prepare for 0.91

we can now know how big the batches we drop are

.github/workflows/format.yml

@@ -1,5 +1,3 @@
-
-
 name: format
 
 on:
@@ -11,20 +9,10 @@ on:
 jobs:
   format:
     name: format
-    strategy:
+    runs-on: ubuntu-latest
-      matrix:
+    container: ghcr.io/ocaml-tracing/ocaml-opentelemetry/ci-4.14:latest
-        ocaml-compiler:
+
-            - '5.3'
-    runs-on: 'ubuntu-latest'
     steps:
-      - uses: actions/checkout@main
+      - uses: actions/checkout@v6
-      - name: Use OCaml ${{ matrix.ocaml-compiler }}
-        uses: ocaml/setup-ocaml@v3
-        with:
-          ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          dune-cache: true
-          allow-prerelease-opam: true
 
-      - run: opam install ocamlformat.0.27.0 lwt.6.1.1
       - run: opam exec -- make format-check
-

.github/workflows/gh-pages.yml

@@ -0,0 +1,38 @@
+name: github pages
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: write
+  packages: read
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    container: ghcr.io/ocaml-tracing/ocaml-opentelemetry/ci-5.4:latest
+
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          submodules: recursive
+
+      - name: Install local packages
+        run: opam exec -- dune build @install && opam exec -- dune install
+
+      - name: Build documentation
+        run: |
+          opam exec -- odig odoc --cache-dir=_doc/ \
+            opentelemetry opentelemetry-client opentelemetry-lwt \
+            opentelemetry-cohttp-lwt opentelemetry-client-ocurl \
+            opentelemetry-client-ocurl-lwt opentelemetry-client-cohttp-lwt \
+            opentelemetry-client-cohttp-eio opentelemetry-logs
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_doc/html
+          enable_jekyll: false

.github/workflows/main.yml

@@ -11,65 +11,37 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os:
+        include:
-          - ubuntu-latest
+          - ocaml-version: "4.08"
-            #- windows-latest
+            container: ghcr.io/ocaml-tracing/ocaml-opentelemetry/ci-4.08:latest
-            #- macos-latest
+            eio: false
-        ocaml-compiler:
+          - ocaml-version: "4.14"
-          - 4.08.x
+            container: ghcr.io/ocaml-tracing/ocaml-opentelemetry/ci-4.14:latest
-          - 4.13.x
+            eio: false
-          - 5.0.x
+          - ocaml-version: "5.4"
-          - 5.3.x
+            container: ghcr.io/ocaml-tracing/ocaml-opentelemetry/ci-5.4:latest
+            eio: true
 
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
+    container: ${{ matrix.container }}
 
     steps:
-      - name: Checkout code
+      - uses: actions/checkout@v6
-        uses: actions/checkout@v4
         with:
           submodules: recursive
 
-      # needed for depext to work
+      - name: Build
-      - run: sudo apt-get update && sudo apt-get install mccs
+        run: opam exec -- dune build @install -p opentelemetry,opentelemetry-client,opentelemetry-lwt,opentelemetry-cohttp-lwt,opentelemetry-client-ocurl,opentelemetry-client-ocurl-lwt,opentelemetry-client-cohttp-lwt,opentelemetry-logs
-        if: ${{ matrix.os == 'ubuntu-latest' }}
 
-      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+      - name: Build eio packages
-        uses: ocaml/setup-ocaml@v3
+        if: ${{ matrix.eio }}
-        with:
+        run: opam exec -- dune build @install -p opentelemetry-client-cohttp-eio,opentelemetry,opentelemetry-client,opentelemetry-lwt,opentelemetry-cohttp-lwt,opentelemetry-client-ocurl,opentelemetry-client-ocurl-lwt,opentelemetry-client-cohttp-lwt,opentelemetry-logs
-          ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          opam-depext-flags: --with-test
-          dune-cache: true
-          allow-prerelease-opam: true
 
-      - run: |
+      - name: Lint (protoc check)
-          opam install pbrt.4.0 -y
+        run: opam exec -- dune build @lint
-          opam install ambient-context lwt.5.9.2
 
-      # We cannot install packages that need eio on ocaml versions before 5
+      - name: Check no generated files changed
-      - run: |
+        run: git diff --exit-code
-          packages=$(ls ./*.opam | grep -v eio)
-          opam install $packages --deps-only --with-test --solver=mccs
-        if: ${{ ! (startsWith(matrix.ocaml-compiler, '5')) }}
 
-      # We should be able to install all packages on ocaml 5
+      - name: Run tests
-      - run: opam install . --deps-only --with-test --solver=mccs
+        run: opam exec -- dune build @runtest
-        if: ${{ startsWith(matrix.ocaml-compiler, '5') }}
-
-      - run: opam exec -- dune build @install -p opentelemetry,opentelemetry-client,opentelemetry-lwt,opentelemetry-client-ocurl,opentelemetry-cohttp-lwt,opentelemetry-client-cohttp-lwt,opentelemetry-logs
-
-      - run: opam install trace
-      - run: opam exec -- dune build @install -p opentelemetry
-
-      - run: opam install lwt.6.1.1 -y
-        if: ${{ matrix.ocaml-compiler == '5.3.x' }}
-      - run: opam exec -- dune build @install -p opentelemetry,opentelemetry-client,opentelemetry-lwt,opentelemetry-client-cohttp-lwt
-        if: ${{ matrix.ocaml-compiler == '5.3.x' }}
-
-      - run: opam install ocaml-protoc
-      - run: opam exec -- dune build @lint
-
-      # check that nothing changed
-      - run: git diff --exit-code
-
-      - run: opam exec -- dune build @runtest
-        if: ${{ matrix.os == 'ubuntu-latest' }}

.gitignore

@@ -7,3 +7,4 @@ _opam
 *.install
 *.exe
 *.tmp
+/.env

CHANGES.md

@@ -1,4 +1,14 @@
 
+## 0.91
+
+- expose Self_debug.level_above
+- config: better defaults in Sdk, have batching enabled by default
+
+- better error message for otlp http failures
+- bounded queue: provide a per-item measure function for better errors/metrics
+- fix: retries are self_debug logged at warning level
+- move from ocurl to curl as a dep
+
 ## 0.90
 
 - major refactor: split library into `opentelemetry.core`, `opentelemetry`,

Makefile

@@ -36,6 +36,8 @@ WATCH ?= @all
 watch:
 	@dune build $(WATCH) -w $(OPTS)
 
+include deps/Makefile.ci
+
 VERSION=$(shell awk '/^version:/ {print $$2}' opentelemetry.opam)
 update_next_tag:
 	@echo "update version to $(VERSION)..."

deps/Makefile.ci

@@ -0,0 +1,44 @@
+# CI Docker images — included by top-level Makefile
+CI_REGISTRY = ghcr.io/ocaml-tracing/ocaml-opentelemetry
+CI_VERSIONS = 4.08 4.14 5.4
+# To update: curl -s https://api.github.com/repos/ocaml/opam-repository/commits/master | jq -r .sha
+OPAM_REPO_COMMIT ?= 67472cd54293d750a62d6d4423024d55f77268b0
+CI_BASE_OS_PACKAGES = pkg-config libcurl4-openssl-dev libgmp-dev mccs
+
+CI_COMMON_PACKAGES = ptime hmap pbrt pbrt_yojson ambient-context mtime \
+    thread-local-storage lwt_ppx ambient-context-lwt \
+    cohttp cohttp-lwt cohttp-lwt-unix \
+    ezcurl ezcurl-lwt ocurl logs alcotest containers \
+    trace ocaml-protoc
+
+CI_PACKAGES_408 = $(CI_COMMON_PACKAGES) lwt.5.9.2
+CI_PACKAGES_414 = $(CI_COMMON_PACKAGES) lwt.5.9.2 ocamlformat.0.27.0
+CI_PACKAGES_54  = $(CI_COMMON_PACKAGES) lwt.6.1.1 \
+    ambient-context-eio cohttp-eio tls-eio ca-certs mirage-crypto-rng eio_main odig
+
+CI_BUILD = docker build -f deps/dockerfile.ocaml \
+    --build-arg OPAM_REPO_COMMIT=$(OPAM_REPO_COMMIT) \
+    --build-arg "BASE_OS_PACKAGES=$(CI_BASE_OS_PACKAGES)"
+
+build-ci-docker:
+	$(CI_BUILD) --build-arg OCAML_VERSION=4.08.1 --build-arg "BASE_PACKAGES=$(CI_PACKAGES_408)" -t $(CI_REGISTRY)/ci-4.08:latest .
+	$(CI_BUILD) --build-arg OCAML_VERSION=4.14.2 --build-arg "BASE_PACKAGES=$(CI_PACKAGES_414)" -t $(CI_REGISTRY)/ci-4.14:latest .
+	$(CI_BUILD) --build-arg OCAML_VERSION=5.4.1  --build-arg "BASE_PACKAGES=$(CI_PACKAGES_54)"  -t $(CI_REGISTRY)/ci-5.4:latest .
+
+CI_NON_EIO_PACKAGES = opentelemetry,opentelemetry-client,opentelemetry-lwt,opentelemetry-cohttp-lwt,opentelemetry-client-ocurl,opentelemetry-client-ocurl-lwt,opentelemetry-client-cohttp-lwt,opentelemetry-logs
+CI_RUN = docker run --pull=never --rm -t -v $(PWD):/src:z -w /src
+
+run-ci:
+	@for v in $(CI_VERSIONS); do \
+		echo "=== OCaml $$v ===" ; \
+		$(CI_RUN) $(CI_REGISTRY)/ci-$$v:latest \
+			sh -c "opam exec -- dune build @install -p $(CI_NON_EIO_PACKAGES) && opam exec -- dune build @runtest" \
+		|| exit 1 ; \
+	done
+	$(CI_RUN) $(CI_REGISTRY)/ci-5.4:latest \
+		opam exec -- dune build @install -p opentelemetry-client-cohttp-eio
+
+upload-ci-docker:
+	@for v in $(CI_VERSIONS); do \
+		docker push $(CI_REGISTRY)/ci-$$v:latest ; \
+	done || ( echo  "to login:  docker login ghcr.io -u <your-github-username>" ; exit 1 )

deps/dockerfile.ocaml

@@ -0,0 +1,40 @@
+ARG BASE_OS=ubuntu:24.04
+
+# --- Stage 1: base (shared, no OCaml) ---
+FROM $BASE_OS AS base
+ARG BASE_OS_PACKAGES=""
+ENV OPAMROOTISOK=1 OPAMYES=1 OPAMCONFIRMLEVEL=unsafe-yes
+RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
+    --mount=type=cache,target=/var/lib/apt,sharing=locked \
+    rm -f /etc/apt/apt.conf.d/docker-clean && \
+    apt-get update && \
+    apt-get install -y --no-install-recommends ca-certificates curl git unzip build-essential netbase $BASE_OS_PACKAGES
+RUN curl -fsSL https://github.com/ocaml/opam/releases/download/2.5.0/opam-2.5.0-x86_64-linux -o /usr/local/bin/opam && \
+    chmod +x /usr/local/bin/opam && \
+    git config --system --add safe.directory '*'
+WORKDIR /root/w
+
+# --- Stage 2: opam-setup (builds the switch, discarded) ---
+FROM base AS opam-setup
+ARG OCAML_VERSION
+ARG OPAM_REPO_COMMIT=master
+ARG BASE_PACKAGES=""
+
+RUN git init /tmp/opam-repo && cd /tmp/opam-repo && \
+    git remote add origin https://github.com/ocaml/opam-repository.git && \
+    git fetch --depth 1 origin $OPAM_REPO_COMMIT && \
+    git checkout FETCH_HEAD
+
+RUN opam init --disable-sandboxing --bare --no-setup -k local /tmp/opam-repo && \
+    opam switch create /root/w --packages=ocaml-base-compiler.$OCAML_VERSION
+
+RUN opam install --no-depexts $BASE_PACKAGES && \
+    opam clean -a -y && \
+    rm -rf /tmp/opam-repo
+
+# --- Stage 3: final image (base + switch only) ---
+FROM base
+COPY --from=opam-setup /root/.opam /root/.opam
+COPY --from=opam-setup /root/w/_opam /root/w/_opam
+ENV OPAMROOT=/root/.opam OPAMSWITCH=/root/w PATH=/root/w/_opam/bin:$PATH
+WORKDIR /root/w

dune-project

@@ -7,7 +7,7 @@
 (source
  (github ocaml-tracing/ocaml-opentelemetry))
 
-(version 0.90)
+(version 0.91)
 
 (implicit_transitive_deps false)
 
@@ -31,10 +31,6 @@
   hmap
   (odoc :with-doc)
   (alcotest :with-test)
-  (opentelemetry-client
-   (and
-    :with-test
-    (= :version)))
   (pbrt
    (and
     (>= 4.0)
@@ -98,7 +94,7 @@
  (name opentelemetry-client-ocurl)
  (depends
   (ocaml
-   (>= "4.08"))
+   (>= "4.11"))
   (mtime
    (>= "1.4"))
   ; for spans
@@ -110,7 +106,7 @@
   (odoc :with-doc)
   (ezcurl
    (>= 0.2.3))
-  ocurl
+  curl
   (alcotest :with-test)
   (cohttp-lwt-unix :with-test)
   (containers :with-test)
@@ -121,7 +117,7 @@
  (name opentelemetry-client-ocurl-lwt)
  (depends
   (ocaml
-   (>= "4.08"))
+   (>= "4.11"))
   (mtime
    (>= "1.4"))
   (opentelemetry
@@ -209,11 +205,7 @@
   cohttp-lwt
   cohttp-lwt-unix
   (alcotest :with-test)
-  (containers :with-test)
+  (containers :with-test))
-  (opentelemetry-lwt
-   (and
-    :with-test
-    (= :version))))
  (synopsis "Collector client for opentelemetry, using cohttp + lwt"))
 
 (package

opentelemetry-client-cohttp-eio.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Collector client for opentelemetry, using cohttp + eio"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]

opentelemetry-client-cohttp-lwt.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Collector client for opentelemetry, using cohttp + lwt"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]
@@ -22,7 +22,6 @@ depends: [
   "cohttp-lwt-unix"
   "alcotest" {with-test}
   "containers" {with-test}
-  "opentelemetry-lwt" {with-test & = version}
 ]
 build: [
   ["dune" "subst"] {dev}

opentelemetry-client-ocurl-lwt.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Collector client for opentelemetry, using ezcurl-lwt"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]
@@ -9,7 +9,7 @@ homepage: "https://github.com/ocaml-tracing/ocaml-opentelemetry"
 bug-reports: "https://github.com/ocaml-tracing/ocaml-opentelemetry/issues"
 depends: [
   "dune" {>= "3.11"}
-  "ocaml" {>= "4.08"}
+  "ocaml" {>= "4.11"}
   "mtime" {>= "1.4"}
   "opentelemetry" {= version}
   "opentelemetry-client" {= version}

opentelemetry-client-ocurl.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Collector client for opentelemetry, using http + ezcurl"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]
@@ -9,13 +9,13 @@ homepage: "https://github.com/ocaml-tracing/ocaml-opentelemetry"
 bug-reports: "https://github.com/ocaml-tracing/ocaml-opentelemetry/issues"
 depends: [
   "dune" {>= "3.11"}
-  "ocaml" {>= "4.08"}
+  "ocaml" {>= "4.11"}
   "mtime" {>= "1.4"}
   "opentelemetry" {= version}
   "opentelemetry-client" {= version}
   "odoc" {with-doc}
   "ezcurl" {>= "0.2.3"}
-  "ocurl"
+  "curl"
   "alcotest" {with-test}
   "cohttp-lwt-unix" {with-test}
   "containers" {with-test}

opentelemetry-client.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Client SDK for https://opentelemetry.io"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]

opentelemetry-cohttp-lwt.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Opentelemetry tracing for Cohttp HTTP servers"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]

opentelemetry-logs.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Opentelemetry-based reporter for Logs"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]

opentelemetry-lwt.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis: "Lwt-compatible instrumentation for https://opentelemetry.io"
 maintainer: ["ocaml-tracing"]
 authors: ["ocaml-tracing" "ELLIOTTCABLE <opam@ell.io>" "the imandra team"]

opentelemetry.opam

@@ -1,6 +1,6 @@
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
-version: "0.90"
+version: "0.91"
 synopsis:
   "Core library for instrumentation and serialization for https://opentelemetry.io"
 maintainer: ["ocaml-tracing"]
@@ -16,7 +16,6 @@ depends: [
   "hmap"
   "odoc" {with-doc}
   "alcotest" {with-test}
-  "opentelemetry-client" {with-test & = version}
   "pbrt" {>= "4.0" & < "5.0"}
   "pbrt_yojson" {>= "4.0" & < "5.0"}
   "ambient-context" {>= "0.2"}

src/client-cohttp-eio/opentelemetry_client_cohttp_eio.ml

@@ -169,6 +169,7 @@ let create_exporter ?(config = Config.make ()) ~sw ~env () =
   let consumer = create_consumer ~config ~sw ~env () in
   let bq =
     Opentelemetry_client_sync.Bounded_queue_sync.create
+      ~measure:Any_signal_l.length
       ~high_watermark:Bounded_queue.Defaults.high_watermark ()
   in
   Exporter_queued.create ~clock:Clock.ptime_clock ~q:bq ~consumer ()

src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml

@@ -102,6 +102,7 @@ let create_exporter ?(config = Config.make ()) () =
   let consumer = create_consumer ~config () in
   let bq =
     Opentelemetry_client_sync.Bounded_queue_sync.create
+      ~measure:OTEL.Any_signal_l.length
       ~high_watermark:Bounded_queue.Defaults.high_watermark ()
   in
   Exporter_queued.create ~clock:Clock.ptime_clock ~q:bq ~consumer ()

src/client-ocurl-lwt/opentelemetry_client_ocurl_lwt.ml

@@ -79,6 +79,7 @@ let create_exporter ?(config = Config.make ()) () =
   let consumer = create_consumer ~config () in
   let bq =
     Opentelemetry_client_sync.Bounded_queue_sync.create
+      ~measure:OTEL.Any_signal_l.length
       ~high_watermark:Bounded_queue.Defaults.high_watermark ()
   in
   Exporter_queued.create ~clock:Clock.ptime_clock ~q:bq ~consumer ()

src/client-ocurl/opentelemetry_client_ocurl.ml

@@ -81,6 +81,7 @@ let create_exporter ?(config = Config.make ()) () : OTEL.Exporter.t =
   let consumer = consumer ~config () in
   let bq =
     Opentelemetry_client_sync.Bounded_queue_sync.create
+      ~measure:OTEL.Any_signal_l.length
       ~high_watermark:OTELC.Bounded_queue.Defaults.high_watermark ()
   in
 

src/client/export_error.ml

@@ -12,10 +12,12 @@ let str_to_hex (s : string) : string =
   Opentelemetry_util.Util_bytes_.bytes_to_hex (Bytes.unsafe_of_string s)
 
 (** Report the error on stderr. *)
-let report_err ~level:(provided_level : [ `Debug | `Auto ]) (err : t) : unit =
+let report_err ~level:(provided_level : [ `Debug | `Warning | `Auto ]) (err : t)
+    : unit =
   let compute_level lvl =
     match provided_level with
     | `Debug -> Opentelemetry.Self_debug.Debug
+    | `Warning -> Opentelemetry.Self_debug.Warning
     | `Auto -> lvl
   in
   match err with
@@ -24,7 +26,7 @@ let report_err ~level:(provided_level : [ `Debug | `Auto ]) (err : t) : unit =
         "opentelemetry: ctrl-c captured, stopping")
   | `Failure msg ->
     Opentelemetry.Self_debug.log (compute_level Error) (fun () ->
-        Printf.sprintf "opentelemetry: export failed: %s" msg)
+        Printf.sprintf "opentelemetry: export failed:\n%s" msg)
   | `Status
       ( code,
         {
@@ -57,8 +59,9 @@ let decode_invalid_http_response ~attempt_descr ~code ~url (body : string) : t =
     let bt = Printexc.get_backtrace () in
     `Failure
       (Printf.sprintf
-         "httpc: decoding of status (url=%S, code=%d) failed with:\n\
+         "http server at %s returned code %d;\n\
+          trying to decode the body as protobuf failed:\n\
           %s\n\
-          HTTP body: %s\n\
+          raw HTTP body (hex): %s\n\
           %s"
          url code (Printexc.to_string e) (str_to_hex body) bt)

src/client/generic_http_consumer.ml

@@ -82,7 +82,7 @@ end = struct
       | Error err
         when should_retry err && attempt < self.config.retry_max_attempts ->
         let delay_s = delay_ms /. 1000. in
-        Export_error.report_err ~level:`Debug err;
+        Export_error.report_err ~level:`Warning err;
 
         let* () = sleep_s delay_s in
         let next_delay =

src/client/sync/bounded_queue_sync.ml

@@ -88,21 +88,27 @@ type 'a state = {
   high_watermark: int;
   q: 'a Q.t;
   on_non_empty: Cb_set.t;
+  measure: 'a -> int;
 }
 
+let measure_all_ measure xs = List.fold_left (fun acc x -> acc + measure x) 0 xs
+
 let push (self : _ state) x =
   if x <> [] then (
     match
       Q.push_while_not_full self.q ~high_watermark:self.high_watermark x
     with
     | Closed ->
-      ignore (Atomic.fetch_and_add self.n_discarded (List.length x) : int)
+      let n = measure_all_ self.measure x in
+      ignore (Atomic.fetch_and_add self.n_discarded n : int)
     | Pushed { num_discarded } ->
       if num_discarded > 0 then (
-        ignore (Atomic.fetch_and_add self.n_discarded num_discarded : int);
+        let n_signals = measure_all_ self.measure x in
+        let total = Atomic.fetch_and_add self.n_discarded n_signals in
         Opentelemetry.Self_debug.log Warning (fun () ->
-            Printf.sprintf "otel: dropped %d signals (exporter queue full)"
+            Printf.sprintf
-              num_discarded)
+              "otel: dropped %d signals (queue full: %d/%d, total dropped: %d)"
+              n_signals (Q.size self.q) self.high_watermark (total + n_signals))
       );
       (* wake up potentially asleep consumers *)
       Cb_set.trigger self.on_non_empty
@@ -129,13 +135,14 @@ let to_bounded_queue (self : 'a state) : 'a BQ.t =
     recv = { try_pop; on_non_empty; common };
   }
 
-let create ~high_watermark () : _ BQ.t =
+let create ?(measure = fun _ -> 1) ~high_watermark () : _ BQ.t =
   let st =
     {
       high_watermark;
       q = Q.create ();
       n_discarded = Atomic.make 0;
       on_non_empty = Cb_set.create ();
+      measure;
     }
   in
   to_bounded_queue st

src/client/sync/bounded_queue_sync.mli

@@ -2,6 +2,11 @@
 
     This is not the fastest queue but it should be versatile. *)
 
-val create : high_watermark:int -> unit -> 'a Bounded_queue.t
+val create :
+  ?measure:('a -> int) -> high_watermark:int -> unit -> 'a Bounded_queue.t
 (** [create ~high_watermark ()] creates a new bounded queue based on
-    {!Sync_queue} *)
+    {!Sync_queue}.
+    @param measure
+      maps each item to its signal count (e.g. number of spans in a batch). Used
+      to report accurate signal counts when items are dropped. Default:
+      [fun _ -> 1]. *)

src/core/any_signal_l.ml

@@ -19,6 +19,11 @@ let pp out = function
   | Metrics m -> pp_list Proto.Metrics.pp_metric out m
   | Logs l -> pp_list Proto.Logs.pp_log_record out l
 
+let length = function
+  | Spans l -> List.length l
+  | Metrics l -> List.length l
+  | Logs l -> List.length l
+
 let of_logs_or_empty = function
   | [] -> []
   | l -> [ Logs l ]

src/lib/sdk.ml

@@ -54,8 +54,9 @@ let run_tick_callbacks : unit -> unit = Globals.run_tick_callbacks
     from their ticker. *)
 let tick : unit -> unit = Globals.run_tick_callbacks
 
-let set ?(traces = Provider_config.default) ?(metrics = Provider_config.default)
+let set ?(traces = Provider_config.make ~batch:400 ())
-    ?(logs = Provider_config.default) (exp : Exporter.t) : unit =
+    ?(metrics = Provider_config.make ~batch:200 ())
+    ?(logs = Provider_config.make ~batch:400 ()) (exp : Exporter.t) : unit =
   Self_debug.log Info (fun () -> "opentelemetry: SDK set up");
   Atomic.set exporter (Some exp);
   let tracer : Tracer.t =

src/lib/self_debug.ml

@@ -16,17 +16,21 @@ let string_of_level = function
   | Warning -> "warning"
   | Error -> "error"
 
-let to_stderr ?(min_level = Warning) () : unit =
+open struct
   let[@inline] int_of_level_ = function
     | Debug -> 0
     | Info -> 1
     | Warning -> 2
     | Error -> 3
-  in
+end
-  let threshold = int_of_level_ min_level in
+
+let level_above ~min_level level : bool =
+  int_of_level_ level >= int_of_level_ min_level
+
+let to_stderr ?(min_level = Warning) () : unit =
   logger :=
     fun level mk_msg ->
-      if int_of_level_ level >= threshold then (
+      if level_above ~min_level level then (
         let msg = mk_msg () in
         Printf.eprintf "[otel:%s] %s\n%!" (string_of_level level) msg
       )

src/lib/self_debug.mli

@@ -25,6 +25,11 @@ val logger : logger ref
 val string_of_level : level -> string
 (** String representation of a level. *)
 
+val level_above : min_level:level -> level -> bool
+(** [level_above ~min_level lvl] is true if messages at level [lvl] should be
+    logged.
+    @since NEXT_RELEASE *)
+
 val log : level -> (unit -> string) -> unit
 (** [log level mk_msg] emits a diagnostic message if the current logger is
     active. [mk_msg] is called lazily — only if the message will be emitted. *)

src/trace/opentelemetry_trace.ml

@@ -1,6 +1,9 @@
 open Common_
 
 module Extensions = struct
+  (* extend [Trace]'s types with OTEL specific variants, eg to have a
+     [Trace.span] be a wrapper around [OTEL.Span.t], or to declare custom actions
+     to link spans together, or to be able to use [OTEL]-specific metrics types *)
   type Trace.span += Span_otel of OTEL.Span.t
 
   type Trace.extension_event +=
@@ -21,6 +24,14 @@ end
 
 open Extensions
 
+(* Inject ambient span into [Trace], relying on the [Ambient_context]
+   library. We use the generic ambient context to carry a [Hmap.t] around with
+   possible the current [Trace.span], and it is also used by [OTEL] itself
+   (ambient [OTEL.Span_ctx.t]).
+
+   This mechanism is used by [Trace] so that nested [Trace.with_span] can infer
+   the correct parent-child relation from implicit context, and produce OTEL
+   spans accordingly; without it every span would be parentless. *)
 module Ambient_span_provider_ = struct
   let get_current_span () =
     match OTEL.Ambient_span.get () with

tests/client/dune

@@ -1,4 +1,4 @@
 (tests
  (names test_client_lib)
- (package opentelemetry)
+ (package opentelemetry-client)
  (libraries alcotest opentelemetry-client))

tests/core/dune

@@ -1,4 +1,4 @@
 (tests
  (names test_trace_context t_size t_histogram test_span_dummy)
  (package opentelemetry)
- (libraries pbrt opentelemetry opentelemetry-client))
+ (libraries pbrt opentelemetry))

tests/implicit_scope/sync/test_implicit_scope_sync.ml

@@ -19,7 +19,11 @@ let test_exporter : Otel.Exporter.t =
 let with_test_exporter f =
   (* uncomment for eprintf debugging: *)
   (* let test_exporter = Opentelemetry_client.Exporter_debug.debug test_exporter in*)
-  Otel.Sdk.set test_exporter;
+  Otel.Sdk.set
+    ~traces:(Otel.Provider_config.make ())
+    ~metrics:(Otel.Provider_config.make ())
+    ~logs:(Otel.Provider_config.make ())
+    test_exporter;
   Fun.protect f ~finally:(fun () ->
       let sq = Opentelemetry_client_sync.Sync_queue.create () in
       Otel.Sdk.remove