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view src/event/ngx_event_busy_lock.h @ 4385:70ba81827472

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Cache locks initial implementation. New directives: proxy_cache_lock on/off, proxy_cache_lock_timeout. With proxy_cache_lock set to on, only one request will be allowed to go to upstream for a particular cache item. Others will wait for a response to appear in cache (or cache lock released) up to proxy_cache_lock_timeout. Waiting requests will recheck if they have cached response ready (or are allowed to run) every 500ms. Note: we intentionally don't intercept NGX_DECLINED possibly returned by ngx_http_file_cache_read(). This needs more work (possibly safe, but needs further investigation). Anyway, it's exceptional situation. Note: probably there should be a way to disable caching of responses if there is already one request fetching resource to cache (without waiting at all). Two possible ways include another cache lock option ("no_cache") or using proxy_no_cache with some supplied variable. Note: probably there should be a way to lock updating requests as well. For now "proxy_cache_use_stale updating" is available.
author Maxim Dounin <mdounin@mdounin.ru>
date Mon, 26 Dec 2011 11:15:23 +0000
parents 4c43e25d11ea
children d620f497c50f
line wrap: on
line source


/*
 * 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_ */