In proto3, this doesn't change anything. However, since the
`CreatedTimestamp` field is generated as a pointer
(`*types.Timestamp`), we are still able to detect the unset state.
(This is in contrast to the `timestamp_ms` field, which is a plain
int64, for which we cannot enforce generation as a pointer, see
comment updated in the previous commit for future actions.)
Signed-off-by: beorn7 <beorn@grafana.com>
Native histograms without observations and with a zero threshold of
zero look the same as classic histograms in the protobuf exposition
format. According to
https://github.com/prometheus/client_golang/issues/1127 , the idea is
to add a no-op span to those histograms to mark them as native
histograms. This commit enables Prometheus to detect that no-op span
and adds a doc comment to the proto spec describing the behavior.
Signed-off-by: beorn7 <beorn@grafana.com>
We cannot just use prometheus/client_model directly because we want to
stay consistent with the use of gogo-protobuf. So this converts
metrics.proto to proto3 and edits it lightly so that it fits into
the framework how prometheus/prometheus handles protobuf.
Note that metrics.proto couldn't be merged into the prompb package
because prompb already has an Exemplar type, which is different from
the Exemplar type in metrics.proto. The directory structure seems to
play a role in the protobuf world, so I better kept it.
Signed-off-by: beorn7 <beorn@grafana.com>
