := stream.server.Send(targetspb.NewWarningTargetsResponse(err)); err != nil {
 				return errors.Wrapf(err, "sending targets error to server %v", stream.server)
 			}
-
-			continue
+			// Not an error if response strategy is warning.
+			return nil
 		}
 
 		if w := target.GetWarning(); w != "" {