Drawing realtime graph with SyncGateway and Plot.ly

sync-streaming.js

/*
# ===================
# How to execute
# ===================
# Install dependencies.
$ npm install plotly
$ npm install request
$ npm install moment
# Execute.
$ node sync-streaming.js
*/
var plotly = require('plotly')('your-plotly-account', 'your-api-token');
var request = require('request');
var moment = require('moment');

var graphOptions = {
  // fileopt : "extend",
  fileopt : "overwrite",
  filename : "sync-stream-test",
  layout: {
    title: "Changes stream",
    xaxis: {
      type: "date",
      autorange: true
    },
    yaxis: {
      type: "linear",
      range: [0, 50],
      autorange: true
    }
  }
};

var streamToken = 'jcrlj19ki1';
var init_data = [{
    x : [], y : [],
    stream : {
      token : streamToken,
      maxpoints : 20
    }
}];

plotly.plot(init_data, graphOptions, function (err, msg) {
  if (err) return console.log(err);
  console.log(msg);

  var stream = plotly.stream(streamToken, function (err, res) {
    console.log(err, res);
    clearInterval(loop); // once stream is closed, stop writing
  });

  var since = 0;
  var limit = 10;
  var fetchFreqInMillis = 1000;
  var noDataCnt = 0;
  var noDataFreq = 3;
  var dateFormat = 'YYYY-MM-DD HH:mm:ss.SSS';
  console.log('Start streaming...');
  var loop = setInterval(function () {
    var option = {
      url: 'http://localhost:4984/kitchen-sync/_changes',
      json: true,
      body: {
        include_docs: true,
        since: since,
        limit: limit
      }
    };
    console.log('Fetching changes...');
    request.post(option, function(err, httpResponse, body){
      if(err){
              return console.error('Failed to fetch changes.', err);
      }
  
      var emitted = false;
      for(var i = 0; i < body.results.length; i++){
        if(typeof(body.results) === 'undefined') continue;
        var r = body.results[i];
        if((typeof(r.doc) === 'undefined')
          || (r.doc._deleted)
          || (typeof(r.doc.created_at) === 'undefined')) {
          continue;
        }
        console.log(body.results[i]);
      
        var streamObject = {
          x: moment(r.doc.created_at).format(dateFormat),
          y: r.doc.text.length
        };
        stream.write(JSON.stringify(streamObject)+'\n');
        emitted = true;
      }
  
      if(emitted) noDataCnt = 0;
      else noDataCnt++;
  
      if(noDataCnt > noDataFreq){
        var streamObject = {
                x: moment(new Date())
                        .subtract(fetchFreqInMillis, 'millisecond').format(dateFormat),
                y: 0
        };
        console.log('Writing no data...', streamObject);
        stream.write(JSON.stringify(streamObject)+'\n');
        noDataCnt = 0;
      }
  
      since = body.last_seq;
    });
  }, fetchFreqInMillis);

});