From b7a3754eff26f73c509671168c6814d0621f0fde Mon Sep 17 00:00:00 2001
From: Balazs Scheidler <balazs.scheidler@axoflow.com>
Date: Mon, 13 May 2024 18:37:29 +0200
Subject: [PATCH] filterx: skip FilterXScope sync if possible

Signed-off-by: Balazs Scheidler <balazs.scheidler@axoflow.com>
---
 lib/filterx/filterx-scope.c | 38 +++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/lib/filterx/filterx-scope.c b/lib/filterx/filterx-scope.c
index fbf757459b3..21c5b760e49 100644
--- a/lib/filterx/filterx-scope.c
+++ b/lib/filterx/filterx-scope.c
@@ -96,9 +96,7 @@ struct _FilterXScope
 {
   GAtomicCounter ref_cnt;
   GArray *variables;
-  gboolean write_protected;
-  gboolean dirty;
-  gint generation;
+  guint32 generation:20, write_protected, dirty, syncable;
 };
 
 static gboolean
@@ -215,6 +213,10 @@ filterx_scope_register_variable(FilterXScope *self,
   FilterXVariable *v = _register_variable(self, handle, initial_value);
   v->declared = FALSE;
 
+  /* the scope needs to be synced with the message if it holds a
+   * message-tied variable (e.g.  $MSG) */
+  if (!filterx_variable_handle_is_floating(handle))
+    self->syncable = TRUE;
   return v;
 }
 
@@ -245,6 +247,13 @@ filterx_scope_sync(FilterXScope *self, LogMessage *msg)
                 evt_tag_printf("scope", "%p", self));
       return;
     }
+  if (!self->syncable)
+    {
+      msg_trace("Filterx sync: not syncing as there are no variables to sync",
+                evt_tag_printf("scope", "%p", self));
+      self->dirty = FALSE;
+      return;
+    }
 
   GString *buffer = scratch_buffers_alloc();
 
@@ -262,17 +271,16 @@ filterx_scope_sync(FilterXScope *self, LogMessage *msg)
        */
       if (filterx_variable_is_floating(v))
         {
-          if (!v->declared)
-            {
-              msg_trace("Filterx sync: undeclared floating variable, unsetting",
-                        evt_tag_str("variable", log_msg_get_value_name(filterx_variable_get_nv_handle(v), NULL)));
-              filterx_variable_set_value(v, NULL);
-            }
-          else
-            {
-              msg_trace("Filterx sync: declared floating variable, keeping it",
-                        evt_tag_str("variable", log_msg_get_value_name(filterx_variable_get_nv_handle(v), NULL)));
-            }
+          /* we could unset undeclared, floating values here as we are
+           * transitioning to the next filterx block.  But this is also
+           * addressed by the variable generation counter mechanism.  This
+           * means that we will unset those if some expr actually refers to
+           * it.  Also, we skip the entire sync exercise, unless we have
+           * message tied values, so we need to work even if floating
+           * variables are not synced.
+           *
+           * With that said, let's not clear these.
+           */
         }
       else if (v->value == NULL)
         {
@@ -343,10 +351,12 @@ filterx_scope_clone(FilterXScope *other)
 
   if (other->variables->len > 0)
     self->dirty = other->dirty;
+  self->syncable = other->syncable;
   msg_trace("Filterx clone finished",
             evt_tag_printf("scope", "%p", self),
             evt_tag_printf("other", "%p", other),
             evt_tag_int("dirty", self->dirty),
+            evt_tag_int("syncable", self->syncable),
             evt_tag_int("write_protected", self->write_protected));
   /* NOTE: we don't clone weak references, those only relate to mutable
    * objects, which we are cloning anyway */