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| <li>Summary: </li> |
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| <div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">org.apache.storm.starter.tools</a></div> |
| <h1 title="Class SlidingWindowCounter" class="title">Class SlidingWindowCounter<T></h1> |
| </div> |
| <div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">java.lang.Object</a> |
| <div class="inheritance">org.apache.storm.starter.tools.SlidingWindowCounter<T></div> |
| </div> |
| <section class="class-description" id="class-description"> |
| <dl class="notes"> |
| <dt>Type Parameters:</dt> |
| <dd><code>T</code> - The type of those objects we want to count.</dd> |
| </dl> |
| <dl class="notes"> |
| <dt>All Implemented Interfaces:</dt> |
| <dd><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/Serializable.html" title="class or interface in java.io" class="external-link">Serializable</a></code></dd> |
| </dl> |
| <hr> |
| <div class="type-signature"><span class="modifiers">public final class </span><span class="element-name type-name-label">SlidingWindowCounter<T></span> |
| <span class="extends-implements">extends <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a> |
| implements <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/io/Serializable.html" title="class or interface in java.io" class="external-link">Serializable</a></span></div> |
| <div class="block">This class counts objects in a sliding window fashion. |
| <p/> |
| It is designed 1) to give multiple "producer" threads write access to the counter, i.e. being able to increment |
| counts of objects, and 2) to give a single "consumer" thread (e.g. <a href="../bolt/RollingCountBolt.html" title="class in org.apache.storm.starter.bolt"><code>RollingCountBolt</code></a>) |
| read access to the counter. Whenever the consumer thread performs a read operation, this class will advance the head slot |
| of the sliding window counter. This means that the consumer thread indirectly controls where writes of the producer threads |
| will go to. Also, by itself this class will not advance the head slot. |
| <p/> |
| A note for analyzing data based on a sliding window count: During the initial <code>windowLengthInSlots</code> |
| iterations, this sliding window counter will always return object counts that are equal or greater than in the |
| previous iteration. This is the effect of the counter "loading up" at the very start of its existence. Conceptually, |
| this is the desired behavior. |
| <p/> |
| To give an example, using a counter with 5 slots which for the sake of this example represent 1 minute of time each: |
| <p/> |
| <pre> |
| <code> |
| Sliding window counts of an object X over time |
| |
| Minute (timeline): |
| 1 2 3 4 5 6 7 8 |
| |
| Observed counts per minute: |
| 1 1 1 1 0 0 0 0 |
| |
| Counts returned by counter: |
| 1 2 3 4 4 3 2 1 |
| </code> |
| </pre> |
| <p/> |
| As you can see in this example, for the first <code>windowLengthInSlots</code> (here: the first five minutes) the |
| counter will always return counts equal or greater than in the previous iteration (1, 2, 3, 4, 4). This initial load |
| effect needs to be accounted for whenever you want to perform analyses such as trending topics; otherwise your |
| analysis algorithm might falsely identify the object to be trending as the counter seems to observe continuously |
| increasing counts. Also, note that during the initial load phase <em>every object</em> will exhibit increasing |
| counts. |
| <p/> |
| On a high-level, the counter exhibits the following behavior: If you asked the example counter after two minutes, |
| "how often did you count the object during the past five minutes?", then it should reply "I have counted it 2 times |
| in the past five minutes", implying that it can only account for the last two of those five minutes because the |
| counter was not running before that time.</div> |
| <dl class="notes"> |
| <dt>See Also:</dt> |
| <dd> |
| <ul class="see-list"> |
| <li><a href="../../../../../serialized-form.html#org.apache.storm.starter.tools.SlidingWindowCounter">Serialized Form</a></li> |
| </ul> |
| </dd> |
| </dl> |
| </section> |
| <section class="summary"> |
| <ul class="summary-list"> |
| <!-- ======== CONSTRUCTOR SUMMARY ======== --> |
| <li> |
| <section class="constructor-summary" id="constructor-summary"> |
| <h2>Constructor Summary</h2> |
| <div class="caption"><span>Constructors</span></div> |
| <div class="summary-table two-column-summary"> |
| <div class="table-header col-first">Constructor</div> |
| <div class="table-header col-last">Description</div> |
| <div class="col-constructor-name even-row-color"><code><a href="#%3Cinit%3E(int)" class="member-name-link">SlidingWindowCounter</a><wbr>(int windowLengthInSlots)</code></div> |
| <div class="col-last even-row-color"> </div> |
| </div> |
| </section> |
| </li> |
| <!-- ========== METHOD SUMMARY =========== --> |
| <li> |
| <section class="method-summary" id="method-summary"> |
| <h2>Method Summary</h2> |
| <div id="method-summary-table"> |
| <div class="table-tabs" role="tablist" aria-orientation="horizontal"><button id="method-summary-table-tab0" role="tab" aria-selected="true" aria-controls="method-summary-table.tabpanel" tabindex="0" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table', 3)" class="active-table-tab">All Methods</button><button id="method-summary-table-tab2" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab2', 3)" class="table-tab">Instance Methods</button><button id="method-summary-table-tab4" role="tab" aria-selected="false" aria-controls="method-summary-table.tabpanel" tabindex="-1" onkeydown="switchTab(event)" onclick="show('method-summary-table', 'method-summary-table-tab4', 3)" class="table-tab">Concrete Methods</button></div> |
| <div id="method-summary-table.tabpanel" role="tabpanel"> |
| <div class="summary-table three-column-summary" aria-labelledby="method-summary-table-tab0"> |
| <div class="table-header col-first">Modifier and Type</div> |
| <div class="table-header col-second">Method</div> |
| <div class="table-header col-last">Description</div> |
| <div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Map.html" title="class or interface in java.util" class="external-link">Map</a><<a href="SlidingWindowCounter.html" title="type parameter in SlidingWindowCounter">T</a>,<wbr><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Long.html" title="class or interface in java.lang" class="external-link">Long</a>></code></div> |
| <div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="#getCountsThenAdvanceWindow()" class="member-name-link">getCountsThenAdvanceWindow</a>()</code></div> |
| <div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"> |
| <div class="block">Return the current (total) counts of all tracked objects, then advance the window.</div> |
| </div> |
| <div class="col-first odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code>void</code></div> |
| <div class="col-second odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="#incrementCount(T)" class="member-name-link">incrementCount</a><wbr>(<a href="SlidingWindowCounter.html" title="type parameter in SlidingWindowCounter">T</a> obj)</code></div> |
| <div class="col-last odd-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"> </div> |
| </div> |
| </div> |
| </div> |
| <div class="inherited-list"> |
| <h3 id="methods-inherited-from-class-java.lang.Object">Methods inherited from class java.lang.<a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></h3> |
| <code><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#clone()" title="class or interface in java.lang" class="external-link">clone</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#equals(java.lang.Object)" title="class or interface in java.lang" class="external-link">equals</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#finalize()" title="class or interface in java.lang" class="external-link">finalize</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#getClass()" title="class or interface in java.lang" class="external-link">getClass</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#hashCode()" title="class or interface in java.lang" class="external-link">hashCode</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#notify()" title="class or interface in java.lang" class="external-link">notify</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#notifyAll()" title="class or interface in java.lang" class="external-link">notifyAll</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#toString()" title="class or interface in java.lang" class="external-link">toString</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait()" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait(long)" title="class or interface in java.lang" class="external-link">wait</a>, <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Object.html#wait(long,int)" title="class or interface in java.lang" class="external-link">wait</a></code></div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| <section class="details"> |
| <ul class="details-list"> |
| <!-- ========= CONSTRUCTOR DETAIL ======== --> |
| <li> |
| <section class="constructor-details" id="constructor-detail"> |
| <h2>Constructor Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="<init>(int)"> |
| <h3>SlidingWindowCounter</h3> |
| <div class="member-signature"><span class="modifiers">public</span> <span class="element-name">SlidingWindowCounter</span><wbr><span class="parameters">(int windowLengthInSlots)</span></div> |
| </section> |
| </li> |
| </ul> |
| </section> |
| </li> |
| <!-- ============ METHOD DETAIL ========== --> |
| <li> |
| <section class="method-details" id="method-detail"> |
| <h2>Method Details</h2> |
| <ul class="member-list"> |
| <li> |
| <section class="detail" id="incrementCount(T)"> |
| <h3 id="incrementCount(java.lang.Object)">incrementCount</h3> |
| <div class="member-signature"><span class="modifiers">public</span> <span class="return-type">void</span> <span class="element-name">incrementCount</span><wbr><span class="parameters">(<a href="SlidingWindowCounter.html" title="type parameter in SlidingWindowCounter">T</a> obj)</span></div> |
| </section> |
| </li> |
| <li> |
| <section class="detail" id="getCountsThenAdvanceWindow()"> |
| <h3>getCountsThenAdvanceWindow</h3> |
| <div class="member-signature"><span class="modifiers">public</span> <span class="return-type"><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Map.html" title="class or interface in java.util" class="external-link">Map</a><<a href="SlidingWindowCounter.html" title="type parameter in SlidingWindowCounter">T</a>,<wbr><a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/Long.html" title="class or interface in java.lang" class="external-link">Long</a>></span> <span class="element-name">getCountsThenAdvanceWindow</span>()</div> |
| <div class="block">Return the current (total) counts of all tracked objects, then advance the window. |
| <p/> |
| Whenever this method is called, we consider the counts of the current sliding window to be available to and |
| successfully processed "upstream" (i.e. by the caller). Knowing this we will start counting any subsequent |
| objects within the next "chunk" of the sliding window.</div> |
| <dl class="notes"> |
| <dt>Returns:</dt> |
| <dd>The current (total) counts of all tracked objects.</dd> |
| </dl> |
| </section> |
| </li> |
| </ul> |
| </section> |
| </li> |
| </ul> |
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