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| <h2 title="Class RestrictionTracker" class="title">Class RestrictionTracker<RestrictionT,PositionT></h2> |
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| <li>java.lang.Object</li> |
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| <li>org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker<RestrictionT,PositionT></li> |
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| <pre>public abstract class <span class="typeNameLabel">RestrictionTracker<RestrictionT,PositionT></span> |
| extends java.lang.Object</pre> |
| <div class="block">Manages access to the restriction and keeps track of its claimed part for a <a |
| href="https://s.apache.org/splittable-do-fn">splittable</a> <a href="../../../../../../org/apache/beam/sdk/transforms/DoFn.html" title="class in org.apache.beam.sdk.transforms"><code>DoFn</code></a>.</div> |
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| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#RestrictionTracker--">RestrictionTracker</a></span>()</code> </td> |
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| <td class="colFirst"><code>abstract void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#checkDone--">checkDone</a></span>()</code> |
| <div class="block">Called by the runner after <code>DoFn.ProcessElement</code> returns.</div> |
| </td> |
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| <td class="colFirst"><code>abstract <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">RestrictionT</a></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#currentRestriction--">currentRestriction</a></span>()</code> |
| <div class="block">Returns a restriction accurately describing the full range of work the current <code>DoFn.ProcessElement</code> call will do, including already completed work.</div> |
| </td> |
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| <td class="colFirst"><code>abstract boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#tryClaim-PositionT-">tryClaim</a></span>(<a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">PositionT</a> position)</code> |
| <div class="block">Attempts to claim the block of work in the current restriction identified by the given |
| position.</div> |
| </td> |
| </tr> |
| <tr id="i3" class="rowColor"> |
| <td class="colFirst"><code>abstract <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/SplitResult.html" title="class in org.apache.beam.sdk.transforms.splittabledofn">SplitResult</a><<a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">RestrictionT</a>></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#trySplit-double-">trySplit</a></span>(double fractionOfRemainder)</code> |
| <div class="block">Splits current restriction based on <code>fractionOfRemainder</code>.</div> |
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| <h4>RestrictionTracker</h4> |
| <pre>public RestrictionTracker()</pre> |
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| <h4>tryClaim</h4> |
| <pre>public abstract boolean tryClaim(<a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">PositionT</a> position)</pre> |
| <div class="block">Attempts to claim the block of work in the current restriction identified by the given |
| position. |
| |
| <p>If this succeeds, the DoFn MUST execute the entire block of work. If this fails: |
| |
| <ul> |
| <li><code>DoFn.ProcessElement</code> MUST return <code>DoFn.ProcessContinuation#stop</code> without |
| performing any additional work or emitting output (note that emitting output or |
| performing work from <code>DoFn.ProcessElement</code> is also not allowed before the first |
| call to this method). |
| <li><a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#checkDone--"><code>checkDone()</code></a> MUST succeed. |
| </ul></div> |
| </li> |
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| <h4>currentRestriction</h4> |
| <pre>public abstract <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">RestrictionT</a> currentRestriction()</pre> |
| <div class="block">Returns a restriction accurately describing the full range of work the current <code>DoFn.ProcessElement</code> call will do, including already completed work.</div> |
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| <h4>trySplit</h4> |
| <pre>public abstract <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/SplitResult.html" title="class in org.apache.beam.sdk.transforms.splittabledofn">SplitResult</a><<a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html" title="type parameter in RestrictionTracker">RestrictionT</a>> trySplit(double fractionOfRemainder)</pre> |
| <div class="block">Splits current restriction based on <code>fractionOfRemainder</code>. |
| |
| <p>If splitting the current restriction is possible, the current restriction is split into a |
| primary and residual restriction pair. This invocation updates the <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/RestrictionTracker.html#currentRestriction--"><code>currentRestriction()</code></a> to be the primary restriction effectively having the current <code>DoFn.ProcessElement</code> execution responsible for performing the work that the primary restriction |
| represents. The residual restriction will be executed in a separate <code>DoFn.ProcessElement</code> |
| invocation (likely in a different process). The work performed by executing the primary and |
| residual restrictions as separate <code>DoFn.ProcessElement</code> invocations MUST be equivalent to |
| the work performed as if this split never occurred. |
| |
| <p>The <code>fractionOfRemainder</code> should be used in a best effort manner to choose a primary |
| and residual restriction based upon the fraction of the remaining work that the current <code>DoFn.ProcessElement</code> invocation is responsible for. For example, if a <code>DoFn.ProcessElement</code> was reading a file with a restriction representing the offset range <code>[100, 200)</code> and has processed up to offset 130 with a <code>fractionOfRemainder</code> of <code>0.7</code>, the primary and residual restrictions returned would be <code>[100, 179), [179, 200)</code> |
| (note: <code>currentOffset + fractionOfRemainder * remainingWork = 130 + 0.7 * 70 = 179</code>). |
| |
| <p><code>fractionOfRemainder = 0</code> means a checkpoint is required. |
| |
| <p>The API is recommended to be implemented for batch pipeline given that it is very important |
| for pipeline scaling and end to end pipeline execution. |
| |
| <p>The API is required to be implemented for a streaming pipeline.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>fractionOfRemainder</code> - A hint as to the fraction of work the primary restriction should |
| represent based upon the current known remaining amount of work.</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>a <a href="../../../../../../org/apache/beam/sdk/transforms/splittabledofn/SplitResult.html" title="class in org.apache.beam.sdk.transforms.splittabledofn"><code>SplitResult</code></a> if a split was possible, otherwise returns <code>null</code>.</dd> |
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| <h4>checkDone</h4> |
| <pre>public abstract void checkDone() |
| throws java.lang.IllegalStateException</pre> |
| <div class="block">Called by the runner after <code>DoFn.ProcessElement</code> returns. |
| |
| <p>Must throw an exception with an informative error message, if there is still any unclaimed |
| work remaining in the restriction.</div> |
| <dl> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code>java.lang.IllegalStateException</code></dd> |
| </dl> |
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