GetOrRegisterHistogram requires us to track samples separately or risk wasteful allocations

[Sandip Bhattacharya]

I usually use counters, gauges and timers in code somewhat like this:

metrics.GetOrRegisterCounter(metricName, metricsRegistry).Inc(amount)

But doing the same thing with Histograms are a problem. This is the call signature.

GetOrRegisterHistogram(name string, r Registry, s Sample) Histogram

If I want to use an UniformSample, am I supposed to use it like this?

metrics.GetOrRegisterHistogram(metricName, metricsRegistry, NewUniformSample(size)).Inc(amount)

But that would create a new sample on every call.

To prevent that, we would need to make sure we create a sample only if a histogram is not present. At present, I am doing this with a mutex protected dict, but this is annoying.

Can we turn this function into accepting a Sample generator callback instead?

type NewSampleFunc func() Sample

// GetOrRegisterHistogramWithSampleFunc(name string,
//                                      r Registry,
//                                      s NewSampleFunc) Histogram

metrics.GetOrRegisterHistogramWithSampleFunc(metricName,
                                             metricsRegistry,
                                             func(){return NewUniformSample(size)}).Inc(amount)

[David Strauss]

+1 on this change. It's otherwise awkward to efficiently use lazy sample instantiations.

[Péter Szilágyi]

+1, though I don't think this will ever land :)