DelayNoMore/frontend/assets/scripts/NetworkDoctor.js

const RingBuffer = require('./RingBuffer');

var NetworkDoctor = function(capacity) {
  this.reset(capacity);
};

NetworkDoctor.prototype.reset = function(capacity) {
  this.sendingQ = new RingBuffer(capacity);
  this.inputFrameDownsyncQ = new RingBuffer(capacity);
  this.peerInputFrameUpsyncQ = new RingBuffer(capacity);
  this.peerInputFrameUpsyncCnt = 0;
  this.immediateRollbackFrames = 0;
  this.skippedRenderFrameCnt = 0;

  this.inputRateThreshold = gopkgs.ConvertToNoDelayInputFrameId(60);
  this.peerUpsyncThreshold = 8;
  this.rollbackFramesThreshold = 8; // Roughly the same as TurnAroundFramesToRecover
};

NetworkDoctor.prototype.logSending = function(stFrameId, edFrameId) {
  this.sendingQ.put({
    i: stFrameId,
    j: edFrameId,
    t: Date.now()
  });
};

NetworkDoctor.prototype.logInputFrameDownsync = function(stFrameId, edFrameId) {
  this.inputFrameDownsyncQ.put({
    i: stFrameId,
    j: edFrameId,
    t: Date.now()
  });
};

NetworkDoctor.prototype.logPeerInputFrameUpsync = function(stFrameId, edFrameId) {
  const firstPopped = this.peerInputFrameUpsyncQ.put({
    i: stFrameId,
    j: edFrameId,
    t: Date.now()
  });
  if (null != firstPopped) {
    this.peerInputFrameUpsyncCnt -= (firstPopped.j - firstPopped.i + 1);
  }
  this.peerInputFrameUpsyncCnt += (edFrameId - stFrameId + 1);
};

NetworkDoctor.prototype.logRollbackFrames = function(x) {
  this.immediateRollbackFrames = x;
};

NetworkDoctor.prototype.stats = function() {
  let sendingFps = 0,
    srvDownsyncFps = 0,
    peerUpsyncFps = 0,
    rollbackFrames = this.immediateRollbackFrames;
  if (1 < this.sendingQ.cnt) {
    const st = this.sendingQ.getByFrameId(this.sendingQ.stFrameId);
    const ed = this.sendingQ.getByFrameId(this.sendingQ.edFrameId - 1);
    const elapsedMillis = ed.t - st.t;
    sendingFps = Math.round((ed.j - st.i) * 1000 / elapsedMillis);
  }
  if (1 < this.inputFrameDownsyncQ.cnt) {
    const st = this.inputFrameDownsyncQ.getByFrameId(this.inputFrameDownsyncQ.stFrameId);
    const ed = this.inputFrameDownsyncQ.getByFrameId(this.inputFrameDownsyncQ.edFrameId - 1);
    const elapsedMillis = ed.t - st.t;
    srvDownsyncFps = Math.round((ed.j - st.i) * 1000 / elapsedMillis);
  }
  if (1 < this.peerInputFrameUpsyncQ.cnt) {
    const st = this.peerInputFrameUpsyncQ.getByFrameId(this.peerInputFrameUpsyncQ.stFrameId);
    const ed = this.peerInputFrameUpsyncQ.getByFrameId(this.peerInputFrameUpsyncQ.edFrameId - 1);
    const elapsedMillis = ed.t - st.t;
    peerUpsyncFps = Math.round(this.peerInputFrameUpsyncCnt * 1000 / elapsedMillis);
  }
  return [sendingFps, srvDownsyncFps, peerUpsyncFps, rollbackFrames, this.skippedRenderFrameCnt];
};

NetworkDoctor.prototype.logSkippedRenderFrameCnt = function() {
  this.skippedRenderFrameCnt += 1;
}

NetworkDoctor.prototype.isTooFast = function() {
  const [sendingFps, srvDownsyncFps, peerUpsyncFps, rollbackFrames, skippedRenderFrameCnt] = this.stats();
  if (sendingFps >= this.inputRateThreshold && srvDownsyncFps >= this.inputRateThreshold) {
    // At least my network is OK for both TX & RX directions. 
    if (rollbackFrames >= this.rollbackFramesThreshold && peerUpsyncFps < this.peerUpsyncThreshold) {
      // I got many frames rolled back while none of my peers effectively helped my preciction.  
      return true;
    }
  }
  return false;
};

module.exports = NetworkDoctor;