Writer is the expfmt cursor: help, kind, name, value, and line write one record each, and writeMetric, writeFamily, writeHistogram, and the series form are methods on it built only out of those five.Writer.writeMetric writes one sample line, Writer.writeFamily writes # HELP and # TYPE and returns the handle for its samples, and Writer.writeHistogram writes a classic histogram. Each is built only from Writer methods.FamilyWriter.writeHistogramSeries writes one series with no header, so a multi-series histogram family writes the header once and loops. sum is anytype in both histogram writers, so a u64 above 2^53 keeps every digit.- Values follow
prometheus/common's rule: a float that reads back as an integer is written as one, so 1e6 is 1000000 and -0 is 0; NaN and the infinities are canonical; everything else is Go's 'g' with the shortest digits. A value outside the i64 range falls through instead of trapping.
- Label values and help text are escaped. A metric name or label name a parser would reject does not compile, and a label in the reserved
__ namespace does not either.
