29 lines
1.4 KiB
Markdown
29 lines
1.4 KiB
Markdown
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# Frequently Asked Questions (FAQ)
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## Stream Modality
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Questions related to stream modality (e.g., [MultiStreamTracker][multi-stream-tracker]).
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### What is the impact of transitioning my KCL app from single-stream to multi-stream?
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This answer assumes the [StreamTracker][stream-tracker] implementation is being changed.
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From KCL's perspective, there is no modality change by decreasing a multi-stream tracker from `N` streams to `1` stream.
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The DDB `leaseKey`, used to persist metadata including lease checkpoint, has a modality-dependent format:
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| Modality | `leaseKey` Format |
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| --- | --- |
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| single-stream | `<shardId>` |
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| multi-stream | `<accountId>:<streamName>:<streamCreationTimestamp>:<shardId>` |
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Transitioning an app -- either from single- to multi-, or vice versa -- creates a backwards-incompatible expectation on the `leaseKey`.
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As a result, a KCL app will be blind to any `leaseKey`, and its checkpoint, that does not match the expected format.
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## Resources
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For additional information, please consider reading:
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* https://docs.aws.amazon.com/streams/latest/dev/kcl-migration.html
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* https://docs.aws.amazon.com/streams/latest/dev/shared-throughput-kcl-consumers.html
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[multi-stream-tracker]: /amazon-kinesis-client/src/main/java/software/amazon/kinesis/processor/MultiStreamTracker.java
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[stream-tracker]: /amazon-kinesis-client/src/main/java/software/amazon/kinesis/processor/StreamTracker.java
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