[libmicrohttpd] Connection time out and MHD_USE_POLL_INTERNALLY causes b
[libmicrohttpd] Connection time out and MHD_USE_POLL_INTERNALLY causes busy loop
Tue, 14 Apr 2015 17:14:48 -0400
The MHD goes in a busy loop when it is configured with MHD_USE_POLL_INTERNALLY and a connection times out. When the connection times out, the connection is closed at connection.c:2646, which sets connection->event_loop_info = MHD_EVENT_LOOP_INFO_CLEANUP. When the loop info is set to MHD_EVENT_LOOP_INFO_CLEANUP, the main function of the thread loop, MHD_poll_all, never calls back the connection idle callback, which would have cleaned the connection and exit the loop. I resolved the issue in my development code by adding pos->idle_handler (pos) at daemon.c:2477 in MHD_poll_all (SVN 35533).
The busy loop could be tested using a small enough connection timeout and netcat: nc -v -w 100 <IP ADDRESS> <IP PORT>
CPU usage will reach 100% in one of the CPU and will remain at that level even when the netcat has closed its end of the connection.