alpinegizmo commented on a change in pull request #13:
URL: https://github.com/apache/flink-training/pull/13#discussion_r473075894
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File path: long-ride-alerts/README.md
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@@ -62,13 +62,11 @@ The resulting stream should be printed to standard out.
<details>
<summary><strong>Overall approach</strong></summary>
-This exercise revolves around using a `ProcessFunction` to manage some keyed
state and event time timers, and doing so in a way that works even when the END
event for a given `rideId` arrives before the START (which will happen). The
challenge is figuring out what state to keep, and when to set and clear that
state.
-</details>
-
-<details>
-<summary><strong>Timers and State</strong></summary>
-
-You will want to use event time timers that fire two hours after the incoming
events, and in the `onTimer()` method, collect START events to the output only
if a matching END event hasn't yet arrived. As for what state to keep, it is
enough to remember the "last" event for each `rideId`, where "last" is based on
event time and ride type (START vs END — yes, there are rides where the
START and END have the same timestamp), rather than the order in which the
events are processed. The `TaxiRide` class implements `Comparable`; feel free
to take advantage of that, and be sure to eventually clear any state you create.
Review comment:
That hint was somewhat wrong-headed. I've written a new hint that points
(rather strongly) toward the new solution.
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