#moonp8s

#Install

moon add moonbitstack/moonp8s

#Annotations

#p8s.counter("orders_total", help="Orders asked for.")
#p8s.counter("orders_refused_total", help="Orders refused.", on=raised)
#p8s.timed("order_seconds", help="Seconds to place an order.", buckets="0.5, 1, 5")
fn place(item : String) -> Int raise Sold {
  ...
}

let registry = @moonp8s.Registry::new()
register_metrics(registry)
let receipt = place_metered("tea", now=clock)

rule(name: "metrics", command: "moonx moonbitstack/moonp8s/cmd/metrics -C \"$mod_dir\" \"$input\" -o \"$output\"")

dev_build(rule: "metrics", input: "orders.mbt", output: "orders.g.mbt")
formatter(ignore: [ "orders.g.mbt" ])

#Quick start

import {
  "moonbitstack/moonp8s",
  "moonbitstack/moonp8s/metric",
}

try {
  let registry = @moonp8s.Registry::new()
  let requests = registry.counter("http_requests", "HTTP requests.")
  requests.inc()
  let latency = registry.histogram("request_latency_seconds", "Latency.")
  latency.observe(0.25)
  println(@moonp8s.text(registry.collect()))
} catch {
  @metric.Refused(message) => println("refused: " + message)
}

let body = @moonp8s.openmetrics(registry.collect())
let content_type = @moonp8s.Format::OpenMetrics100.content_type()

#Metric types

let shard = requests.shard()
shard.inc()
shard.flush()

let h = @moonp8s.Histogram::new(buckets=@moonp8s.linear(1.0, 1.0, 5))

let s = @moonp8s.Summary::new(quantiles=[(0.5, 0.01), (0.9, 0.01), (0.99, 0.001)])

#Labels and families

let requests = @moonp8s.Family::new(["method", "code"], fn() {
  @moonp8s.Counter::new()
})
requests.labels(["GET", "200"]).inc()
requests.labels(["POST", "500"]).inc(by=2.0)

struct Route {
  method : String
  path : String
} derive(Eq, Hash)

impl @moonp8s.LabelSet for Route with pairs(self) {
  [("method", self.method), ("path", self.path)]
}

#Registry

let registry = @moonp8s.Registry::new(prefix="app", labels=[("region", "eu")])
let requests = registry.counter("http_requests", "HTTP requests.")
let sub = registry.sub(prefix="http", labels=[("server", "a")])

#Several processes

// moon.pkg: import { "moonbitstack/moonp8s/multiproc/directory" }
let written = @directory.write(
  dir,
  7,
  registry.collect(),
  modes=[("queue_depth", @moonp8s.Mode::Sum)],
)

let families = @directory.collect(dir, at=1_700_000_015.0)
let body = @moonp8s.openmetrics(families)

@directory.mark_dead(dir, 7)

#Exposition

#Push gateway

let request = @moonp8s.push(
  "pushgateway.local",
  "batch",
  registry.collect(),
  grouping_key=[("instance", "worker-1")],
)
println(request.http_method + " " + request.path)
println(request.body)

#ASGI

let handler = @moonp8s.app(registry)
let wrapped = @moonp8s.middleware(registry)

#Packages

#Conformance

• Negative observations. A histogram or summary that records a negative value carries a negative sum, which the specification forbids because a sum is a counter. Both official clients accept negative observations and document the consequence, and a temperature delta is a real thing to record; refusing them would move the problem from the exposition to the caller's arithmetic.
• Reserved names. Label names beginning with an underscore belong to the ingestor. A registry here accepts them: __name__ is the ingestor's to set, but a metric named _internal_total is a naming mistake, not an unreadable exposition.
• Counts rendered as floats. Counts and bucket values are integers in the model, and written 17.0 rather than 17, as every official client writes them. The format's own grammar accepts both, and a reader must not reject either.

#Migration

#License