[Project] Implement fuzzy check retransmits backpressure

src/plugins/fuzzy_check.c

@@ -139,7 +139,7 @@ struct fuzzy_client_session {
 	struct rspamd_io_ev ev;
 	int state;
 	int fd;
-	unsigned int retransmits;
+	int retransmits;
 };
 
 struct fuzzy_learn_session {
@@ -157,7 +157,7 @@ struct fuzzy_learn_session {
 	struct ev_loop *event_loop;
 	struct rspamd_io_ev ev;
 	int fd;
-	unsigned int retransmits;
+	int retransmits;
 };
 
 #define FUZZY_CMD_FLAG_REPLIED (1 << 0)
@@ -208,11 +208,11 @@ module_t fuzzy_check_module = {
 	(unsigned int) -1,
 };
 
-INIT_LOG_MODULE(N)
-#define msg_debug_fuzzy_check(...) rspamd_conditional_debug_fast(NULL,                                                          \
-																 task ? task->from_addr : NULL,                                 \
-																 rspamd_task_log_id, M, task ? task->task_pool->tag.uid : NULL, \
-																 RSPAMD_LOG_FUNC,                                               \
+INIT_LOG_MODULE(fuzzy_check)
+#define msg_debug_fuzzy_check(...) rspamd_conditional_debug_fast(NULL,                                                                 \
+																 task ? task->from_addr : NULL,                                        \
+																 rspamd_fuzzy_check_log_id, M, task ? task->task_pool->tag.uid : NULL, \
+																 RSPAMD_LOG_FUNC,                                                      \
 																 __VA_ARGS__)
 
 static inline struct fuzzy_ctx *
@@ -2660,25 +2660,45 @@ fuzzy_check_timer_callback(int fd, short what, void *arg)
 		}
 	}
 
-	if (session->retransmits >= session->rule->retransmits) {
-		msg_err_task("got IO timeout with server %s(%s), after %d/%d retransmits",
-					 rspamd_upstream_name(session->server),
-					 rspamd_inet_address_to_string_pretty(
-						 rspamd_upstream_addr_cur(session->server)),
-					 session->retransmits,
-					 session->rule->retransmits);
-		rspamd_upstream_fail(session->server, TRUE, "timeout");
+	if (session->retransmits >= 0) {
+		if (session->retransmits >= session->rule->retransmits) {
+			msg_err_task("got IO timeout with server %s(%s), after %d/%d retransmits",
+						 rspamd_upstream_name(session->server),
+						 rspamd_inet_address_to_string_pretty(
+							 rspamd_upstream_addr_cur(session->server)),
+						 session->retransmits,
+						 session->rule->retransmits);
+			rspamd_upstream_fail(session->server, TRUE, "timeout");
 
-		if (session->item) {
-			rspamd_symcache_item_async_dec_check(session->task, session->item, M);
+			if (session->item) {
+				rspamd_symcache_item_async_dec_check(session->task, session->item, M);
+			}
+			rspamd_session_remove_event(session->task->s, fuzzy_io_fin, session);
+		}
+		else {
+			/* Apply backpressure here: at least 100ms up to 500ms */
+			session->retransmits++;
+			double backpressure_time = MAX(session->rule->io_timeout * 0.1, 0.1) * session->retransmits;
+			/* Do not make delay more than 500ms for performance considerations */
+			backpressure_time = MIN(backpressure_time, 0.5);
+			/* Inverse to distinguish */
+			msg_debug_fuzzy_check("backpressure for %.2f milliseconds (server=%s), retransmits: %d;",
+								  backpressure_time * 1000,
+								  rspamd_upstream_name(session->server),
+								  session->retransmits);
+			session->retransmits = -(session->retransmits);
+			/* Disable write event for the time of backpressure */
+			rspamd_ev_watcher_reschedule_at(session->event_loop,
+											&session->ev, EV_READ,
+											backpressure_time);
 		}
-		rspamd_session_remove_event(session->task->s, fuzzy_io_fin, session);
 	}
 	else {
 		/* Plan write event */
-		rspamd_ev_watcher_reschedule(session->event_loop,
-									 &session->ev, EV_READ | EV_WRITE);
-		session->retransmits++;
+		rspamd_ev_watcher_reschedule_at(session->event_loop,
+										&session->ev, EV_READ | EV_WRITE,
+										session->rule->io_timeout);
+		session->retransmits = -(session->retransmits);
 	}
 }
 
@@ -2801,51 +2821,71 @@ fuzzy_controller_timer_callback(int fd, short what, void *arg)
 
 	task = session->task;
 
-	if (session->retransmits >= session->rule->retransmits) {
-		rspamd_upstream_fail(session->server, TRUE, "timeout");
-		msg_err_task_check("got IO timeout with server %s(%s), "
-						   "after %d/%d retransmits",
-						   rspamd_upstream_name(session->server),
-						   rspamd_inet_address_to_string_pretty(
-							   rspamd_upstream_addr_cur(session->server)),
-						   session->retransmits,
-						   session->rule->retransmits);
-
-		if (session->session) {
-			rspamd_session_remove_event(session->session, fuzzy_controller_lua_fin,
-										session);
-		}
-		else {
-			if (session->http_entry) {
-				rspamd_controller_send_error(session->http_entry,
-											 500, "IO timeout with fuzzy storage");
+	if (session->retransmits >= 0) {
+		if (session->retransmits >= session->rule->retransmits) {
+			rspamd_upstream_fail(session->server, TRUE, "timeout");
+			msg_err_task_check("got IO timeout with server %s(%s), "
+							   "after %d/%d retransmits",
+							   rspamd_upstream_name(session->server),
+							   rspamd_inet_address_to_string_pretty(
+								   rspamd_upstream_addr_cur(session->server)),
+							   session->retransmits,
+							   session->rule->retransmits);
+
+			if (session->session) {
+				rspamd_session_remove_event(session->session, fuzzy_controller_lua_fin,
+											session);
 			}
+			else {
+				if (session->http_entry) {
+					rspamd_controller_send_error(session->http_entry,
+												 500, "IO timeout with fuzzy storage");
+				}
 
-			if (*session->saved > 0) {
-				(*session->saved)--;
-				if (*session->saved == 0) {
-					if (session->http_entry) {
-						rspamd_task_free(session->task);
+				if (*session->saved > 0) {
+					(*session->saved)--;
+					if (*session->saved == 0) {
+						if (session->http_entry) {
+							rspamd_task_free(session->task);
+						}
+
+						session->task = NULL;
 					}
+				}
 
-					session->task = NULL;
+				if (session->http_entry) {
+					rspamd_http_connection_unref(session->http_entry->conn);
 				}
-			}
 
-			if (session->http_entry) {
-				rspamd_http_connection_unref(session->http_entry->conn);
+				rspamd_ev_watcher_stop(session->event_loop,
+									   &session->ev);
+				close(session->fd);
 			}
-
-			rspamd_ev_watcher_stop(session->event_loop,
-								   &session->ev);
-			close(session->fd);
+		}
+		else {
+			/* Apply backpressure here: at least 100ms up to 500ms */
+			session->retransmits++;
+			double backpressure_time = MAX(session->rule->io_timeout * 0.1, 0.1) * session->retransmits;
+			/* Do not make delay more than 500ms for performance considerations */
+			backpressure_time = MIN(backpressure_time, 0.5);
+			/* Inverse to distinguish */
+			msg_debug_fuzzy_check("backpressure for %.2f milliseconds (server=%s), retransmits: %d;",
+								  backpressure_time * 1000,
+								  rspamd_upstream_name(session->server),
+								  session->retransmits);
+			session->retransmits = -(session->retransmits);
+			/* Disable write event for the time of backpressure */
+			rspamd_ev_watcher_reschedule_at(session->event_loop,
+											&session->ev, EV_READ,
+											backpressure_time);
 		}
 	}
 	else {
-		/* Plan write event */
-		rspamd_ev_watcher_reschedule(session->event_loop,
-									 &session->ev, EV_READ | EV_WRITE);
-		session->retransmits++;
+		/* Backpressure done, plan write event */
+		rspamd_ev_watcher_reschedule_at(session->event_loop,
+										&session->ev, EV_READ | EV_WRITE,
+										session->rule->io_timeout);
+		session->retransmits = -(session->retransmits);
 	}
 }