Nginx 之HTTP-FLV解析

参考：
https://blog.csdn.net/xiaofeilong89/article/details/106028379
其实上述文章介绍的很清楚了，在这里进行一些补充。

下面是http-flv模块的基本数据结构：
注意的是该模块是NGX_HTTP_MODULE模块

static ngx_http_module_t ngx_http_flv_live_module_ctx = {
    NULL,
    //这里是配置文件解析完毕后的后处理
    ngx_http_flv_live_init,            /* postconfiguration */
    NULL,
    NULL,
    NULL,
    NULL,
    ngx_http_flv_live_create_loc_conf, /* create location configuration */
    ngx_http_flv_live_merge_loc_conf   /* merge location configuration */
};


static ngx_command_t ngx_http_flv_live_commands[] = {
    { ngx_string("flv_live"),
      NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_flv_live_conf_t, flv_live),
      NULL },

    ngx_null_command
};


ngx_module_t ngx_http_flv_live_module = {
    NGX_MODULE_V1,
    &ngx_http_flv_live_module_ctx,
    ngx_http_flv_live_commands,
    NGX_HTTP_MODULE,
    NULL,
    NULL,
    //此处对process初始化，在main函数中先处理完这里，然后才进行主循环
    //一般来说在这里就是添加事件到主循环的epoll中
    ngx_http_flv_live_init_process,
    NULL,
    NULL,
    NULL,
    NULL,
    NGX_MODULE_V1_PADDING
};

先来看ngx_http_flv_live_init_process做了些什么。

static ngx_int_t
ngx_http_flv_live_init_process(ngx_cycle_t *cycle)
{
    return ngx_http_flv_live_init_handlers(cycle);
}

ngx_int_t
ngx_http_flv_live_init_handlers(ngx_cycle_t *cycle)
{
    ngx_rtmp_core_main_conf_t *cmcf;
    ngx_rtmp_handler_pt       *h;

    cmcf = ngx_rtmp_cycle_get_module_main_conf(cycle, ngx_rtmp_core_module);
    if (cmcf == NULL) {
        return NGX_OK;
    }

    /* rtmp live conf aready exsits, so add additional event handlers */
    //主要就是在epoll中添加了一个NGX_HTTP_FLV_LIVE_REQUEST事件，这个事件由
    //ngx_http_flv_live_handler触发
    h = ngx_array_push(&cmcf->events[NGX_HTTP_FLV_LIVE_REQUEST]);
    //事件回调函数
    *h = ngx_http_flv_live_request;

    next_play = http_flv_live_next_play;
    next_close_stream = http_flv_live_next_close_stream;

    http_flv_live_next_play = NULL;
    http_flv_live_next_close_stream = NULL;

    return NGX_OK;
}

static ngx_int_t
ngx_http_flv_live_request(ngx_rtmp_session_t *s, ngx_rtmp_header_t *h,
    ngx_chain_t *in)
{
    static ngx_rtmp_play_t       v;

    ngx_int_t                    rc;
    ngx_http_request_t          *r;
    ngx_http_flv_live_ctx_t     *ctx;

    r = s->data;
    ctx = ngx_http_get_module_ctx(r, ngx_http_flv_live_module);

    rc = ngx_http_flv_live_connect_init(s, &ctx->app, &ctx->stream);
    if (rc != NGX_OK) {
        return NGX_ERROR;
    }

    if (s->notify_connect) {
        return NGX_OK;
    }

    ngx_memzero(&v, sizeof(ngx_rtmp_play_t));

    ngx_memcpy(v.name, ctx->stream.data, ngx_min(ctx->stream.len,
            sizeof(v.name) - 1));
    ngx_memcpy(v.args, s->args.data, ngx_min(s->args.len,
            sizeof(v.args) - 1));

    ngx_log_error(NGX_LOG_INFO, s->connection->log, 0,
           "flv live: name='%s' args='%s' start=%i duration=%i "
           "reset=%i silent=%i",
           v.name, v.args, (ngx_int_t) v.start,
           (ngx_int_t) v.duration, (ngx_int_t) v.reset,
           (ngx_int_t) v.silent);
//这里开始发送数据
    return ngx_rtmp_play(s, &v);
}

然后来看ngx_http_flv_live_init，当解析完配置文件后触发，这里就是将http-flv添加到NGX_HTTP_CONTENT_PHASE阶段，主要的回调函数是ngx_http_flv_live_handler

static ngx_int_t
ngx_http_flv_live_init(ngx_conf_t *cf)
{
    ngx_http_handler_pt       *h;
    ngx_http_core_main_conf_t *cmcf;

    cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

    /* insert in the NGX_HTTP_CONTENT_PHASE */
    h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
    if (h == NULL) {
        return NGX_ERROR;
    }
//回调处理函数
    *h = ngx_http_flv_live_handler;

    return NGX_OK;
}


static ngx_int_t
ngx_http_flv_live_handler(ngx_http_request_t *r)
{
    ngx_int_t                        rc;
    ngx_http_flv_live_conf_t        *hfcf;
    ngx_http_cleanup_t              *cln;
    ngx_http_flv_live_ctx_t         *ctx;
    ngx_rtmp_session_t              *s;
    ngx_rtmp_connection_t           *rconn;

    if (ngx_exiting || ngx_terminate) {
        return NGX_HTTP_CLOSE;
    }

    hfcf = ngx_http_get_module_loc_conf(r, ngx_http_flv_live_module);
    if (!hfcf->flv_live) {
        return NGX_DECLINED;
    }

    if (!(r->method & (NGX_HTTP_GET))) {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                      "flv live: HTTP method was not \"GET\"");

        return NGX_HTTP_NOT_ALLOWED;
    }

    if (r->http_version == NGX_HTTP_VERSION_9
#if (NGX_HTTP_V2)
        || r->http_version == NGX_HTTP_VERSION_20
#endif
       )
    {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
                      "flv live: HTTP version 0.9 or 2.0 not supported");

        return NGX_HTTP_NOT_ALLOWED;
    }

    if (r->uri.data[r->uri.len - 1] == '/') {
        return NGX_DECLINED;
    }
//因为我们不处理接受到的包体，所以全部丢弃
    rc = ngx_http_discard_request_body(r);

    if (rc != NGX_OK) {
        return rc;
    }

    ctx = ngx_http_get_module_ctx(r, ngx_http_flv_live_module);
    if (ctx == NULL) {
        ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_flv_live_ctx_t));

        if (ctx == NULL) {
            return NGX_HTTP_INTERNAL_SERVER_ERROR;
        }

        ngx_http_set_ctx(r, ctx, ngx_http_flv_live_module);
    }

    rconn = ngx_pcalloc(r->pool, sizeof(ngx_rtmp_connection_t));
    if (rconn == NULL) {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }

    if (ngx_http_flv_live_preprocess(r, rconn) != NGX_OK) {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }
//这里就是构造一个rtmp 的session,相当于play阶段
    s = ngx_http_flv_live_init_connection(r, rconn);
    if (s == NULL) {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }

    ctx->s = s;

    /* live, ranges not allowed */
    r->allow_ranges = 0;
    r->read_event_handler = ngx_http_test_reading;

    cln = ngx_http_cleanup_add(r, 0);
    if (cln == NULL) {
        return NGX_DECLINED;
    }

    cln->handler = ngx_http_flv_live_cleanup;
    cln->data = s;
//这里将这个事件发送出去，epoll主循环就会接受到这个事件，然后开始朝着客户端发送http-flv数据
    if (ngx_rtmp_fire_event(s, NGX_HTTP_FLV_LIVE_REQUEST, NULL, NULL)
        != NGX_OK)
    {
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }

    r->main->count++;

    return NGX_DONE;
}