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lab_19.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<!--[if IE]><meta http-equiv="X-UA-Compatible" content="IE=edge"><![endif]-->
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="generator" content="Asciidoctor 1.5.2">
<title>Lab 19 - Fault-Tolerance with Hystrix</title>
<style>
/*! normalize.css v2.1.2 | MIT License | git.io/normalize */
/* ========================================================================== HTML5 display definitions ========================================================================== */
/** Correct `block` display not defined in IE 8/9. */
article, aside, details, figcaption, figure, footer, header, hgroup, main, nav, section, summary { display: block; }
/** Correct `inline-block` display not defined in IE 8/9. */
audio, canvas, video { display: inline-block; }
/** Prevent modern browsers from displaying `audio` without controls. Remove excess height in iOS 5 devices. */
audio:not([controls]) { display: none; height: 0; }
/** Address `[hidden]` styling not present in IE 8/9. Hide the `template` element in IE, Safari, and Firefox < 22. */
[hidden], template { display: none; }
script { display: none !important; }
/* ========================================================================== Base ========================================================================== */
/** 1. Set default font family to sans-serif. 2. Prevent iOS text size adjust after orientation change, without disabling user zoom. */
html { font-family: sans-serif; /* 1 */ -ms-text-size-adjust: 100%; /* 2 */ -webkit-text-size-adjust: 100%; /* 2 */ }
/** Remove default margin. */
body { margin: 0; }
/* ========================================================================== Links ========================================================================== */
/** Remove the gray background color from active links in IE 10. */
a { background: transparent; }
/** Address `outline` inconsistency between Chrome and other browsers. */
a:focus { outline: thin dotted; }
/** Improve readability when focused and also mouse hovered in all browsers. */
a:active, a:hover { outline: 0; }
/* ========================================================================== Typography ========================================================================== */
/** Address variable `h1` font-size and margin within `section` and `article` contexts in Firefox 4+, Safari 5, and Chrome. */
h1 { font-size: 2em; margin: 0.67em 0; }
/** Address styling not present in IE 8/9, Safari 5, and Chrome. */
abbr[title] { border-bottom: 1px dotted; }
/** Address style set to `bolder` in Firefox 4+, Safari 5, and Chrome. */
b, strong { font-weight: bold; }
/** Address styling not present in Safari 5 and Chrome. */
dfn { font-style: italic; }
/** Address differences between Firefox and other browsers. */
hr { -moz-box-sizing: content-box; box-sizing: content-box; height: 0; }
/** Address styling not present in IE 8/9. */
mark { background: #ff0; color: #000; }
/** Correct font family set oddly in Safari 5 and Chrome. */
code, kbd, pre, samp { font-family: monospace, serif; font-size: 1em; }
/** Improve readability of pre-formatted text in all browsers. */
pre { white-space: pre-wrap; }
/** Set consistent quote types. */
q { quotes: "\201C" "\201D" "\2018" "\2019"; }
/** Address inconsistent and variable font size in all browsers. */
small { font-size: 80%; }
/** Prevent `sub` and `sup` affecting `line-height` in all browsers. */
sub, sup { font-size: 75%; line-height: 0; position: relative; vertical-align: baseline; }
sup { top: -0.5em; }
sub { bottom: -0.25em; }
/* ========================================================================== Embedded content ========================================================================== */
/** Remove border when inside `a` element in IE 8/9. */
img { border: 0; }
/** Correct overflow displayed oddly in IE 9. */
svg:not(:root) { overflow: hidden; }
/* ========================================================================== Figures ========================================================================== */
/** Address margin not present in IE 8/9 and Safari 5. */
figure { margin: 0; }
/* ========================================================================== Forms ========================================================================== */
/** Define consistent border, margin, and padding. */
fieldset { border: 1px solid #c0c0c0; margin: 0 2px; padding: 0.35em 0.625em 0.75em; }
/** 1. Correct `color` not being inherited in IE 8/9. 2. Remove padding so people aren't caught out if they zero out fieldsets. */
legend { border: 0; /* 1 */ padding: 0; /* 2 */ }
/** 1. Correct font family not being inherited in all browsers. 2. Correct font size not being inherited in all browsers. 3. Address margins set differently in Firefox 4+, Safari 5, and Chrome. */
button, input, select, textarea { font-family: inherit; /* 1 */ font-size: 100%; /* 2 */ margin: 0; /* 3 */ }
/** Address Firefox 4+ setting `line-height` on `input` using `!important` in the UA stylesheet. */
button, input { line-height: normal; }
/** Address inconsistent `text-transform` inheritance for `button` and `select`. All other form control elements do not inherit `text-transform` values. Correct `button` style inheritance in Chrome, Safari 5+, and IE 8+. Correct `select` style inheritance in Firefox 4+ and Opera. */
button, select { text-transform: none; }
/** 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio` and `video` controls. 2. Correct inability to style clickable `input` types in iOS. 3. Improve usability and consistency of cursor style between image-type `input` and others. */
button, html input[type="button"], input[type="reset"], input[type="submit"] { -webkit-appearance: button; /* 2 */ cursor: pointer; /* 3 */ }
/** Re-set default cursor for disabled elements. */
button[disabled], html input[disabled] { cursor: default; }
/** 1. Address box sizing set to `content-box` in IE 8/9. 2. Remove excess padding in IE 8/9. */
input[type="checkbox"], input[type="radio"] { box-sizing: border-box; /* 1 */ padding: 0; /* 2 */ }
/** 1. Address `appearance` set to `searchfield` in Safari 5 and Chrome. 2. Address `box-sizing` set to `border-box` in Safari 5 and Chrome (include `-moz` to future-proof). */
input[type="search"] { -webkit-appearance: textfield; /* 1 */ -moz-box-sizing: content-box; -webkit-box-sizing: content-box; /* 2 */ box-sizing: content-box; }
/** Remove inner padding and search cancel button in Safari 5 and Chrome on OS X. */
input[type="search"]::-webkit-search-cancel-button, input[type="search"]::-webkit-search-decoration { -webkit-appearance: none; }
/** Remove inner padding and border in Firefox 4+. */
button::-moz-focus-inner, input::-moz-focus-inner { border: 0; padding: 0; }
/** 1. Remove default vertical scrollbar in IE 8/9. 2. Improve readability and alignment in all browsers. */
textarea { overflow: auto; /* 1 */ vertical-align: top; /* 2 */ }
/* ========================================================================== Tables ========================================================================== */
/** Remove most spacing between table cells. */
table { border-collapse: collapse; border-spacing: 0; }
meta.foundation-mq-small { font-family: "only screen and (min-width: 768px)"; width: 768px; }
meta.foundation-mq-medium { font-family: "only screen and (min-width:1280px)"; width: 1280px; }
meta.foundation-mq-large { font-family: "only screen and (min-width:1440px)"; width: 1440px; }
*, *:before, *:after { -moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box; }
html, body { font-size: 100%; }
body { background: white; color: #222222; padding: 0; margin: 0; font-family: "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif; font-weight: normal; font-style: normal; line-height: 1; position: relative; cursor: auto; }
a:hover { cursor: pointer; }
img, object, embed { max-width: 100%; height: auto; }
object, embed { height: 100%; }
img { -ms-interpolation-mode: bicubic; }
#map_canvas img, #map_canvas embed, #map_canvas object, .map_canvas img, .map_canvas embed, .map_canvas object { max-width: none !important; }
.left { float: left !important; }
.right { float: right !important; }
.text-left { text-align: left !important; }
.text-right { text-align: right !important; }
.text-center { text-align: center !important; }
.text-justify { text-align: justify !important; }
.hide { display: none; }
.antialiased, body { -webkit-font-smoothing: antialiased; }
img { display: inline-block; vertical-align: middle; }
textarea { height: auto; min-height: 50px; }
select { width: 100%; }
p.lead, .paragraph.lead > p, #preamble > .sectionbody > .paragraph:first-of-type p { font-size: 1.21875em; line-height: 1.6; }
.subheader, .admonitionblock td.content > .title, .audioblock > .title, .exampleblock > .title, .imageblock > .title, .listingblock > .title, .literalblock > .title, .stemblock > .title, .openblock > .title, .paragraph > .title, .quoteblock > .title, table.tableblock > .title, .verseblock > .title, .videoblock > .title, .dlist > .title, .olist > .title, .ulist > .title, .qlist > .title, .hdlist > .title { line-height: 1.4; color: #6f6f6f; font-weight: 300; margin-top: 0.2em; margin-bottom: 0.5em; }
/* Typography resets */
div, dl, dt, dd, ul, ol, li, h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6, pre, form, p, blockquote, th, td { margin: 0; padding: 0; direction: ltr; }
/* Default Link Styles */
a { color: #2ba6cb; text-decoration: none; line-height: inherit; }
a:hover, a:focus { color: #2795b6; }
a img { border: none; }
/* Default paragraph styles */
p { font-family: inherit; font-weight: normal; font-size: 1em; line-height: 1.6; margin-bottom: 1.25em; text-rendering: optimizeLegibility; }
p aside { font-size: 0.875em; line-height: 1.35; font-style: italic; }
/* Default header styles */
h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { font-family: "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif; font-weight: bold; font-style: normal; color: #222222; text-rendering: optimizeLegibility; margin-top: 1em; margin-bottom: 0.5em; line-height: 1.2125em; }
h1 small, h2 small, h3 small, #toctitle small, .sidebarblock > .content > .title small, h4 small, h5 small, h6 small { font-size: 60%; color: #6f6f6f; line-height: 0; }
h1 { font-size: 2.125em; }
h2 { font-size: 1.6875em; }
h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.375em; }
h4 { font-size: 1.125em; }
h5 { font-size: 1.125em; }
h6 { font-size: 1em; }
hr { border: solid #dddddd; border-width: 1px 0 0; clear: both; margin: 1.25em 0 1.1875em; height: 0; }
/* Helpful Typography Defaults */
em, i { font-style: italic; line-height: inherit; }
strong, b { font-weight: bold; line-height: inherit; }
small { font-size: 60%; line-height: inherit; }
code { font-family: Consolas, "Liberation Mono", Courier, monospace; font-weight: bold; color: #7f0a0c; }
/* Lists */
ul, ol, dl { font-size: 1em; line-height: 1.6; margin-bottom: 1.25em; list-style-position: outside; font-family: inherit; }
ul, ol { margin-left: 1.5em; }
ul.no-bullet, ol.no-bullet { margin-left: 1.5em; }
/* Unordered Lists */
ul li ul, ul li ol { margin-left: 1.25em; margin-bottom: 0; font-size: 1em; /* Override nested font-size change */ }
ul.square li ul, ul.circle li ul, ul.disc li ul { list-style: inherit; }
ul.square { list-style-type: square; }
ul.circle { list-style-type: circle; }
ul.disc { list-style-type: disc; }
ul.no-bullet { list-style: none; }
/* Ordered Lists */
ol li ul, ol li ol { margin-left: 1.25em; margin-bottom: 0; }
/* Definition Lists */
dl dt { margin-bottom: 0.3125em; font-weight: bold; }
dl dd { margin-bottom: 1.25em; }
/* Abbreviations */
abbr, acronym { text-transform: uppercase; font-size: 90%; color: #222222; border-bottom: 1px dotted #dddddd; cursor: help; }
abbr { text-transform: none; }
/* Blockquotes */
blockquote { margin: 0 0 1.25em; padding: 0.5625em 1.25em 0 1.1875em; border-left: 1px solid #dddddd; }
blockquote cite { display: block; font-size: 0.8125em; color: #555555; }
blockquote cite:before { content: "\2014 \0020"; }
blockquote cite a, blockquote cite a:visited { color: #555555; }
blockquote, blockquote p { line-height: 1.6; color: #6f6f6f; }
/* Microformats */
.vcard { display: inline-block; margin: 0 0 1.25em 0; border: 1px solid #dddddd; padding: 0.625em 0.75em; }
.vcard li { margin: 0; display: block; }
.vcard .fn { font-weight: bold; font-size: 0.9375em; }
.vevent .summary { font-weight: bold; }
.vevent abbr { cursor: auto; text-decoration: none; font-weight: bold; border: none; padding: 0 0.0625em; }
@media only screen and (min-width: 768px) { h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }
h1 { font-size: 2.75em; }
h2 { font-size: 2.3125em; }
h3, #toctitle, .sidebarblock > .content > .title { font-size: 1.6875em; }
h4 { font-size: 1.4375em; } }
/* Tables */
table { background: white; margin-bottom: 1.25em; border: solid 1px #dddddd; }
table thead, table tfoot { background: whitesmoke; font-weight: bold; }
table thead tr th, table thead tr td, table tfoot tr th, table tfoot tr td { padding: 0.5em 0.625em 0.625em; font-size: inherit; color: #222222; text-align: left; }
table tr th, table tr td { padding: 0.5625em 0.625em; font-size: inherit; color: #222222; }
table tr.even, table tr.alt, table tr:nth-of-type(even) { background: #f9f9f9; }
table thead tr th, table tfoot tr th, table tbody tr td, table tr td, table tfoot tr td { display: table-cell; line-height: 1.4; }
h1, h2, h3, #toctitle, .sidebarblock > .content > .title, h4, h5, h6 { line-height: 1.4; }
.clearfix:before, .clearfix:after, .float-group:before, .float-group:after { content: " "; display: table; }
.clearfix:after, .float-group:after { clear: both; }
*:not(pre) > code { font-size: inherit; font-style: normal !important; letter-spacing: 0; padding: 0; line-height: inherit; }
pre, pre > code { line-height: 1.4; color: black; font-family: monospace, serif; font-weight: normal; }
.keyseq { color: #555555; }
kbd { display: inline-block; color: #222222; font-size: 0.75em; line-height: 1.4; background-color: #f7f7f7; border: 1px solid #ccc; -webkit-border-radius: 3px; border-radius: 3px; -webkit-box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 0.1em white inset; margin: -0.15em 0.15em 0 0.15em; padding: 0.2em 0.6em 0.2em 0.5em; vertical-align: middle; white-space: nowrap; }
.keyseq kbd:first-child { margin-left: 0; }
.keyseq kbd:last-child { margin-right: 0; }
.menuseq, .menu { color: #090909; }
b.button:before, b.button:after { position: relative; top: -1px; font-weight: normal; }
b.button:before { content: "["; padding: 0 3px 0 2px; }
b.button:after { content: "]"; padding: 0 2px 0 3px; }
#header, #content, #footnotes, #footer { width: 100%; margin-left: auto; margin-right: auto; margin-top: 0; margin-bottom: 0; max-width: 62.5em; *zoom: 1; position: relative; padding-left: 0.9375em; padding-right: 0.9375em; }
#header:before, #header:after, #content:before, #content:after, #footnotes:before, #footnotes:after, #footer:before, #footer:after { content: " "; display: table; }
#header:after, #content:after, #footnotes:after, #footer:after { clear: both; }
#content { margin-top: 1.25em; }
#content:before { content: none; }
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</head>
<body class="article">
<div id="header">
<h1>Lab 19 - Fault-Tolerance with Hystrix</h1>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="quoteblock abstract">
<blockquote>
<div class="paragraph">
<p>Let’s continue learning the components found in Spring Cloud to implement patterns for distributed systems.
We’ll again use Spring Cloud Netflix to implement client-side load balancing with Ribbon.
However, this time we’ll add an implementation of the Circuit Breaker pattern using Netflix Hystrix.</p>
</div>
<div class="paragraph">
<p>In this lab, we’ll do the following:</p>
</div>
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Refactor the consumer application from <a href="../../session_06/lab_17/lab_17.html">Lab 17</a> to add a slightly different <code>ProducerClient</code> than we added in <a href="../../session_06/lab_18/lab_18.html">Lab 18</a>.</p>
</li>
<li>
<p>Test the new consumer version against our local pool of producers</p>
</li>
<li>
<p>Kill one of the producers and watch the consumer failover.</p>
</li>
<li>
<p>Kill the remaining producer and watch the circuit breaker fallback behavior.</p>
</li>
<li>
<p>Restart a producer and watch the consumer recover.</p>
</li>
</ol>
</div>
</blockquote>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_setup">Setup</h2>
<div class="sectionbody">
<div class="olist arabic">
<ol class="arabic">
<li>
<p>A completed <code>springbox-config-server</code> project has been placed in <code>$COURSE_HOME/day_02/session_06/lab_19/initial/springbox-config-server</code> for your convenience.
In a terminal window, change to that directory, rebuild, and run the application:</p>
<div class="listingblock">
<div class="content">
<pre>$ cd $COURSE_HOME/day_02/session_06/lab_19/initial/springbox-config-server
$ mvn package
$ java -jar target/springbox-config-server-0.0.1-SNAPSHOT.jar</pre>
</div>
</div>
</li>
<li>
<p>A completed <code>springbox-eureka</code> project has been placed in <code>$COURSE_HOME/day_02/session_06/lab_19/initial/springbox-eureka</code> for your convenience.
In a separate terminal window, change to that directory, rebuild, and run the application:</p>
<div class="listingblock">
<div class="content">
<pre>$ cd $COURSE_HOME/day_02/session_06/lab_19/initial/springbox-eureka
$ mvn package
$ java -jar target/springbox-eureka-0.0.1-SNAPSHOT.jar</pre>
</div>
</div>
</li>
<li>
<p>A completed <code>springbox-producer</code> project has been placed in <code>$COURSE_HOME/day_02/session_06/lab_19/initial/springbox-producer</code> for your convenience.
In two separate terminal windows, change to that directory, rebuild, and run the application (on different ports):</p>
<div class="listingblock">
<div class="content">
<pre>$ cd $COURSE_HOME/day_02/session_06/lab_19/initial/springbox-producer
$ mvn package
$ SERVER_PORT=8080 java -jar target/springbox-producer-0.0.1-SNAPSHOT.jar
$ SERVER_PORT=8082 java -jar target/springbox-producer-0.0.1-SNAPSHOT.jar</pre>
</div>
</div>
</li>
<li>
<p>Ensure you have two instances of the producer service registered in Eureka:</p>
<div class="imageblock">
<div class="content">
<img src="../../../Common/images/ribbon_1.png" alt="ribbon 1">
</div>
</div>
</li>
</ol>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_using_hystrix">Using Hystrix</h2>
<div class="sectionbody">
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Change to the lab directory:</p>
<div class="listingblock">
<div class="content">
<pre>$ cd $COURSE_HOME/day_02/session_06/lab_19/initial/springbox-consumer</pre>
</div>
</div>
<div class="paragraph">
<p>and import the project (via <code>pom.xml</code>) into your IDE of choice.</p>
</div>
</li>
<li>
<p>Add the following dependency to <code>pom.xml</code>:</p>
<div class="listingblock">
<div class="content">
<pre><dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency></pre>
</div>
</div>
</li>
<li>
<p>Add a <code>@EnableCircuitBreaker</code> annotation to the class <code>io.springbox.consumer.SpringboxConsumerApplication</code>.</p>
</li>
<li>
<p>Add two constructors to the class <code>io.springbox.consumer.ProducerResponse</code>:</p>
<div class="listingblock">
<div class="content">
<pre>public ProducerResponse() {
}
public ProducerResponse(int value) {
this.value = value;
}</pre>
</div>
</div>
</li>
<li>
<p>Create the class <code>io.springbox.consumer.ProducerClient</code> and into it paste the following code:</p>
<div class="listingblock">
<div class="content">
<pre>@Component
public class ProducerClient {
@Autowired
@LoadBalanced
RestTemplate restTemplate;
@HystrixCommand(fallbackMethod = "getProducerFallback")
public ProducerResponse getValue() {
return restTemplate.getForObject("http://producer", ProducerResponse.class);
}
private ProducerResponse getProducerFallback() {
return new ProducerResponse(42);
}
}</pre>
</div>
</div>
</li>
<li>
<p>Refactor the class <code>io.springbox.consumer.ConsumerController</code> to autowire the <code>ProducerClient</code> instead of <code>RestTemplate</code>, and then use it to obtain the <code>ProducerResponse</code>:</p>
<div class="listingblock">
<div class="content">
<pre>@Autowired
ProducerClient client;
@RequestMapping(value = "/", produces = "application/json")
String consume() {
ProducerResponse response = client.getValue();
return String.format("{\"value\":%d}", response.getValue());
}</pre>
</div>
</div>
</li>
<li>
<p>To the file <code>src/main/resources/application.properties</code> add the following:</p>
<div class="listingblock">
<div class="content">
<pre>producer.ribbon.ServerListRefreshInterval=5000</pre>
</div>
</div>
</li>
<li>
<p>Build the application:</p>
<div class="listingblock">
<div class="content">
<pre>$ mvn package</pre>
</div>
</div>
</li>
<li>
<p>Run the application:</p>
<div class="listingblock">
<div class="content">
<pre>$ java -jar target/springbox-consumer-0.0.1-SNAPSHOT.jar</pre>
</div>
</div>
</li>
<li>
<p>Using <code>curl</code>, test the consumer application and show that it is still receiving values from the producers.
Also, watch the producers and observe that Ribbon is performing round robin load balancing across the two producers:</p>
<div class="listingblock">
<div class="content">
<pre>$ curl -i localhost:8081
HTTP/1.1 200 OK
Content-Length: 11
Content-Type: application/json;charset=UTF-8
Date: Tue, 24 Feb 2015 05:47:33 GMTServer: Apache-Coyote/1.1X-Application-Context: consumer:8081
{
"value": 5
}</pre>
</div>
</div>
</li>
</ol>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_failover">Failover</h2>
<div class="sectionbody">
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Shut down one of the two producer processes.</p>
</li>
<li>
<p>Using <code>curl</code>, test the consumer application and show that it is still receiving values from one of the producers.</p>
<div class="paragraph">
<p>You may get the fallback value of <code>42</code> a few times due to the lag in removing the failed instance from the Ribbon cache. Eventually it will converge to hitting the only remaining healthy instance.</p>
</div>
</li>
</ol>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_fallback">Fallback</h2>
<div class="sectionbody">
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Shut down the remaining producer process.</p>
</li>
<li>
<p>Using <code>curl</code>, test the consumer application and show that it is only emitting the fallback value of <code>42</code>.</p>
</li>
</ol>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_recovery">Recovery</h2>
<div class="sectionbody">
<div class="olist arabic">
<ol class="arabic">
<li>
<p>Restart one of the producer processes. Wait for it to register with Eureka.</p>
</li>
<li>
<p>Using <code>curl</code>, test the consumer application and show that eventually recovers and starts hitting the new producer process. This can take several seconds as the Eureka and Ribbon caches repopulate.</p>
</li>
</ol>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_next_steps">Next Steps</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Do not shut anything down when you complete this lab. We will add one additional component in <a href="../../session_06/lab_20/lab_20.html">Lab 20</a>.</p>
</div>
</div>
</div>
</div>
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<div id="footer-text">
Last updated 2015-05-05 09:26:47 CDT
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