diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index aebd8efa..ff924cff 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -3,8 +3,6 @@ name: build
 on:
   pull_request:
   push:
-    branches:
-      - master
 
 jobs:
   build:
@@ -18,6 +16,7 @@ jobs:
         ocaml-compiler:
           - 4.08.x
           - 4.13.x
+          - 5.0.x
 
     runs-on: ${{ matrix.os }}
 
diff --git a/Makefile b/Makefile
index 811e33c0..d20dde92 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,6 @@
 
-OPTS=--profile=release
+OPTS=--profile=release --ignore-promoted-rules
+
 all:
 	@dune build @all $(OPTS)
 
diff --git a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
index 4bae616f..d86e5279 100644
--- a/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
+++ b/src/client-cohttp-lwt/opentelemetry_client_cohttp_lwt.ml
@@ -93,7 +93,14 @@ end = struct
   (* send the content to the remote endpoint/path *)
   let send (_self : t) ~(config : Config.t) ~path ~decode (bod : string) :
       ('a, error) result Lwt.t =
-    let full_url = config.url ^ path in
+    let url =
+      let url = config.url in
+      if url <> "" && String.get url (String.length url - 1) = '/' then
+        String.sub url 0 (String.length url - 1)
+      else
+        url
+    in
+    let full_url = url ^ path in
     let uri = Uri.of_string full_url in
 
     let open Cohttp in
@@ -552,6 +559,9 @@ end
 
 let create_backend ?(stop = Atomic.make false) ?(config = Config.make ()) () =
   debug_ := config.debug;
+
+  if config.url <> get_url () then set_url config.url;
+
   let module B =
     Backend
       (struct
diff --git a/src/client-ocurl/opentelemetry_client_ocurl.ml b/src/client-ocurl/opentelemetry_client_ocurl.ml
index 2ad72b95..c8396d06 100644
--- a/src/client-ocurl/opentelemetry_client_ocurl.ml
+++ b/src/client-ocurl/opentelemetry_client_ocurl.ml
@@ -66,8 +66,17 @@ end
 (** start a thread in the background, running [f()] *)
 let start_bg_thread (f : unit -> unit) : Thread.t =
   let run () =
-    (* block some signals: USR1 USR2 TERM PIPE ALARM STOP, see [$ kill -L] *)
-    ignore (Thread.sigmask Unix.SIG_BLOCK [ 10; 12; 13; 14; 15; 19 ] : _ list);
+    let signals =
+      [
+        Sys.sigusr1;
+        Sys.sigusr2;
+        Sys.sigterm;
+        Sys.sigpipe;
+        Sys.sigalrm;
+        Sys.sigstop;
+      ]
+    in
+    ignore (Thread.sigmask Unix.SIG_BLOCK signals : _ list);
     f ()
   in
   Thread.create run ()
@@ -114,7 +123,14 @@ end = struct
     Pbrt.Encoder.reset encoder;
     encode x encoder;
     let data = Pbrt.Encoder.to_string encoder in
-    let url = config.Config.url ^ path in
+    let url =
+      let url = config.Config.url in
+      if url <> "" && String.get url (String.length url - 1) = '/' then
+        String.sub url 0 (String.length url - 1)
+      else
+        url
+    in
+    let url = url ^ path in
     if !debug_ || config.debug then
       Printf.eprintf "opentelemetry: send http POST to %s (%dB)\n%!" url
         (String.length data);
@@ -420,10 +436,12 @@ let create_backend ?(stop = Atomic.make false)
 let setup_ticker_thread ~stop ~sleep_ms (module B : Collector.BACKEND) () =
   let sleep_s = float sleep_ms /. 1000. in
   let tick_loop () =
-    while not @@ Atomic.get stop do
-      Thread.delay sleep_s;
-      B.tick ()
-    done
+    try
+      while not @@ Atomic.get stop do
+        Thread.delay sleep_s;
+        B.tick ()
+      done
+    with B_queue.Closed -> ()
   in
   start_bg_thread tick_loop
 
@@ -432,6 +450,8 @@ let setup_ ?(stop = Atomic.make false) ?(config : Config.t = Config.make ()) ()
   let ((module B) as backend) = create_backend ~stop ~config () in
   Opentelemetry.Collector.set_backend backend;
 
+  if config.url <> get_url () then set_url config.url;
+
   if config.ticker_thread then (
     let sleep_ms = min 5_000 (max 2 config.batch_timeout_ms) in
     ignore (setup_ticker_thread ~stop ~sleep_ms backend () : Thread.t)
diff --git a/src/dune b/src/dune
index 8faa01ee..99867650 100644
--- a/src/dune
+++ b/src/dune
@@ -9,7 +9,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets status_types.ml status_types.mli status_pb.ml status_pb.mli
    status_pp.ml status_pp.mli)
  (deps
@@ -20,7 +20,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets common_types.ml common_types.mli common_pb.ml common_pb.mli
    common_pp.ml common_pp.mli)
  (deps
@@ -33,7 +33,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets resource_types.ml resource_types.mli resource_pb.ml resource_pb.mli
    resource_pp.ml resource_pp.mli)
  (deps
@@ -46,7 +46,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets trace_types.ml trace_types.mli trace_pb.ml trace_pb.mli trace_pp.ml
    trace_pp.mli)
  (deps
@@ -59,7 +59,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets metrics_types.ml metrics_types.mli metrics_pb.ml metrics_pb.mli
    metrics_pp.ml metrics_pp.mli)
  (deps
@@ -72,7 +72,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets logs_types.ml logs_types.mli logs_pb.ml logs_pb.mli logs_pp.ml
    logs_pp.mli)
  (deps
@@ -85,7 +85,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets metrics_service_types.ml metrics_service_types.mli
    metrics_service_pp.ml metrics_service_pp.mli metrics_service_pb.ml
    metrics_service_pb.mli)
@@ -99,7 +99,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets trace_service_types.ml trace_service_types.mli trace_service_pp.ml
    trace_service_pp.mli trace_service_pb.ml trace_service_pb.mli)
  (deps
@@ -112,7 +112,7 @@
 
 (rule
  (alias lint)
- (mode fallback)
+ (mode promote)
  (targets logs_service_types.ml logs_service_types.mli logs_service_pp.ml
    logs_service_pp.mli logs_service_pb.ml logs_service_pb.mli)
  (deps
diff --git a/src/logs_pb.ml b/src/logs_pb.ml
index b604b0d9..2ad391c5 100644
--- a/src/logs_pb.ml
+++ b/src/logs_pb.ml
@@ -244,8 +244,8 @@ let rec decode_logs_data d =
 
 let rec decode_log_record_flags d = 
   match Pbrt.Decoder.int_as_varint d with
-  | 0 -> (Logs_types.Log_record_flag_unspecified:Logs_types.log_record_flags)
-  | 255 -> (Logs_types.Log_record_flag_trace_flags_mask:Logs_types.log_record_flags)
+  | 0 -> (Logs_types.Log_record_flags_do_not_use:Logs_types.log_record_flags)
+  | 255 -> (Logs_types.Log_record_flags_trace_flags_mask:Logs_types.log_record_flags)
   | _ -> Pbrt.Decoder.malformed_variant "log_record_flags"
 
 let rec encode_severity_number (v:Logs_types.severity_number) encoder =
@@ -344,5 +344,5 @@ let rec encode_logs_data (v:Logs_types.logs_data) encoder =
 
 let rec encode_log_record_flags (v:Logs_types.log_record_flags) encoder =
   match v with
-  | Logs_types.Log_record_flag_unspecified -> Pbrt.Encoder.int_as_varint (0) encoder
-  | Logs_types.Log_record_flag_trace_flags_mask -> Pbrt.Encoder.int_as_varint 255 encoder
+  | Logs_types.Log_record_flags_do_not_use -> Pbrt.Encoder.int_as_varint (0) encoder
+  | Logs_types.Log_record_flags_trace_flags_mask -> Pbrt.Encoder.int_as_varint 255 encoder
diff --git a/src/logs_pp.ml b/src/logs_pp.ml
index 99a084a3..408f01d9 100644
--- a/src/logs_pp.ml
+++ b/src/logs_pp.ml
@@ -67,5 +67,5 @@ let rec pp_logs_data fmt (v:Logs_types.logs_data) =
 
 let rec pp_log_record_flags fmt (v:Logs_types.log_record_flags) =
   match v with
-  | Logs_types.Log_record_flag_unspecified -> Format.fprintf fmt "Log_record_flag_unspecified"
-  | Logs_types.Log_record_flag_trace_flags_mask -> Format.fprintf fmt "Log_record_flag_trace_flags_mask"
+  | Logs_types.Log_record_flags_do_not_use -> Format.fprintf fmt "Log_record_flags_do_not_use"
+  | Logs_types.Log_record_flags_trace_flags_mask -> Format.fprintf fmt "Log_record_flags_trace_flags_mask"
diff --git a/src/logs_types.ml b/src/logs_types.ml
index 49c11502..4a383ff7 100644
--- a/src/logs_types.ml
+++ b/src/logs_types.ml
@@ -58,8 +58,8 @@ type logs_data = {
 }
 
 type log_record_flags =
-  | Log_record_flag_unspecified 
-  | Log_record_flag_trace_flags_mask 
+  | Log_record_flags_do_not_use 
+  | Log_record_flags_trace_flags_mask 
 
 let rec default_severity_number () = (Severity_number_unspecified:severity_number)
 
@@ -113,4 +113,4 @@ let rec default_logs_data
   resource_logs;
 }
 
-let rec default_log_record_flags () = (Log_record_flag_unspecified:log_record_flags)
+let rec default_log_record_flags () = (Log_record_flags_do_not_use:log_record_flags)
diff --git a/src/logs_types.mli b/src/logs_types.mli
index ab599f1c..7a9cc1a3 100644
--- a/src/logs_types.mli
+++ b/src/logs_types.mli
@@ -61,8 +61,8 @@ type logs_data = {
 }
 
 type log_record_flags =
-  | Log_record_flag_unspecified 
-  | Log_record_flag_trace_flags_mask 
+  | Log_record_flags_do_not_use 
+  | Log_record_flags_trace_flags_mask 
 
 
 (** {2 Default values} *)
diff --git a/src/metrics_pb.ml b/src/metrics_pb.ml
index 56362ba7..d85e1e72 100644
--- a/src/metrics_pb.ml
+++ b/src/metrics_pb.ml
@@ -116,6 +116,7 @@ type exponential_histogram_data_point_mutable = {
   mutable exemplars : Metrics_types.exemplar list;
   mutable min : float option;
   mutable max : float option;
+  mutable zero_threshold : float;
 }
 
 let default_exponential_histogram_data_point_mutable () : exponential_histogram_data_point_mutable = {
@@ -132,6 +133,7 @@ let default_exponential_histogram_data_point_mutable () : exponential_histogram_
   exemplars = [];
   min = None;
   max = None;
+  zero_threshold = 0.;
 }
 
 type exponential_histogram_mutable = {
@@ -625,6 +627,11 @@ let rec decode_exponential_histogram_data_point d =
     end
     | Some (13, pk) -> 
       Pbrt.Decoder.unexpected_payload "Message(exponential_histogram_data_point), field(13)" pk
+    | Some (14, Pbrt.Bits64) -> begin
+      v.zero_threshold <- Pbrt.Decoder.float_as_bits64 d;
+    end
+    | Some (14, pk) -> 
+      Pbrt.Decoder.unexpected_payload "Message(exponential_histogram_data_point), field(14)" pk
     | Some (_, payload_kind) -> Pbrt.Decoder.skip d payload_kind
   done;
   ({
@@ -641,6 +648,7 @@ let rec decode_exponential_histogram_data_point d =
     Metrics_types.exemplars = v.exemplars;
     Metrics_types.min = v.min;
     Metrics_types.max = v.max;
+    Metrics_types.zero_threshold = v.zero_threshold;
   } : Metrics_types.exponential_histogram_data_point)
 
 let rec decode_exponential_histogram d =
@@ -924,8 +932,8 @@ let rec decode_metrics_data d =
 
 let rec decode_data_point_flags d = 
   match Pbrt.Decoder.int_as_varint d with
-  | 0 -> (Metrics_types.Flag_none:Metrics_types.data_point_flags)
-  | 1 -> (Metrics_types.Flag_no_recorded_value:Metrics_types.data_point_flags)
+  | 0 -> (Metrics_types.Data_point_flags_do_not_use:Metrics_types.data_point_flags)
+  | 1 -> (Metrics_types.Data_point_flags_no_recorded_value_mask:Metrics_types.data_point_flags)
   | _ -> Pbrt.Decoder.malformed_variant "data_point_flags"
 
 let rec encode_exemplar_value (v:Metrics_types.exemplar_value) encoder = 
@@ -1138,6 +1146,8 @@ let rec encode_exponential_histogram_data_point (v:Metrics_types.exponential_his
     Pbrt.Encoder.float_as_bits64 x encoder;
   | None -> ();
   end;
+  Pbrt.Encoder.key (14, Pbrt.Bits64) encoder; 
+  Pbrt.Encoder.float_as_bits64 v.Metrics_types.zero_threshold encoder;
   ()
 
 let rec encode_exponential_histogram (v:Metrics_types.exponential_histogram) encoder = 
@@ -1268,5 +1278,5 @@ let rec encode_metrics_data (v:Metrics_types.metrics_data) encoder =
 
 let rec encode_data_point_flags (v:Metrics_types.data_point_flags) encoder =
   match v with
-  | Metrics_types.Flag_none -> Pbrt.Encoder.int_as_varint (0) encoder
-  | Metrics_types.Flag_no_recorded_value -> Pbrt.Encoder.int_as_varint 1 encoder
+  | Metrics_types.Data_point_flags_do_not_use -> Pbrt.Encoder.int_as_varint (0) encoder
+  | Metrics_types.Data_point_flags_no_recorded_value_mask -> Pbrt.Encoder.int_as_varint 1 encoder
diff --git a/src/metrics_pp.ml b/src/metrics_pp.ml
index b0bf4a25..838343ff 100644
--- a/src/metrics_pp.ml
+++ b/src/metrics_pp.ml
@@ -96,6 +96,7 @@ let rec pp_exponential_histogram_data_point fmt (v:Metrics_types.exponential_his
     Pbrt.Pp.pp_record_field ~first:false "exemplars" (Pbrt.Pp.pp_list pp_exemplar) fmt v.Metrics_types.exemplars;
     Pbrt.Pp.pp_record_field ~first:false "min" (Pbrt.Pp.pp_option Pbrt.Pp.pp_float) fmt v.Metrics_types.min;
     Pbrt.Pp.pp_record_field ~first:false "max" (Pbrt.Pp.pp_option Pbrt.Pp.pp_float) fmt v.Metrics_types.max;
+    Pbrt.Pp.pp_record_field ~first:false "zero_threshold" Pbrt.Pp.pp_float fmt v.Metrics_types.zero_threshold;
   in
   Pbrt.Pp.pp_brk pp_i fmt ()
 
@@ -172,5 +173,5 @@ let rec pp_metrics_data fmt (v:Metrics_types.metrics_data) =
 
 let rec pp_data_point_flags fmt (v:Metrics_types.data_point_flags) =
   match v with
-  | Metrics_types.Flag_none -> Format.fprintf fmt "Flag_none"
-  | Metrics_types.Flag_no_recorded_value -> Format.fprintf fmt "Flag_no_recorded_value"
+  | Metrics_types.Data_point_flags_do_not_use -> Format.fprintf fmt "Data_point_flags_do_not_use"
+  | Metrics_types.Data_point_flags_no_recorded_value_mask -> Format.fprintf fmt "Data_point_flags_no_recorded_value_mask"
diff --git a/src/metrics_types.ml b/src/metrics_types.ml
index bc923ef4..4cd9c09e 100644
--- a/src/metrics_types.ml
+++ b/src/metrics_types.ml
@@ -79,6 +79,7 @@ type exponential_histogram_data_point = {
   exemplars : exemplar list;
   min : float option;
   max : float option;
+  zero_threshold : float;
 }
 
 type exponential_histogram = {
@@ -136,8 +137,8 @@ type metrics_data = {
 }
 
 type data_point_flags =
-  | Flag_none 
-  | Flag_no_recorded_value 
+  | Data_point_flags_do_not_use 
+  | Data_point_flags_no_recorded_value_mask 
 
 let rec default_exemplar_value () : exemplar_value = As_double (0.)
 
@@ -247,6 +248,7 @@ let rec default_exponential_histogram_data_point
   ?exemplars:((exemplars:exemplar list) = [])
   ?min:((min:float option) = None)
   ?max:((max:float option) = None)
+  ?zero_threshold:((zero_threshold:float) = 0.)
   () : exponential_histogram_data_point  = {
   attributes;
   start_time_unix_nano;
@@ -261,6 +263,7 @@ let rec default_exponential_histogram_data_point
   exemplars;
   min;
   max;
+  zero_threshold;
 }
 
 let rec default_exponential_histogram 
@@ -343,4 +346,4 @@ let rec default_metrics_data
   resource_metrics;
 }
 
-let rec default_data_point_flags () = (Flag_none:data_point_flags)
+let rec default_data_point_flags () = (Data_point_flags_do_not_use:data_point_flags)
diff --git a/src/metrics_types.mli b/src/metrics_types.mli
index 5e045f98..8cf43dbf 100644
--- a/src/metrics_types.mli
+++ b/src/metrics_types.mli
@@ -82,6 +82,7 @@ type exponential_histogram_data_point = {
   exemplars : exemplar list;
   min : float option;
   max : float option;
+  zero_threshold : float;
 }
 
 type exponential_histogram = {
@@ -139,8 +140,8 @@ type metrics_data = {
 }
 
 type data_point_flags =
-  | Flag_none 
-  | Flag_no_recorded_value 
+  | Data_point_flags_do_not_use 
+  | Data_point_flags_no_recorded_value_mask 
 
 
 (** {2 Default values} *)
@@ -233,6 +234,7 @@ val default_exponential_histogram_data_point :
   ?exemplars:exemplar list ->
   ?min:float option ->
   ?max:float option ->
+  ?zero_threshold:float ->
   unit ->
   exponential_histogram_data_point
 (** [default_exponential_histogram_data_point ()] is the default value for type [exponential_histogram_data_point] *)
diff --git a/src/opentelemetry.ml b/src/opentelemetry.ml
index 4ad36206..12f43f56 100644
--- a/src/opentelemetry.ml
+++ b/src/opentelemetry.ml
@@ -479,7 +479,7 @@ module Globals = struct
   let service_instance_id = ref None
 
   let instrumentation_library =
-    default_instrumentation_scope ~version:"0.2" ~name:"ocaml-opentelemetry" ()
+    default_instrumentation_scope ~version:"0.2" ~name:"ocaml-otel" ()
 
   (** Global attributes, initially set
       via OTEL_RESOURCE_ATTRIBUTES and modifiable
@@ -507,10 +507,11 @@ module Globals = struct
     List.rev_append (List.filter not_redundant !global_attributes) into
 
   (** Default span kind in {!Span.create}.
-      This will be used in all spans that do not specify [~kind] explicitly.
+      This will be used in all spans that do not specify [~kind] explicitly;
+      it is set to "internal", following directions from the [.proto] file.
       It can be convenient to set "client" or "server" uniformly in here.
       @since 0.4 *)
-  let default_span_kind = ref Proto.Trace.Span_kind_unspecified
+  let default_span_kind = ref Proto.Trace.Span_kind_internal
 
   let mk_attributes ?(service_name = !service_name) ?(attrs = []) () : _ list =
     let l = List.map _conv_key_value attrs in
@@ -1011,8 +1012,8 @@ module Logs = struct
   let pp_severity = Logs_pp.pp_severity_number
 
   type flags = Logs_types.log_record_flags =
-    | Log_record_flag_unspecified
-    | Log_record_flag_trace_flags_mask
+    | Log_record_flags_do_not_use
+    | Log_record_flags_trace_flags_mask
 
   let pp_flags = Logs_pp.pp_log_record_flags
 
diff --git a/tests/dune b/tests/dune
index d2246b32..2d608045 100644
--- a/tests/dune
+++ b/tests/dune
@@ -1,3 +1,6 @@
 (tests
- (names test_trace_context)
- (libraries opentelemetry))
+ (names test_trace_context test_get_url)
+ (libraries
+  opentelemetry
+  opentelemetry-client-ocurl
+  opentelemetry-client-cohttp-lwt))
diff --git a/tests/test_get_url.expected b/tests/test_get_url.expected
new file mode 100644
index 00000000..bafd6ea4
--- /dev/null
+++ b/tests/test_get_url.expected
@@ -0,0 +1,2 @@
+ocurl url = http://localhost:3000
+cohttp url = http://localhost:3000
diff --git a/tests/test_get_url.ml b/tests/test_get_url.ml
new file mode 100644
index 00000000..397996d3
--- /dev/null
+++ b/tests/test_get_url.ml
@@ -0,0 +1,17 @@
+let url = "http://localhost:3000"
+
+let ocurl () =
+  let config = Opentelemetry_client_ocurl.Config.make ~url () in
+  Opentelemetry_client_ocurl.with_setup ~config () @@ fun () ->
+  let url = Opentelemetry_client_ocurl.get_url () in
+  print_endline @@ Printf.sprintf "ocurl url = %s" url
+
+let cohttp () =
+  let config = Opentelemetry_client_cohttp_lwt.Config.make ~url () in
+  Opentelemetry_client_cohttp_lwt.with_setup ~config () @@ fun () ->
+  let url = Opentelemetry_client_cohttp_lwt.get_url () in
+  print_endline @@ Printf.sprintf "cohttp url = %s" url
+
+let () =
+  ocurl ();
+  cohttp ()
diff --git a/vendor/opentelemetry-proto b/vendor/opentelemetry-proto
index 6459e1aa..c4dfbc51 160000
--- a/vendor/opentelemetry-proto
+++ b/vendor/opentelemetry-proto
@@ -1 +1 @@
-Subproject commit 6459e1aae1c22e273ac92be86016f0ae55a2430a
+Subproject commit c4dfbc51f3cd4089778555a2ac5d9bc093ed2956