Mediasoup在node.js下多线程实现

mediasoup基于socket.io的交互消息来完成join-room的请求过程。Join的过程,实际就是获取stream的过程,也就是视频加载时间(video-load-speed)。在RTMP系统,视频加载时间是秒开。Mediasoup给出的第一个frame是I-frame,但由于交互的消息较多(8条),node.js是单线程处理框架,并发处理能力明显不足。即使50个并发,也有超过20%的用户视频加载时间>1000ms。

Join-room的过程,由8条消息组成:

#1: roomEventHandler:createRoom,roomId=demo-ch-12

#2: roomEventHandler:join,roomId=demo-ch-12

- addPeer:tXYB1vc5tzNaPQ3TAAFX,demo-ch-12-10.146.11.63 peers=46

- {"event":"User joined","roomId":"demo-ch-12","name":"user_270","ip":"10.146.1.169","peers":1,"routerId":"6e981d85-386b-4fab-b693-9c3fd733d228"}

#3: roomEventHandler:getRouterRtpCapabilities,roomId=demo-ch-12

#4: roomEventHandler:createWebRtcTransport,roomId=demo-ch-12

#5: roomEventHandler:getProducers,roomId=demo-ch-12

#6: roomEventHandler:consume,roomId=demo-ch-12

#7: roomEventHandler:consume,roomId=demo-ch-12

#8: roomEventHandler:connectTransport,roomId=demo-ch-12

Exit-room过程,仅一条消息:

#1: roomEventHandler:exitRoom,roomId=demo-ch-12

- removePeer:tXYB1vc5tzNaPQ3TAAFX,demo-ch-12-10.146.11.63 peers=45

- {"event":"exitRoom","reason":{}}

Mediasoup-client在获取到webrtc streaming data后,交给chrome等浏览器提供的api进行render渲染。这个还需要几十ms时间才能真正观看到视频。

在对node.js框架下的webrtc-server进行多进程MP/多线程MT改造前,先要对消息处理模块socket.io和webrtc流媒体处理模块mediasoup-worker进行介绍。

app = express()

httpsServer = httpolyglot.createServer(credentials, app)

httpsServer.listen(config.listenPort)

iowsSvr = sockio(httpsServer, {cors:true, cookie:{name:"iows",sameSite:"strict",maxAge:86400} })

httpServer是一个单进程,基于它的socket.io-event处理程序是多线程。

for (let i = 0; i < numWorkers; i++) {
      let worker = await mediasoup.createWorker({
        logLevel: config.mediasoup.worker.logLevel,
        logTags: config.mediasoup.worker.logTags,
        rtcMinPort: minPort,
        rtcMaxPort: maxPort
      })        //一个mediasoup-worker fork出一个子进程。
    }

首先尝试多线程MT方案,用node.js的worker_threads模块。

const { Worker, isMainThread, parentPort, workerData } = require('worker_threads')

function iowsSvrListener (ioSvr) {

  ioSvr.on('connection', (socket) => {

    if (isMainThread){

      const wsWorker = new Worker(__filename, { workerData: socket })



      wsWorker.on('exit', () => {

        console.warn("wsWorker exit.")

        wsWorker.terminate()

      })



      wsWorker.on('message', (msg) => {

        console.debug("wsWorker recv:", msg)

        let socket = msg.socket

        socket.onAny(async (eventName, args, cbFunc) => {

          await roomEventHandler(eventName, args, socket, cbFunc)

        })

        socket.on('disconnect', async (args) => {

          await roomEventHandler('disconnect', args, socket)

        })

      })

    }

    else {

      parentPort.postMessage(workerData)

      setInterval(() => {

      }, 60e3)

    }

  })

}

上面这段代码,运行报错:

  - exitHandler:[object Promise],error=function noop() { } could not be cloned.

  >> socket is a complicated object which can not be passed to worker.

实际上,socket.io就是多线程框架,因此,我认为在多线程里面再去实现一个multi-threads是没有意义的。

下面再尝试一下多进程,用const cluster = require('cluster')

由于mediasoup-worker也是多进程,因此就成为socket.io server + mediasoup-worker的架构,这种框架,就大大增加SFU这种webrtc-server处理的复杂性。比如一个broadcaster在processor#1上进行直播,有一个room#1,一个观众从processor#2上来,他根本就无法join到room#1。这种情况就得要求processor#1上的mediasoup-worker pipe到processor#2上来才行。当然还有一个办法是processor#1上的socket.io forward msg to processor#2上的socket.io进行处理(内部转发),消息处理流程显得复杂了,多进程带来的效率提升恐怕也会被吃掉。

最终的结论就是,只能维持当前单进程socket.io server + 多进程mediasoup-worker的框架不变。如果想要进一步提升单台SFU-server的join速度,只能采用Go语言的协程(goroutine)机制了,但这能带来多大的性能提升呢?毕竟node.js的socket.io server性能也不差!而且,整体来说,mediasoup worker能够处理多大的视频流量,这受限于VPS服务器的bandwidth。

1 Gbps的网络,单进程mediasoup-worker就可以轻松处理(cpu load < 60%),可支持到200 peers(video + audio)。那么一个5Gbps的网络,满负荷运行需要5颗cpu,加上socket.io需要一颗cpu,那么6 core cpu的VPS就行了。

Mediasoup在node.js下多线程实现_第1张图片

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