PromQL doesn’t support many-to-many label matching. So if you want to enrich multiple metrics with labels from an info metric, e.g.

{__name__=~"node_timex_.+",job="node-exporter"}
* on (pod,namespace) group_left (node) group by (namespace, pod, node) (kube_pod_info)

it’ll tend to fall over with:

query error: execution: multiple matches for labels: grouping labels must ensure unique matches

Is there a convention or idiom in PromQL for working around this?

The desired outcome here is adding the node label to every result time-series, matching by node-exporter (pod,namespace) to find the associated node.