Simple timeout module

[Valentin V. Bartenev]

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

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