KERNEL: Refine logger and error

[winlinvip]

The logger should only log the "BIG" events, which are not error. In addition, logger should support context. The errors should, not only the error code, but indicates the context such as the stack and description. For detail information about errors, please read https://gocn.io/article/348.

For SRS, it confuses the error and logger, that is SRS output error in logger and in each function calls. There is a example, when error cames from SrsSource::on_video_imp, each function will print a error:

int SrsSource::on_video_imp(SrsSharedPtrMessage* msg) {
    if ((ret = hub->on_video(msg, is_sequence_header)) != ERROR_SUCCESS) {
        srs_error("origin hub error, ret=%d", ret);
        return ret;
    }
}

int SrsOriginHub::on_video(SrsSharedPtrMessage* shared_video, bool is_sequence_header) {
    if ((ret = format->on_video(msg)) != ERROR_SUCCESS) {
        srs_error("Codec parse video failed, ret=%d", ret);
        return ret;
    }
}

int SrsFormat::on_video(int64_t timestamp, char* data, int size) {
    return video_avc_demux(buffer, timestamp);
}

int SrsFormat::video_avc_demux(SrsBuffer* stream, int64_t timestamp) {
    if (!stream->require(4)) {
        ret = ERROR_HLS_DECODE_ERROR;
        srs_error("avc decode avc_packet_type failed. ret=%d", ret);
        return ret;
    }
}

Let's have a look what happends when there is a decode error:

avc decode avc_packet_type failed. ret=3001
Codec parse video failed, ret=3001
origin hub error, ret=3001

Is it useful? Yes, it's useful than just an error code like Failed, code is 3001, but it's not enough:

1. There is no stack info.
2. The logs are not simply enough.

I'll be better if the error is like this:

Error processing video, code=3001 : origin hub : codec parser : avc decoder
[100] video_avc_demux() at [srs_kernel_codec.cpp:676]
[100] on_video() at [srs_app_source.cpp:1076]
[101] on_video_imp() at [srs_app_source:2357]

For logger, it should log some important events, the error should be one event.

[winlinvip]

We use variable ret:int as simple error code, while using err:srs_error_t for complex error. In addition, use macro ERROR_SUCCESS:int and srs_success:srs_error_t.

For some error in underlayer, for example, for daemon to fork processes, we can just use error without logger:

    if(pid < 0) {
        return srs_error_new(-1, "fork failed");
    }

Replace the old logger+error:

    if(pid < 0) {
        srs_error("create process error. ret=-1"); //ret=0
        return -1;
    }

That's the point. After refined, the error is a single event to log:

[2017-06-09 11:47:44.954][Error][65476][0][0] Failed, code=1005 : server initialize : http api initialize
thread #0: run() [src/main/srs_main_server.cpp:375][errno=0]
thread #0: initialize() [src/app/srs_app_server.cpp:583][errno=0]

For each call function, use srs_error_wrap to attach the stack:

    if ((err = svr->initialize_st()) != srs_success) {
        return srs_error_wrap(err, "initialize st");
    }

That's right~

[winlinvip]

Here we confused the log and error:

            if ((ret = rtsp->send_message(res)) != ERROR_SUCCESS) {
                if (!srs_is_client_gracefully_close(ret)) {
                    srs_error("rtsp: send SETUP response failed. ret=%d", ret);
                }
                return ret;
            }

Instead, we should return a error:

            if ((ret = rtsp->send_message(res)) != ERROR_SUCCESS) {
                return srs_error_new(ret, "send message");
            }

Finally at the top of call, such as the thread cycle or main cycle, we can decide whether to print the error or not.

[winlinvip]

Fixed.