Simple timeout module

Server NGINX
1

I’m trying to build a simple timeout module using nginx timers. At the
beginning of a request I’m firing up a timer and after time interval
elapses
I want to check if request has already completed, and if not, finalize
it,
for example it with NGX_HTTP_REQUEST_TIME_OUT. I have created a filter
module. I’m creating a timer in filter headers:

static ngx_int_t simple_timeout_filter_headers(ngx_http_request_t*
request)
{
ngx_event_t* timeout_event;

timeout_event = ngx_pcalloc(request->pool, sizeof(ngx_event_t));
if (timeout_event == NULL)
{
return NGX_ERROR;
}

timeout_event->handler = simple_timeout_handler;
timeout_event->data = request;
timeout_event->log = request->connection->log;

ngx_log_debug0(NGX_LOG_DEBUG_HTTP, request->connection->log, 0,
“SIMPLE TIMEOUT TIMER START”);

ngx_add_timer(timeout_event, 3000); /* wait for 3 seconds */

return next_header_filter(request);
}

Simple timeout handler looks like this:

static void simple_timeout_handler(ngx_event_t* timeout_event)
{
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, timeout_event->log, 0,
“SIMPLE TIMEOUT TIMER END”);
}

And it works if I issue a request, and wait for a timer to fire. If I
issue
several requests while the previous timer is already in progress, I get
a
SEGFAULT.

A SEGFAULT happens here, while inserting a node into rbtree:

ngx_rbtree_insert() at ngx_rbtree.c:32 0x40d3c0
ngx_event_add_timer() at ngx_event_timer.h:84 0x42fc32
ngx_http_init_connection() at ngx_http_request.c:363 0x42fc32
ngx_event_accept() at ngx_event_accept.c:360 0x41c9ec
ngx_epoll_process_events() at ngx_epoll_module.c:822 0x424a00
ngx_process_events_and_timers() at ngx_event.c:248 0x41bb2c
ngx_single_process_cycle() at ngx_process_cycle.c:308 0x423c8b
main() at nginx.c:416 0x403bc6

So what I’m missing in my simple_timeout_filter_headers method?

Nginx version 1.8

Posted at Nginx Forum:

2

Hello!

On Wed, May 20, 2015 at 01:03:19PM -0400, donatasm wrote:

timeout_event = ngx_pcalloc(request->pool, sizeof(ngx_event_t));
“SIMPLE TIMEOUT TIMER START”);
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, timeout_event->log, 0,
“SIMPLE TIMEOUT TIMER END”);
}

And it works if I issue a request, and wait for a timer to fire. If I issue
several requests while the previous timer is already in progress, I get a
SEGFAULT.

At least you don’t remove the timer if the request completes
before the timer is triggered. This is enough to trigger a
segmentation fault.

–
Maxim D.
http://nginx.org/

3

On Wednesday 20 May 2015 13:03:19 donatasm wrote:

timeout_event = ngx_pcalloc(request->pool, sizeof(ngx_event_t));
“SIMPLE TIMEOUT TIMER START”);
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, timeout_event->log, 0,
ngx_event_add_timer() at ngx_event_timer.h:84 0x42fc32
Nginx version 1.8

You have allocated timer from a request memory pool. After the request
is
completed, the pool is freed, but you timer is still in the tree.

You should cleanup your timer.

wbr, Valentin V. Bartenev

4

Thanks, it worked as I added ngx_del_timer call in ngx_pool_cleanup_t
handler of a request

Posted at Nginx Forum: