nginx cache重构

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");

    tree.init_handler = NULL;
    tree.file_handler = ngx_http_file_cache_manage_file;
    tree.pre_tree_handler = ngx_http_file_cache_noop;
    tree.post_tree_handler = ngx_http_file_cache_noop;
    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;

    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);
}

==== 最后分析ngx_walk_tree方法：

/* ngx_walk_tree是递归函数，打开每层路径(dir)直到每个文件(file)，根据其路径和文件名得到key，在缓存的rbtree(红黑树)里面找这个key(部分)， 如果没有找到的话，就在内存中分配一个映射这个文件的node(但是不会把文件的内容进行缓存)，然后插入到红黑树中和加入队列。    

             ngx_http_file_cache_loader

              ctx->file_handler=> 

              ngx_http_file_cache_manage_file=> 

              ngx_http_file_cache_add_file=>      

              ngx_http_file_cache_add 

              从n = ngx_read_file(...)函数可以看出，每个磁盘缓存文件的开头的sizeof(ngx_http_file_cache_header_t)个byte存放了跟缓存相关的信息   */

ngx_int_t
ngx_walk_tree(ngx_tree_ctx_t *ctx, ngx_str_t*tree)
{
    void *data, *prev;
    u_char *p, *name;
    size_t len;
    ngx_int_t   rc;
    ngx_err_t err;
    ngx_str_t   file, buf;
    ngx_dir_t   dir;
    ngx_str_null(&buf);
    ngx_log_debug1(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                   "walk tree\"%V\"", tree);
    //打开name指定的目录，并将返回值以DIR*的形式赋值给dir->dir后面对该目录下所有文件的访问都可以通过dir->dir进行
    if(ngx_open_dir(tree, &dir) == NGX_ERROR)
    {
        ngx_log_error(NGX_LOG_CRIT, ctx->log, ngx_errno,
                      ngx_open_dir_n "\"%s\" failed", tree->data);
        return NGX_ERROR;
    }
    prev = ctx->data;
    if(ctx->alloc)
    {
        data = ngx_alloc(ctx->alloc, ctx->log);
        if (data == NULL)
        {
            goto failed;

        }
        if (ctx->init_handler(data, prev) == NGX_ABORT)
        {
            goto failed;
        }
        ctx->data = data;
    }
    else
    {
        data = NULL;
    }
    for ( ;; )
    {
        ngx_set_errno(0);
        //返回下一个目录进入点，并赋值给dir->de
        if (ngx_read_dir(&dir) == NGX_ERROR)
        {
            err = ngx_errno;
            if (err == NGX_ENOMOREFILES)
            {
                rc = NGX_OK;
            }
            else
            {
                ngx_log_error(NGX_LOG_CRIT,ctx->log, err,
                              ngx_read_dir_n" \"%s\" failed", tree->data);
                rc = NGX_ERROR;
            }
            goto done;
        }
        len = ngx_de_namelen(&dir);
        name = ngx_de_name(&dir);
        ngx_log_debug2(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                       "tree name%uz:\"%s\"", len, name);
        if (len == 1 && name[0] == '.')
        {
            continue;
        }
        if (len == 2 && name[0] == '.' && name[1] == '.')
        {
            continue;
        }
        file.len = tree->len + 1 + len;
        if (file.len + NGX_DIR_MASK_LEN > buf.len)
        {
            if (buf.len)
            {
                ngx_free(buf.data);
            }
            buf.len = tree->len + 1 + len + NGX_DIR_MASK_LEN;
            buf.data = ngx_alloc(buf.len + 1, ctx->log);
            if (buf.data == NULL)
            {
                goto failed;
            }
        }
        p = ngx_cpymem(buf.data, tree->data, tree->len);
        *p++ = '/';
        ngx_memcpy(p, name, len + 1);
        file.data = buf.data;
        ngx_log_debug1(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                       "tree path \"%s\"",file.data);
        if (!dir.valid_info)
        {
            if (ngx_de_info(file.data, &dir) == NGX_FILE_ERROR)
            {
                ngx_log_error(NGX_LOG_CRIT,ctx->log, ngx_errno,
                              ngx_de_info_n" \"%s\" failed", file.data);
                continue;
            }
        }
        //dir->de指向的是文件
        if (ngx_de_is_file(&dir))
        {
            ngx_log_debug1(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                           "tree file\"%s\"", file.data);
            ctx->size = ngx_de_size(&dir);
            ctx->fs_size = ngx_de_fs_size(&dir);
            ctx->access = ngx_de_access(&dir);
            ctx->mtime = ngx_de_mtime(&dir);
            ////////////////////////////////////////////////////////////////进行索引重建
            //ngx_http_file_cache_loader中将其设置为tree.file_handler = ngx_http_file_cache_manage_file;
            if (ctx->file_handler(ctx, &file) == NGX_ABORT)
            {
                goto failed;
            }
            //dir->de指向的是目录
        }
        else if (ngx_de_is_dir(&dir))
        {
            ngx_log_debug1(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                           "tree enter dir\"%s\"", file.data);
            ctx->access = ngx_de_access(&dir);
            ctx->mtime = ngx_de_mtime(&dir);
            //其实在ngx_http_file_cache_loader方法中已经完成了注册，只是返回NGX_OK
            if (ctx->pre_tree_handler(ctx, &file) == NGX_ABORT)
            {
                goto failed;
            }

            //针对于子目录进行递归调用
            if (ngx_walk_tree(ctx, &file) == NGX_ABORT)
            {
                goto failed;
            }
            ctx->access = ngx_de_access(&dir);
            ctx->mtime = ngx_de_mtime(&dir);
            //其实在ngx_http_file_cache_loader方法中已经完成了注册，只是返回NGX_OK

            if (ctx->post_tree_handler(ctx, &file) == NGX_ABORT)
            {
                goto failed;
            }
        }
        else
        {
            ngx_log_debug1(NGX_LOG_DEBUG_CORE, ctx->log, 0,
                           "tree special\"%s\"", file.data);
            if (ctx->spec_handler(ctx, &file) == NGX_ABORT)
            {
                goto failed;
            }
        }
    }
failed:
    rc= NGX_ABORT;
done:
    if(buf.len)
    {
        ngx_free(buf.data);
    }

    if(data)
    {
        ngx_free(data);
        ctx->data = prev;
    }

    if(ngx_close_dir(&dir) == NGX_ERROR)
    {
        ngx_log_error(NGX_LOG_CRIT, ctx->log, ngx_errno,
                      ngx_close_dir_n "\"%s\" failed", tree->data);
    }
    return rc;
}