ocurl backend: ticker thread

src/client/opentelemetry_client_ocurl.ml

@@ -33,17 +33,19 @@ module Config = struct
     batch_metrics: int option;
     batch_timeout_ms: int;
     thread: bool;
+    ticker_thread: bool;
   }
 
   let pp out self =
     let ppiopt = Format.pp_print_option Format.pp_print_int in
     let {debug; url; batch_traces; batch_metrics;
-         batch_timeout_ms; thread} = self in
-    Format.fprintf out "{@[ debug=%B;@ url=%S;@ \
-                        batch_traces=%a;@ batch_metrics=%a;@
-                        batch_timeout_ms=%d; thread=%B @]}"
+         batch_timeout_ms; thread; ticker_thread} = self in
+    Format.fprintf out
+      "{@[ debug=%B;@ url=%S;@ \
+       batch_traces=%a;@ batch_metrics=%a;@ \
+       batch_timeout_ms=%d; thread=%B;@ ticker_thread=%B @]}"
       debug url ppiopt batch_traces ppiopt batch_metrics
-      batch_timeout_ms thread
+      batch_timeout_ms thread ticker_thread
 
   let make
       ?(debug= !debug_)
@@ -52,9 +54,10 @@ module Config = struct
       ?(batch_metrics=None)
       ?(batch_timeout_ms=500)
       ?(thread=true)
+      ?(ticker_thread=true)
       () : t =
     { debug; url; batch_traces; batch_metrics; batch_timeout_ms;
-      thread; }
+      thread; ticker_thread; }
 end
 
 (* critical section for [f()] *)
@@ -393,6 +396,7 @@ let mk_emitter ~(config:Config.t) () : (module EMITTER) =
     let m = Mutex.create() in
     let cond = Condition.create() in
 
+    (* loop for the thread that processes events and sends them to collector *)
     let bg_thread () =
       while !continue do
         let@ () = guard in
@@ -413,8 +417,7 @@ let mk_emitter ~(config:Config.t) () : (module EMITTER) =
         C.cleanup();
       end
     in
-
-    let _: Thread.t = Thread.create bg_thread () in
+    let _th_process_batches: Thread.t = Thread.create bg_thread () in
 
     let wakeup () =
       with_mutex_ m (fun () -> Condition.signal cond);
@@ -429,6 +432,19 @@ let mk_emitter ~(config:Config.t) () : (module EMITTER) =
       if batch_timeout() then wakeup()
     in
 
+    if config.ticker_thread then (
+      (* thread that calls [tick()] regularly, to help enforce timeouts *)
+      let tick_thread () =
+        while true do
+          Thread.delay 0.5;
+          tick();
+        done
+      in
+
+      let _th_ticker : Thread.t = Thread.create tick_thread () in
+      ()
+    );
+
     let module M = struct
       let push_trace e =
         E_trace.push e;

src/client/opentelemetry_client_ocurl.mli

@@ -46,6 +46,12 @@ module Config : sig
 
     thread: bool;
     (** Is there a background thread? Default [true] *)
+
+    ticker_thread: bool;
+    (** Is there a ticker thread? Default [true].
+        This thread will regularly call [tick()] on the backend, to make
+        sure it makes progress, and regularly send events to the collector.
+        This option is ignored if [thread=false]. *)
   }
 
   val make :
@@ -54,6 +60,7 @@ module Config : sig
     ?batch_metrics:int option ->
     ?batch_timeout_ms:int ->
     ?thread:bool ->
+    ?ticker_thread:bool ->
     unit -> t
   (** Make a configuration *)