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| <html> |
| <h2>Early Triggers</h2> |
| <p> |
| Triggers allow Beam to emit early results, before all the data in a given window has arrived. |
| For example, emitting after a certain amount of time elapses, or after a certain number of |
| elements arrives. |
| </p> |
| <p> |
| <b>Kata:</b> Given that events are being generated every second and a fixed window of 1-day |
| duration, please implement an early trigger that emits the number of events count immediately |
| after new element is processed. |
| </p> |
| <br> |
| <div class="hint"> |
| Use <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/windowing/AfterWatermark.AfterWatermarkEarlyAndLate.html#withEarlyFirings-org.apache.beam.sdk.transforms.windowing.Trigger.OnceTrigger-"> |
| withEarlyFirings</a> to set early firing triggers. |
| </div> |
| <div class="hint"> |
| Use <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/windowing/FixedWindows.html"> |
| FixedWindows</a> with 1-day duration using |
| <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/windowing/AfterWatermark.html#pastEndOfWindow--"> |
| AfterWatermark.pastEndOfWindow()</a> trigger. |
| </div> |
| <div class="hint"> |
| Set the <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/windowing/Window.html#withAllowedLateness-org.joda.time.Duration-"> |
| allowed lateness</a> to 0 with |
| <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/windowing/Window.html#discardingFiredPanes--"> |
| discarding accumulation mode</a>. |
| </div> |
| <div class="hint"> |
| Use <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/Combine.html#globally-org.apache.beam.sdk.transforms.CombineFnBase.GlobalCombineFn-"> |
| Combine.globally</a> and |
| <a href="https://beam.apache.org/releases/javadoc/current/org/apache/beam/sdk/transforms/Count.html#combineFn--"> |
| Count.combineFn</a> to calculate the count of events. |
| </div> |
| <div class="hint"> |
| Refer to the Beam Programming Guide |
| <a href="https://beam.apache.org/documentation/programming-guide/#event-time-triggers"> |
| "Event time triggers"</a> section for more information. |
| </div> |
| </html> |
