CP-48676: Don't check resuable pool session validity by default

Add a new flag validate-reusable-pool-session to xapi globs which skips
the reusable pool session validity check if it is false. This saves time
as we are no longer calling pool.get_all for each session.

Signed-off-by: Steven Woods <[email protected]>

Author: snwoods

ocaml/xapi/xapi_globs.ml

@@ -1078,6 +1078,9 @@ let disable_webserver = ref false
 let reuse_pool_sessions = ref true
 (* Enables the reuse of pool sessions, speeding up intrapool communication *)
 
+let validate_reusable_pool_session = ref false
+(* Validate a reusable session before each use. This is slower and should not be required *)
+
 let test_open = ref 0
 
 let tgroups_enabled = ref false
@@ -1717,6 +1720,11 @@ let other_options =
     , (fun () -> string_of_bool !reuse_pool_sessions)
     , "Enable the reuse of pool sessions"
     )
+  ; ( "validate-reusable-pool-session"
+    , Arg.Set validate_reusable_pool_session
+    , (fun () -> string_of_bool !validate_reusable_pool_session)
+    , "Enable validation of reusable pool sessions before use"
+    )
   ]
 
 (* The options can be set with the variable xapiflags in /etc/sysconfig/xapi.

ocaml/xapi/xapi_session.ml

@@ -671,9 +671,12 @@ let login_no_password_common ~__context ~uname ~originator ~host ~pool
     ~rbac_permissions ~db_ref ~client_certificate =
   Context.with_tracing ~originator ~__context __FUNCTION__ @@ fun __context ->
   let is_valid_session session_id =
-    if session_id = Ref.null then
-      false
-    else
+    match (session_id, !Xapi_globs.validate_reusable_pool_session) with
+    | session, _ when session = Ref.null ->
+        false
+    | _, false ->
+        true
+    | session_id, true -> (
       try
         (* Call an API function to check the session is still valid *)
         let rpc = Helpers.make_rpc ~__context in
@@ -682,6 +685,7 @@ let login_no_password_common ~__context ~uname ~originator ~host ~pool
       with Api_errors.Server_error (err, _) ->
         debug "%s: Invalid session: %s" __FUNCTION__ err ;
         false
+    )
   in
   let create_session () =
     login_no_password_common_create_session ~__context ~uname ~originator ~host