Add sensor details to documentation

phantom/webapp.rst

@@ -137,19 +137,64 @@ the *Refresh* button to see updated information.
 
 When you see that your VM is RUNNING, it is now ready to use.
 
+Creating a sensor autoscaling domain
+------------------------------------
+
+If you would like to create a sensor autoscaling domain, ensure that you
+have tcollector installed and configured on your VM image, then:
+
+1. Click *Add Domain*
+2. Choose a name for the domain in the popup window
+3. Pick the Launch Configuration you created earlier
+4. Type a Sensors to Monitor at the *Add Sensor* box, and then a space
+5. Make sure *Scaling Policy* is set to "Sensor"
+6. Fill out the sensor policy parameters:
+   a) *Metric* is the metric to base scaling actions on
+   b) *Cooldown* is the number of seconds Phantom should wait between scaling 
+   actions. This prevents Phantom from starting and stopping VMs too often
+   c) *Minimum* is the minimum number of VMs to maintain
+   d) *Maximum* is the maximum number of VMs to start
+   e) *Scale Up Threshold*: When the metric value is above this value, Phantom
+   will start VMs to compensate
+   f) *Scale Up By*: The number of VMs to start when the Scale Up Threshold is
+   exceeded
+   g) *Scale Down Threshold*: When the metric value is below this value, Phantom
+   will terminate VMs to compensate
+   h) *Scale Down By*: The number of VMs to terminate when the Scale Down Threshold is
+   exceeded
+7. Click *Start*
+
 Update a domain
 ===============
 
 Once you have started a Domain, you may wish to adjust the settings you picked 
-earlier. For example, you may wish to increase or decrease the number of VMs
+earlier.
+
+Changing the number of running VMs
+----------------------------------
+
+For example, you may wish to increase or decrease the number of VMs
 that are running as a part of your domain. To do this:
 
 1. Select your domain from the list of domains on the left
 2. Change the number of VMs in the domain
 3. Click Update
 
 You should now see the status bar working and the details view should show the 
-updated number of VMs. 
+updated number of VMs.
+
+Adding a sensor to monitor
+--------------------------
+
+If you would like to start monitoring specific sensors for your domain:
+
+1. Select your domain from the list of domains on the left
+2. Type the name of a tcollector sensor, like *proc.loadavg.1min* in the
+   *Add Sensor* box, and then a space
+3. Click Update
+
+If your VM image has tcollector installed on it, you should now see the status
+bar working and the details view should show the sensor value.
 
 Terminate a domain
 ===============