Introduce new config option worker_accept_treshold

This configuration option limits the maximum number
of connections a worker process can accept() in a single
event loop.

It can be used to more evenly spread out incoming connections
across workers when new connections arrive in a burst.

conf/kore.conf.example

@@ -24,6 +24,14 @@ workers		4
 # Limit of maximum open files per worker.
 #worker_rlimit_nofiles		1024
 
+# Limit the number of new connections a worker can accept
+# in a single event loop.
+# NOTE: This can have a *MASSIVE* impact as this controls
+# how new connections are spread across worker processes.
+#
+# This is disabled by default.
+#worker_accept_treshold		0
+
 # Store the main process its pid in this file.
 #pidfile	kore.pid
 

includes/kore.h

@@ -361,6 +361,7 @@ extern u_int8_t			worker_count;
 extern u_int32_t		worker_rlimit_nofiles;
 extern u_int32_t		worker_max_connections;
 extern u_int32_t		worker_active_connections;
+extern u_int32_t		worker_accept_treshold;
 extern u_int64_t		kore_websocket_maxframe;
 extern u_int64_t		kore_websocket_timeout;
 extern u_int32_t		kore_socket_backlog;

src/bsd.c

@@ -153,6 +153,10 @@ kore_platform_event_wait(u_int64_t timer)
 
 			while (worker_active_connections <
 			    worker_max_connections) {
+				if (worker_accept_treshold != 0 &&
+				    r >= worker_accept_treshold)
+					break;
+
 				if (!kore_connection_accept(l, &c)) {
 					r = 1;
 					break;

src/config.c

@@ -44,6 +44,7 @@ static int		configure_certfile(char **);
 static int		configure_certkey(char **);
 static int		configure_rlimit_nofiles(char **);
 static int		configure_max_connections(char **);
+static int		configure_accept_treshold(char **);
 static int		configure_ssl_cipher(char **);
 static int		configure_ssl_dhparam(char **);
 static int		configure_ssl_no_compression(char **);
@@ -92,6 +93,7 @@ static struct {
 	{ "workers",			configure_workers },
 	{ "worker_max_connections",	configure_max_connections },
 	{ "worker_rlimit_nofiles",	configure_rlimit_nofiles },
+	{ "worker_accept_treshold",	configure_accept_treshold },
 	{ "pidfile",			configure_pidfile },
 	{ "accesslog",			configure_accesslog },
 	{ "certfile",			configure_certfile },
@@ -572,6 +574,23 @@ configure_rlimit_nofiles(char **argv)
 	return (KORE_RESULT_OK);
 }
 
+static int
+configure_accept_treshold(char **argv)
+{
+	int		err;
+
+	if (argv[1] == NULL)
+		return (KORE_RESULT_ERROR);
+
+	worker_accept_treshold = kore_strtonum(argv[1], 0, 1, UINT_MAX, &err);
+	if (err != KORE_RESULT_OK) {
+		printf("bad value for worker_accept_treshold: %s\n", argv[1]);
+		return (KORE_RESULT_ERROR);
+	}
+
+	return (KORE_RESULT_OK);
+}
+
 static int
 configure_http_header_max(char **argv)
 {

src/linux.c

@@ -130,6 +130,10 @@ kore_platform_event_wait(u_int64_t timer)
 
 			while (worker_active_connections <
 			    worker_max_connections) {
+				if (worker_accept_treshold != 0 &&
+				    r >= worker_accept_treshold)
+					break;
+
 				if (!kore_connection_accept(l, &c)) {
 					r = 1;
 					break;

src/worker.c

@@ -68,6 +68,7 @@ static struct wlock			*accept_lock;
 extern volatile sig_atomic_t	sig_recv;
 struct kore_worker		*worker = NULL;
 struct connection_list		worker_clients;
+u_int32_t			worker_accept_treshold = 0;
 u_int32_t			worker_rlimit_nofiles = 1024;
 u_int32_t			worker_max_connections = 250;
 u_int32_t			worker_active_connections = 0;