xapi.conf: introduce test_open

Default is 0 but can be set to 1024 to test for the absence of Unix.select.

Signed-off-by: Edwin Török <[email protected]>

ocaml/xapi/xapi.ml

@@ -922,12 +922,21 @@ let report_tls_verification ~__context =
   let value = Stunnel_client.get_verify_by_default () in
   Db.Host.set_tls_verification_enabled ~__context ~self ~value
 
+let test_open () =
+  let count = !Xapi_globs.test_open in
+  if count > 0 then begin
+    debug "TEST: opening %d file descriptors" count;
+    Xapi_stdext_unix.Unixext.test_open count;
+    debug "TEST: opened %d files" count
+  end
+
 let server_init () =
   let print_server_starting_message () =
     debug "(Re)starting xapi, pid: %d" (Unix.getpid ()) ;
     debug "on_system_boot=%b pool_role=%s" !Xapi_globs.on_system_boot
       (Pool_role.string_of (Pool_role.get_role ()))
   in
+  test_open ();
   Unixext.unlink_safe "/etc/xensource/boot_time_info_updated" ;
   (* Record the initial value of Master_connection.connection_timeout and set it to 'never'. When we are a slave who
      has just started up we want to wait forever for the master to appear. (See CA-25481) *)

ocaml/xapi/xapi_globs.ml

@@ -1029,6 +1029,8 @@ let python3_path = ref "/usr/bin/python3"
 let observer_experimental_components =
   ref (StringSet.singleton Constants.observer_component_smapi)
 
+let test_open = ref 0
+
 let xapi_globs_spec =
   [
     ( "master_connection_reset_timeout"
@@ -1114,6 +1116,7 @@ let xapi_globs_spec =
   ; ("max_spans", Int max_spans)
   ; ("max_traces", Int max_traces)
   ; ("max_observer_file_size", Int max_observer_file_size)
+  ; ("test_open", Int test_open)
   ]
 
 let timeout ref str = ref := Xapi_stdext_unix.Unixext.Timeout.of_string str

ocaml/xenopsd/lib/xenopsd.ml

@@ -128,6 +128,8 @@ let max_bytes_of_xenstore_entries entries =
 
 let vm_guest_agent_xenstore_quota_bytes = ref (25 * 1024 * 1024)
 
+let test_open = ref 0
+
 let options =
   [
     ( "queue"
@@ -276,6 +278,11 @@ let options =
     , "Maximum size in bytes of VM xenstore-data field, and guest metrics \
        copied from guest's vm-data/ and data/ xenstore tree"
     )
+  ; ( "test-open"
+    , Arg.Set_int test_open
+    , (fun () -> string_of_int !test_open)
+    , "TESTING only: open N file descriptors"
+    )
   ]
 
 let path () = Filename.concat !sockets_path "xenopsd"
@@ -424,9 +431,18 @@ let log_uncaught_exception e bt =
   error "xenopsd exitted with an uncaught exception: %s" (Printexc.to_string e) ;
   log_raw_backtrace bt
 
+let test_open () =
+  let count = !test_open in
+  if count > 0 then (
+    debug "TEST: opening %d file descriptors" count ;
+    Xapi_stdext_unix.Unixext.test_open count ;
+    debug "TEST: opened %d file descriptors" count
+  )
+
 let main backend =
   Printexc.record_backtrace true ;
   Printexc.set_uncaught_exception_handler log_uncaught_exception ;
+  test_open () ;
   (* Set service name for Tracing *)
   Tracing_export.set_service_name "xenopsd" ;
   (* Listen for transferred file descriptors *)