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view src/event/ngx_event_posted.h @ 4207:4fc91bae6f83

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Better recheck of dead upstream servers. Previously nginx used to mark backend again as live as soon as fail_timeout passes (10s by default) since last failure. On the other hand, detecting dead backend takes up to 60s (proxy_connect_timeout) in typical situation "backend is down and doesn't respond to any packets". This resulted in suboptimal behaviour in the above situation (up to 23% of requests were directed to dead backend with default settings). More detailed description of the problem may be found here (in Russian): http://mailman.nginx.org/pipermail/nginx-ru/2011-August/042172.html Fix is to only allow one request after fail_timeout passes, and mark backend as "live" only if this request succeeds. Note that with new code backend will not be marked "live" unless "check" request is completed, and this may take a while in some specific workloads (e.g. streaming). This is believed to be acceptable.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 12 Oct 2011 14:22:48 +0000
parents 9c2f3ed7a247
children d620f497c50f
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 */


#ifndef _NGX_EVENT_POSTED_H_INCLUDED_
#define _NGX_EVENT_POSTED_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


#if (NGX_THREADS)
extern ngx_mutex_t  *ngx_posted_events_mutex;
#endif


#define ngx_locked_post_event(ev, queue)                                      \
                                                                              \
    if (ev->prev == NULL) {                                                   \
        ev->next = (ngx_event_t *) *queue;                                    \
        ev->prev = (ngx_event_t **) queue;                                    \
        *queue = ev;                                                          \
                                                                              \
        if (ev->next) {                                                       \
            ev->next->prev = &ev->next;                                       \
        }                                                                     \
                                                                              \
        ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0, "post event %p", ev);  \
                                                                              \
    } else  {                                                                 \
        ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0,                        \
                       "update posted event %p", ev);                         \
    }


#define ngx_post_event(ev, queue)                                             \
                                                                              \
    ngx_mutex_lock(ngx_posted_events_mutex);                                  \
    ngx_locked_post_event(ev, queue);                                         \
    ngx_mutex_unlock(ngx_posted_events_mutex);


#define ngx_delete_posted_event(ev)                                           \
                                                                              \
    *(ev->prev) = ev->next;                                                   \
                                                                              \
    if (ev->next) {                                                           \
        ev->next->prev = ev->prev;                                            \
    }                                                                         \
                                                                              \
    ev->prev = NULL;                                                          \
    ngx_log_debug1(NGX_LOG_DEBUG_CORE, ev->log, 0,                            \
                   "delete posted event %p", ev);



void ngx_event_process_posted(ngx_cycle_t *cycle,
    ngx_thread_volatile ngx_event_t **posted);
void ngx_wakeup_worker_thread(ngx_cycle_t *cycle);

#if (NGX_THREADS)
ngx_int_t ngx_event_thread_process_posted(ngx_cycle_t *cycle);
#endif


extern ngx_thread_volatile ngx_event_t  *ngx_posted_accept_events;
extern ngx_thread_volatile ngx_event_t  *ngx_posted_events;


#endif /* _NGX_EVENT_POSTED_H_INCLUDED_ */