Merge pull request #5241 from snwoods/private/stevenwo/CP-46004

CP-46004: Finish eventgen span to remove spans table clutter

ocaml/libs/tracing/tracing.ml

@@ -774,6 +774,12 @@ module Export = struct
               [
                 ("export.span.count", List.length all_spans |> string_of_int)
               ; ("export.endpoint", endpoint_to_string endpoint)
+              ; ( "xs.tracing.spans_table.count"
+                , Hashtbl.length Spans.spans |> string_of_int
+                )
+              ; ( "xs.tracing.finished_spans_table.count"
+                , Hashtbl.length traces |> string_of_int
+                )
               ]
             in
             let@ _ = with_tracing ~parent ~attributes ~name in

ocaml/xapi/eventgen.ml

@@ -95,8 +95,7 @@ let events_of_other_tbl_refs other_tbl_refs =
 open Db_cache_types
 open Db_action_helper
 
-let database_callback event db =
-  let context = Context.make "eventgen" in
+let database_callback_inner event db context =
   let other_tbl_refs tblname = follow_references tblname in
   let other_tbl_refs_for_this_field tblname fldname =
     List.filter (fun (_, fld) -> fld = fldname) (other_tbl_refs tblname)
@@ -258,3 +257,9 @@ let database_callback event db =
               events_notify ~snapshot:s tbl "mod" ref
           )
         other_tbl_events
+
+let database_callback event db =
+  let context = Context.make "eventgen" in
+  Xapi_stdext_pervasives.Pervasiveext.finally
+    (fun () -> database_callback_inner event db context)
+    (fun () -> Context.complete_tracing context)