Enable multiple event listeners to consume for Polaris events by nandorKollar · Pull Request #3973 · apache/polaris

nandorKollar · 2026-03-11T13:43:10Z

This PR enables multiple event listeners watching for Polaris events.

Checklist

🛡️ Don't disclose security issues! (contact security@apache.org)
🔗 Clearly explained why the changes are needed, or linked related issues: Fixes #
🧪 Added/updated tests with good coverage, or manually tested (and explained how)
💡 Added comments for complex logic
🧾 Updated CHANGELOG.md (if needed)
📚 Updated documentation in site/content/in-dev/unreleased (if needed)

nandorKollar · 2026-03-11T13:50:33Z

@jbonofre @adutra @adnanhemani would you mind share your thoughts about this approach?

adutra

@nandorKollar this is look promising thanks!

I think we should avoid calling dispatch() altogether (and avoid materializing the PolarisEvent instance on the heap) if we know the event type is not needed. I would like us to consider that, if a user deactivates all listeners, they would get a performance comparable to what they would get if there were no events in Polaris at all.

jbonofre · 2026-03-15T10:48:32Z

+  public void onStartup(@Observes StartupEvent event) {
+    String listerTypes = configuration.types().orElse("");
+    if (listerTypes.isBlank()) {
+      return;


If we don't have types here, it means we never reach type() merging bellow (line 51).

If a user only set polaris.event-listener.type (the old config) without setting types, the onStartup() method just returns directly, and no listener is registered.

It means it's a breaking change.

Imho, the type() merge logic should be before the early return, or this check should check both types and type (to be backward compatible).

Good point, thanks! This is indeed broken, fixed in 1a0aaa5

adutra · 2026-03-16T11:20:58Z

+   * Comma separated list of event listers, each item must be a registered {@link
+   * PolarisEventListener} identifier.
+   */
+  Optional<String> types();


Suggested change

Optional<String> types();

Optional<List<String>> types();

It's a bit odd to see an Optional<List<...> – but that's how SmallRye Config wants it 😅

Update: Optional<Set<String>> types(); is probably better.

…tomatically by smallrye

nandorKollar · 2026-03-17T07:22:32Z

@nandorKollar this is look promising thanks!

I think we should avoid calling dispatch() altogether (and avoid materializing the PolarisEvent instance on the heap) if we know the event type is not needed. I would like us to consider that, if a user deactivates all listeners, they would get a performance comparable to what they would get if there were no events in Polaris at all.

Thanks, this makes sense, however I've further questions related to this. Do you happen to know why does AwsCloudWatchEventListener filter only for a single event type? I think event listeners should accept any event type, and allow users to configure a particular event listener to listen for only a certain events, but the listener code itself should not assume that it is working only with event type xyz.

adutra · 2026-03-17T10:09:04Z

Do you happen to know why does AwsCloudWatchEventListener filter only for a single event type? I think event listeners should accept any event type, and allow users to configure a particular event listener to listen for only a certain events, but the listener code itself should not assume that it is working only with event type xyz.

Completely agree here. Listeners should NOT filter events, and especially not in a hard-coded fashion – that's a user decision. @adnanhemani may know why the CoudWatch listener was designed that way. Imho it's not very useful – it can only be useful if you are interested in after-refresh-table events, and hence, in certain table optimization use cases.

dimas-b

Sorry about last minute comments. The PR LGTM overall. My only suggestion is to try and add automatic redirects for the old config name.

…er_service_bus # Conflicts: # runtime/service/src/main/java/org/apache/polaris/service/config/ServiceProducers.java

flyrain · 2026-03-21T07:41:36Z


 - The configuration option `polaris.rate-limiter.token-bucket.window` is no longer supported and should be removed.
 - `PolarisConfigurationStore` has been deprecated for removal.
+- The configuration option `polaris.event-listener.type` is no longer supported and should be removed. Please use `polaris.event-listener.types` instead.


~~It mighty be OK to make this breaking change, given event listener are not widely used ATM. Could we share it in the mailing list to gather more feedback to double check? cc @adnanhemani .~~

~~If it turns out to be fine, we should call it out here that it's a breaking change.~~

NVM. It seems to be deprecated. I think the word here isn't accurate.

Suggested change

- The configuration option `polaris.event-listener.type` is no longer supported and should be removed. Please use `polaris.event-listener.types` instead.

- The configuration option `polaris.event-listener.type` is deprecated and will be removed later. Please use `polaris.event-listener.types` instead.

flyrain

Thanks @nandorKollar for working on it. Can we add test to configure polaris.event-listener.types with 2+ listeners (e.g., 'test,in-memory-buffer') and verify all receive events? Can we add test to verify deprecated polaris.event-listener.type still works?

jbonofre · 2026-03-22T05:35:48Z

nit: I updated the PR title (typo on lister instead of listener 😄 ).

… multiple event listener

dimas-b

LGTM, pending resolution of open comment threads 👍 Thanks, @nandorKollar !

nandorKollar · 2026-03-23T19:54:28Z

Great, thanks @dimas-b , @flyrain would you mind also have a look at the latest version? @jbonofre @adutra is there any unresolved comment on your end that I may have forgotten to address?

adnanhemani · 2026-03-23T20:15:55Z

I will look into this later today, please hold merging until then.

adnanhemani

Looks almost there, just a few questions on my end - and then one comment from @flyrain about adding a Javadoc. Will approve it after those are done!

adnanhemani · 2026-03-24T00:51:58Z

+
+@ApplicationScoped
+public class EventBusConfigurer {
+  private static final String LOCAL_CODEC_NAME = "local";


I'm not an expert but after searching around, it seems like this value is supposed to be unique per codec. So shouldn't we name this something like "polaris-events-local" or something to ensure there is no potential future clash naming-wise?

nandorKollar · 2026-03-24T07:45:13Z

Looks almost there, just a few questions on my end - and then one comment from @flyrain about adding a Javadoc. Will approve it after those are done!

@adnanhemani which Javadoc do you refer to? I already added Javadoc to PolarisServiceBusEventDispatcher.

adnanhemani

Thank you for this @nandorKollar!

flyrain

Thanks @nandorKollar !

nandorKollar · 2026-03-25T18:48:15Z

Thank you all for the help and reviews!

github-project-automation Bot added this to Basic Kanban Board Mar 11, 2026

github-project-automation Bot moved this to PRs In Progress in Basic Kanban Board Mar 11, 2026

jbonofre self-requested a review March 11, 2026 13:58

nandorKollar force-pushed the multiple_event_listener_service_bus branch 7 times, most recently from d0242ed to 09c5600 Compare March 11, 2026 19:59

Enable multiple event listers to consume for Polaris events

aad3caf

nandorKollar force-pushed the multiple_event_listener_service_bus branch from 09c5600 to aad3caf Compare March 11, 2026 20:13

adutra mentioned this pull request Mar 13, 2026

(Proposal) REST API for Events #3924

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adutra reviewed Mar 13, 2026

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nandorKollar added 2 commits March 14, 2026 20:41

Rewrite listener creation logic + cleanup

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Backward compatibility: take old listener config into account

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nandorKollar force-pushed the multiple_event_listener_service_bus branch from 8b05fcf to 1c71676 Compare March 14, 2026 20:20

adjust doc

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jbonofre reviewed Mar 15, 2026

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Fix backward compatibility

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adutra reviewed Mar 16, 2026

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Fix tests

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nandorKollar force-pushed the multiple_event_listener_service_bus branch from 48b5fbd to c9f843b Compare March 16, 2026 22:43

nandorKollar commented Mar 16, 2026

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Comment thread runtime/defaults/src/main/resources/application.properties

Simplify parsing of types config: no need to split, it can be done au…

716f6db

…tomatically by smallrye

nandorKollar force-pushed the multiple_event_listener_service_bus branch from ee21f22 to 716f6db Compare March 16, 2026 23:13

nandorKollar marked this pull request as ready for review March 17, 2026 07:22

dimas-b reviewed Mar 19, 2026

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Address code review comments

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nandorKollar force-pushed the multiple_event_listener_service_bus branch from 16170de to b570a2e Compare March 20, 2026 13:16

Merge remote-tracking branch 'origin/main' into multiple_event_listen…

0c39bd6

…er_service_bus # Conflicts: # runtime/service/src/main/java/org/apache/polaris/service/config/ServiceProducers.java

flyrain requested a review from adnanhemani March 21, 2026 06:34

flyrain reviewed Mar 21, 2026

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Comment thread ...ervice/src/main/java/org/apache/polaris/service/events/PolarisServiceBusEventDispatcher.java

flyrain reviewed Mar 21, 2026

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Comment thread runtime/service/src/main/java/org/apache/polaris/service/events/EventBusConfigurer.java

flyrain reviewed Mar 21, 2026

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jbonofre changed the title ~~Enable multiple event listers to consume for Polaris events~~ Enable multiple event listeners to consume for Polaris events Mar 22, 2026

nandorKollar added 2 commits March 23, 2026 09:27

fix changelog, add javadoc, add @ApplicationScoped, add test case for…

719823d

… multiple event listener

Fallback to old property, add a test case for verification

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nandorKollar requested review from dimas-b and flyrain March 23, 2026 09:51

dimas-b previously approved these changes Mar 23, 2026

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adnanhemani reviewed Mar 24, 2026

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rename codec

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nandorKollar dismissed dimas-b’s stale review via fda9fc9 March 24, 2026 08:05

adnanhemani approved these changes Mar 24, 2026

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nandorKollar requested a review from dimas-b March 24, 2026 13:04

dimas-b approved these changes Mar 24, 2026

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flyrain approved these changes Mar 25, 2026

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flyrain merged commit e94fdff into apache:main Mar 25, 2026
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github-project-automation Bot moved this from Ready to merge to Done in Basic Kanban Board Mar 25, 2026

nandorKollar mentioned this pull request Apr 7, 2026

docs(site): add Delegation Service documentation #3990

Draft

	- The configuration option `polaris.event-listener.type` is no longer supported and should be removed. Please use `polaris.event-listener.types` instead.
	- The configuration option `polaris.event-listener.type` is deprecated and will be removed later. Please use `polaris.event-listener.types` instead.

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