[FLINK-20630][dynamodb] DynamoDB Streams Consumer fails to consume from Latest

[dannycranmer]

What is the purpose of the change

When consuming from LATEST, the KinesisDataFetcher converts the shard iterator type into an AT_TIMESTAMP to ensure all shards start from the same position. When LATEST is used each shared would effectively start from a different point in the time.

DynamoDB streams do not support AT_TIMESTAMP iterator type and consuming from latest is broken

Brief change log

• Remove shard iterator type transform for DynamoDB streams consumer to fix consume from LATEST

Verifying this change

• Added unit test: DynamoDBStreamsDataFetcherTest
• Deployed application to local Flink cluster and verified consumer works as expected

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[dannycranmer]

This overridden method was identical to the super class, hence deleted

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Automated Checks

Last check on commit 898816c (Wed Dec 16 14:11:28 UTC 2020)

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[tzulitai]

+1, LGTM. Thanks for fixing this @dannycranmer! Merging this master and release-1.12.