Allow users to override Flink PubSub subscriber settings

[piyush-zlai]

Summary

While letting the PubSub canary job run for a prolonged period of time with the timeout updates in #877 I noticed that they were set too low. PubSub seems to refresh connections / credentials every hour or so which results in a bit of a latency spike while pulling messages. At 1s we hit this timeout and as the underlying PubSub source throws rather than swallows the error we see the Flink job restart (which results in a couple of mins of ensuing lag). I have bumped this timeout further to 5s and let the job run for a few hours and we don't see the restarts kicking in. We still see the periodic spikes (digging into that async) that result in lag going up to 2-2.5s every hour ish but that's a lot better than the full job restart.

I made this and some of the other settings configurable (similar to what we have for Kafka sources) so bumping timeouts / retries etc won't require a core chronon engine change and deploy going forward.

Checklist

• Added Unit Tests
• Covered by existing CI
• Integration tested
• Documentation update

Summary by CodeRabbit

• New Features

  • Added support for customizing message pull behavior in PubSub sources using properties, including messages per pull, maximum retries, and pull timeout.

• Chores

  • Updated default values for message pulling and made them configurable via user-defined properties.

[coderabbitai]

Walkthrough

The PubSubFlinkSource now supports user-configurable message pulling parameters via properties, replacing previously hardcoded values for messages per pull, pull timeout, and max retries. New property keys and default values are introduced, and the builder is updated to use these configurable options.

Changes

File(s)	Change Summary
flink/.../PubSubFlinkSource.scala	Replaced fixed message pulling constants with configurable properties; added public keys and updated builder.

Sequence Diagram(s)

sequenceDiagram
    participant User
    participant PubSubFlinkSource
    participant Builder

    User->>PubSubFlinkSource: Provide properties map
    PubSubFlinkSource->>PubSubFlinkSource: Read messages_per_pull, max_retries, pull_timeout_ms (with defaults)
    PubSubFlinkSource->>Builder: Pass parameters to builder
    Builder-->>PubSubFlinkSource: Build source with user or default configs

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Possibly related PRs

• Lower PubSub Flink pull timeouts #877: Adds user-configurable subscriber factory parameters, closely related to the new configuration options in this PR.

Suggested reviewers

• david-zlai
• tchow-zlai

Poem

Configs unlocked, the code now sings,
No more constants, just flexible things.
Pulls and retries, set as you please,
PubSub flows onward, with elegant ease.
🎛️✨

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📥 Commits

Reviewing files that changed from the base of the PR and between ad32e77 and 98ce344.

📒 Files selected for processing (1)

• flink/src/main/scala/ai/chronon/flink_connectors/pubsub/PubSubFlinkSource.scala (3 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (14)

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🔇 Additional comments (5)

flink/src/main/scala/ai/chronon/flink_connectors/pubsub/PubSubFlinkSource.scala (5)

37-42: LGTM: Clean configuration pattern.

Follows existing codebase conventions with proper fallback to sensible default.

---

43-47: LGTM: Consistent implementation.

Matches the pattern established for other configurable parameters.

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48-52: LGTM: Addresses the core timeout issue.

The 5-second default resolves the credential refresh timeouts mentioned in the PR objectives.

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66-66: LGTM: Proper use of configurable parameters.

Correctly replaces hardcoded values with the new configurable options.

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83-85: LGTM: Clear property naming.

Property keys are descriptive and follow consistent naming conventions.

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