Prevent sending parts of different messages to upstream proxies

src/generator.c

@@ -115,6 +115,7 @@ struct proxy_instance {
 	bool reconnecting; /* Testing of parent in progress */
 	int64_t recruit; /* No of recruiting requests in progress */
 	bool alive;
+	bool sending; /* Are we in the middle of a blocked write? */
 
 	pthread_t pth_precv;
 
@@ -1533,10 +1534,17 @@ static void send_json_msgq(gdata_t *gdata, cs_msg_t **csmsgq)
 	int ret;
 
 	DL_FOREACH_SAFE(*csmsgq, csmsg, tmp) {
+		proxy_instance_t *proxy = csmsg->proxy;
+
+		/* Only try to send one message at a time to each proxy
+		 * to avoid sending parts of different messages */
+		if (proxy->sending)
+			continue;
 		while (csmsg->len) {
-			proxy_instance_t *proxy = csmsg->proxy;
-			int fd = proxy->cs.fd;
+			int fd;
 
+			proxy->sending = true;
+			fd = proxy->cs.fd;
 			ret = send(fd, csmsg->buf + csmsg->ofs, csmsg->len, MSG_DONTWAIT);
 			if (ret < 1) {
 				if (errno == EAGAIN || errno == EWOULDBLOCK || !ret)
@@ -1550,6 +1558,7 @@ static void send_json_msgq(gdata_t *gdata, cs_msg_t **csmsgq)
 			csmsg->len -= ret;
 		}
 		if (!csmsg->len) {
+			proxy->sending = false;
 			DL_DELETE(*csmsgq, csmsg);
 			free(csmsg->buf);
 			free(csmsg);