Merge pull request #55 from imandra-ai/simon/fix-gc-metrics-2024-07-22

fix: emit GC metrics even in the absence of custom metrics

src/client-ocurl/opentelemetry_client_ocurl.ml

@@ -289,8 +289,8 @@ end = struct
 
   let batch_max_size_ = 200
 
-  let should_send_batch_ ~config ~now (b : _ Batch.t) : bool =
-    Batch.len b > 0
+  let should_send_batch_ ?(side = []) ~config ~now (b : _ Batch.t) : bool =
+    (Batch.len b > 0 || side != [])
     && (Batch.len b >= batch_max_size_
        ||
        let timeout = Mtime.Span.(config.Config.batch_timeout_ms * ms) in
@@ -348,12 +348,17 @@ end = struct
         Queue.clear local_q;
 
         if !must_flush_all then (
-          if Batch.len batches.metrics > 0 then send_metrics ();
+          if Batch.len batches.metrics > 0 || not (AList.is_empty gc_metrics)
+          then
+            send_metrics ();
           if Batch.len batches.logs > 0 then send_logs ();
           if Batch.len batches.traces > 0 then send_traces ()
         ) else (
           let now = Mtime_clock.now () in
-          if should_send_batch_ ~config ~now batches.metrics then
+          if
+            should_send_batch_ ~config ~now batches.metrics
+              ~side:(AList.get gc_metrics)
+          then
             send_metrics ();
 
           if should_send_batch_ ~config ~now batches.traces then send_traces ();

src/core/AList.ml

@@ -4,6 +4,11 @@ type 'a t = 'a list Atomic.t
 
 let make () = Atomic.make []
 
+let[@inline] is_empty self : bool =
+  match Atomic.get self with
+  | [] -> true
+  | _ :: _ -> false
+
 let get = Atomic.get
 
 let add self x =

src/core/AList.mli

@@ -5,6 +5,8 @@ type 'a t
 val get : 'a t -> 'a list
 (** Snapshot *)
 
+val is_empty : _ t -> bool
+
 val make : unit -> 'a t
 
 val add : 'a t -> 'a -> unit