Custom stacked row chart

This chart renders custom stacked row chart to represent bunch of servers, their up time and health level at different intervlas

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    svg { width:100%; height: 100% }
    text {
  
  font: 11px sans-serif;
}
  
.axis path, .axis line {
    fill: none;
    stroke: #000;
    shape-rendering: crispEdges;
}
    
.axis text {
    font-family: sans-serif;
    font-size: 11px;
}
ul
{
    list-style-type: none;
  
}
  </style>
</head>

<body>
  <span><strong>Searver uptime and health</strong></span>
  <ul>
  <li><span style="background-color: #84CA50; padding-left: 15px;"></span> - good</li>
  <li><span style="background-color: #F07D02; padding-left: 15px;"></span> - bad 1</li>
  <li><span style="background-color: #E60000; padding-left: 15px;"></span> - bad 2</li>
    <li><span style="background-color: #9E1313; padding-left: 15px;"></span> - bad 3</li>
</ul>
  <script>
var chartData = [
  {
    TenantName: 'server 1', 
    BakeTimes: [
     {start: 0, end: 5, level: 0},
     {start: 5, end: 10, level: 1},
     {start: 10, end: 16, level: 2},
     {start: 19, end: 26, level: 4}, // 4 maps to level 3 color, anything grater than 3 = dark red
     {start: 26, end: 35, level: 0}
   ]
  },
  {
    TenantName: 'server 2', 
    BakeTimes: [
     {start: 10, end: 15, level: 0},
     {start: 15, end: 16, level: 1},
     {start: 16, end: 20, level: 2},
     {start: 20, end: 23, level: 4},
     {start: 23, end: 30, level: 0}
   ]
  },
  {
    TenantName: 'server 3', 
    BakeTimes: [
     {start: 9, end: 15, level: 0},
     {start: 1, end: 6, level: 1}, //start,end not in any particular order
     {start: 16, end: 20, level: 2},
     {start: 20, end: 21, level: 4},
     {start: 21, end: 22, level: 1},
     {start: 22, end: 33, level: 0}
   ]
  },
  {
    TenantName: 'server 4', 
    BakeTimes: [
     {start: 2, end: 5, level: 0},
     {start: 7, end: 10, level: 1},
     {start: 13, end: 20, level: 0},
     {start: 20, end: 23, level: 4},
     {start: 23, end: 35, level: 0}
   ]
  },
   {
    TenantName: 'server 5', 
    BakeTimes: [
     
     {start: 23, end: 35, level: 0}
   ]
  }
];

var maxVal = d3.max(chartData, function(data){
  return d3.max(data.BakeTimes, function(d){
    return d.end;
  });
});

//console.log(maxVal);

var id = 'body';
var tenantRowColor = '#84CA50';

var warningLevels = ['#84CA50', '#F07D02', '#E60000','#9E1313'];

var margin = {
    top: 20,
    right: 20,
    bottom: 20,
    left: 20
};
    
var chartWidth = 500,
    width = chartWidth - margin.left - margin.right,
    barHeight = 20,
    height = ((barHeight * chartData.length)+25) - margin.top - margin.bottom;
var leftPadding = 180;

var xScale = d3.scale.linear()
    .domain([0, d3.max(chartData, function(data){
                return d3.max(data.BakeTimes, function(d){
                  return d.end;
                });
            })
    ])
    .range([0, width-(leftPadding+20)]);

var yScale = d3.scale.ordinal()
    // SECOND PARAM IS PADDING
    .rangeRoundBands([0, (barHeight * chartData.length)], 0)
    .domain(chartData.map(function (d) { return d.TenantName; }));

var chart = d3.select(id).append('svg')
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom+40)
    .append('g')
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var lines = chart.append('g').selectAll('g')
     .data(chartData)
     .enter()
     .append('g')
     .attr("transform", 
                     function(d, i) { return "translate(0," + i * barHeight + ")"; });

lines.each(function(d){
  d3.select(this).append("line")
                         .attr("x1", leftPadding)
                         .attr("y1", 10)
                         .attr("x2", 300+leftPadding)
                         .attr("y2", 10)
                         .attr("stroke-width", 0.5)
                        .attr("stroke", "black")
                        .attr('stroke-dasharray', '3,3');
  
});

//render rectangle for each health level as bars
var newBar = chart.append('g').selectAll('g')
     .data(chartData)
     .enter()
     .append('g')
     .attr("transform", 
                     function(d, i) { return "translate(0," + i * barHeight + ")"; });

newBar
  .each(function(d) {
    var bakeTimes = d.BakeTimes;
      d3.select(this).selectAll('rect').data(bakeTimes)
      .enter()
        .append('rect')
        .attr('x', function(d) { return xScale(d.start) + leftPadding; })
        .attr('width', function(d) { return xScale(d.end) - xScale(d.start);})
        .attr('height', barHeight -3)
        .attr('fill', function(d){ 
          var colorLevel = d.level;
          if(colorLevel > 3)
            {
              colorLevel = 3;
            }
          return warningLevels[colorLevel];
        });
  });

//axis
var xAxis = d3.svg.axis()
    .scale(xScale)
    .orient('bottom')
    .ticks(5);

chart.append('g')
    .attr('class', 'x axis')
    .attr('transform', 'translate('+ leftPadding +',' + (height+15) + ')')
    .call(xAxis);

//y axis
var yAxis = d3.svg.axis()
    .scale(yScale)
    .orient('left');

chart.append("g")
    .attr("class", "y axis")
   .attr('transform', 'translate('+leftPadding + ',' + 0 + ')')
    .call(yAxis);
  </script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js