Add a maxclients directive that stops accepting clients when there are too many

src/ckpool.c

@@ -997,6 +997,7 @@ static void parse_config(ckpool_t *ckp)
 	json_get_int64(&ckp->startdiff, json_conf, "startdiff");
 	json_get_int64(&ckp->maxdiff, json_conf, "maxdiff");
 	json_get_string(&ckp->logdir, json_conf, "logdir");
+	json_get_int(&ckp->maxclients, json_conf, "maxclients");
 	arr_val = json_object_get(json_conf, "proxy");
 	if (arr_val && json_is_array(arr_val)) {
 		int arr_size = json_array_size(arr_val);

src/ckpool.h

@@ -113,6 +113,8 @@ struct ckpool_instance {
 	int oldconnfd;
 	/* Should we inherit a running instance's socket and shut it down */
 	bool handover;
+	/* How many clients maximum to accept before rejecting further */
+	int maxclients;
 
 	/* Logger message queue NOTE: Unique per process */
 	ckmsgq_t *logger;

src/connector.c

@@ -90,8 +90,18 @@ static pthread_cond_t sender_cond;
 static int accept_client(conn_instance_t *ci)
 {
 	client_instance_t *client, *old_client;
+	ckpool_t *ckp = ci->pi->ckp;
+	int fd, port, no_clients;
 	socklen_t address_len;
-	int fd, port;
+
+	ck_rlock(&ci->lock);
+	no_clients = HASH_COUNT(clients);
+	ck_runlock(&ci->lock);
+
+	if (ckp->maxclients && no_clients >= ckp->maxclients) {
+		LOGWARNING("Server full with %d clients", no_clients);
+		return 0;
+	}
 
 	client = ckzalloc(sizeof(client_instance_t));
 	address_len = sizeof(client->address);