[Feature] Implement real priorities for pre and post filters

Now pre and post filters with higher priorities have guarantee to be
finished before (or after in case of postfilters) filters with lower priorities.
Previously, there was a guarantee for start time which was not enough
for many use cases.

src/libserver/symbols_cache.c

@@ -1488,6 +1488,7 @@ rspamd_symbols_cache_process_symbols (struct rspamd_task * task,
 	gint i;
 	gdouble total_microseconds = 0;
 	gboolean all_done;
+	gint saved_priority;
 	const gdouble max_microseconds = 3e5;
 	guint start_events_pending;
 	gdouble pr = rspamd_random_double_fast ();
@@ -1512,19 +1513,38 @@ rspamd_symbols_cache_process_symbols (struct rspamd_task * task,
 
 	switch (checkpoint->pass) {
 	case RSPAMD_CACHE_PASS_INIT:
+	case RSPAMD_CACHE_PASS_PREFILTERS:
 		/* Check for prefilters */
+		saved_priority = G_MININT;
+
 		for (i = 0; i < (gint)cache->prefilters->len; i ++) {
 			item = g_ptr_array_index (cache->prefilters, i);
 
-			if (!isset (checkpoint->processed_bits, item->id * 2)) {
+			if (!isset (checkpoint->processed_bits, item->id * 2) &&
+					!isset (checkpoint->processed_bits, item->id * 2 + 1)) {
+				/* Check priorities */
+				if (saved_priority == G_MININT) {
+					saved_priority = item->priority;
+				}
+				else {
+					if (item->priority < saved_priority &&
+							rspamd_session_events_pending (task->s) > start_events_pending) {
+						/*
+						 * Delay further checks as we have higher
+						 * priority filters to be processed
+						 */
+						checkpoint->pass = RSPAMD_CACHE_PASS_PREFILTERS;
+						return TRUE;
+					}
+				}
 				rspamd_symbols_cache_check_symbol (task, cache, item,
 						checkpoint, &total_microseconds, pr);
 			}
 		}
+
 		checkpoint->pass = RSPAMD_CACHE_PASS_WAIT_PREFILTERS;
 		break;
 
-	case RSPAMD_CACHE_PASS_PREFILTERS:
 	case RSPAMD_CACHE_PASS_WAIT_PREFILTERS:
 		all_done = TRUE;
 
@@ -1643,11 +1663,29 @@ rspamd_symbols_cache_process_symbols (struct rspamd_task * task,
 		break;
 
 	case RSPAMD_CACHE_PASS_POSTFILTERS:
-		/* Check for prefilters */
+		/* Check for postfilters */
+		saved_priority = G_MININT;
+
 		for (i = 0; i < (gint)cache->postfilters->len; i ++) {
 			item = g_ptr_array_index (cache->postfilters, i);
 
-			if (!isset (checkpoint->processed_bits, item->id * 2)) {
+			if (!isset (checkpoint->processed_bits, item->id * 2) &&
+					!isset (checkpoint->processed_bits, item->id * 2 + 1)) {
+				/* Check priorities */
+				if (saved_priority == G_MININT) {
+					saved_priority = item->priority;
+				}
+				else {
+					if (item->priority < saved_priority &&
+							rspamd_session_events_pending (task->s) > start_events_pending) {
+						/*
+						 * Delay further checks as we have higher
+						 * priority filters to be processed
+						 */
+						checkpoint->pass = RSPAMD_CACHE_PASS_POSTFILTERS;
+						return TRUE;
+					}
+				}
 				rspamd_symbols_cache_check_symbol (task, cache, item,
 						checkpoint, &total_microseconds, pr);
 			}