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| <h2 title="Class WithFailures" class="title">Class WithFailures</h2> |
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| <li>java.lang.Object</li> |
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| <li>org.apache.beam.sdk.transforms.WithFailures</li> |
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| <pre><a href="../../../../../org/apache/beam/sdk/annotations/Experimental.html" title="annotation in org.apache.beam.sdk.annotations">@Experimental</a>(<a href="../../../../../org/apache/beam/sdk/annotations/Experimental.html#value--">value</a>=<a href="../../../../../org/apache/beam/sdk/annotations/Experimental.Kind.html#WITH_EXCEPTIONS">WITH_EXCEPTIONS</a>) |
| public class <span class="typeNameLabel">WithFailures</span> |
| extends java.lang.Object</pre> |
| <div class="block">A collection of utilities for writing transforms that can handle exceptions raised during |
| processing of elements. |
| |
| <p>Consuming transforms such as <a href="../../../../../org/apache/beam/sdk/transforms/MapElements.MapWithFailures.html" title="class in org.apache.beam.sdk.transforms"><code>MapElements.MapWithFailures</code></a> follow the general pattern of |
| taking in a user-defined exception handler of type <code>ProcessFunction<ExceptionElement<InputT>, FailureOutputT></code> where the input <a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionElement.html" title="class in org.apache.beam.sdk.transforms"><code>WithFailures.ExceptionElement</code></a> contains an exception along with the input element that was being processed |
| when the exception was raised. This handler is responsible for producing some output element that |
| captures relevant details of the failure and can be encoded as part of a failure output <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a>. Transforms can then package together their output and failure collections in a |
| <a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.Result.html" title="class in org.apache.beam.sdk.transforms"><code>WithFailures.Result</code></a> that avoids users needing to interact with <code>TupleTag</code>s and |
| indexing into a <a href="../../../../../org/apache/beam/sdk/values/PCollectionTuple.html" title="class in org.apache.beam.sdk.values"><code>PCollectionTuple</code></a>. |
| |
| <p>Exception handlers can narrow their scope by rethrowing the passed <a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionElement.html#exception--"><code>WithFailures.ExceptionElement.exception()</code></a> and catching only specific subclasses of <code>Exception</code>. |
| Unhandled exceptions will generally bubble up to a top-level <a href="../../../../../org/apache/beam/sdk/Pipeline.PipelineExecutionException.html" title="class in org.apache.beam.sdk"><code>Pipeline.PipelineExecutionException</code></a> that halts progress. |
| |
| <p>Users can take advantage of <a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.Result.html#failuresTo-java.util.List-"><code>WithFailures.Result.failuresTo(List)</code></a> for fluent chaining of transforms |
| that handle exceptions: |
| |
| <pre><code> |
| PCollection<Integer> input = ... |
| List<PCollection<Map<String, String>> failureCollections = new ArrayList<>(); |
| input.apply(MapElements.via(...).exceptionsVia(...)) |
| .failuresTo(failureCollections) |
| .apply(MapElements.via(...).exceptionsVia(...)) |
| .failuresTo(failureCollections); |
| PCollection<Map<String, String>> failures = PCollectionList.of(failureCollections) |
| .apply("FlattenFailureCollections", Flatten.pCollections()); |
| </code></pre></div> |
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| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionAsMapHandler.html" title="class in org.apache.beam.sdk.transforms">WithFailures.ExceptionAsMapHandler</a><<a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionAsMapHandler.html" title="type parameter in WithFailures.ExceptionAsMapHandler">T</a>></span></code> |
| <div class="block">A simple handler that extracts information from an exception to a <code>Map<String, String></code> |
| and returns a <a href="../../../../../org/apache/beam/sdk/values/KV.html" title="class in org.apache.beam.sdk.values"><code>KV</code></a> where the key is the input element that failed processing, and the |
| value is the map of exception attributes.</div> |
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| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionElement.html" title="class in org.apache.beam.sdk.transforms">WithFailures.ExceptionElement</a><<a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.ExceptionElement.html" title="type parameter in WithFailures.ExceptionElement">T</a>></span></code> |
| <div class="block">The value type passed as input to exception handlers.</div> |
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| <td class="colFirst"><code>static class </code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.Result.html" title="class in org.apache.beam.sdk.transforms">WithFailures.Result</a><<a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.Result.html" title="type parameter in WithFailures.Result">OutputT</a> extends <a href="../../../../../org/apache/beam/sdk/values/POutput.html" title="interface in org.apache.beam.sdk.values">POutput</a>,<a href="../../../../../org/apache/beam/sdk/transforms/WithFailures.Result.html" title="type parameter in WithFailures.Result">FailureElementT</a>></span></code> |
| <div class="block">An intermediate output type for PTransforms that allows an output collection to live alongside |
| a collection of elements that failed the transform.</div> |
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