fix increment of thanos_compact_downsample_total counter (#2895)

`thanos_compact_downsample_total` metric was not incremented for ResLevel1

Signed-off-by: John Belmonte <john@neggie.net>

CHANGELOG.md

@@ -16,7 +16,8 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 - [#2665](https://github.com/thanos-io/thanos/pull/2665) Swift: fix issue with missing Content-Type HTTP headers.
 - [#2800](https://github.com/thanos-io/thanos/pull/2800) Query: Fix handling of `--web.external-prefix` and `--web.route-prefix`
 - [#2834](https://github.com/thanos-io/thanos/pull/2834) Query: Fix rendered JSON state value for rules and alerts should be in lowercase
-- [#2866](https://github.com/thanos-io/thanos/pull/2866) Receive, Querier: Fixed leaks on receive and qwuerier Store API Series, which were leaking on errors.
+- [#2866](https://github.com/thanos-io/thanos/pull/2866) Receive, Querier: Fixed leaks on receive and querier Store API Series, which were leaking on errors.
+- [#2895](https://github.com/thanos-io/thanos/pull/2895) Compact: Fix increment of `thanos_compact_downsample_total` metric for downsample of 5m resolution blocks.
 
 ### Added
 

cmd/thanos/downsample.go

@@ -234,7 +234,7 @@ func downsampleBucket(
 				metrics.downsampleFailures.WithLabelValues(compact.DefaultGroupKey(m.Thanos))
 				return errors.Wrap(err, "downsampling to 60 min")
 			}
-			metrics.downsamples.WithLabelValues(compact.DefaultGroupKey(m.Thanos))
+			metrics.downsamples.WithLabelValues(compact.DefaultGroupKey(m.Thanos)).Inc()
 		}
 	}
 	return nil