Merge pull request #1633 from stephenc/fix-load-stat-description

Fix load statistics description

core/src/main/resources/hudson/model/LoadStatistics/main.properties

@@ -22,22 +22,31 @@
 
 title=Load statistics: {0}
 blurb=\
-  Load statistics keep track of three key metrics of resource utilization: \
+  Load statistics keep track of four key metrics of resource utilization: \
   <dl> \
-    <dt>Total number of executors</dt> \
+    <dt>Number of online executors</dt> \
     <dd>\
-      For a computer, this is the number of executors that the computer has. \
-      For a label, this is the sum of all executors across all computers in this label. \
-      For the entire Jenkins, this is the sum of all executors across all computers in this Jenkins installation. \
+      For a computer: if the computer is online then this is the number of executors that \
+      the computer has; if the computer is offline then this is zero. <br />\
+      For a label: this is the sum of all executors across all online computers in this label. <br />\
+      For the entire Jenkins: this is the sum of all executors across all online computers in this Jenkins \
+      installation. <br /> \
       Other than configuration changes, this value can also change when slaves go offline. \
     </dd> \
     <dt>Number of busy executors</dt> \
     <dd>\
       This line tracks the number of executors (among the executors counted above) \
-      that are carrying out builds. The ratio of this to the total number of executors \
+      that are carrying out builds. The ratio of this to the number of online executors \
       gives you the resource utilization. If all your executors are busy for \
       a prolonged period of time, consider adding more computers to your Jenkins cluster.\
     </dd>\
+    <dt>Number of available executors</dt> \
+    <dd>\
+      This line tracks the number of executors (among the online executors counted above) \
+      that are available to carry out builds. The ratio of this to the total number of executors \
+      gives you the resource availability. If none of your executors are available for \
+      a prolonged period of time, consider adding more computers to your Jenkins cluster.\
+    </dd>\
     <dt>Queue length</dt>\
     <dd>\
       This is the number of jobs that are in the build queue, waiting for an \
@@ -48,5 +57,8 @@ blurb=\
       adding more computers.\
     </dd>\
   </dl>\
-  The graph is exponential moving average of periodically collected data values. \
-  3 timespans are updated every 10 seconds, 1 minute, and 1 hour respectively.
+  <p><b>Note:</b>The number of busy executors and the number of available executors need not \
+  necessarily be equal to the number of online executors as executors can be suspended from\
+  accepting builds and thus be neither busy nor available.</p>\
+  <p>The graph is an exponential moving average of periodically collected data values. \
+  3 timespans are updated every 10 seconds, 1 minute and 1 hour respectively.</p>