Specify and document the Signal_gatherer API

tests/client_e2e/signal_gatherer.ml

@@ -2,7 +2,6 @@
 
 module Client = Opentelemetry_client
 module Signal = Client.Signal
-module Proto = Opentelemetry.Proto
 open Lwt.Syntax
 
 (* Server to collect telemetry data *)
@@ -18,11 +17,6 @@ module Server = struct
     (* in *)
     Lwt.return ()
 
-  let metrics req data =
-    let metrics = Signal.Decode.metrics data in
-    let+ () = dbg_request "metrics" req Signal.Pp.metrics metrics in
-    Signal.Metrics metrics
-
   let handler push_signal _socket (request : Http.Request.t)
       (body : Cohttp_lwt.Body.t) =
     let* data = Cohttp_lwt.Body.to_string body in
@@ -89,14 +83,6 @@ module Tested_program = struct
     validate_exit result
 end
 
-let collect_traces ~port program_to_test push_signals () =
-  let* () =
-    Lwt.pick
-      [ Server.run port push_signals; Tested_program.run program_to_test ]
-  in
-  (* Let the tester know all the signals have be sent *)
-  Lwt.return (push_signals None)
-
 let default_port =
   String.split_on_char ':' Client.Config.default_url |> function
   (* Extracting the port from 'http://foo:<port>' *)
@@ -107,7 +93,11 @@ let gather_signals ?(port = default_port) program_to_test =
   Lwt_main.run
   @@
   let stream, push = Lwt_stream.create () in
-  let* () = collect_traces ~port program_to_test push () in
+  let* () =
+    Lwt.pick [ Server.run port push; Tested_program.run program_to_test ]
+  in
+  (* Close out the stream *)
+  push None;
   Lwt_stream.to_list stream
 
 (* Just run the server, and print the signals gathered. *)

tests/client_e2e/signal_gatherer.mli

@@ -0,0 +1,21 @@
+(** A test utility for running a signal emitting executable alongside a minimal
+    server that can receive the signals make them available for inspection. *)
+
+val gather_signals :
+  ?port:int -> string list -> Opentelemetry_client.Signal.t list
+(** [gather_signals program_to_test] is a list of all the signals emitted by the
+    [program_to_test], which the server was able to record. This function
+    assumes that the program to test will be sending its signals to the
+    localhost on [port].
+
+    @param port
+      the port where signals will be received. Default is port set in
+      {!Opentelemetry_client.Config.default_url}. *)
+
+val run : ?port:int -> unit -> unit
+(** [run ()] runs a signal gathering server and prints all batches of signals
+    received to stdout.
+
+    @param port
+      the port where signals will be received. Default is port set in
+      {!Opentelemetry_client.Config.default_url}. *)