Nginx

Nginx缓存清理

1、相关配置

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proxy_cache_path /dev/sda1/data inactive=60m max_size=10G;

proxy_cache_path指令的inactive参数和max_size参数用来维护缓存队列大小

2、源码解析

  1. 首先来看看配置解析函数
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char *
ngx_http_file_cache_set_slot(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    char  *confp = conf;

    off_t                   max_size;
    u_char                 *last, *p;
    time_t                  inactive;
    ssize_t                 size;
    ngx_str_t               s, name, *value;
    ngx_int_t               loader_files, manager_files;
    ngx_msec_t              loader_sleep, manager_sleep, loader_threshold,
                            manager_threshold;
    ngx_uint_t              i, n, use_temp_path;
    ngx_array_t            *caches;
    ngx_http_file_cache_t  *cache, **ce;

    cache = ngx_pcalloc(cf->pool, sizeof(ngx_http_file_cache_t));
    if (cache == NULL) {
        return NGX_CONF_ERROR;
    }

    cache->path = ngx_pcalloc(cf->pool, sizeof(ngx_path_t));
    if (cache->path == NULL) {
        return NGX_CONF_ERROR;
    }

    use_temp_path = 1;

    inactive = 600;

    loader_files = 100;
    loader_sleep = 50;
    loader_threshold = 200;

    manager_files = 100;
    manager_sleep = 50;
    manager_threshold = 200;

    name.len = 0;
    size = 0;
    max_size = NGX_MAX_OFF_T_VALUE;

    value = cf->args->elts;
    //指定路径名称
    cache->path->name = value[1];

    if (cache->path->name.data[cache->path->name.len - 1] == '/') {
        cache->path->name.len--;
    }

    if (ngx_conf_full_name(cf->cycle, &cache->path->name, 0) != NGX_OK) {
        return NGX_CONF_ERROR;
    }

    //解析proxy_cache_path指令后的参数
    for (i = 2; i < cf->args->nelts; i++) {
        //解析目录层级参数
        if (ngx_strncmp(value[i].data, "levels=", 7) == 0) {

            p = value[i].data + 7;
            last = value[i].data + value[i].len;

            for (n = 0; n < NGX_MAX_PATH_LEVEL && p < last; n++) {

                if (*p > '0' && *p < '3') {

                    cache->path->level[n] = *p++ - '0';
                    cache->path->len += cache->path->level[n] + 1;

                    if (p == last) {
                        break;
                    }

                    if (*p++ == ':' && n < NGX_MAX_PATH_LEVEL - 1 && p < last) {
                        continue;
                    }

                    goto invalid_levels;
                }

                goto invalid_levels;
            }

            if (cache->path->len < 10 + NGX_MAX_PATH_LEVEL) {
                continue;
            }

        invalid_levels:

            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                               "invalid \"levels\" \"%V\"", &value[i]);
            return NGX_CONF_ERROR;
        }

        if (ngx_strncmp(value[i].data, "use_temp_path=", 14) == 0) {

            if (ngx_strcmp(&value[i].data[14], "on") == 0) {
                use_temp_path = 1;

            } else if (ngx_strcmp(&value[i].data[14], "off") == 0) {
                use_temp_path = 0;

            } else {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "invalid use_temp_path value \"%V\", "
                                   "it must be \"on\" or \"off\"",
                                   &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析共享内存名称参数
        if (ngx_strncmp(value[i].data, "keys_zone=", 10) == 0) {

            name.data = value[i].data + 10;

            p = (u_char *) ngx_strchr(name.data, ':');

            if (p == NULL) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "invalid keys zone size \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            name.len = p - name.data;

            s.data = p + 1;
            s.len = value[i].data + value[i].len - s.data;

            size = ngx_parse_size(&s);

            if (size == NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "invalid keys zone size \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            if (size < (ssize_t) (2 * ngx_pagesize)) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "keys zone \"%V\" is too small", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析缓存分片活跃时间
        if (ngx_strncmp(value[i].data, "inactive=", 9) == 0) {

            s.len = value[i].len - 9;
            s.data = value[i].data + 9;

            inactive = ngx_parse_time(&s, 1);
            if (inactive == (time_t) NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "invalid inactive value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析配置的目录最大能保存多少缓存分片
        if (ngx_strncmp(value[i].data, "max_size=", 9) == 0) {

            s.len = value[i].len - 9;
            s.data = value[i].data + 9;

            max_size = ngx_parse_offset(&s);
            if (max_size < 0) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                   "invalid max_size value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析缓存加载进程暂停阈值
        if (ngx_strncmp(value[i].data, "loader_files=", 13) == 0) {

            loader_files = ngx_atoi(value[i].data + 13, value[i].len - 13);
            if (loader_files == NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid loader_files value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析缓存加载进程暂停时间
        if (ngx_strncmp(value[i].data, "loader_sleep=", 13) == 0) {

            s.len = value[i].len - 13;
            s.data = value[i].data + 13;

            loader_sleep = ngx_parse_time(&s, 0);
            if (loader_sleep == (ngx_msec_t) NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid loader_sleep value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }

        if (ngx_strncmp(value[i].data, "loader_threshold=", 17) == 0) {

            s.len = value[i].len - 17;
            s.data = value[i].data + 17;

            loader_threshold = ngx_parse_time(&s, 0);
            if (loader_threshold == (ngx_msec_t) NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid loader_threshold value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }
        //解析缓存管理进程暂停阈值
        if (ngx_strncmp(value[i].data, "manager_files=", 14) == 0) {

            manager_files = ngx_atoi(value[i].data + 14, value[i].len - 14);
            if (manager_files == NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid manager_files value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }

        //manager进程达到阈值后的睡眠时间
        if (ngx_strncmp(value[i].data, "manager_sleep=", 14) == 0) {

            s.len = value[i].len - 14;
            s.data = value[i].data + 14;

            manager_sleep = ngx_parse_time(&s, 0);
            if (manager_sleep == (ngx_msec_t) NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid manager_sleep value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }

        if (ngx_strncmp(value[i].data, "manager_threshold=", 18) == 0) {

            s.len = value[i].len - 18;
            s.data = value[i].data + 18;

            manager_threshold = ngx_parse_time(&s, 0);
            if (manager_threshold == (ngx_msec_t) NGX_ERROR) {
                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid manager_threshold value \"%V\"", &value[i]);
                return NGX_CONF_ERROR;
            }

            continue;
        }

        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "invalid parameter \"%V\"", &value[i]);
        return NGX_CONF_ERROR;
    }

    if (name.len == 0 || size == 0) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "\"%V\" must have \"keys_zone\" parameter",
                           &cmd->name);
        return NGX_CONF_ERROR;
    }

    //设置loader跟manager进程的回调函数
    cache->path->manager = ngx_http_file_cache_manager;
    cache->path->loader = ngx_http_file_cache_loader;
    cache->path->data = cache;
    cache->path->conf_file = cf->conf_file->file.name.data;
    cache->path->line = cf->conf_file->line;
    cache->loader_files = loader_files;
    cache->loader_sleep = loader_sleep;
    cache->loader_threshold = loader_threshold;
    cache->manager_files = manager_files;
    cache->manager_sleep = manager_sleep;
    cache->manager_threshold = manager_threshold;
    //将缓存路径添加到全局管理
    if (ngx_add_path(cf, &cache->path) != NGX_OK) {
        return NGX_CONF_ERROR;
    }
    //添加共享内存名称
    cache->shm_zone = ngx_shared_memory_add(cf, &name, size, cmd->post);
    if (cache->shm_zone == NULL) {
        return NGX_CONF_ERROR;
    }

    if (cache->shm_zone->data) {
        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                           "duplicate zone \"%V\"", &name);
        return NGX_CONF_ERROR;
    }

    //设置共享内存初始化函数指针
    cache->shm_zone->init = ngx_http_file_cache_init;
    cache->shm_zone->data = cache;

    cache->use_temp_path = use_temp_path;

    cache->inactive = inactive;
    cache->max_size = max_size;

    caches = (ngx_array_t *) (confp + cmd->offset);
    //保存cache结构体
    ce = ngx_array_push(caches);
    if (ce == NULL) {
        return NGX_CONF_ERROR;
    }

    *ce = cache;

    return NGX_CONF_OK;
}
  1. 上述代码中我们只关注inactive，max_size参数解析、cache->path相关成员赋值以及loader和manager相关的赋值代码，如下所示：
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cache->path->manager = ngx_http_file_cache_manager;
cache->path->loader = ngx_http_file_cache_loader;
cache->path->data = cache;
cache->path->conf_file = cf->conf_file->file.name.data;
cache->path->line = cf->conf_file->line;
cache->loader_files = loader_files;
cache->loader_sleep = loader_sleep;
cache->loader_threshold = loader_threshold;
cache->manager_files = manager_files;
cache->manager_sleep = manager_sleep;
cache->manager_threshold = manager_threshold;

if (ngx_add_path(cf, &cache->path) != NGX_OK) {
    return NGX_CONF_ERROR;
}
//添加共享内存名称
cache->shm_zone = ngx_shared_memory_add(cf, &name, size, cmd->post);
if (cache->shm_zone == NULL) {
    return NGX_CONF_ERROR;
}

if (cache->shm_zone->data) {
    ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                       "duplicate zone \"%V\"", &name);
    return NGX_CONF_ERROR;
}

//设置共享内存初始化函数
cache->shm_zone->init = ngx_http_file_cache_init;
cache->shm_zone->data = cache;

cache->use_temp_path = use_temp_path;

cache->inactive = inactive;
cache->max_size = max_size;
//保存cache
caches = (ngx_array_t *) (confp + cmd->offset);

ce = ngx_array_push(caches);
if (ce == NULL) {
    return NGX_CONF_ERROR;
}

*ce = cache;

  1. path结构体初始化完成之后，ngx_add_path函数将配置的路径添加到nginx全局路径管理器后，配置解析完成之后会统一管理，接下来我们来看看几个跟目录相关的回调函数。
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ngx_http_file_cache_manager
//加载本地已有缓存函数
ngx_http_file_cache_loader

  1. 首先来看看ngx_http_file_cache_manager函数的具体实现
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static ngx_msec_t
ngx_http_file_cache_manager(void *data)
{
    ngx_http_file_cache_t  *cache = data;

    off_t       size;
    time_t      wait;
    ngx_msec_t  elapsed, next;
    ngx_uint_t  count, watermark;

    cache->last = ngx_current_msec;
    cache->files = 0;
    //查找过期缓存结点
    next = (ngx_msec_t) ngx_http_file_cache_expire(cache) * 1000;

    if (next == 0) {
        next = cache->manager_sleep;
        goto done;
    }

    for ( ;; ) {
        ngx_shmtx_lock(&cache->shpool->mutex);

        size = cache->sh->size;
        count = cache->sh->count;
        watermark = cache->sh->watermark;

        ngx_shmtx_unlock(&cache->shpool->mutex);

        ngx_log_debug3(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
                       "http file cache size: %O c:%ui w:%i",
                       size, count, (ngx_int_t) watermark);

        if (size < cache->max_size && count < watermark) {
            break;
        }
        //处理缓存目录已经满了的情况
        wait = ngx_http_file_cache_forced_expire(cache);

        if (wait > 0) {
            next = (ngx_msec_t) wait * 1000;
            break;
        }

        if (ngx_quit || ngx_terminate) {
            break;
        }

        if (++cache->files >= cache->manager_files) {
            next = cache->manager_sleep;
            break;
        }

        ngx_time_update();

        elapsed = ngx_abs((ngx_msec_int_t) (ngx_current_msec - cache->last));

        if (elapsed >= cache->manager_threshold) {
            next = cache->manager_sleep;
            break;
        }
    }

done:

    elapsed = ngx_abs((ngx_msec_int_t) (ngx_current_msec - cache->last));

    ngx_log_debug3(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
                   "http file cache manager: %ui e:%M n:%M",
                   cache->files, elapsed, next);

    return next;
}


  1. 这个函数主要的功能就是遍历缓存结点数，找出过期结点，并删除，接下来看看ngx_http_file_cache_loader函数实现
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static void
ngx_http_file_cache_loader(void *data)
{
    ngx_http_file_cache_t  *cache = data;

    ngx_tree_ctx_t  tree;

    if (!cache->sh->cold || cache->sh->loading) {
        return;
    }

    if (!ngx_atomic_cmp_set(&cache->sh->loading, 0, ngx_pid)) {
        return;
    }

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, ngx_cycle->log, 0,
                   "http file cache loader");
    //设置遍历目录时所需的函数指针
    tree.init_handler = NULL;
    //遍历目录时，遇到文件处理函数
    tree.file_handler = ngx_http_file_cache_manage_file;
    //遍历目录时，遇到文件处理函数
    tree.pre_tree_handler = ngx_http_file_cache_manage_directory;
    tree.post_tree_handler = ngx_http_file_cache_noop;
    //缓存目录中有不符合规则的缓存文件，会删除文件
    tree.spec_handler = ngx_http_file_cache_delete_file;
    tree.data = cache;
    tree.alloc = 0;
    tree.log = ngx_cycle->log;

    cache->last = ngx_current_msec;
    cache->files = 0;
    //遍历配置路径下所有文件
    if (ngx_walk_tree(&tree, &cache->path->name) == NGX_ABORT) {
        cache->sh->loading = 0;
        return;
    }

    cache->sh->cold = 0;
    cache->sh->loading = 0;

    ngx_log_error(NGX_LOG_NOTICE, ngx_cycle->log, 0,
                  "http file cache: %V %.3fM, bsize: %uz",
                  &cache->path->name,
                  ((double) cache->sh->size * cache->bsize) / (1024 * 1024),
                  cache->bsize);
}

>6. 此函数功能就是绑定回调函数，然后遍历配置的目录，根据目录中不同的对象调用不同的回调函数

3、总结

以上就是nginx缓存管理的主要代码，总的来说就是在解析配置时设置ngx_path_t结构体的回调函数，cache_manager进程定时启动扫描LRU队列，删除过期结点