in geronimo-microprofile-reporter/src/main/java/org/apache/geronimo/microprofile/reporter/storage/front/ReporterEndpoints.java [171:181]
public Html getGauge(@QueryParam("gauge") final String name) {
final InMemoryDatabase<Double> db = database.getGauges().get(name);
return new Html("main.html")
.with("view", "gauge.html")
.with("colors", COLORS)
.with("title", "Gauges")
.with("name", name)
.with("unit", db == null ? null : db.getUnit())
.with("message", db == null ? "No matching gauge for name '" + name + "'" : null)
.with("points", db == null ? null : db.snapshot().stream().map(Point::new).collect(toList()));
}