Add checks for invalid metric names and labels.

[brian-brazil]

Document who's responsible for checking produced metrics are valid.

Closes #28
@juliusv

[juliusv]

👍 in principle, but the build is failing with OOM. @brian-brazil @beorn7 Is lack of memory for Java client library tests a known issue?

[brian-brazil]

This happens a fair bit of the time on the pushgateway test. All tests are passing on my laptop.

[checketts]

This fix doesn't catch hyphens in the metric name.

Gauge.build().name("a-invalidname").labelNames("validLabel").help("h").create();

[brian-brazil]

Are you sure your're using a recent enough version of the code?

[checketts]

Sorry for leaving that off. I'm using version 0.0.19

[checketts]

Oh my code snippet was misleading. My actual code (in an exporter) is doing:

return new MetricFamilySamples(cleanName, Type.GAUGE, help, samples);

So it is bypassing the check. Sorry for the noise.

[brian-brazil]

Custom collectors don't have sanity checks, it's up to you to ensure they're sane.