gazagnaire.org
Logging, runtime tracing, and the obs performance profiler for OCaml
obs: keep eio out of every instrumented binary
observe depends on observe.producer, which depended on observe.producer.core, which depended on eio. Every CLI that calls Observe.setup therefore linked eio, and with it bigstringaf, cstruct, eio.core, lwt-dllist and optint -- to print log lines. The forwarder never touches Eio: the only users inside producer.core were Ring_eio, an Eio driver the forwarder path never calls, and Clock.of_eio, two clock reads.
Both move to a new observe.producer.core.eio, linked explicitly by the two Eio unikernel examples and the ring tests. producer.core now needs neither eio nor mtime, and obs_guest (observe.producer + probe) no longer drags the Eio core into a guest image. Clock_eio gets its own test module, split out of test_clock.
author
Thomas Gazagnaire
date
(Jul 9, 2026, 6:59 PM UTC)
commit
88370eaf
88370eafbc0e84afd35223f3f4aa7acb92c73bda
parent
d7f74cf2
d7f74cf200c9e63344c924345a1b242431ac9b7d
+86
-40
-6
lib/producer/core/clock.ml
-6
lib/producer/core/clock.ml
···
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type t = { unix_ns : unit -> int64; mono_ns : unit -> int64 }
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-
let of_eio ~clock ~mono =
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{
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unix_ns = (fun () -> Int64.of_float (Eio.Time.now clock *. 1e9));
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mono_ns = (fun () -> Mtime.to_uint64_ns (Eio.Time.Mono.now mono));
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}
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-
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let pp ppf t =
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Fmt.pf ppf "clock(unix=%Ldns mono=%Ldns)" (t.unix_ns ()) (t.mono_ns ())
+3
-7
lib/producer/core/clock.mli
+3
-7
lib/producer/core/clock.mli
···
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clock read together for the {!Direct} producer's Hello sync sample and to
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stamp its frames.
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A freestanding producer (a solo5 unikernel, with no Unix or [mtime.clock])
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builds one from its Eio environment with {!of_eio}; the host does the same,
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so the producer code is identical on both. *)
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A value is a pair of closures, one reading wall time and one reading
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monotonic time, each in nanoseconds. The caller supplies both, so the type
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carries no dependency on any particular time source. *)
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type t = { unix_ns : unit -> int64; mono_ns : unit -> int64 }
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-
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val of_eio : clock:_ Eio.Time.clock -> mono:_ Eio.Time.Mono.t -> t
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(** [of_eio ~clock ~mono] reads wall time from the Eio [clock] and monotonic
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time from [mono]. Works on any Eio backend, host or [eio-solo5]. *)
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val pp : Format.formatter -> t -> unit
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(** [pp ppf t] prints [t]'s current wall and monotonic readings. *)
-2
lib/producer/core/dune
-2
lib/producer/core/dune
+8
lib/producer/core/eio/clock_eio.ml
+8
lib/producer/core/eio/clock_eio.ml
+9
lib/producer/core/eio/clock_eio.mli
+9
lib/producer/core/eio/clock_eio.mli
···
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(** Build a {!Observe_producer_core.Clock.t} from an Eio environment. *)
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val v :
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clock:_ Eio.Time.clock ->
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mono:_ Eio.Time.Mono.t ->
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Observe_producer_core.Clock.t
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(** [v ~clock ~mono] reads wall time from the Eio [clock] and monotonic time
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from [mono], each in nanoseconds. Works on any Eio backend, host or
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[eio-solo5], so a host producer and a solo5 unikernel take the same path. *)
+4
lib/producer/core/eio/dune
+4
lib/producer/core/eio/dune
+1
lib/producer/core/ring_eio.ml
lib/producer/core/eio/ring_eio.ml
+1
lib/producer/core/ring_eio.ml
lib/producer/core/eio/ring_eio.ml
+1
lib/producer/core/ring_eio.mli
lib/producer/core/eio/ring_eio.mli
+1
lib/producer/core/ring_eio.mli
lib/producer/core/eio/ring_eio.mli
+1
test/producer/dune
+1
test/producer/dune
+1
test/producer/test.ml
+1
test/producer/test.ml
+1
-22
test/producer/test_clock.ml
+1
-22
test/producer/test_clock.ml
···
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"pp" "clock(unix=42ns mono=7ns)"
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(Fmt.to_to_string Clock.pp c)
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(* A clock built from an Eio env: monotonic advances across a sleep and the wall
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clock reads positive. This is the path a host producer and a solo5 unikernel
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both take. *)
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let test_of_eio () =
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Eio_main.run @@ fun env ->
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let clock = Eio.Stdenv.clock env in
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let mono = Eio.Stdenv.mono_clock env in
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let c = Clock.of_eio ~clock ~mono in
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let m0 = c.Clock.mono_ns () in
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Eio.Time.sleep clock 0.01;
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let m1 = c.Clock.mono_ns () in
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Alcotest.(check bool) "mono advances" true (Int64.compare m1 m0 > 0);
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Alcotest.(check bool)
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"wall positive" true
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(Int64.compare (c.Clock.unix_ns ()) 0L > 0)
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-
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let suite =
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( "clock",
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[
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Alcotest.test_case "constant" `Quick test_constant;
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Alcotest.test_case "of_eio" `Quick test_of_eio;
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] )
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let suite = ("clock", [ Alcotest.test_case "constant" `Quick test_constant ])
+48
test/producer/test_clock_eio.ml
+48
test/producer/test_clock_eio.ml
···
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module Clock = Observe_producer_core.Clock
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module Clock_eio = Observe_producer_core_eio.Clock_eio
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(* [v] wraps the live Eio clocks rather than sampling them once: a second call
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to [mono_ns] must see time that passed between the two. A 10ms sleep is
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checked against a 5ms floor, since the scheduler only guarantees it slept at
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least the requested time and the clock's resolution is coarser than a ns. *)
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let test_reads_live_clocks () =
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Eio_main.run @@ fun env ->
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let clock = Eio.Stdenv.clock env in
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let mono = Eio.Stdenv.mono_clock env in
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let c = Clock_eio.v ~clock ~mono in
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let m0 = c.Clock.mono_ns () in
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Eio.Time.sleep clock 0.01;
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let m1 = c.Clock.mono_ns () in
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let elapsed = Int64.sub m1 m0 in
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Alcotest.(check bool)
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(Fmt.str "monotonic advanced by at least 5ms (got %Ldns)" elapsed)
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true
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(Int64.compare elapsed 5_000_000L >= 0)
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(* The two readings come from different clocks and must not be confused: the
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wall reading is a Unix epoch stamp, so it tracks [gettimeofday], while the
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monotonic reading is an uptime and is far smaller. Getting these backwards
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would put a producer's Hello sync sample decades off. *)
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let test_wall_is_epoch_mono_is_not () =
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Eio_main.run @@ fun env ->
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let clock = Eio.Stdenv.clock env in
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let mono = Eio.Stdenv.mono_clock env in
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let c = Clock_eio.v ~clock ~mono in
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let epoch = Int64.of_float (Unix.gettimeofday () *. 1e9) in
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let skew = Int64.abs (Int64.sub (c.Clock.unix_ns ()) epoch) in
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Alcotest.(check bool)
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(Fmt.str "wall is within 1s of gettimeofday (skew %Ldns)" skew)
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true
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(Int64.compare skew 1_000_000_000L < 0);
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(* An uptime cannot plausibly be an epoch stamp: 2020-01-01 in ns. *)
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Alcotest.(check bool)
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"monotonic is not an epoch stamp" true
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(Int64.compare (c.Clock.mono_ns ()) 1_577_836_800_000_000_000L < 0)
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let suite =
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( "clock_eio",
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[
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Alcotest.test_case "reads live clocks" `Quick test_reads_live_clocks;
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Alcotest.test_case "wall is epoch, mono is not" `Quick
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test_wall_is_epoch_mono_is_not;
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] )
+4
test/producer/test_clock_eio.mli
+4
test/producer/test_clock_eio.mli
+4
-2
test/producer/test_ring_eio.ml
+4
-2
test/producer/test_ring_eio.ml
···
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module Ring = Observe_producer_core.Ring
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module Ring_eio = Observe_producer_core.Ring_eio
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module Ring_eio = Observe_producer_core_eio.Ring_eio
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module Clock = Observe_producer_core.Clock
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module Collector_server = Observer_offline.Collector_server
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module Fxt_adapter = Observer_offline.Fxt_adapter
···
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let clock = Eio.Stdenv.clock env in
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let mono = Eio.Stdenv.mono_clock env in
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Collector_server.serve ~sw ~net ~mono server ~path;
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let t = Ring.v ~clock:(Clock.of_eio ~clock ~mono) () in
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let t =
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Ring.v ~clock:(Observe_producer_core_eio.Clock_eio.v ~clock ~mono) ()
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in
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let stop =
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Ring_eio.attach ~sw ~net ~clock ~interval:0.01 t (`Unix path)
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in
+1
-1
test/producer/test_ring_eio.mli
+1
-1
test/producer/test_ring_eio.mli