add more metadata

src/lwt/opentelemetry_lwt.ml

@@ -4,6 +4,8 @@ open Opentelemetry
 module Span_id = Span_id
 module Trace_id = Trace_id
 module Span = Span
+module Globals = Globals
+module Timestamp_ns = Timestamp_ns
 
 module Trace = struct
   open Proto.Trace

src/opentelemetry.ml

@@ -153,6 +153,36 @@ end = struct
   let of_bytes b = assert(Bytes.length b=8); b
 end
 
+(** Process-wide metadata, environment variables, etc. *)
+module Globals = struct
+  open Proto.Common
+
+  let service_name = ref "unknown_service"
+  (** Main service name metadata *)
+
+  let service_namespace = ref None
+  (** Namespace for the service *)
+
+  let instrumentation_library =
+    default_instrumentation_library
+      ~name:"ocaml-opentelemetry" () (* TODO: version, perhaps with dune subst? *)
+
+  (** Global attributes, set via OTEL_RESOURCE_ATTRIBUTE *)
+  let global_attributes : key_value list =
+    let parse_pair s = match String.split_on_char '=' s with
+      | [a;b] -> default_key_value ~key:a  ~value:(Some (String_value b)) ()
+      | _ -> failwith (Printf.sprintf "invalid attribute: %S" s)
+    in
+    try
+      Sys.getenv "OTEL_RESOURCE_ATTRIBUTE" |> String.split_on_char ','
+      |> List.map parse_pair
+    with _ -> []
+
+  (* add global attributes to this list *)
+  let merge_global_attributes_ into : _ list =
+    let not_redundant kv = List.for_all (fun kv' -> kv.key <> kv'.key) into in
+    List.rev_append (List.filter not_redundant global_attributes) into
+end
 
 (* TODO: Event.t, use it in Span *)
 
@@ -241,7 +271,7 @@ end = struct
       ?(kind=Span_kind_unspecified)
       ?(id=Span_id.create())
       ?trace_state
-      ?service_name
+      ?(service_name= !Globals.service_name)
       ?(attrs=[])
       ?status
       ~trace_id ?parent ?(links=[])
@@ -263,13 +293,17 @@ end = struct
              default_key_value ~key:k ~value ())
           attrs
       in
-      let l = match service_name with
+      let l =
+        default_key_value ~key:"service.name"
+          ~value:(Some (String_value service_name)) () :: l
+      in
+      let l = match !Globals.service_namespace with
         | None -> l
         | Some v ->
-          default_key_value ~key:"service.name"
+          default_key_value ~key:"service.namespace"
             ~value:(Some (String_value v)) () :: l
       in
-      l
+      l |> Globals.merge_global_attributes_
     in
 
     let links =
@@ -305,7 +339,9 @@ module Trace = struct
   (** Sync emitter *)
   let emit (spans:span list) : unit =
     let ils =
-      default_instrumentation_library_spans ~spans () in
+      default_instrumentation_library_spans
+        ~instrumentation_library:(Some Globals.instrumentation_library)
+        ~spans () in
     let rs = default_resource_spans ~instrumentation_library_spans:[ils] () in
     Collector.send_trace [rs] ~over:(fun () -> ()) ~ret:(fun () -> ())
 
@@ -396,7 +432,9 @@ module Metrics = struct
   (** Emit some metrics to the collector (sync). *)
   let emit (l:t list) : unit =
     let lm =
-      default_instrumentation_library_metrics ~metrics:l () in
+      default_instrumentation_library_metrics
+        ~instrumentation_library:(Some Globals.instrumentation_library)
+        ~metrics:l () in
     let rm = default_resource_metrics
         ~instrumentation_library_metrics:[lm] () in
     Collector.send_metrics [rm] ~over:ignore ~ret:ignore

tests/emit1.ml

@@ -3,20 +3,18 @@ module T = Opentelemetry
 let spf = Printf.sprintf
 let (let@) f x = f x
 
-let service_name = "t1"
-
 let run () =
   Printf.printf "collector is on %S\n%!" (Opentelemetry_client_ocurl.get_url());
   let i = ref 0 in
   while true do
     let@ (tr,sp) = T.Trace.with_ ~kind:T.Span.Span_kind_producer
-        ~service_name "loop.outer" ~attrs:["i", `Int !i] in
+        "loop.outer" ~attrs:["i", `Int !i] in
 
     for j=0 to 4 do
 
       let@ (_,sp) = T.Trace.with_ ~kind:T.Span.Span_kind_internal
           ~trace_id:tr ~parent:sp
-          ~service_name ~attrs:["j", `Int j]
+          ~attrs:["j", `Int j]
           "loop.inner" in
       Unix.sleepf 2.;
 
@@ -34,7 +32,6 @@ let run () =
         let@ _ =
           T.Trace.with_ ~kind:T.Span.Span_kind_internal
             ~trace_id:tr ~parent:sp
-            ~service_name
             "alloc" in
         (* allocate some stuff *)
         let _arr = Sys.opaque_identity @@ Array.make (25 * 25551) 42.0 in
@@ -47,4 +44,6 @@ let run () =
   done
 
 let () =
+  T.Globals.service_name := Some "t1";
+  T.Globals.service_namespace := Some "ocaml-otel.test";
   Opentelemetry_client_ocurl.with_setup run