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| <h2 title="Class Watch" class="title">Class Watch</h2> |
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| <ul class="inheritance"> |
| <li>java.lang.Object</li> |
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| <ul class="inheritance"> |
| <li>org.apache.beam.sdk.transforms.Watch</li> |
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| <br> |
| <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#SPLITTABLE_DO_FN">SPLITTABLE_DO_FN</a>) |
| public class <span class="typeNameLabel">Watch</span> |
| extends java.lang.Object</pre> |
| <div class="block">Given a "poll function" that produces a potentially growing set of outputs for an input, this |
| transform simultaneously continuously watches the growth of output sets of all inputs, until a |
| per-input termination condition is reached. |
| |
| <p>The output is returned as an unbounded <a href="../../../../../org/apache/beam/sdk/values/PCollection.html" title="class in org.apache.beam.sdk.values"><code>PCollection</code></a> of <code>KV<InputT, OutputT></code>, |
| where each <code>OutputT</code> is associated with the <code>InputT</code> that produced it, and is |
| assigned with the timestamp that the poll function returned when this output was detected for the |
| first time. |
| |
| <p>Hypothetical usage example for watching new files in a collection of directories, where for |
| each directory we assume that new files will not appear if the directory contains a file named |
| ".complete": |
| |
| <pre><code> |
| PCollection<String> directories = ...; // E.g. Create.of(single directory) |
| PCollection<KV<String, String>> matches = filepatterns.apply(Watch.<String, String>growthOf( |
| new PollFn<String, String>() { |
| public PollResult<String> apply(TimestampedValue<String> input) { |
| String directory = input.getValue(); |
| List<TimestampedValue<String>> outputs = new ArrayList<>(); |
| ... List the directory and get creation times of all files ... |
| boolean isComplete = ... does a file ".complete" exist in the directory ... |
| return isComplete ? PollResult.complete(outputs) : PollResult.incomplete(outputs); |
| } |
| }) |
| // Poll each directory every 5 seconds |
| .withPollInterval(Duration.standardSeconds(5)) |
| // Stop watching each directory 12 hours after it's seen even if it's incomplete |
| .withTerminationPerInput(afterTotalOf(Duration.standardHours(12))); |
| </code></pre> |
| |
| <p>By default, the watermark for a particular input is computed from a poll result as "earliest |
| timestamp of new elements in this poll result". It can also be set explicitly via <a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollResult.html#withWatermark-org.joda.time.Instant-"><code>Watch.Growth.PollResult.withWatermark(org.joda.time.Instant)</code></a> if the <a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms"><code>Watch.Growth.PollFn</code></a> can provide a more optimistic |
| estimate. |
| |
| <p>Note: This transform works only in runners supporting Splittable DoFn: see <a |
| href="https://beam.apache.org/documentation/runners/capability-matrix/">capability matrix</a>.</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/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="type parameter in Watch.Growth">InputT</a>,<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="type parameter in Watch.Growth">OutputT</a>,<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="type parameter in Watch.Growth">KeyT</a>></span></code> |
| <div class="block">Implementation of <a href="../../../../../org/apache/beam/sdk/transforms/Watch.html#growthOf-org.apache.beam.sdk.transforms.Watch.Growth.PollFn-org.apache.beam.sdk.transforms.Requirements-"><code>growthOf(org.apache.beam.sdk.transforms.Watch.Growth.PollFn<InputT, OutputT>, org.apache.beam.sdk.transforms.Requirements)</code></a>.</div> |
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| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Watch.html#Watch--">Watch</a></span>()</code> </td> |
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| <td class="colFirst"><code>static <InputT,OutputT,KeyT><br><a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,KeyT></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Watch.html#growthOf-org.apache.beam.sdk.transforms.Contextful-org.apache.beam.sdk.transforms.SerializableFunction-">growthOf</a></span>(<a href="../../../../../org/apache/beam/sdk/transforms/Contextful.html" title="class in org.apache.beam.sdk.transforms">Contextful</a><<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT>> pollFn, |
| <a href="../../../../../org/apache/beam/sdk/transforms/SerializableFunction.html" title="interface in org.apache.beam.sdk.transforms">SerializableFunction</a><OutputT,KeyT> outputKeyFn)</code> |
| <div class="block">Watches the growth of the given poll function, using the given "key function" to deduplicate |
| outputs.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>static <InputT,OutputT><br><a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,OutputT></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Watch.html#growthOf-org.apache.beam.sdk.transforms.Watch.Growth.PollFn-">growthOf</a></span>(<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT> pollFn)</code> |
| <div class="block">Watches the growth of the given poll function.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>static <InputT,OutputT><br><a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,OutputT></code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/beam/sdk/transforms/Watch.html#growthOf-org.apache.beam.sdk.transforms.Watch.Growth.PollFn-org.apache.beam.sdk.transforms.Requirements-">growthOf</a></span>(<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT> pollFn, |
| <a href="../../../../../org/apache/beam/sdk/transforms/Requirements.html" title="class in org.apache.beam.sdk.transforms">Requirements</a> requirements)</code> |
| <div class="block">Watches the growth of the given poll function.</div> |
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| <h4>Watch</h4> |
| <pre>public Watch()</pre> |
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| <pre>public static <InputT,OutputT> <a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,OutputT> growthOf(<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT> pollFn, |
| <a href="../../../../../org/apache/beam/sdk/transforms/Requirements.html" title="class in org.apache.beam.sdk.transforms">Requirements</a> requirements)</pre> |
| <div class="block">Watches the growth of the given poll function. See class documentation for more details.</div> |
| </li> |
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| <pre>public static <InputT,OutputT> <a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,OutputT> growthOf(<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT> pollFn)</pre> |
| <div class="block">Watches the growth of the given poll function. See class documentation for more details.</div> |
| </li> |
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| <h4>growthOf</h4> |
| <pre>public static <InputT,OutputT,KeyT> <a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth</a><InputT,OutputT,KeyT> growthOf(<a href="../../../../../org/apache/beam/sdk/transforms/Contextful.html" title="class in org.apache.beam.sdk.transforms">Contextful</a><<a href="../../../../../org/apache/beam/sdk/transforms/Watch.Growth.PollFn.html" title="class in org.apache.beam.sdk.transforms">Watch.Growth.PollFn</a><InputT,OutputT>> pollFn, |
| <a href="../../../../../org/apache/beam/sdk/transforms/SerializableFunction.html" title="interface in org.apache.beam.sdk.transforms">SerializableFunction</a><OutputT,KeyT> outputKeyFn)</pre> |
| <div class="block">Watches the growth of the given poll function, using the given "key function" to deduplicate |
| outputs. For example, if OutputT is a filename + file size, this can be a function that returns |
| just the filename, so that if the same file is observed multiple times with different sizes, |
| only the first observation is emitted. |
| |
| <p>By default, this is the identity function, i.e. the output is used as its own key.</div> |
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