CP-48195: Instrument forkhelpers with tracing

Instrument `forkhelpers.ml` with tracing.

Signed-off-by: Gabriel Buica <[email protected]>

ocaml/forkexecd/lib/dune

@@ -12,6 +12,7 @@
    xapi-log
    xapi-stdext-pervasives
    xapi-stdext-unix
+   xapi-tracing
  )
  (preprocess
   (pps ppx_deriving_rpc)))

ocaml/forkexecd/lib/forkhelpers.ml

@@ -36,6 +36,10 @@ let test_path =
 
 let runtime_path = Option.value ~default:"/var" test_path
 
+let with_tracing ?traceparent ~name f =
+  let name = "forkhelpers" ^ "." ^ name in
+  Tracing.with_tracing ?parent:traceparent ~name f
+
 let finally = Xapi_stdext_pervasives.Pervasiveext.finally
 
 type pidty = Unix.file_descr * int
@@ -300,8 +304,9 @@ let safe_close_and_exec ?env stdin stdout stderr
     )
     close_fds
 
-let execute_command_get_output_inner ?env ?stdin ?(syslog_stdout = NoSyslogging)
-    ?(redirect_stderr_to_stdout = false) ?(timeout = -1.0) cmd args =
+let execute_command_get_output_inner ?traceparent ?env ?stdin
+    ?(syslog_stdout = NoSyslogging) ?(redirect_stderr_to_stdout = false)
+    ?(timeout = -1.0) cmd args =
   let to_close = ref [] in
   let close fd =
     if List.mem fd !to_close then (
@@ -357,10 +362,12 @@ let execute_command_get_output_inner ?env ?stdin ?(syslog_stdout = NoSyslogging)
     )
     (fun () -> List.iter Unix.close !to_close)
 
-let execute_command_get_output ?env ?(syslog_stdout = NoSyslogging)
+let execute_command_get_output ?traceparent ?env ?(syslog_stdout = NoSyslogging)
     ?(redirect_stderr_to_stdout = false) ?timeout cmd args =
-  execute_command_get_output_inner ?env ?stdin:None ?timeout ~syslog_stdout
-    ~redirect_stderr_to_stdout cmd args
+  with_tracing ~traceparent ~name:"execute_command_get_output"
+  @@ fun traceparent ->
+  execute_command_get_output_inner ?traceparent ?env ?stdin:None ?timeout
+    ~syslog_stdout ~redirect_stderr_to_stdout cmd args
 
 let execute_command_get_output_send_stdin ?env ?(syslog_stdout = NoSyslogging)
     ?(redirect_stderr_to_stdout = false) ?timeout cmd args stdin =

ocaml/forkexecd/lib/forkhelpers.mli

@@ -44,7 +44,8 @@ val default_path : string list
 val default_path_env_pair : string array
 
 val execute_command_get_output :
-     ?env:string array
+     ?traceparent:Tracing.Span.t
+  -> ?env:string array
   -> ?syslog_stdout:syslog_stdout_t
   -> ?redirect_stderr_to_stdout:bool
   -> ?timeout:float

ocaml/xapi/sm_exec.ml

@@ -363,7 +363,8 @@ let exec_xmlrpc ~dbg ?context:_ ?(needs_session = true) (driver : string)
                       ~component:Xapi_observer_components.SMApi ~traceparent
                       ~exe ~args
               in
-              Forkhelpers.execute_command_get_output ?env exe args
+              Forkhelpers.execute_command_get_output ?traceparent:di.tracing
+                ?env exe args
             in
             try (Xml.parse_string output, stderr)
             with e ->