[FLINK-15571][connector] Redis Stream connector for Flink

[sazzad16]

What is the purpose of the change

Introduce a new Flink connector with Redis Stream data structure.

Brief change log

• Implement a new Flink connector with Redis Stream.

Verifying this change

This change added tests and can be verified as follows:

• Added basic tests

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

• Dependencies (does it add or upgrade a dependency): yes
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: don't know
• 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? yes
• If yes, how is the feature documented? not documented

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Automated Checks

Last check on commit 5f3ad56 (Fri May 28 11:06:32 UTC 2021)

Warnings:

• 2 pom.xml files were touched: Check for build and licensing issues.
• No documentation files were touched! Remember to keep the Flink docs up to date!
• This pull request references an unassigned Jira ticket. According to the code contribution guide, tickets need to be assigned before starting with the implementation work.

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Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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CI report:

• 5f3ad56 Azure: SUCCESS

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[sazzad16]

@rmetzger How to improve from review=[description]? Is there anything I can do from my side?

PS: I plan to add documentation after the implementation is finalized.

Thank you.

[KarmaGYZ]

Hi, @sazzad16 . Thanks for opening the PR. However, as the Automated Checks describe, we should first reach a consensus in JIRA ticket and then push the PR. I think you can:

1. Open a discussion thread in user/dev ML on whether we need this connector.
2. Attach a design doc of this connector to the ticket.

[sazzad16]

@KarmaGYZ Thank you for your response.

Briefly speaking, this is a simple idea. i) Save data into Redis. ii) Get data from Redis. So I'm not sure about what to do here.

Could you please refer to an example (design doc)? Thanks again!

[KarmaGYZ]

@sazzad16 Maybe you can refer to this FLIP. All in all, I think we should reach a consensus on whether we need this connector first. Just like Yun Tang's comment on FLINK-15571.

[sazzad16]

@KarmaGYZ It'll be helpful. Thank you.

[gkorland]

@KarmaGYZ how one can add a new FLIP?

[MartijnVisser]

@sazzad16 @gkorland Hi! Sorry for the late reply. Are you still interested in contributing/maintaining a Redis connector for Flink?

[sazzad16]

@MartijnVisser We'd love to. Let us know how to proceed.

[MartijnVisser]

@sazzad16 We're currently in the process of externalizing connectors from Flink's main repository to their own individual repositories. For example, the Elasticsearch connector is being moved from this repo to https://github.com/apache/flink-connector-elasticsearch. While working on moving out Elasticsearch, we're also creating some templates/examples/archetype for all other connectors.

The idea would be that we create a new repo for Redis, flink-connector-redis. You could open up PRs against that repo. A Source should be build via the Source API (see FLIP-27 https://cwiki.apache.org/confluence/display/FLINK/FLIP-27%3A+Refactor+Source+Interface) and Sinks using the Unified Sink API / ASync API (see FLIP-143 https://cwiki.apache.org/confluence/display/FLINK/FLIP-143%3A+Unified+Sink+API and FLIP-171 https://cwiki.apache.org/confluence/display/FLINK/FLIP-171%3A+Async+Sink). This also depends on the level of guarantees (at least once, at most once, exactly once etc) you want to guarantee. There are maintainers in the Flink community who can help with reviews for these type of implementations.

[gkorland]

@MartijnVisser that sounds like a great plan, when do you plan to open the new repo?

(@chayim)

[MartijnVisser]

@gkorland I'll open an announce thread on the Dev mailing list today and I'll find a PMC who can create a repo. Would take a couple of days at most

[MartijnVisser]

@gkorland @chayim Apologies for the slight delay, but the repo is there. You can find it at https://github.com/apache/flink-connector-redis

The current best implementation can be found at https://github.com/apache/flink-connector-elasticsearch

Please ping me in case you have any questions or remarks

[chayim]

Thanks @MartijnVisser. Appreciate it!

[sazzad16]

@MartijnVisser Just submitted the PR apache/flink-connector-redis-streams#2 in the new repo. Please consider that as work in progress and it would be great to get some initial reviews.

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