Dear Jon,
I've tried (and failed) to reproduce your problem. I've attached my
modified version of 'minimal_example.c' (modified to use a thread pool).
When I connect to the server with firefox, the socket stays open (will
be re-used by the browser) but MHD does NOT use any CPU after the page
is served initially.
I do recall a bugs that could cause similar behavior of MHD looping in
older MHD versions (prior to 4.5) and there was also a bug with looping
for up to 1s before 0.9.12. Which MHD version are you using? (We're
currently at 0.9.15, another release might happen later this weekend.)
Happy hacking!
Christian
On 10/27/2011 10:07 PM, Jon Nalley wrote:
Hi,
I am seeing some odd behavior when using MHD_USE_SELECT_INTERNALLY +
MHD_OPTION_THREAD_POOL_SIZE.
When a request is handled, my CPU usage goes to 100% (I am running on a
PowerPC 405ex - Linux+uClibc).
I was able to determine that MHD_select() in src/daemon/daemon.c is setting
the select timeout to 0.
The following check is true, and ltimeout is 0 which causes the timeout
passed to select() to be 0.
else if ( (0 == (daemon->options& MHD_USE_THREAD_PER_CONNECTION))&&
(MHD_YES == MHD_get_timeout (daemon,<imeout)) )
If I use MHD_USE_THREAD_PER_CONNECTION instead of MHD_USE_SELECT_INTERNALLY
+ MHD_OPTION_THREAD_POOL_SIZE I do *NOT* see the issue.
I took a look at MHD_get_timeout() and noticed I am hitting the following:
if (earliest_deadline< now)
*timeout = 0;
I also confirmed that if I close my browser, the connections are closed and
the select() is once again called with a NULL timeout (blocking forever).
I am not sure exactly what is going on here. It seems like the browser (I
tested with Chrome and Firefox) is keeping the connection open, which causes
MHD_get_timeout() to return MHD_YES (and set ltimeout = 0 in MHD_select())
which results in my process effectively entering a "busy loop" calling
select with a timeout of 0 repeatedly. The page has been fully loaded by
the browser, so I am not sure why the connections remain "ESTABLISHED" (as
reported by netstat -atn). Perhaps the browser keeps the connections open
in order to speed up subsequent requests?
I would appreciate any feedback as to what I may be overlooking and how I
can resolve this issue.
Regards,
Jon Nalley
/*
This file is part of libmicrohttpd
(C) 2007 Christian Grothoff (and other contributing authors)
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file minimal_example.c
* @brief minimal example for how to use libmicrohttpd
* @author Christian Grothoff
*/
#include "platform.h"
#include <microhttpd.h>
#define PAGE "<html><head><title>libmicrohttpd demo</title></head><body>libmicrohttpd demo</body></html>"
static int
ahc_echo (void *cls,
struct MHD_Connection *connection,
const char *url,
const char *method,
const char *version,
const char *upload_data, size_t *upload_data_size, void **ptr)
{
static int aptr;
const char *me = cls;
struct MHD_Response *response;
int ret;
if (0 != strcmp (method, "GET"))
return MHD_NO; /* unexpected method */
if (&aptr != *ptr)
{
/* do never respond on first call */
*ptr = &aptr;
return MHD_YES;
}
*ptr = NULL; /* reset when done */
response = MHD_create_response_from_buffer (strlen (me),
(void *) me,
MHD_RESPMEM_PERSISTENT);
ret = MHD_queue_response (connection, MHD_HTTP_OK, response);
MHD_destroy_response (response);
return ret;
}
int
main (int argc, char *const *argv)
{
struct MHD_Daemon *d;
if (argc != 2)
{
printf ("%s PORT\n", argv[0]);
return 1;
}
d = MHD_start_daemon (// MHD_USE_SELECT_INTERNALLY | MHD_USE_DEBUG | MHD_USE_POLL,
MHD_USE_SELECT_INTERNALLY | MHD_USE_DEBUG,
// MHD_USE_THREAD_PER_CONNECTION | MHD_USE_DEBUG | MHD_USE_POLL,
// MHD_USE_THREAD_PER_CONNECTION | MHD_USE_DEBUG,
atoi (argv[1]),
NULL, NULL, &ahc_echo, PAGE,
MHD_OPTION_CONNECTION_TIMEOUT, (unsigned int) 120,
MHD_OPTION_THREAD_POOL_SIZE, (unsigned int) 2,
MHD_OPTION_END);
if (d == NULL)
return 1;
(void) getc (stdin);
MHD_stop_daemon (d);
return 0;
}
