230 lines
14 KiB
HTML
230 lines
14 KiB
HTML
<!DOCTYPE HTML>
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<html lang="en">
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<!-- Generated by javadoc (21) on Tue May 12 14:36:52 UTC 2026 -->
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<title>SlidingWindowStrategy (flash-parent 2.1.0-SNAPSHOT API)</title>
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<meta name="dc.created" content="2026-05-12">
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<meta name="description" content="declaration: package: dev.relism.flash.ext.limiter.strategy, class: SlidingWindowStrategy">
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<p>Summary:</p>
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<li>Nested</li>
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<li><a href="#constructor-summary">Constr</a></li>
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<!-- ======== START OF CLASS DATA ======== -->
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<div class="header">
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<div class="sub-title"><span class="package-label-in-type">Package</span> <a href="package-summary.html">dev.relism.flash.ext.limiter.strategy</a></div>
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<h1 title="Class SlidingWindowStrategy" class="title">Class SlidingWindowStrategy</h1>
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</div>
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<div class="inheritance" title="Inheritance Tree"><a href="https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">java.lang.Object</a>
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<div class="inheritance">dev.relism.flash.ext.limiter.strategy.SlidingWindowStrategy</div>
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</div>
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<section class="class-description" id="class-description">
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<dl class="notes">
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<dt>All Implemented Interfaces:</dt>
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<dd><code><a href="../RateLimitStrategy.html" title="interface in dev.relism.flash.ext.limiter">RateLimitStrategy</a></code></dd>
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</dl>
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<hr>
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<div class="type-signature"><span class="modifiers">public final class </span><span class="element-name type-name-label">SlidingWindowStrategy</span>
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<span class="extends-implements">extends <a href="https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a>
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implements <a href="../RateLimitStrategy.html" title="interface in dev.relism.flash.ext.limiter">RateLimitStrategy</a></span></div>
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<div class="block">Sliding-window counter rate limit: approximates a true sliding window by interpolating
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between the previous fixed window's count and the current window's count.
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<pre>
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estimate = prevCount × (1 − elapsed / windowMs) + currentCount
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</pre>
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<p>This is the same approximation used by Redis. It eliminates the boundary burst
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problem of <a href="FixedWindowStrategy.html" title="class in dev.relism.flash.ext.limiter.strategy"><code>FixedWindowStrategy</code></a> while staying O(1) memory and lock-free.
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The error is bounded: in the worst case the true rate at the boundary can exceed
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the limit by at most <code>limit × (1 − elapsed/windowMs)</code> — typically a few percent.
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<h3 id="slot-layout-heading">Slot layout</h3>
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<ul>
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<li><a href="../Bucket.html#slot0"><code>Bucket.slot0</code></a> — packed <code>(reducedEpoch << 32 | currentCount)</code></li>
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<li><a href="../Bucket.html#slot1"><code>Bucket.slot1</code></a> — count from the immediately preceding epoch (0 = none)</li>
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</ul>
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<p>On a window transition the thread that wins the <code>slot0</code> CAS also writes
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<code>slot1</code>. A concurrent thread that reads <code>slot0</code> after the transition but
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before <code>slot1</code> is written sees a slightly stale previous count — acceptable for
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an approximation algorithm.</div>
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</section>
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<section class="summary">
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<ul class="summary-list">
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<!-- ======== CONSTRUCTOR SUMMARY ======== -->
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<li>
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<section class="constructor-summary" id="constructor-summary">
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<h2>Constructor Summary</h2>
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<div class="caption"><span>Constructors</span></div>
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<div class="summary-table two-column-summary">
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<div class="table-header col-first">Constructor</div>
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<div class="table-header col-last">Description</div>
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<div class="col-constructor-name even-row-color"><code><a href="#%3Cinit%3E()" class="member-name-link">SlidingWindowStrategy</a>()</code></div>
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<div class="col-last even-row-color"> </div>
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</div>
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</section>
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</li>
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<!-- ========== METHOD SUMMARY =========== -->
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<li>
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<section class="method-summary" id="method-summary">
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<h2>Method Summary</h2>
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<div id="method-summary-table">
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<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>
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<div id="method-summary-table.tabpanel" role="tabpanel" aria-labelledby="method-summary-table-tab0">
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<div class="summary-table three-column-summary">
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<div class="table-header col-first">Modifier and Type</div>
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<div class="table-header col-second">Method</div>
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<div class="table-header col-last">Description</div>
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<div class="col-first even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code>boolean</code></div>
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<div class="col-second even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4"><code><a href="#check(dev.relism.flash.ext.limiter.Bucket,dev.relism.flash.ext.limiter.LimitConfig,long%5B%5D)" class="member-name-link">check</a><wbr>(<a href="../Bucket.html" title="class in dev.relism.flash.ext.limiter">Bucket</a> bucket,
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<a href="../LimitConfig.html" title="class in dev.relism.flash.ext.limiter">LimitConfig</a> cfg,
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long[] out)</code></div>
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<div class="col-last even-row-color method-summary-table method-summary-table-tab2 method-summary-table-tab4">
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<div class="block">Checks whether this request is within the limit and updates the bucket atomically.</div>
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</div>
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</div>
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</div>
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</div>
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<div class="inherited-list">
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<h3 id="methods-inherited-from-class-java.lang.Object">Methods inherited from class java.lang.<a href="https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/lang/Object.html" title="class or interface in java.lang" class="external-link">Object</a></h3>
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<code><a href="https://docs.oracle.com/en/java/javase/21/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/21/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/21/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/21/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/21/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/21/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/21/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/21/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/21/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/21/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/21/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>
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</section>
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</li>
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</ul>
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</section>
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<section class="details">
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<ul class="details-list">
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<!-- ========= CONSTRUCTOR DETAIL ======== -->
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<li>
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<section class="constructor-details" id="constructor-detail">
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<h2>Constructor Details</h2>
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<ul class="member-list">
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<li>
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<section class="detail" id="<init>()">
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<h3>SlidingWindowStrategy</h3>
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<div class="member-signature"><span class="modifiers">public</span> <span class="element-name">SlidingWindowStrategy</span>()</div>
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</section>
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</li>
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</ul>
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</section>
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</li>
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<!-- ============ METHOD DETAIL ========== -->
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<li>
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<section class="method-details" id="method-detail">
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<h2>Method Details</h2>
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<ul class="member-list">
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<li>
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<section class="detail" id="check(dev.relism.flash.ext.limiter.Bucket,dev.relism.flash.ext.limiter.LimitConfig,long[])">
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<h3>check</h3>
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<div class="member-signature"><span class="modifiers">public</span> <span class="return-type">boolean</span> <span class="element-name">check</span><wbr><span class="parameters">(<a href="../Bucket.html" title="class in dev.relism.flash.ext.limiter">Bucket</a> bucket,
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<a href="../LimitConfig.html" title="class in dev.relism.flash.ext.limiter">LimitConfig</a> cfg,
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long[] out)</span></div>
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<div class="block"><span class="description-from-type-label">Description copied from interface: <code><a href="../RateLimitStrategy.html#check(dev.relism.flash.ext.limiter.Bucket,dev.relism.flash.ext.limiter.LimitConfig,long%5B%5D)">RateLimitStrategy</a></code></span></div>
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<div class="block">Checks whether this request is within the limit and updates the bucket atomically.
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<p>On return, <code>out</code> contains:
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<ul>
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<li><code>out[0]</code> — remaining allowed requests in the current window (≥ 0).</li>
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<li><code>out[1]</code> — Unix epoch seconds at which the quota resets (for <code>X-RateLimit-Reset</code>
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and <code>Retry-After</code> headers).</li>
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</ul></div>
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<dl class="notes">
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<dt>Specified by:</dt>
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<dd><code><a href="../RateLimitStrategy.html#check(dev.relism.flash.ext.limiter.Bucket,dev.relism.flash.ext.limiter.LimitConfig,long%5B%5D)">check</a></code> in interface <code><a href="../RateLimitStrategy.html" title="interface in dev.relism.flash.ext.limiter">RateLimitStrategy</a></code></dd>
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<dt>Parameters:</dt>
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<dd><code>bucket</code> - per-key state carrier (pre-allocated, never null)</dd>
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<dd><code>cfg</code> - immutable rule configuration</dd>
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<dd><code>out</code> - caller-supplied two-element array; values are overwritten on every call</dd>
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<dt>Returns:</dt>
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<dd><code>true</code> if the request is within the limit and should proceed</dd>
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</dl>
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</section>
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</li>
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</ul>
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</section>
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</li>
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</ul>
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</section>
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<!-- ========= END OF CLASS DATA ========= -->
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