prometheus

Client library for Prometheus monitoring
README

To run services reliably, it is useful if they can report various metrics
(for example, heap size, queue lengths, number of warnings logged, etc).

A monitoring service can be configured to collect this data regularly.
The data can be graphed to help understand the performance of the service over time,
or to help debug problems quickly.
It can also be used to send alerts if a service is down or behaving poorly.

This repository contains code to report metrics to a Prometheus monitoring server.

Use by libraries

Library authors should define a set of metrics that may be useful. For example, the DataKitCI
cache module defines several metrics like this:

module Metrics = struct
  open Prometheus

  let namespace = "DataKitCI"
  let subsystem = "cache"

  let builds_started_total =
    let help = "Total number of builds started" in
    Counter.v_label ~help ~label_name:"name" ~namespace ~subsystem "builds_started_total"

  let builds_succeeded_total =
    let help = "Total number of builds that succeeded" in
    Counter.v_label ~help ~label_name:"name" ~namespace ~subsystem "builds_succeeded_total"

  let builds_failed_total =
    let help = "Total number of builds that failed" in
    Counter.v_label ~help ~label_name:"name" ~namespace ~subsystem "builds_failed_total"

  [...]
end

Each of these metrics has a name label, which allows the reports to be further broken down
by the type of thing being built.

When (for example) a build succeeds, the CI does:

Prometheus.Counter.inc_one (Metrics.builds_succeeded_total build_type)

Use by applications

Applications can enable metric reporting using the prometheus-app opam package.
This depends on cohttp and can serve the metrics collected above over HTTP.

The prometheus-app.unix ocamlfind library provides the Prometheus_unix module,
which includes a cmdliner option and pre-configured web-server.
See the examples/example.ml program for an example, which can be run as:

$ dune exec -- examples/example.exe --listen-prometheus=9090
If run with the option --listen-prometheus=9090, this program serves metrics at
http://localhost:9090/metrics
Tick!
Tick!
...

Unikernels can use Prometheus_app instead of Prometheus_unix to avoid the Unix dependency.

API docs

Generated API documentation is available at https://mirage.github.io/prometheus/.

Licensing

This code is licensed under the Apache License, Version 2.0. See
LICENSE for the full
license text.

Install
Maintainers
Sources
prometheus-v1.1.tbz
sha256=fbcf8bb28c02bfe4f61d2494bc2b70fdedd62f2b41fd1343e6f73d583bf599e4
sha512=9cf49689f6d33138cf41eca585e0d15bd17f670a3334b8235a52cc6c210fdc763fb967b19a91a110759a206aa9223cca1c7064e0eb2e2e6d3d13957ec7a38201
Dependencies
Reverse Dependencies