I'd be careful about that, especially in large deployments where number of namespaces can be large so the label growth could be unbounded.

If you are ok with that you could write a storage middleware (see here for examples of existing middleware) which would add prometheus.NewCounterVec which could look something like this maybe (this is a quickly hacked up pseudocode provided with no warranty!):

var namespacePushCounter = prometheus.NewCounterVec(
    prometheus.CounterOpts{
        Name: "distribution_namespace_push_total",
        Help: "Counts the number of pushes to namespaces.",
    },
    []string{"namespace"},
)

Then in the storage middleware you would extract the namespace and increment the counter for it like so:

namespacePushCounter.With(prometheus.Labels{"namespace": SOME_NAMESPACE}).Inc()

In any case I would recommend to avoid doing this due to what I said above.

Thanks! I will try it out