ocurl: add ticker_interval_ms config

ticker interval will affect how often metrics are emitted,
this doesn't need be related to batch timeouts.

src/client-ocurl/config.ml

@@ -7,6 +7,7 @@ type t = {
   batch_timeout_ms: int;
   bg_threads: int;
   ticker_thread: bool;
+  ticker_interval_ms: int;
   self_trace: bool;
 }
 
@@ -20,19 +21,20 @@ let pp out self =
     batch_timeout_ms;
     bg_threads;
     ticker_thread;
+    ticker_interval_ms;
     self_trace;
   } =
     self
   in
   Format.fprintf out
     "{@[ debug=%B;@ url=%S;@ headers=%a;@ batch_timeout_ms=%d; bg_threads=%d;@ \
-     ticker_thread=%B;@ self_trace=%B @]}"
+     ticker_thread=%B;@ ticker_interval_ms=%d;@ self_trace=%B @]}"
     debug url ppheaders headers batch_timeout_ms bg_threads ticker_thread
-    self_trace
+    ticker_interval_ms self_trace
 
 let make ?(debug = !debug_) ?(url = get_url ()) ?(headers = get_headers ())
-    ?(batch_timeout_ms = 500) ?(bg_threads = 4) ?(ticker_thread = true)
+    ?(batch_timeout_ms = 2_000) ?(bg_threads = 4) ?(ticker_thread = true)
-    ?(self_trace = true) () : t =
+    ?(ticker_interval_ms = 500) ?(self_trace = true) () : t =
   let bg_threads = max 2 (min bg_threads 32) in
   {
     debug;
@@ -41,5 +43,6 @@ let make ?(debug = !debug_) ?(url = get_url ()) ?(headers = get_headers ())
     batch_timeout_ms;
     bg_threads;
     ticker_thread;
+    ticker_interval_ms;
     self_trace;
   }

src/client-ocurl/config.mli

@@ -12,12 +12,18 @@ type t = private {
       (** Number of milliseconds after which we will emit a batch, even
       incomplete.
       Note that the batch might take longer than that, because this is
-      only checked when a new event occurs. Default 500. *)
+      only checked when a new event occurs or when a tick
+      is emitted. Default 2_000. *)
   bg_threads: int;
       (** Are there background threads, and how many? Default [4] *)
   ticker_thread: bool;
       (** If true, start a thread that regularly checks if signals should
           be sent to the collector. Default [true] *)
+  ticker_interval_ms: int;
+      (** Interval for ticker thread, in milliseconds. This is
+          only useful if [ticker_thread] is [true].
+      Default 500.
+      @since NEXT_RELEASE *)
   self_trace: bool;
       (** If true, the OTEL library will also emit its own spans.
           @since NEXT_RELEASE *)
@@ -34,6 +40,7 @@ val make :
   ?batch_timeout_ms:int ->
   ?bg_threads:int ->
   ?ticker_thread:bool ->
+  ?ticker_interval_ms:int ->
   ?self_trace:bool ->
   unit ->
   t

src/client-ocurl/opentelemetry_client_ocurl.ml

@@ -370,14 +370,14 @@ end = struct
           | Event.E_metric m -> Batch.push batches.metrics m
           | Event.E_trace tr -> Batch.push batches.traces tr
           | Event.E_logs logs -> Batch.push batches.logs logs
-          | Event.E_tick -> ()
+          | Event.E_tick ->
+            (* the only impact of "tick" is that it wakes us up regularly *)
+            ()
           | Event.E_flush_all -> must_flush_all := true
         in
 
-        while not (Queue.is_empty local_q) do
+        Queue.iter process_ev local_q;
-          let ev = Queue.pop local_q in
+        Queue.clear local_q;
-          process_ev ev
-        done;
 
         if !must_flush_all then (
           if Batch.len batches.metrics > 0 then send_metrics ();
@@ -545,7 +545,8 @@ let setup_ ?(stop = Atomic.make false) ?(config : Config.t = Config.make ()) ()
   Atomic.set Self_trace.enabled config.self_trace;
 
   if config.ticker_thread then (
-    let sleep_ms = min 5_000 (max 2 config.batch_timeout_ms) in
+    (* at most a minute *)
+    let sleep_ms = min 60_000 (max 2 config.ticker_interval_ms) in
     ignore (setup_ticker_thread ~stop ~sleep_ms backend () : Thread.t)
   );