ingester: use consistent set of instances (#4904)

CHANGELOG.md

@@ -17,7 +17,7 @@
 * [4875](https://github.com/grafana/loki/pull/4875) **trevorwhitney**: Loki: fix bug where common replication factor wasn't always getting applied
 * [4892](https://github.com/grafana/loki/pull/4892) **cristaloleg**: Loki: upgrade cristalhq/hedgedhttp from v0.6.0 to v0.7.0
 * [4902](https://github.com/grafana/loki/pull/4902) **cyriltovena**: Fixes 500 when query is outside of max_query_lookback.
-
+* [4904](https://github.com/grafana/loki/pull/4904) **bboreham**: Fixes rare race condition that could crash an ingester.
 
 # 2.4.1 (2021/11/07)
 

pkg/ingester/checkpoint.go

@@ -207,7 +207,7 @@ type streamIterator struct {
 func newStreamsIterator(ing ingesterInstances) *streamIterator {
 	instances := ing.getInstances()
 	streamInstances := make([]streamInstance, len(instances))
-	for i, inst := range ing.getInstances() {
+	for i, inst := range instances {
 		inst.streamsMtx.RLock()
 		streams := make([]*stream, 0, len(inst.streams))
 		inst.streamsMtx.RUnlock()