nginx ngx_http_addition_module 模块openresty content_by_lua 不能生效的原因

nginx 的ngx_http_addition_module 模块也是一个修改content 的好东西，对于openresty 我们经常使用content_by_lua 阶段处理
但是经过分析ngx_http_addition_module 源码的处理机制，他是基于body_fiter 处理的，所以我们基于content_by_lua 进行数据处理
会有顺序不对的问题

参考源码处理

处理机制
ngx_http_addition_filter_module_ctx上下文定义

static ngx_http_module_t  ngx_http_addition_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_addition_filter_init,         /* postconfiguration */
 
    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */
 
    NULL,                                  /* create server configuration */
    NULL,                                  /* merge server configuration */
 
    ngx_http_addition_create_conf,         /* create location configuration */
    ngx_http_addition_merge_conf           /* merge location configuration */
};
阶段(依赖了header 以及body)

static ngx_int_t
ngx_http_addition_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_addition_header_filter;
 
    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_addition_body_filter;
 
    return NGX_OK;
}
核心处理

static ngx_int_t
ngx_http_addition_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    ngx_int_t                  rc;
    ngx_uint_t                 last;
    ngx_chain_t               *cl;
    ngx_http_request_t        *sr;
    ngx_http_addition_ctx_t   *ctx;
    ngx_http_addition_conf_t  *conf;
 
    if (in == NULL || r->header_only) {
        return ngx_http_next_body_filter(r, in);
    }
 
    ctx = ngx_http_get_module_ctx(r, ngx_http_addition_filter_module);
 
    if (ctx == NULL) {
        return ngx_http_next_body_filter(r, in);
    }
 
    conf = ngx_http_get_module_loc_conf(r, ngx_http_addition_filter_module);
 
    if (!ctx->before_body_sent) {
        ctx->before_body_sent = 1;
 
        if (conf->before_body.len) {
            if (ngx_http_subrequest(r, &conf->before_body, NULL, &sr, NULL, 0)
                != NGX_OK)
            {
                return NGX_ERROR;
            }
        }
    }
 
    if (conf->after_body.len == 0) {
        ngx_http_set_ctx(r, NULL, ngx_http_addition_filter_module);
        return ngx_http_next_body_filter(r, in);
    }
 
    last = 0;
 
    for (cl = in; cl; cl = cl->next) {
        if (cl->buf->last_buf) {
            cl->buf->last_buf = 0;
            cl->buf->last_in_chain = 1;
            cl->buf->sync = 1;
            last = 1;
        }
    }
 
    rc = ngx_http_next_body_filter(r, in);
 
    if (rc == NGX_ERROR || !last || conf->after_body.len == 0) {
        return rc;
    }
    if (ngx_http_subrequest(r, &conf->after_body, NULL, &sr, NULL, 0)
        != NGX_OK)
    {
        return NGX_ERROR;
    }
 
    ngx_http_set_ctx(r, NULL, ngx_http_addition_filter_module);
 
    return ngx_http_send_special(r, NGX_HTTP_LAST);
}

如果需要使用的解决方法

可以直接在body_fiter 阶段进行数据处理，注意此阶段会有一些api 的限制
参考处理（直接输出了，比较简单）

location = /flush2.html {
    add_before_body /before_action;
    add_after_body  /after_action;
}
location  /before_action {
    default_type text/html;
    content_by_lua_block {
            ngx.say("this is before content\n")
            ngx.log(ngx.ERR, "before_action")
    }
}
location  /after_action {
    default_type text/html;
    body_filter_by_lua_block {
              ngx.arg[1] = "this is after content\n"
    }
}

说明

以上是结合源码学习ngx_http_addition_module 与openresty 集成的处理，大家如果碰到类似问题可以参考

参考资料

​​https://github.com/nginx/nginx/blob/master/src/http/modules/ngx_http_addition_filter_module.c#L133​​