Undeterministic order in output about client_rust

[mxinden]

I expect this to be due to the use of HashMap in Family. It could be an option to use a different, ordered datastructure.

Related discussion prometheus/client_golang#483.

I would expect the metrics to be somehow sorted deterministically.

While I understand the value of sorted output for the sake of debugging, I am not sure it is worth than the (expected) performance hit.

[lstrojny]

That makes sense. My use case here is unit testing where I need to assert on a stable output, so I could even make a potential sorting flag dependent on cfg(test). How about adding optional sorting?

[mxinden]

How about adding optional sorting?

Have to give this more thought, though not opposed to it. Might as well always do it in debug mode.

Again, might be worth exploring replacing the HashMap and thus getting sorting for free.

[08d2]

The text encoding of metrics is defined by the spec, and the spec doesn't define any sort order, so callers can't assume any sort order.