Re: [libmicrohttpd] How to close all upgraded connections when shutting down MHD_Daemon?

[Nicolas Mora]

Hi,

Thanks Evgeny and Silvio for your help

Le 2017-05-04 à 03:02, Evgeny Grin a écrit :
> MHD_quiesce_daemon() prevent MHD from accepting new connections but
> allow to continue processing with current connections.
> The returned socket is listening socket.

Actually, I'm not using MHD_quiesce_daemon() at all, just 
MHD_stop_daemon(). I talked about MHD_quiesce_daemon() because in the 
online documentation, the phrase I quote is below MHD_quiesce_daemon().

> You can track quiesced state of MHD in some global variable (if you are
> using single MHD instance) or in local variable associated with MHD
> instance. You will need to update this variable when you quiesced MHD.
> In upgrade_handler you can check current state of MHD by checking variable.
> Keep in mind that MHD will not accept new connection after
> MHD_quiesce_daemon(), so upgrade_handler will be called after
> MHD_quiesce_daemon() if connection was accepted before
> MHD_quiesce_daemon() but not yet "upgraded".
>
> MHD_stop_daemon() will close all connections including "upgraded"
> connections. So you can't use "upgraded" connections after
> MHD_stop_daemon().
The problem I have is that MHD_stop_daemon() doesn't close all the 
connections. Instead, it looks like it waits for the active connections 
to close by themselves and I have the following log message:
Initiated daemon shutdown while "upgraded" connection was not closed.

> Could you explain a bit more situation that you need to solve?
> Do you want to implement graceful MHD shutdown after closing all
> upgraded connections?
I guess what I'd rather have is for the upgraded connections to be 
closed by MHD when MHD_stop_daemon() is called, so the upgrade callback 
could interpret it easily.
Silvio's suggestion might work too, some signal like a 
"MHD_DAEMON_INFO_WAS_QUIESCED" or, in my case "MHD_DAEMON_INFO_WAS_STOPPED".

My current implementation is the following.
When a websocket upgrade is called by the client, the websocket callback 
is executed:
https://github.com/babelouest/ulfius/blob/2.0/src/ulfius.c#L432
Then the program loops on listening to the socket
https://github.com/babelouest/ulfius/blob/2.0/src/u_websocket.c#L115

But in my example program, when the user stops the program by pressing 
the <enter> key while connections are active, the program doesn't stop 
and waits for the open websockets to close.
https://github.com/babelouest/ulfius/blob/2.0/example_programs/websocket_example/websocket_example.c