About Metrics : max duration.

[chenjazz]

If I want to send server request's max duration .Which type can I use?

I find LongCounter can not set a custom value.

[jack-berg]

Histograms have a min / max that are part of the data model, but which have not yet made it to the OTLP protos. Once min/max support is available, I'd say use a histogram to record the duration of all a server's request durations. If a histogram is too heavy weight, you'd be able to configure a single bucket histogram, which essentially just provides a summary style metric capturing min, max, sum, and count.

In the mean time, your best bet may be to use a gauge that reports the max in a callback. Something along the lines of:

    AtomicLong maxDuration = new AtomicLong(0);
    meter.gaugeBuilder("http.server.duration.max")
        .ofLongs()
        .buildWithCallback(measurement -> {
          measurement.record(maxDuration.getAndSet(0));
        });

    .....
   
    maxDuration.set(Math.max(maxDuration.get(), duration));

[jack-berg]

This is a duplicate of #4267. As of now, HistogramPointData has getMin() and getMax() versions. Once new protos are published to include this PR, we'll propagate min and max onto histogram OTLP messages.