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view src/event/ngx_event_busy_lock.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 4c43e25d11ea
children d620f497c50f
line wrap: on
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/*
 * Copyright (C) Igor Sysoev
 */


#ifndef _NGX_EVENT_BUSY_LOCK_H_INCLUDED_
#define _NGX_EVENT_BUSY_LOCK_H_INCLUDED_


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

typedef struct ngx_event_busy_lock_ctx_s  ngx_event_busy_lock_ctx_t;

struct ngx_event_busy_lock_ctx_s {
    ngx_event_t                *event;
    ngx_event_handler_pt        handler;
    void                       *data;
    ngx_msec_t                  timer;

    unsigned                    locked:1;
    unsigned                    waiting:1;
    unsigned                    cache_updated:1;

    char                       *md5;
    ngx_int_t                   slot;

    ngx_event_busy_lock_ctx_t  *next;
};


typedef struct {
    u_char                     *md5_mask;
    char                       *md5;
    ngx_uint_t                  cacheable;

    ngx_uint_t                  busy;
    ngx_uint_t                  max_busy;

    ngx_uint_t                  waiting;
    ngx_uint_t                  max_waiting;

    ngx_event_busy_lock_ctx_t  *events;
    ngx_event_busy_lock_ctx_t  *last;

#if (NGX_THREADS)
    ngx_mutex_t                *mutex;
#endif
} ngx_event_busy_lock_t;


ngx_int_t ngx_event_busy_lock(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx);
ngx_int_t ngx_event_busy_lock_cacheable(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx);
void ngx_event_busy_unlock(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx);
void ngx_event_busy_lock_cancel(ngx_event_busy_lock_t *bl,
    ngx_event_busy_lock_ctx_t *ctx);


#endif /* _NGX_EVENT_BUSY_LOCK_H_INCLUDED_ */