CP-51693: introduce feature flag to use JSONRPC for internal pool communication (#6123)

Author: psafont

ocaml/tests/common/mock_rpc.ml

@@ -25,7 +25,7 @@ let rpc __context call =
       Rpc.
         {
           success= true
-        ; contents= contents |> Xmlrpc.to_string |> Xmlrpc.of_string
+        ; contents= contents |> Jsonrpc.to_string |> Jsonrpc.of_string
         ; is_notification= false
         }
   | "VM.update_allowed_operations", [session_id_rpc; self_rpc] ->

ocaml/xapi/helpers.ml

@@ -395,7 +395,13 @@ let make_rpc ~__context rpc : Rpc.response =
   let subtask_of = Ref.string_of (Context.get_task_id __context) in
   let open Xmlrpc_client in
   let tracing = Context.set_client_span __context in
-  let http = xmlrpc ~subtask_of ~version:"1.1" "/" ~tracing in
+  let dorpc, path =
+    if !Xapi_globs.use_xmlrpc then
+      (XMLRPC_protocol.rpc, "/")
+    else
+      (JSONRPC_protocol.rpc, "/jsonrpc")
+  in
+  let http = xmlrpc ~subtask_of ~version:"1.1" path ~tracing in
   let transport =
     if Pool_role.is_master () then
       Unix Xapi_globs.unix_domain_socket
@@ -407,7 +413,7 @@ let make_rpc ~__context rpc : Rpc.response =
         , !Constants.https_port
         )
   in
-  XMLRPC_protocol.rpc ~srcstr:"xapi" ~dststr:"xapi" ~transport ~http rpc
+  dorpc ~srcstr:"xapi" ~dststr:"xapi" ~transport ~http rpc
 
 let make_timeboxed_rpc ~__context timeout rpc : Rpc.response =
   let subtask_of = Ref.string_of (Context.get_task_id __context) in

ocaml/xapi/xapi_globs.ml

@@ -1025,6 +1025,8 @@ let max_spans = ref 10000
 
 let max_traces = ref 10000
 
+let use_xmlrpc = ref true
+
 let compress_tracing_files = ref true
 
 let prefer_nbd_attach = ref false
@@ -1436,6 +1438,11 @@ let other_options =
     , (fun () -> string_of_bool !allow_host_sched_gran_modification)
     , "Allows to modify the host's scheduler granularity"
     )
+  ; ( "use-xmlrpc"
+    , Arg.Set use_xmlrpc
+    , (fun () -> string_of_bool !use_xmlrpc)
+    , "Use XMLRPC (deprecated) for internal communication or JSONRPC"
+    )
   ; ( "extauth_ad_backend"
     , Arg.Set_string extauth_ad_backend
     , (fun () -> !extauth_ad_backend)