CLOUDSTACK-816. DOC. Document health checks for load balanced instances.

docs/en-US/add-load-balancer-rule.xml

@@ -67,8 +67,8 @@
         </listitem>
         <listitem>
           <para><emphasis role="bold">Stickiness</emphasis>: (Optional) Click Configure and choose
-            the algorithm for the stickiness policy. See Sticky Session Policies for Load Balancer
-            Rules.</para>
+            the algorithm for the stickiness policy. See <xref
+            linkend="sticky-session-policies-for-lb-rules"/>.</para>
         </listitem>
         <listitem>
           <para><emphasis role="bold">AutoScale</emphasis>: Click Configure and complete the
@@ -76,6 +76,22 @@
         </listitem>
       </itemizedlist>
     </listitem>
+    <listitem><para><emphasis role="bold">Health Check</emphasis>: (Optional; NetScaler load balancers only) Click
+        Configure and fill in the characteristics of the health check policy. See <xref
+          linkend="health-checks-for-lb-rules"/>.</para>		
+      <itemizedlist>
+        <listitem><para><emphasis role="bold">Ping path (Optional)</emphasis>: Sequence of destinations to which to send health check queries.
+          Default: / (all).</para></listitem>			
+        <listitem><para><emphasis role="bold">Response time (Optional)</emphasis>: How long to wait for a response from the health check (2 - 60 seconds).
+          Default: 5 seconds.</para></listitem>
+        <listitem><para><emphasis role="bold">Interval time (Optional)</emphasis>: Amount of time between health checks (1 second - 5 minutes).
+          Default value is set in the global configuration parameter lbrule_health check_time_interval.</para></listitem>
+        <listitem><para><emphasis role="bold">Healthy threshold (Optional)</emphasis>: Number of consecutive health check successes
+          that are required before declaring an instance healthy.
+          Default: 2.</para></listitem>
+        <listitem><para><emphasis role="bold">Unhealthy threshold (Optional)</emphasis>: Number of consecutive health check failures that are required before declaring an instance unhealthy. 
+          Default: 10.</para></listitem>     
+      </itemizedlist></listitem>
     <listitem>
       <para>Click Add VMs, then select two or more VMs that will divide the load of incoming
         traffic, and click Apply.</para>

docs/en-US/health-checks-for-lb-rules.xml

@@ -0,0 +1,48 @@
+<?xml version='1.0' encoding='utf-8' ?>
+<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY % BOOK_ENTITIES SYSTEM "cloudstack.ent">
+%BOOK_ENTITIES;
+]>
+
+<!-- Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License.  You may obtain a copy of the License at
+ 
+   http://www.apache.org/licenses/LICENSE-2.0
+ 
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied.  See the License for the
+ specific language governing permissions and limitations
+ under the License.
+-->
+<section id="health-checks-for-lb-rules">
+  <!-- CLOUDSTACK-443 -->
+  <title>Health Checks for Load Balancer Rules</title>
+  <para>(NetScaler load balancer only)
+  </para>
+  <para>Health checks are used in load-balanced applications to ensure that requests are forwarded
+    only to running, available services.
+    When creating a load balancer rule, you can specify a health check policy.
+    This is in addition to specifying the
+    stickiness policy, algorithm, and other load balancer rule options.
+    You can configure one health check policy per load balancer rule.</para>
+  <para>Any load balancer rule defined on a NetScaler load balancer in &PRODUCT; can have a health check policy.
+    The policy consists of a ping path, thresholds to define "healthy" and "unhealthy" states,
+    health check frequency, and timeout wait interval.</para>
+  <para>When a health check policy is in effect,
+    the load balancer will stop forwarding requests to any resources that are found to be unhealthy.
+    If the resource later becomes available again, the periodic health check
+    will discover it, and the resource will once again be added to the pool of resources that can
+    receive requests from the load balancer.</para>
+  <para>You can delete or modify existing health check policies.</para>
+  <para>To configure how often the health check is performed by default, use the global
+    configuration setting lbrule_health check_time_interval.
+    You can override this value for an individual health check policy.</para>
+  <para>For details on how to set a health check policy using the UI, see <xref linkend="add-load-balancer-rule"/>.</para>
+</section>

docs/en-US/load-balancer-rules.xml

@@ -37,4 +37,5 @@
   <xi:include href="add-load-balancer-rule.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
   <xi:include href="sticky-session-policies-for-lb-rules.xml"
     xmlns:xi="http://www.w3.org/2001/XInclude"/>
+  <xi:include href="health-checks-for-lb-rules.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
 </section>