diff --git a/src/client/exporter_stdout.ml b/src/client/exporter_stdout.ml
index 551a5f4f..b65482e6 100644
--- a/src/client/exporter_stdout.ml
+++ b/src/client/exporter_stdout.ml
@@ -7,13 +7,17 @@ open struct
   let pp_span out (sp : OTEL.Span.t) =
     let open OTEL in
     Format.fprintf out
-      "@[<2>SPAN {@ trace_id: %a@ span_id: %a@ name: %S@ start: %a@ end: %a@]}"
+      "@[<2>SPAN {@ trace_id: %a@ span_id: %a@ name: %S@ start: %a@ end: %a@ \
+       dur: %.6fs@]}"
       Trace_id.pp
       (Trace_id.of_bytes sp.trace_id)
       Span_id.pp
       (Span_id.of_bytes sp.span_id)
       sp.name Timestamp_ns.pp_debug sp.start_time_unix_nano
       Timestamp_ns.pp_debug sp.end_time_unix_nano
+      ((Int64.to_float sp.end_time_unix_nano
+       -. Int64.to_float sp.start_time_unix_nano)
+      /. 1e9)
 
   let pp_log out l =
     Format.fprintf out "@[<2>LOG %a@]" Proto.Logs.pp_log_record l
@@ -34,7 +38,7 @@ open struct
     )
 end
 
-let stdout ?(clock = OTEL.Clock.Main.dynamic_main) () : OTEL.Exporter.t =
+let stdout ?(clock = OTEL.Clock.ptime_clock) () : OTEL.Exporter.t =
   let open Opentelemetry_util in
   let out = Format.std_formatter in
   let mutex = Mutex.create () in
diff --git a/src/client/generic_consumer_exporter.ml b/src/client/generic_consumer_exporter.ml
index cbbae6eb..790462b0 100644
--- a/src/client/generic_consumer_exporter.ml
+++ b/src/client/generic_consumer_exporter.ml
@@ -52,10 +52,12 @@ end = struct
 
   let tick (self : state) = Notifier.trigger self.notify
 
-  (** Shutdown one worker, when the queue is closed *)
+  (** Shutdown worker *)
   let shutdown_worker (self : state) : unit =
-    (* we were the last worker *)
-    (* Printf.eprintf "worker %d: last one!\n%!" tid; *)
+    (* only one worker, so, turn off exporter *)
+    OTEL.Exporter.shutdown self.exp;
+
+    (* and we are shut down! *)
     Atomic.set self.status Stopped;
     Aswitch.turn_off self.active_trigger
 
diff --git a/src/client/bounded_queue_sync.ml b/src/client/sync/bounded_queue_sync.ml
similarity index 100%
rename from src/client/bounded_queue_sync.ml
rename to src/client/sync/bounded_queue_sync.ml
diff --git a/src/client/bounded_queue_sync.mli b/src/client/sync/bounded_queue_sync.mli
similarity index 100%
rename from src/client/bounded_queue_sync.mli
rename to src/client/sync/bounded_queue_sync.mli
diff --git a/src/client/sync/common_.ml b/src/client/sync/common_.ml
new file mode 100644
index 00000000..6a337b5c
--- /dev/null
+++ b/src/client/sync/common_.ml
@@ -0,0 +1 @@
+module OTEL = Opentelemetry
diff --git a/src/client/sync/dune b/src/client/sync/dune
new file mode 100644
index 00000000..d9bd0731
--- /dev/null
+++ b/src/client/sync/dune
@@ -0,0 +1,23 @@
+(library
+ (name opentelemetry_client_sync)
+ (public_name opentelemetry-client.sync)
+ (flags
+  :standard
+  -open
+  Opentelemetry_util
+  -open
+  Opentelemetry_client
+  -open
+  Opentelemetry_atomic)
+ (libraries
+  opentelemetry.util
+  opentelemetry.atomic
+  opentelemetry.emitter
+  (re_export opentelemetry.core)
+  (re_export opentelemetry)
+  (re_export opentelemetry-client)
+  (re_export threads)
+  mtime
+  mtime.clock.os
+  unix)
+ (synopsis "Synchronous/threading-related helpers for opentelemetry-client"))
diff --git a/src/client/io_sync.ml b/src/client/sync/io_sync.ml
similarity index 100%
rename from src/client/io_sync.ml
rename to src/client/sync/io_sync.ml
diff --git a/src/client/io_sync.mli b/src/client/sync/io_sync.mli
similarity index 100%
rename from src/client/io_sync.mli
rename to src/client/sync/io_sync.mli
diff --git a/src/client/notifier_sync.ml b/src/client/sync/notifier_sync.ml
similarity index 100%
rename from src/client/notifier_sync.ml
rename to src/client/sync/notifier_sync.ml
diff --git a/src/client/notifier_sync.mli b/src/client/sync/notifier_sync.mli
similarity index 100%
rename from src/client/notifier_sync.mli
rename to src/client/sync/notifier_sync.mli
diff --git a/src/client/sync/shutdown_sync.ml b/src/client/sync/shutdown_sync.ml
new file mode 100644
index 00000000..97ab5c2f
--- /dev/null
+++ b/src/client/sync/shutdown_sync.ml
@@ -0,0 +1,14 @@
+open Common_
+
+(** Shutdown this exporter and block the thread until it's done.
+
+    {b NOTE}: this might deadlock if the exporter runs entirely in the current
+    thread! *)
+let shutdown (exp : OTEL.Exporter.t) : unit =
+  let q = Sync_queue.create () in
+  OTEL.Exporter.on_stop exp (Sync_queue.push q);
+  OTEL.Exporter.shutdown exp;
+  Sync_queue.pop q
+
+(** Shutdown main exporter and wait *)
+let shutdown_main () : unit = Option.iter shutdown (OTEL.Main_exporter.get ())
diff --git a/src/client/sync_queue.ml b/src/client/sync/sync_queue.ml
similarity index 100%
rename from src/client/sync_queue.ml
rename to src/client/sync/sync_queue.ml
diff --git a/src/client/sync_queue.mli b/src/client/sync/sync_queue.mli
similarity index 100%
rename from src/client/sync_queue.mli
rename to src/client/sync/sync_queue.mli
diff --git a/src/client/util_thread.ml b/src/client/sync/util_thread.ml
similarity index 100%
rename from src/client/util_thread.ml
rename to src/client/sync/util_thread.ml