mediasoup源码分析--channel创建及信令交互
概述
在golang实现mediasoup的tcp服务及channel通道一文中，已经介绍过信令服务中tcp和channel的创建，本文主要讲解c++中mediasoup的channel创建，以及信令服务和mediasoup服务如何交互
跨职能图
业务流程图
数据发送有两种方式:
应用层发送的request最后被封装在Requst对象中，其中包含着"id"，因为Request对象中包含着Channel::UnixStreamSocket对象，所以可以直接调用Request::Accept()将处理后的结果告诉应用层进程。
Worker进程也可以主动给应用层进程发送消息，通过Notifier::Emit()即可以给应用进程发送消息，Notifier类中有Channel::UnixStreamSocket，所以直接调用Channel::UnixStreamSocket::Send()就可以发送消息。Notifier类内部的数据成员和函数成员都是静态的，所以在任意位置可以直接通过Channel::Notifier::Emit()函数发送消息。
代码剖析
1.channel创建
cpp
int main(int argc, char* argv[])
{
// Ensure we are called by our Node library.
if (argc == 1)
{
std::cerr << "ERROR: you don't seem to be my real father" << std::endl;
std::_Exit(EXIT_FAILURE);
}
std::string id = std::string(argv[1]);
std::string ip = std::string(argv[2]);
int port = atoi(argv[3]);
int iperfPort = atoi(argv[4]);
// Initialize libuv stuff (we need it for the Channel).
DepLibUV::ClassInit();
//..........省略部分代码..............
// Set the Channel socket (this will be handled and deleted by the Worker).
printf("new Channel to %s:%d\n",ip.c_str(),port);
auto* channel = new Channel::UnixStreamSocket(ip,port);
//..........省略部分代码..............
try
{
// Run the Worker.
Worker worker(id,channel);
// Worker ended.
destroy();
exitSuccess();
}
catch (const MediaSoupError& error)
{
MS_ERROR_STD("failure exit: %s", error.what());
destroy();
exitWithError();
}
}UnixStreamSocket构造函数
cpp
UnixStreamSocket::UnixStreamSocket(const std::string& ip,int port) : ::UnixStreamSocket::UnixStreamSocket(ip,port, MaxSize)
{
MS_TRACE_STD();
// Create the JSON reader.
{
Json::CharReaderBuilder builder;
Json::Value settings = Json::nullValue;
Json::Value invalidSettings;
builder.strictMode(&settings);
MS_ASSERT(builder.validate(&invalidSettings), "invalid Json::CharReaderBuilder");
this->jsonReader = builder.newCharReader();
}
// Create the JSON writer.
{
Json::StreamWriterBuilder builder;
Json::Value invalidSettings;
builder["commentStyle"] = "None";
builder["indentation"] = "";
builder["enableYAMLCompatibility"] = false;
builder["dropNullPlaceholders"] = false;
MS_ASSERT(builder.validate(&invalidSettings), "invalid Json::StreamWriterBuilder");
this->jsonWriter = builder.newStreamWriter();
}
}跳转到handles\UnixStreamSocket.cpp下
cpp
UnixStreamSocket::UnixStreamSocket( const std::string& ip,int port,size_t bufferSize) : bufferSize(bufferSize)
{
printf("::UnixStreamSocket::UnixStreamSocket\n");
MS_TRACE_STD();
int err;
this->uvHandle = new uv_tcp_t;
this->uvHandle->data = (void*)this;
err = uv_tcp_init(DepLibUV::GetLoop(), this->uvHandle);
if (err != 0)
{
delete this->uvHandle;
this->uvHandle = nullptr;
printf("uv_tcp_init() failed: %s\n", uv_strerror(err));
MS_THROW_ERROR_STD("uv_tcp_init() failed: %s", uv_strerror(err));
}
struct sockaddr_in dest;
uv_ip4_addr(ip.c_str(), port, &dest);
this->connect = new uv_connect_t;
printf("will connect to %s:%d\n",ip.c_str(),port);
err = uv_tcp_connect(this->connect, this->uvHandle, (const struct sockaddr*)&dest, onConnect);
if (err != 0)
{
delete this->uvHandle;
this->uvHandle = nullptr;
printf("uv_tcp_connect() failed: %s\n", uv_strerror(err));
MS_THROW_ERROR_STD("uv_tcp_connect() failed: %s", uv_strerror(err));
}
// Start reading.
err = uv_read_start(
reinterpret_cast<uv_stream_t*>(this->uvHandle),
static_cast<uv_alloc_cb>(onAlloc),
static_cast<uv_read_cb>(onRead));
if (err != 0)
{
uv_close(reinterpret_cast<uv_handle_t*>(this->uvHandle), static_cast<uv_close_cb>(onClose));
MS_THROW_ERROR_STD("uv_read_start() failed: %s", uv_strerror(err));
}
// NOTE: Don't allocate the buffer here. Instead wait for the first uv_alloc_cb().
}代码中的uv_read_start接口中onRead回调
cpp
err = uv_read_start(
reinterpret_cast<uv_stream_t*>(this->uvHandle),
static_cast<uv_alloc_cb>(onAlloc),
static_cast<uv_read_cb>(onRead));跳转到onRead中
cpp
inline static void onRead(uv_stream_t* handle, ssize_t nread, const uv_buf_t* buf)
{
auto* socket = static_cast<UnixStreamSocket*>(handle->data);
if (socket == nullptr)
return;
socket->OnUvRead(nread, buf);
}OnUvRead中调用UserOnUnixStreamRead
cpp
void UnixStreamSocket::UserOnUnixStreamRead()
{
MS_TRACE_STD();
// Be ready to parse more than a single message in a single TCP chunk.
while (true)
{
if (IsClosed())
return;
size_t readLen = this->bufferDataLen - this->msgStart;
char* jsonStart = nullptr;
size_t jsonLen;
int nsRet = netstring_read(
reinterpret_cast<char*>(this->buffer + this->msgStart), readLen, &jsonStart, &jsonLen);
//.............省略部分代码..............
// If here it means that jsonStart points to the beginning of a JSON string
// with jsonLen bytes length, so recalculate readLen.
readLen =
reinterpret_cast<const uint8_t*>(jsonStart) - (this->buffer + this->msgStart) + jsonLen + 1;
Json::Value json;
std::string jsonParseError;
if (this->jsonReader->parse(
(const char*)jsonStart, (const char*)jsonStart + jsonLen, &json, &jsonParseError))
{
Channel::Request* request = nullptr;
try
{
request = new Channel::Request(this, json);
}
catch (const MediaSoupError& error)
{
MS_ERROR_STD("discarding wrong Channel request");
}
if (request != nullptr)
{
// Notify the listener.
this->listener->OnChannelRequest(this, request);
// Delete the Request.
delete request;
}
//.............省略部分代码..............
...
}
}channel创建完成，至此，跳转到worker.cpp中的OnChannelRequest接口。mediasoup监听channel信令并根据request->methodId分类处理
根据request->methodId，分别执行不同的业务
request->methodId有如下分类
cpp
std::unordered_map<std::string, Request::MethodId> Request::string2MethodId =
{
{ "worker.dump", Request::MethodId::WORKER_DUMP },
{ "worker.updateSettings", Request::MethodId::WORKER_UPDATE_SETTINGS },
{ "worker.createRouter", Request::MethodId::WORKER_CREATE_ROUTER },
{ "router.close", Request::MethodId::ROUTER_CLOSE },
{ "router.dump", Request::MethodId::ROUTER_DUMP },
{ "router.createWebRtcTransport", Request::MethodId::ROUTER_CREATE_WEBRTC_TRANSPORT },
{ "router.createPlainRtpTransport", Request::MethodId::ROUTER_CREATE_PLAIN_RTP_TRANSPORT },
{ "router.createProducer", Request::MethodId::ROUTER_CREATE_PRODUCER },
{ "router.createConsumer", Request::MethodId::ROUTER_CREATE_CONSUMER },
{ "router.setAudioLevelsEvent", Request::MethodId::ROUTER_SET_AUDIO_LEVELS_EVENT },
{ "transport.close", Request::MethodId::TRANSPORT_CLOSE },
{ "transport.dump", Request::MethodId::TRANSPORT_DUMP },
{ "transport.getStats", Request::MethodId::TRANSPORT_GET_STATS },
{ "transport.setRemoteDtlsParameters", Request::MethodId::TRANSPORT_SET_REMOTE_DTLS_PARAMETERS },
{ "transport.setRemoteParameters", Request::MethodId::TRANSPORT_SET_REMOTE_PARAMETERS },
{ "transport.setMaxBitrate", Request::MethodId::TRANSPORT_SET_MAX_BITRATE },
{ "transport.changeUfragPwd", Request::MethodId::TRANSPORT_CHANGE_UFRAG_PWD },
{ "transport.startMirroring", Request::MethodId::TRANSPORT_START_MIRRORING },
{ "transport.stopMirroring", Request::MethodId::TRANSPORT_STOP_MIRRORING },
{ "producer.close", Request::MethodId::PRODUCER_CLOSE },
{ "producer.dump", Request::MethodId::PRODUCER_DUMP },
{ "producer.getStats", Request::MethodId::PRODUCER_GET_STATS },
{ "producer.pause", Request::MethodId::PRODUCER_PAUSE },
{ "producer.resume" , Request::MethodId::PRODUCER_RESUME },
{ "producer.setPreferredProfile", Request::MethodId::PRODUCER_SET_PREFERRED_PROFILE },
{ "consumer.close", Request::MethodId::CONSUMER_CLOSE },
{ "consumer.dump", Request::MethodId::CONSUMER_DUMP },
{ "consumer.getStats", Request::MethodId::CONSUMER_GET_STATS },
{ "consumer.enable", Request::MethodId::CONSUMER_ENABLE },
{ "consumer.pause", Request::MethodId::CONSUMER_PAUSE },
{ "consumer.resume", Request::MethodId::CONSUMER_RESUME },
{ "consumer.setPreferredProfile", Request::MethodId::CONSUMER_SET_PREFERRED_PROFILE },
{ "consumer.setEncodingPreferences", Request::MethodId::CONSUMER_SET_ENCODING_PREFERENCES },
{ "consumer.requestKeyFrame", Request::MethodId::CONSUMER_REQUEST_KEY_FRAME }
};下一章节介绍mediasoup如何将信令返回值及其他通知信息推送到信令服务，敬请期待！