MetricVec is un-experted by now. godoc handles that correctly by
showing the methods of the embedded un-exported metricVec with the
exported type (CounterVec, SummaryVec, ...) that embeds metricVec.
This is in preparation for "curried" metric vecs, as discussed.
And it's a good thing anyway. The exported MetricVec was from a time
when I thought people would define own Metric types and then create
Vecs of it. That has never happened.
As it turned out, it's not that esay to guess "common" combination of
interface upgrades. So I decided to just implement all 32 possible
combination of interface upgrades. (Only 16 with Go 1.7 and earlier.)
Clearly, this calls for code generation. But right now, we still need
to find out what's the best form of the code. For later additions,
implementing code generation might be useful.
Note that newDelegator is called for each HTTP request. Thus, this
commit aims to make the upgrade selection quick. (After the type
checks, it's just directly accessing an element in a slice.)
The example method is assumed to be used as main() function. As a main()
function doesn't have any return values, the example doesn't compile and
is invalid.
This also updates all tests and examples to use explicitly set
objectives.
In v0.10, DefObjectives will be completely removed, and the default
Summary will have no objectives then.
Fixes#118
This finally makes the (presumably) common simple case as simple as it
gets.
The still quite common (but less common) case of using a Gauge is
slightly more verbose now, but not needing to provide a separate
constructor is totally worth it.
Finally, the advanced use case is not really more verbose as in my
original suggestion. However, the logic to decide which Observer to
use is now all in the ObserverFunc handed in at construction
time. This is deliberate and desired. It makes sure the selection
mechanism is all spelled out there. No surprises buried deep in the
function code somewhere.
Lynn Lin