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<p>New Hawkular blog post from noreply@hawkular.org (Lucas Ponce): http://ift.tt/2uIqytE<br><br></p>
<div class="sect1">
<h2 id="_modeling_conditions">Modeling Conditions</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Hawkular Alerting offers several types of <a href="http://ift.tt/2w7EXTT">Conditions</a> for defining Triggers. Most of the Conditions deal with numeric data but String, Availability and Event data are also supported.</p>
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<div class="paragraph">
<p>Modeling scenarios for detecting behaviours is highly dependent on the nature of the Domain being represented. The Domain may only require simple numeric threshold conditions to efficiently detect unexpected situations.</p>
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<div class="paragraph">
<p>In other domains, it can be non-trivial to identify unusual metric variations that may lead to a problem. Simple thresholds are not expressive enough to detect metric patterns or trends that can identify potential problems.</p>
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<div class="sect1">
<h2 id="_nelson_rules">Nelson Rules</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Hawkular Alerting supports Conditions based on <a href="http://ift.tt/1NSoAtz">Nelson Rules</a> to enable advanced detection on Numeric metrics.</p>
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<div class="paragraph">
<p>These rules are based on the mean and the standard deviation of the samples and offer additional techniques for modeling complex scenarios.</p>
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<div class="paragraph">
<p>For example,</p>
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<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">
<code class="language-json" data-lang="json">...
"trigger":{
"id": "nelson-rule-trigger",
"name": "Nelson Rule Trigger",
"description": "An example Trigger that uses Nelson Rules Conditions.",
"enabled": true,
"actions":[]
},
"conditions":[
{
"type": "NELSON", <b class="conum">(1)</b>
"dataId": "metric-data-id",
"activeRules": ["Rule1","Rule2"], <b class="conum">(2)</b>
"sampleSize": 75 <b class="conum">(3)</b>
}
]
...</code>
</pre>
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<div class="colist arabic">
<ol>
<li>
<p>Mark this Condition as a NelsonRule</p>
</li>
<li>
<p>Define the Nelson Rules to activate (Rule1, Rule2, …, Rule8) for metric-data-id (all rules are activated by default)</p>
</li>
<li>
<p>Define the sampleSize (by default this value is set to 50)</p>
</li>
</ol>
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<div class="paragraph">
<p>Each rule represents a specific pattern as described below:</p>
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<div class="sect2">
<h3 id="_rule_1">Rule 1</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2w7Sx9V" alt="Nelson Rule 1"></div>
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<div class="paragraph">
<p>One sample is grossly out of control.</p>
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<div class="sect2">
<h3 id="_rule_2">Rule 2</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2uIpNkm" alt="Nelson Rule 2"></div>
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<div class="paragraph">
<p>Some prolonged error has been detected.</p>
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</div>
<div class="sect2">
<h3 id="_rule_3">Rule 3</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2w7YjIF" alt="Nelson Rule 3"></div>
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<div class="paragraph">
<p>An unusual trend has been detected.</p>
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</div>
<div class="sect2">
<h3 id="_rule_4">Rule 4</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2uIy1cv" alt="Nelson Rule 4"></div>
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<div class="paragraph">
<p>The oscillation of a metric is beyond an expected amount of noise.</p>
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<div class="paragraph">
<p>Note that the rule is concerned with directionality only. The position of the mean and the size of the standard deviation have no bearing.</p>
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<div class="sect2">
<h3 id="_rule_5">Rule 5</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2w7YlQN" alt="Nelson Rule 5"></div>
</div>
<div class="paragraph">
<p>There is a medium tendency for samples to be mediumly out of control.</p>
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<div class="paragraph">
<p>The side of the mean for the third point is unspecified.</p>
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<div class="sect2">
<h3 id="_rule_6">Rule 6</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2uIhrJC" alt="Nelson Rule 6"></div>
</div>
<div class="paragraph">
<p>There is a strong tendency for samples to be out of control.</p>
</div>
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<div class="sect2">
<h3 id="_rule_7">Rule 7</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2uIhrJC" alt="Nelson Rule 7"></div>
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<div class="paragraph">
<p>A greater variation would be expected.</p>
</div>
</div>
<div class="sect2">
<h3 id="_rule_7_2">Rule 7</h3>
<div class="imageblock">
<div class="content"><img src="http://ift.tt/2uIhrJC" alt="Nelson Rule 7"></div>
</div>
<div class="paragraph">
<p>Jumping from above to below whilst missing the first standard deviation band is rarely random.</p>
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<div class="sect1">
<h2 id="_conclusion">Conclusion</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Applying Nelson Rules in our scenario can help to detect potential "out of control" situations.</p>
</div>
<div class="paragraph">
<p>But as discussed, modeling scenarios are highly dependent of the nature of the Domain; applying Nelson Rules is a useful tool to help identify a problem. Although, the alerts are predictive and a Domain’s Analyst may need to evaluate the quality of the model.</p>
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<br><br>
from Hawkular Blog
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