I responded to a question Prometheus metric protocol buffer in gRPC on Stackoverflow and it piqued my curiosity and got me yak shaving. Prometheus used to support two exposition formats including Protocol Buffers, then dropped Protocol Buffer and has since re-added it (see Protobuf format). The Protobuf format has returned to support the experimental Native Histograms feature. I’m interested in adding Native Histogram support to Ackal so thought I’d learn more about this metric.