From a6bf8171bbc952cc7032c0ff2ddc13a269c28a70 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Wed, 10 Dec 2025 11:53:07 -0500
Subject: [PATCH] better semantic conventions for self tracing;
 bounded_queue.high_watermark

---
 src/client/bounded_queue.ml      |  7 +++++++
 src/client/bounded_queue_sync.ml |  5 +++--
 src/client/exporter_queued.ml    | 10 ++++++----
 src/client/generic_consumer.ml   |  2 +-
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/client/bounded_queue.ml b/src/client/bounded_queue.ml
index 07d43ada..4c60d967 100644
--- a/src/client/bounded_queue.ml
+++ b/src/client/bounded_queue.ml
@@ -23,6 +23,7 @@ module Common = struct
     num_discarded: unit -> int;  (** How many items were discarded? *)
     size: unit -> int;
         (** Snapshot of how many items are currently in the queue *)
+    high_watermark: unit -> int;  (** Maximum size of the queue *)
   }
 
   let[@inline] num_discarded self = self.num_discarded ()
@@ -30,6 +31,8 @@ module Common = struct
   let[@inline] closed (self : t) : bool = self.closed ()
 
   let[@inline] size (self : t) : int = self.size ()
+
+  let[@inline] high_watermark self = self.high_watermark ()
 end
 
 (** Receiving side *)
@@ -52,6 +55,8 @@ module Recv = struct
 
   let[@inline] size self = self.common.size ()
 
+  let[@inline] high_watermark self = self.common.high_watermark ()
+
   let map (type a b) (f : a -> b) (self : a t) : b t =
     {
       self with
@@ -86,6 +91,8 @@ module Send = struct
 
   let[@inline] size self = self.common.size ()
 
+  let[@inline] high_watermark self = self.common.high_watermark ()
+
   let map (type a b) (f : a list -> b list) (self : b t) : a t =
     {
       self with
diff --git a/src/client/bounded_queue_sync.ml b/src/client/bounded_queue_sync.ml
index 55207d64..7b0a2b8e 100644
--- a/src/client/bounded_queue_sync.ml
+++ b/src/client/bounded_queue_sync.ml
@@ -43,7 +43,7 @@ end = struct
     a value of type [bool] which OCaml's memory model should guarantee. *)
   let[@inline] closed self = self.closed
 
-  (* NOTE: race condition here is also benign in absoence of tearing. *)
+  (* NOTE: race condition here is also benign in absence of tearing. *)
   let[@inline] size self = Queue.length self.q
 
   let close (self : _ t) =
@@ -115,12 +115,13 @@ let to_bounded_queue (self : 'a state) : 'a BQ.t =
   let on_non_empty = Cb_set.register self.on_non_empty in
   let try_pop () = try_pop self in
   let size () = Q.size self.q in
+  let high_watermark () = self.high_watermark in
   let close () =
     Q.close self.q;
     (* waiters will want to know *)
     Cb_set.trigger self.on_non_empty
   in
-  let common = { BQ.Common.closed; num_discarded; size } in
+  let common = { BQ.Common.closed; num_discarded; size; high_watermark } in
   {
     BQ.send = { push; close; common };
     recv = { try_pop; on_non_empty; common };
diff --git a/src/client/exporter_queued.ml b/src/client/exporter_queued.ml
index 65e73999..883bef48 100644
--- a/src/client/exporter_queued.ml
+++ b/src/client/exporter_queued.ml
@@ -50,15 +50,17 @@ let create ~(q : OTEL.Any_signal_l.t Bounded_queue.t)
   let self_metrics () : _ list =
     let now = OTEL.Timestamp_ns.now_unix_ns () in
     let m_size =
-      OTEL.Metrics.gauge ~name:"otel_ocaml.exporter_queue.size"
+      OTEL.Metrics.gauge ~name:"otel.sdk.exporter.queue.size"
         [ OTEL.Metrics.int ~now (Bounded_queue.Recv.size q.recv) ]
-    in
-    let m_discarded =
+    and m_cap =
+      OTEL.Metrics.gauge ~name:"otel.sdk.exporter.queue.capacity"
+        [ OTEL.Metrics.int ~now (Bounded_queue.Recv.high_watermark q.recv) ]
+    and m_discarded =
       OTEL.Metrics.sum ~is_monotonic:true
         ~name:"otel_ocaml.exporter_queue.discarded"
         [ OTEL.Metrics.int ~now (Bounded_queue.Recv.num_discarded q.recv) ]
     in
-    m_size :: m_discarded :: Consumer.self_metrics consumer
+    m_size :: m_cap :: m_discarded :: Consumer.self_metrics consumer
   in
 
   let shutdown () =
diff --git a/src/client/generic_consumer.ml b/src/client/generic_consumer.ml
index 89d6198b..afa5ad99 100644
--- a/src/client/generic_consumer.ml
+++ b/src/client/generic_consumer.ml
@@ -209,7 +209,7 @@ end = struct
     let now = OTEL.Timestamp_ns.now_unix_ns () in
     let attrs = [ "otel.component.name", `String "otel_ocaml" ] in
     [
-      sum ~name:"otel.sd.exporter.errors" ~is_monotonic:true
+      sum ~name:"otel.sdk.exporter.errors" ~is_monotonic:true
         [ int ~now (Atomic.get n_errors) ~attrs ];
       sum ~name:"otel.sdk.exporter.span.exported" ~is_monotonic:true
         [ int ~now (Atomic.get self.m_spans) ~attrs ];