package prometheus-reporter

v2.0 (2026-08-21)

• Add a new prometheus-eio serving package (@mtelvers @avsm #60)

  Prometheus_eio.callback is a cohttp-eio handler that serves the default registry at /metrics. It depends only on prometheus-reporter, so no Lwt or cohttp-lwt code is linked into an Eio application.

• Add a new prometheus-reporter package with the cohttp-free parts of prometheus-app (@ulrikstrid @avsm #39 #46)

  Prometheus_reporter renders the text format and registers the GC collectors. Prometheus_reporter_unix adds the process start-time metric and the Logs reporter. prometheus-app reexports both so existing code keeps working. Applications can now serve the rendered metrics with any web server of choice.

• Remove Lwt from the prometheus core (@mtelvers @avsm #60 #65)

  The deprecated Lwt functions are removed from the core package, and CollectorRegistry.collect now returns a snapshot directly. Lwt collectors are all in prometheus-lwt, whose interface is unchanged from the v1.4 release.

  Applications that collected via the core in an Lwt context should use Prometheus_lwt.CollectorRegistry.collect.

• prometheus-app: add Prometheus_unix.config to build a configuration without cmdliner (@avsm @talex5 requested by @Nymphium #44 #73)

• prometheus-app: allow serving a registry other than the default one. (@avsm #54)

  Prometheus_app.Cohttp(S).callback and Prometheus_unix.serve take an optional ?registry argument.

• prometheus-app: allow specifying the address as well as the port to bind to with --listen-prometheus.

  As well as a bare port number, the option now accepts tcp:HOST[:PORT] (with IPv6 addresses in square brackets, and the port defaulting to 9090) and unix:PATH for domain sockets, in the same syntax as capnp-rpc-unix. (@rbjorklin @avsm @talex5 #51 #72)

v1.4 (2026-08-09)

Core/Lwt split:

• Add a new prometheus-lwt metrics package. (@avsm @mtelvers @talex5 #66 #67 #68 #69, reviewed by @dinosaure)

  This release is not a breaking change, but instead prepares for deprecation of Lwt in the core package so a future release can remove Lwt from the prometheus core. Users of the core's Lwt-typed functions should migrate to Prometheus_lwt now. Code using the new interface will keep working unchanged in future releases.

• Add synchronous variants of the timing helpers to the core. Metric recording is synchronous and these will become the only core timing helpers once the Lwt-typed ones move to prometheus-lwt.
• The replacement time-based functions no longer take a gettime argument. Instead, this is provided once by the new Prometheus.init function, which is called automatically when using Prometheus_unix.

To migrate existing code, add a dep on prometheus-lwt and rename following the deprecation warnings from the compiler.

Bug fixes:

• Format floats with %.17g (@samoht @talex5 #62). The text exposition formatter printed metric values with %f, so any magnitude below ~5e-7 was reported as 0.000000.

Other changes:

• Remove Astring dependency (@talex5 #63).
• Remove Asetmap dependency (@talex5 #64). This changes the types of LabelSetMap and MetricFamilyMap slightly, which might affect custom reporters.

v1.3 (2025-12-08)

• Make help / type information be OpenMetrics compatible (@Nymphium @tmcgilchrist #47). e.g. using # TYPE rather than #TYPE in the output.
• Minor documentation fixes (@tmcgilchrist @vch9 #50 #53).
• Make default Makefile target run tests (@talex5 #49).

v1.2 (2022-06-16)

• Add lwt collectors and pre-collectors (@killian-delarue, #43). Note that this is a temporary feature while we wait for OCaml 5 to be released, when this can be replaced by the use of effects.
• Fix deprecations in Fmt 0.8.10 (@MisterDA, #36).
• General build updates, upstream deprecations, etc (@talex5, #33 #34 #35 #40 #42).

v1.1 (2021-06-08)

• Allow using a custom formatter for log output (@MisterDA #31). Windows services crash if they try to use stderr.

v1.0 (2020-12-22)

• Add logging configuration (#29, @talex5). To configure a server to report counts for log messages:

  let () = Prometheus_unix.Logging.init ()

  This installs a reporter that reports the number of messages logged by each log source and at each level. The reporter also displays the timestamp and log source with each message, which is a more suitable configuration for servers.

• Add bounds on cohttp to prepare for cohttp 3 release (#28, @talex5).

v0.7 (2020-03-03)

• switch float representation to OCaml's default "%f" (#22, @toots)
• use Gc.quick_stat for faster stats (#25, @talex5)

v0.6 (2019-11-23)

• upgrade build to dune (@talex5)
• upgrade to opam2 format (@talex5)

v0.5 (2017-12-20)

• prometheus-app: update to cohttp.1.0.0 API (#15, @djs55)
• add support for histograms (#14, @stijn-devriendt and @talex5)
• add Sample_set module to clean up the API a bit (#13, @talex5)
• fix gettimeofday parameter not used in favor of Unix.gettimeofdaya (#12, @stijn-devriendt)

v0.4 (2017-08-02)

• unix: update to cohttp >= 0.99.0. Note this means the unix package requires OCaml 4.03+. The main library still only requires OCaml 4.01+

v0.3 (2017-07-03)

• Build tweaks to support topkg versioning (@avsm)

v0.2 (2017-05-18)

• add example program and update README
• switch to jbuilder
• throw a clearer error on registering a duplicate metric
• use Re rather than Str

v0.1

• Initial release.