add config parameter for self_metrics

src/client-cohttp-eio/opentelemetry_client_cohttp_eio.ml

@@ -186,7 +186,8 @@ let setup_ ~sw ~config env : unit =
 
   Opentelemetry.Self_debug.log Opentelemetry.Self_debug.Info (fun () ->
       "opentelemetry: cohttp-eio exporter installed");
-  Opentelemetry_client.Self_trace.set_enabled config.self_trace
+  Opentelemetry_client.Self_trace.set_enabled config.self_trace;
+  if config.self_metrics then Opentelemetry.Sdk.setup_self_metrics ()
 
 let setup ?(config = Config.make ()) ?(enable = true) ~sw env =
   if enable && not config.sdk_disabled then setup_ ~sw ~config env

src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml

@@ -120,6 +120,7 @@ let setup_ ~config () : unit =
   Opentelemetry.Self_debug.log Opentelemetry.Self_debug.Info (fun () ->
       "opentelemetry: cohttp-lwt exporter installed");
   Opentelemetry_client.Self_trace.set_enabled config.self_trace;
+  if config.self_metrics then Opentelemetry.Sdk.setup_self_metrics ();
   ()
 
 let setup ?(config = Config.make ()) ?(enable = true) () =

src/client-ocurl-lwt/opentelemetry_client_ocurl_lwt.ml

@@ -95,6 +95,7 @@ let setup_ ~config () : Exporter.t =
   Opentelemetry.Self_debug.log Opentelemetry.Self_debug.Info (fun () ->
       "opentelemetry: ocurl-lwt exporter installed");
   Opentelemetry_client.Self_trace.set_enabled config.self_trace;
+  if config.self_metrics then Opentelemetry.Sdk.setup_self_metrics ();
 
   exp
 

src/client-ocurl/opentelemetry_client_ocurl.ml

@@ -100,6 +100,7 @@ let setup_ ~config () : OTEL.Exporter.t =
       "opentelemetry: ocurl exporter installed");
 
   OTELC.Self_trace.set_enabled config.common.self_trace;
+  if config.common.self_metrics then Opentelemetry.Sdk.setup_self_metrics ();
   exporter
 
 let remove_exporter () : unit =

src/client/exporter_config.ml

@@ -26,6 +26,7 @@ type t = {
   metrics: Opentelemetry.Provider_config.t;
   logs: Opentelemetry.Provider_config.t;
   self_trace: bool;
+  self_metrics: bool;
   http_concurrency_level: int option;
   retry_max_attempts: int;
   retry_initial_delay_ms: float;
@@ -65,6 +66,7 @@ let pp out (self : t) : unit =
     log_level;
     sdk_disabled;
     self_trace;
+    self_metrics;
     url_traces;
     url_metrics;
     url_logs;
@@ -91,7 +93,8 @@ let pp out (self : t) : unit =
   in
   Format.fprintf out
     "{@[ debug=%B;@ log_level=%a;@ sdk_disabled=%B;@ self_trace=%B;@ \
-     url_traces=%S;@ url_metrics=%S;@ url_logs=%S;@ @[<2>headers=@,\
+     self_metrics=%B;@ url_traces=%S;@ url_metrics=%S;@ url_logs=%S;@ \
+     @[<2>headers=@,\
      %a@];@ @[<2>headers_traces=@,\
      %a@];@ @[<2>headers_metrics=@,\
      %a@];@ @[<2>headers_logs=@,\
@@ -100,8 +103,8 @@ let pp out (self : t) : unit =
      logs=%a;@ http_concurrency_level=%a;@ retry_max_attempts=%d;@ \
      retry_initial_delay_ms=%.0f;@ retry_max_delay_ms=%.0f;@ \
      retry_backoff_multiplier=%.1f @]}"
-    debug pp_log_level log_level sdk_disabled self_trace url_traces url_metrics
-    url_logs ppheaders headers ppheaders headers_traces ppheaders
+    debug pp_log_level log_level sdk_disabled self_trace self_metrics url_traces
+    url_metrics url_logs ppheaders headers ppheaders headers_traces ppheaders
     headers_metrics ppheaders headers_logs pp_protocol protocol timeout_ms
     timeout_traces_ms timeout_metrics_ms timeout_logs_ms pp_provider_config
     traces pp_provider_config metrics pp_provider_config logs ppiopt
@@ -135,6 +138,7 @@ type 'k make =
   ?timeout_metrics_ms:int ->
   ?timeout_logs_ms:int ->
   ?self_trace:bool ->
+  ?self_metrics:bool ->
   ?http_concurrency_level:int ->
   ?retry_max_attempts:int ->
   ?retry_initial_delay_ms:float ->
@@ -245,9 +249,9 @@ module Env () : ENV = struct
       ?(protocol = get_protocol_from_env "OTEL_EXPORTER_OTLP_PROTOCOL")
       ?(timeout_ms = get_timeout_from_env "OTEL_EXPORTER_OTLP_TIMEOUT" 10_000)
       ?timeout_traces_ms ?timeout_metrics_ms ?timeout_logs_ms
-      ?(self_trace = false) ?http_concurrency_level ?(retry_max_attempts = 3)
-      ?(retry_initial_delay_ms = 100.) ?(retry_max_delay_ms = 5000.)
-      ?(retry_backoff_multiplier = 2.0) =
+      ?(self_trace = false) ?(self_metrics = false) ?http_concurrency_level
+      ?(retry_max_attempts = 3) ?(retry_initial_delay_ms = 100.)
+      ?(retry_max_delay_ms = 5000.) ?(retry_backoff_multiplier = 2.0) =
     let batch_timeout_ = Mtime.Span.(batch_timeout_ms * ms) in
     let traces =
       match traces with
@@ -375,6 +379,7 @@ module Env () : ENV = struct
         metrics;
         logs;
         self_trace;
+        self_metrics;
         http_concurrency_level;
         retry_max_attempts;
         retry_initial_delay_ms;

src/client/exporter_config.mli

@@ -72,6 +72,10 @@ type t = {
       (** If true, the OTEL library will perform some self-instrumentation.
           Default [false].
           @since 0.7 *)
+  self_metrics: bool;
+      (** If true, the OTEL library will regularly emit metrics about itself.
+          Default [false].
+          @since NEXT_RELEASE *)
   http_concurrency_level: int option;
       (** How many HTTP requests can be done simultaneously (at most)? This can
           be used to represent the size of a pool of workers where each worker
@@ -123,6 +127,7 @@ type 'k make =
   ?timeout_metrics_ms:int ->
   ?timeout_logs_ms:int ->
   ?self_trace:bool ->
+  ?self_metrics:bool ->
   ?http_concurrency_level:int ->
   ?retry_max_attempts:int ->
   ?retry_initial_delay_ms:float ->

src/lib/sdk.ml

@@ -90,9 +90,35 @@ let set ?(traces = Provider_config.default) ?(metrics = Provider_config.default)
   Log_provider.set logger
 
 let self_metrics () : Metrics.t list =
+  let now = Clock.now_main () in
+  let emitter_metrics =
+    Emitter.self_metrics (Trace_provider.get ()).emit ~now
+    @ Emitter.self_metrics (Meter_provider.get ()).emit ~now
+    @ Emitter.self_metrics (Log_provider.get ()).emit ~now
+  in
   match get () with
-  | None -> []
-  | Some exp -> exp.Exporter.self_metrics ()
+  | None -> emitter_metrics
+  | Some exp -> exp.Exporter.self_metrics () @ emitter_metrics
+
+open struct
+  let self_metrics_enabled = Atomic.make false
+end
+
+(** Regularly emit metrics about the OTEL SDK. Idempotent. *)
+let setup_self_metrics () =
+  if not (Atomic.exchange self_metrics_enabled true) then (
+    Self_debug.log Info (fun () -> "enabling self metrics");
+    let interval_limiter =
+      Interval_limiter.create ~min_interval:Mtime.Span.(10 * s) ()
+    in
+    let on_tick () =
+      if Interval_limiter.make_attempt interval_limiter then (
+        let ms = self_metrics () in
+        Meter_provider.emit_l ms
+      )
+    in
+    Globals.add_on_tick_callback on_tick
+  )
 
 (* Permanent tick callback to drive batch timeouts on provider emitters *)
 let () =

tests/client/test_client_lib.ml

@@ -8,7 +8,7 @@ let test_config_printing () =
   in
   let expected =
     "{ debug=false; log_level=info; sdk_disabled=false; self_trace=false;\n\
-    \ url_traces=\"http://localhost:4318/v1/traces\";\n\
+    \ self_metrics=false; url_traces=\"http://localhost:4318/v1/traces\";\n\
     \ url_metrics=\"http://localhost:4318/v1/metrics\";\n\
     \ url_logs=\"http://localhost:4318/v1/logs\"; headers=[]; headers_traces=[];\n\
     \ headers_metrics=[]; headers_logs=[]; protocol=http/protobuf;\n\