[core] update comment about server.max-write-idle
@@ -1494,8 +1494,15 @@ static void connection_check_timeout (connection * const con, const unix_time64_
/* max_write_idle timeout currently functions as backend timeout,
* too, after response has been started.
- * future: have separate backend timeout, and then change this
- * to check for write interest before checking for timeout */
+ * Although backend timeouts now exist, there is no default for timeouts
+ * to backends, so were this client timeout now to be changed to check
+ * for write interest to the client, then timeout would not occur if the
+ * backend hung and there was no backend read timeout set. Therefore,
+ * max_write_idle timeout remains timeout for both reading from backend
+ * and writing to client, though this check here is only for HTTP/1.1.
+ * In the future, if there were a quick way to detect that a backend
+ * read timeout was in effect, then this timeout could check for write
+ * interest to client. (not a priority) */
/*if (waitevents & FDEVENT_OUT)*/
if (r->http_version <= HTTP_VERSION_1_1
&& r->state == CON_STATE_WRITE && con->write_request_ts != 0) {
