Extending responses with the external labelset might lead to unsorted series set response

[GiedriusS]

Essentially prometheus/prometheus#12605 but on any component that implements StoreAPI.

Example response without external labels attached:

aaa{instance="bbb", job="etcd-prometheus-exporter", region="bar", service="etcd-prometheus-exporter", toposphere="test1"} 0
aaa{instance="bbb", job="etcd-prometheus-exporter", region="bar", service="etcd-prometheus-exporter", toposphere="test2"} 0
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test1"} 1
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test2"} 1
aaa{instance="bbb", job="etcd-prometheus-exporter", service="etcd-prometheus-exporter", toposphere="test1"} 1

With external label overwriting region to foo:

aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test1"} 0
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test2"} 0
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test1"} 1
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test2"} 1
aaa{instance="bbb", job="etcd-prometheus-exporter", region="foo", service="etcd-prometheus-exporter", toposphere="test1"} 1

All of these places are probably affected: https://github.com/search?q=repo%3Athanos-io%2Fthanos+labelpb.ExtendSortedLabels&type=code.

I guess we need to return an error in case of duplicated series?

[yeya24]

This issue seems can be closed.