gazagnaire.org
Logging, runtime tracing, and the obs performance profiler for OCaml
observe: delete Observe_eio
Observe_eio.setup was Observe.setup composed with Probe_eio.install. Bolting a scheduler's span provider onto a logging library gave observe a dependency on eio for one function call, and gave every Eio program a second setup entry point to choose between.
A library exposing an Eio interface installs the provider for its users, which is what quic_eio, h2_eio, slirp_eio and iperf3_eio already do. The two programs that drove Eio themselves now do the same. Observe.setup is the single call for Eio and non-Eio programs alike.
author
Thomas Gazagnaire
date
(Jul 9, 2026, 11:28 PM UTC)
commit
40046bbe
40046bbe05e51e77a14106895f32bcc4b5bb1574
parent
c1a1f74c
c1a1f74c30d1bbe09b3184790464df358ae847fb
+7
-58
+1
-1
bench/dune
+1
-1
bench/dune
+6
-2
bench/workload.ml
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-2
bench/workload.ml
···
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[Probe.span] / [Probe.with_span]; obs is expected to show them as operations
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in the report. *)
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(* Span context must be fiber-local before any fiber opens a span, or the
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concurrent request fibers below nest under one another. *)
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let () = Probe_eio.install ()
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let request_span =
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Probe.span "workload.request" ~doc:"one synthetic request"
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Probe.Fields.(obj (fun id -> id) |> field "id" int ~enc:Fun.id |> seal)
···
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Term.(
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const (fun () child phase requests fibers ->
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if child then run_child () else run phase requests fibers)
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$ Observe_eio.setup "workload"
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$ child_arg $ phase_arg $ requests_arg $ fibers_arg)
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$ Observe.setup "workload" $ child_arg $ phase_arg $ requests_arg
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$ fibers_arg)
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let () = exit (Cmd.eval cmd)
-4
lib/eio/dune
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lib/eio/dune
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lib/eio/observe_eio.ml
-4
lib/eio/observe_eio.ml
-11
lib/eio/observe_eio.mli
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lib/eio/observe_eio.mli
···
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(** Eio-aware {!Observe} setup.
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-
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The single setup call for an Eio program: it configures logging exactly like
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{!Observe.setup} and also installs the ocaml-probe Eio provider
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({!Probe_eio.install}), so {!Probe.with_span} span context is fiber-local
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without a separate call. *)
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val setup :
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?json_reporter:Observe.json_reporter option -> string -> unit Cmdliner.Term.t
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(** [setup app] is {!Observe.setup} [app] composed with {!Probe_eio.install}, so
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an Eio program's probe spans nest per fiber with nothing else to wire. *)
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test/eio/dune
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test/eio/dune
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test/eio/test.ml
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test/eio/test.ml
···
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let () = Alcotest.run "observe_eio" [ Test_observe_eio.suite ]
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test/eio/test_observe_eio.ml
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test/eio/test_observe_eio.ml
···
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let span = Probe.span "observe_eio.test" Probe.Fields.unit
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(* Observe_eio.setup must install the Probe Eio provider as a side effect of
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evaluating its term. With it installed, a span entered in one fiber is not
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observed by a concurrent sibling of the same domain; this test runs the setup
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term (rather than calling Probe_eio.install directly) and checks that
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isolation, so it fails if setup forgot to install. *)
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let test_setup_installs_provider () =
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let cmd =
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Cmdliner.Cmd.v (Cmdliner.Cmd.info "test") (Observe_eio.setup "test")
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in
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ignore (Cmdliner.Cmd.eval ~argv:[| "test" |] cmd);
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Probe.set_sampling_active true;
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Fun.protect ~finally:(fun () -> Probe.set_sampling_active false) @@ fun () ->
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Eio_main.run @@ fun _ ->
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let sibling = ref (Some (Probe.Span_id.of_int64 0L)) in
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Eio.Fiber.both
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(fun () -> Probe.with_span span () (fun () -> Eio.Fiber.yield ()))
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(fun () -> sibling := Probe.current ());
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Alcotest.(check bool)
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"setup installed fiber-local span context" true (Option.is_none !sibling)
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-
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let suite =
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( "observe_eio",
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[
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Alcotest.test_case "setup installs provider" `Quick
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test_setup_installs_provider;
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] )