[SPARK-8399] [STREAMING] [WEB UI] Overlap between histograms and axis' name in Spark Streaming UI

Moved where the X axis' name (#batches) is written in histograms in the spark streaming web ui so the histograms and the axis' name do not overlap.

Author: BenFradet <benjamin.fradet@gmail.com>

Closes apache#6845 from BenFradet/SPARK-8399 and squashes the following commits:

b63695f [BenFradet] adjusted inner histograms
eb610ee [BenFradet] readjusted #batches on the x axis
dd46f98 [BenFradet] aligned all unit labels and ticks
0564b62 [BenFradet] readjusted #batches placement
edd0936 [BenFradet] moved where the X axis' name (#batches) is written in histograms in the spark streaming web ui

Author: BenFradet

streaming/src/main/resources/org/apache/spark/streaming/ui/static/streaming-page.js

@@ -31,6 +31,8 @@ var maxXForHistogram = 0;
 var histogramBinCount = 10;
 var yValueFormat = d3.format(",.2f");
 
+var unitLabelYOffset = -10;
+
 // Show a tooltip "text" for "node"
 function showBootstrapTooltip(node, text) {
     $(node).tooltip({title: text, trigger: "manual", container: "body"});
@@ -133,7 +135,7 @@ function drawTimeline(id, data, minX, maxX, minY, maxY, unitY, batchInterval) {
         .attr("class", "y axis")
         .call(yAxis)
         .append("text")
-            .attr("transform", "translate(0," + (-3) + ")")
+            .attr("transform", "translate(0," + unitLabelYOffset + ")")
             .text(unitY);
 
 
@@ -223,10 +225,10 @@ function drawHistogram(id, values, minY, maxY, unitY, batchInterval) {
         .style("border-left", "0px solid white");
 
     var margin = {top: 20, right: 30, bottom: 30, left: 10};
-    var width = 300 - margin.left - margin.right;
+    var width = 350 - margin.left - margin.right;
     var height = 150 - margin.top - margin.bottom;
 
-    var x = d3.scale.linear().domain([0, maxXForHistogram]).range([0, width]);
+    var x = d3.scale.linear().domain([0, maxXForHistogram]).range([0, width - 50]);
     var y = d3.scale.linear().domain([minY, maxY]).range([height, 0]);
 
     var xAxis = d3.svg.axis().scale(x).orient("top").ticks(5);
@@ -248,7 +250,7 @@ function drawHistogram(id, values, minY, maxY, unitY, batchInterval) {
         .attr("class", "x axis")
         .call(xAxis)
         .append("text")
-            .attr("transform", "translate(" + (margin.left + width - 40) + ", 15)")
+            .attr("transform", "translate(" + (margin.left + width - 45) + ", " + unitLabelYOffset + ")")
             .text("#batches");
 
     svg.append("g")

streaming/src/main/scala/org/apache/spark/streaming/ui/StreamingPage.scala

@@ -310,7 +310,7 @@ private[ui] class StreamingPage(parent: StreamingTab)
         <tr>
           <th style="width: 160px;"></th>
           <th style="width: 492px;">Timelines (Last {batchTimes.length} batches, {numActiveBatches} active, {numCompletedBatches} completed)</th>
-          <th style="width: 300px;">Histograms</th></tr>
+          <th style="width: 350px;">Histograms</th></tr>
       </thead>
       <tbody>
         <tr>
@@ -456,7 +456,7 @@ private[ui] class StreamingPage(parent: StreamingTab)
       <td>{receiverActive}</td>
       <td>{receiverLocation}</td>
       <td>{receiverLastErrorTime}</td>
-      <td><div style="width: 292px;">{receiverLastError}</div></td>
+      <td><div style="width: 342px;">{receiverLastError}</div></td>
     </tr>
     <tr>
       <td colspan="3" class="timeline">