Listen with the maximum backlog when we first start for more seamless restarts and then drop to the minimum afterwards to effectively ratelimit new connections

src/connector.c

@@ -294,8 +294,8 @@ void *receiver(void *arg)
 	conn_instance_t *ci = (conn_instance_t *)arg;
 	client_instance_t *client, *tmp;
 	int ret, nfds, i, maxfds = 1;
+	bool update, maxconn = true;
 	struct pollfd *fds;
-	bool update;
 
 	rename_proc("creceiver");
 
@@ -379,6 +379,14 @@ repoll:
 
 	if (update)
 		goto rebuild_fds;
+	else if (unlikely(maxconn)) {
+		/* When we first start we listen to as many connections as
+		 * possible. Once we stop receiving connections we drop the
+		 * listen to the minimum to effectively ratelimit how fast we
+		 * can receive connections. */
+		maxconn = false;
+		listen(ci->serverfd, 0);
+	}
 	goto repoll;
 out:
 	free(fds);
@@ -748,7 +756,7 @@ int connector(proc_instance_t *pi)
 	if (tries)
 		LOGWARNING("Connector successfully bound to socket");
 
-	ret = listen(sockd, 10);
+	ret = listen(sockd, SOMAXCONN);
 	if (ret < 0) {
 		LOGERR("Connector failed to listen on socket");
 		Close(sockd);