Function sample 

pub fn sample(
    node: &str,
    now: u64,
    start: u64,
    uptime_s: u64,
    peak_rss: u64,
    free_fraction: Option<f64>,
    blocks: [Option<u64>; 3],
) -> ExportMetricsServiceRequest

Everything this node currently knows about itself, as OTLP.

start is the process start in Unix nanoseconds and goes on every point: without it a cumulative counter has no way to say “this stream began here”, and a consumer computing a rate across a restart reads the reset as a enormous negative delta. blocks is None for a signal whose directory would not list, and a point that cannot be measured is omitted rather than sent as zero — the same rule /api/v1/stats follows with null.