If there is a way to do this, I'm in favor of putting that in place for the time being and marking it as deprecated on day 1 with a note that the interceptor API will eventually replace this logic.
Best, Adnan Hemani On Tue, Nov 18, 2025 at 9:33 AM Pierre Laporte <[email protected]> wrote: > I agree with the move to the Reactive Event Bus. So the code will indeed > move to an asynchronous (think `Future<?>`) model for events. > > That being said, for users who currently rely on the Polaris Events > framework to implement sync/blocking hooks, there might be a way to keep > this (incorrect, IMO) behavior. If Polaris includes an abstraction for the > event bus publishing logic, then it will be possible for those users to > provide a different implementation. The OSS Polaris code will have a > fire-and-forget mode, but users would be free to use another mode > like request/reply. > > There will be drawbacks for the request/reply mode, like the ability to > only send events to a single receiver. But those matches what the code > currently does so it could be acceptable. And in any case, it should only > be considered as an interim solution until the interceptor SPI is > implemented. > > Wdyt? > > -- > > Pierre > > > On Tue, Nov 18, 2025 at 2:11 AM Adnan Hemani > <[email protected]> wrote: > > > Hi all, > > > > I still don't agree with us effectively removing the "intercepting" > > use-case without adding a solid proposal/roadmap on how we plan to > > re-introduce this behavior in the near future - if the "Events" > > functionality wasn't in "Beta", this would be completely unacceptable > IMO. > > But I don't have a concern with Alex's proposal (on its own) given that > we > > all are agreeing to re-introduce the pruned "interceptor" functionality > > through a different proposal. > > > > Best, > > Adnan Hemani > > > > > > On Mon, Nov 17, 2025 at 11:33 AM Dmitri Bourlatchkov <[email protected]> > > wrote: > > > > > Hi Yufei, > > > > > > Sorry, I misread your previous message. I think we're in agreement on > > > "interceptors" . Sorry about the confusion. > > > > > > Cheers, > > > Dmitri. > > > > > > On 2025/11/17 15:23:47 Dmitri Bourlatchkov wrote: > > > > Hi Yufei, > > > > > > > > I have to disagree on the "interceptor" point. As I commented > > > previously, I > > > > do believe that event listeners should not be used as interceptors. > > > > Specifically, exceptions and return values from event listeners > should > > > not > > > > affect the processing of the request in Polaris (i.e. requests should > > > work > > > > as if no event listeners are present). > > > > > > > > I do not mind adding a separate interceptor SPI with well-defined > > > > proceed/abort semantics. My objection relates only to overloading > > current > > > > event listeners with the assumption that they can influence request > > > > processing in the server. > > > > > > > > Thanks, > > > > Dmitri. > > > > > > > > On Sat, Nov 15, 2025 at 4:47 PM Yufei Gu <[email protected]> > wrote: > > > > > > > > > To move forward, we may decouple two debates. Supporting multiple > > > listeners > > > > > is generally uncontroversial, while whether events should act as > > > > > interception points has mixed thoughts. > > > > > > > > > > We may proceed with async multiple listeners as an enhancement. > These > > > > > listeners should be notification-only, independent, and > non-blocking. > > > > > > > > > > For those who rely on sync/blocking hooks, we can open a dedicated > > > > > discussion about creating a separate SPI for policy or > > > server-interception > > > > > logic, which gives us a clean and explicit place for policy > > > enforcement, or > > > > > general data governance use cases, without overloading the event > API. > > > > > > > > > > Yufei > > > > > > > > > > > > > > > On Fri, Nov 14, 2025 at 1:43 PM Adnan Hemani > > > > > <[email protected]> wrote: > > > > > > > > > > > Hi all, > > > > > > > > > > > > +1 to Eric's statements: "Events as they stand today can and do > > > function > > > > > as > > > > > > injection points for arbitrary code" and "if we intend to change > > the > > > > > > functionality / scope of events we > > > > > > should do that in clear terms and with a well-considered design" > > > > > > > > > > > > I likely will not be supporting any proposal where the current > > > > > synchronous > > > > > > functionality is no longer allowed as part of the events feature > > > (unless > > > > > > there is compelling evidence to back up the claims that this > > > > > functionality > > > > > > cannot be used today or will not be useful in the future), > although > > > I am > > > > > > still in heavy support of adding functionality for multiple event > > > > > > listeners. > > > > > > > > > > > > Best, > > > > > > Adnan Hemani > > > > > > > > > > > > On Thu, Nov 13, 2025 at 8:01 AM Alexandre Dutra < > [email protected] > > > > > > > > wrote: > > > > > > > > > > > > > > Why is this behavior change being coupled with a proposal to > > > support > > > > > > > multiple event listeners, anyway? > > > > > > > > > > > > > > My proposal couples both because 1) synchronous listeners could > > > > > > > monopolize the event loop (cf. AWS CloudWatch sink), and 2) a > > > > > > > composite listener is imho not an elegant solution to the > > multiple > > > > > > > listeners problem. > > > > > > > > > > > > > > Thanks, > > > > > > > Alex > > > > > > > > > > > > > > On Thu, Nov 13, 2025 at 12:35 PM Eric Maynard < > > > > > [email protected]> > > > > > > > wrote: > > > > > > > > > > > > > > > > It's true that the listener methods return void -- I think > they > > > > > should > > > > > > > > probably have always returned events -- but that doesn't mean > > you > > > > > can't > > > > > > > do > > > > > > > > interesting things with the current (blocking) methods. > Besides > > > the > > > > > > > > already-given example of throwing an exception from within a > > > > > listener, > > > > > > > some > > > > > > > > listener methods take an immutable parameter that has mutable > > > objects > > > > > > > held > > > > > > > > within. Michael rightly points out above that even an > > > > > > accidentally-thrown > > > > > > > > exception may stop processing, which in some cases can be > > > valuable. > > > > > > > > > > > > > > > > Why is this behavior change being coupled with a proposal to > > > support > > > > > > > > multiple event listeners, anyway? Yufei brought the issue of > > > multiple > > > > > > > > listeners up on the original PR > > > > > > > > < > > > https://github.com/apache/polaris/pull/922#discussion_r1985409710> > > > > > > and > > > > > > > > IIRC there were some followup discussions about a way to wrap > > > > > multiple > > > > > > > > listeners in one. I think it can be done, and might be > useful. > > > But I > > > > > > > > suspect that this can be done without losing functionality, > and > > > > > further > > > > > > > it > > > > > > > > seems that if we intend to change the functionality / scope > of > > > events > > > > > > we > > > > > > > > should do that in clear terms and with a well-considered > > design. > > > > > > > > > > > > > > > > --EM > > > > > > > > > > > > > > > > On Thu, Nov 13, 2025 at 4:24 AM Alexandre Dutra < > > > [email protected]> > > > > > > > wrote: > > > > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > Events as they stand today can and do function as > injection > > > > > points > > > > > > > for > > > > > > > > > arbitrary code. > > > > > > > > > > > > > > > > > > I don't think so? How would one "hook into various parts of > > the > > > > > > > > > Polaris functionality" with this API? All listener methods > > take > > > > > > > > > immutable parameters and return nothing: this opinionated > > > design > > > > > > > > > forbids "arbitrary code" to be injected. I cannot, for > > > instance, > > > > > > > > > intercept some endpoint and modify the REST response to my > > > needs. > > > > > > > > > > > > > > > > > > Whatever the original intent of this API was, it's a fact > > that > > > in > > > > > its > > > > > > > > > current state it is not suitable for implementing > > > interceptors. My > > > > > > > > > proposal doesn't change the statu quo, only makes it > > official. > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > Alex > > > > > > > > > > > > > > > > > > On Thu, Nov 13, 2025 at 2:32 AM Eric Maynard < > > > > > > [email protected] > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > I mentioned Java and React because they're very clear > > > examples of > > > > > > how > > > > > > > > > > the term "event listener" is generally understood, and > > Spark > > > only > > > > > > > because > > > > > > > > > > it was referenced by name in the initial proposal email. > > > Spark's > > > > > > > > > > listeners *have > > > > > > > > > > to be* async due to the nature of Spark as something that > > > runs > > > > > > across > > > > > > > > > > threads (/ VMs / processes). That said, it's still > possible > > > if > > > > > not > > > > > > > common > > > > > > > > > > to implement a Spark listener that does something like > > cancel > > > > > > > > > long-running > > > > > > > > > > jobs. This is neither here nor there, though -- my point > is > > > not > > > > > > that > > > > > > > we > > > > > > > > > > should copy Spark or React, but rather that to say events > > > are not > > > > > > > > > intended > > > > > > > > > > as injection points is perhaps revisionist history. > > > > > > > > > > > > > > > > > > > > The original design proposal was sent out with this > > passage: > > > > > > > > > > > > > > > > > > > > It would be useful to add a generic event listener > > interface > > > to > > > > > > > Polaris, > > > > > > > > > > consistent with other OSS projects. Users of the project > > may > > > > > > require > > > > > > > > > > additional functionality that doesn't have a clear enough > > > value > > > > > > > > > proposition > > > > > > > > > > to be in OSS. Instead, there can be event listeners that > > let > > > you > > > > > > hook > > > > > > > > > into > > > > > > > > > > various parts of the Polaris functionality (i.e. "before > > > table > > > > > > > commit") > > > > > > > > > > without OSS prescribing the limits of the extra > > > functionality. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Events as they stand today can and do function as > injection > > > > > points > > > > > > > for > > > > > > > > > > arbitrary code. It's my understanding that they were > > > designed to > > > > > > > serve > > > > > > > > > this > > > > > > > > > > role and that this aspect of the design was in part a > > > reaction to > > > > > > > debates > > > > > > > > > > happening at the time around API stability, refactors, > and > > > > > > extension > > > > > > > > > > points. We were still dreaming about killing CallContext. > > The > > > > > > Iceberg > > > > > > > > > > events proposal did not yet exist. And at least my own > > > > > endorsement > > > > > > of > > > > > > > > > > the proposal / PR was contingent on this functionality. > > > > > > > > > > > > > > > > > > > > If we as a community align on removing this functionality > > > from > > > > > the > > > > > > > events > > > > > > > > > > framework, we should be intentional about that. Currently > > the > > > > > > > (re)design > > > > > > > > > of > > > > > > > > > > events seems to be taking place across many email threads > > > without > > > > > > > clear > > > > > > > > > > arguments about what the framework should support or why. > > > > > > > > > > > > > > > > > > > > --EM > > > > > > > > > > > > > > > > > > > > On Wed, Nov 12, 2025 at 1:08 PM Alexandre Dutra < > > > > > [email protected] > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > > > Several people mentioned Spark event listeners. After > > > looking > > > > > > more > > > > > > > > > > > closely into this feature, I think it actually looks > very > > > > > similar > > > > > > > to > > > > > > > > > > > what I'm proposing: > > > > > > > > > > > > > > > > > > > > > > - The primary intended use cases that I could find are > : > > > > > > monitoring > > > > > > > > > > > job progress, tracking stages and task completion, > > > gathering > > > > > > > metrics > > > > > > > > > > > [1]. > > > > > > > > > > > > > > > > > > > > > > - Events are distributed asynchronously via an internal > > > > > component > > > > > > > > > > > called SparkListenerBus [2], which manages an event bus > > > and a > > > > > > > > > > > single-threaded event queue. > > > > > > > > > > > > > > > > > > > > > > - The API consists solely of methods that return void > > > without > > > > > > > checked > > > > > > > > > > > exceptions: IOW, the API wasn't designed to allow for > > > listeners > > > > > > to > > > > > > > > > > > interact with the server (other than throwing an > > unchecked > > > > > > > exception, > > > > > > > > > > > of course). > > > > > > > > > > > > > > > > > > > > > > - Afaict if a listener throws, the bus catches the > > > exception > > > > > and > > > > > > > moves > > > > > > > > > on. > > > > > > > > > > > > > > > > > > > > > > I'm not an expert in this topic so I might be wrong > here, > > > but > > > > > the > > > > > > > > > > > suggestion that Spark event listeners were designed to > > > allow > > > > > > > listeners > > > > > > > > > > > to modify Spark's behavior doesn't look accurate to me. > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > Alex > > > > > > > > > > > > > > > > > > > > > > [1]: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://www.ibm.com/think/insights/apache-spark-monitoring-using-listeners-and-data-quality-libraries > > > > > > > > > > > [2]: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://spark.apache.org/docs/latest/api/java/org/apache/spark/scheduler/SparkListenerBus.html > > > > > > > > > > > > > > > > > > > > > > On Tue, Nov 11, 2025 at 1:30 PM Dmitri Bourlatchkov < > > > > > > > [email protected]> > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > Hi Eric, > > > > > > > > > > > > > > > > > > > > > > > > I would very much prefer not to use the event > listener > > > SPI > > > > > as a > > > > > > > > > means to > > > > > > > > > > > > control the operation of the Polaris Server. > > > > > > > > > > > > > > > > > > > > > > > > More specifically, I believe that any error / > exception > > > in an > > > > > > > event > > > > > > > > > > > > listener should not affect the processing of the > > request. > > > > > > > > > > > > > > > > > > > > > > > > If we need custom callbacks to control some aspects > of > > > the > > > > > > server > > > > > > > > > > > > behaviour, let's define a dedicated SPI for that, > but, > > > IMHO, > > > > > it > > > > > > > > > should be > > > > > > > > > > > > outside the scope of events. WDYT? > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > Dmitri. > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Nov 10, 2025 at 8:55 PM Eric Maynard < > > > > > > > > > [email protected]> > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > In fact, shouldn’t it be exclusively a listener’s > > > decision > > > > > on > > > > > > > > > whether > > > > > > > > > > > an > > > > > > > > > > > > > event is handled in a blocking way or not? As was > > > noted in > > > > > a > > > > > > > past > > > > > > > > > > > thread on > > > > > > > > > > > > > events, much of the utility of the event framework > > > comes > > > > > from > > > > > > > the > > > > > > > > > > > ability > > > > > > > > > > > > > to introduce custom logic and hooks into the normal > > > > > operation > > > > > > > of > > > > > > > > > > > Polaris. > > > > > > > > > > > > > > > > > > > > > > > > > > If you wish, for example, to prevent the creation > of > > > more > > > > > > than > > > > > > > 1k > > > > > > > > > > > tables > > > > > > > > > > > > > with some given prefix, you can do so using a > > > listener. If > > > > > > the > > > > > > > > > event > > > > > > > > > > > which > > > > > > > > > > > > > might trigger that logic becomes non-blocking, you > > > would no > > > > > > > longer > > > > > > > > > be > > > > > > > > > > > able > > > > > > > > > > > > > to block/fail the create table request. > > > > > > > > > > > > > > > > > > > > > > > > > > I think maybe it’s the name “event”, but we seem to > > > keep > > > > > > > conflating > > > > > > > > > > > these > > > > > > > > > > > > > hooks with the iceberg events or auditing events > when > > > they > > > > > > are > > > > > > > not > > > > > > > > > > > exactly > > > > > > > > > > > > > the same thing. > > > > > > > > > > > > > > > > > > > > > > > > > > —EM > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Nov 10, 2025 at 8:47 PM Adnan Hemani > > > > > > > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Alex, > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks for writing down the proposal for this! > As I > > > had > > > > > > > > > previously > > > > > > > > > > > > > > suggested this when implementing the Persistence > of > > > > > Polaris > > > > > > > > > Events > > > > > > > > > > > > > > <https://github.com/apache/polaris/pull/1844>, I > > am > > > > > > > obviously > > > > > > > > > very > > > > > > > > > > > much > > > > > > > > > > > > > in > > > > > > > > > > > > > > favor of doing this :) > > > > > > > > > > > > > > > > > > > > > > > > > > > > A few questions I have regarding your vision of > how > > > we > > > > > > should > > > > > > > > > > > implement > > > > > > > > > > > > > > this: > > > > > > > > > > > > > > * Are you envisioning anything for being able to > > make > > > > > > > > > dependencies > > > > > > > > > > > > > between > > > > > > > > > > > > > > event listeners? Or are we taking a set direction > > > that > > > > > > Event > > > > > > > > > > > Listeners > > > > > > > > > > > > > > should be independent of each other? > > > > > > > > > > > > > > * In some listeners we have the ability to make > > > events > > > > > > > emission > > > > > > > > > > > > > synchronous > > > > > > > > > > > > > > [example > > > > > > > > > > > > > > < > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/apache/polaris/blob/main/runtime/service/src/main/java/org/apache/polaris/service/events/jsonEventListener/aws/cloudwatch/AwsCloudWatchEventListener.java#L186 > > > > > > > > > > > > > > >]. > > > > > > > > > > > > > > How do we plan to support/advise (or not...) that > > > with > > > > > the > > > > > > > > > > > introduction > > > > > > > > > > > > > > of @Blocking annotations. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > > > > > Adnan Hemani > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Nov 10, 2025 at 11:29 AM Yufei Gu < > > > > > > > [email protected]> > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks for the reply. It's overall a good idea > to > > > have > > > > > > > async > > > > > > > > > event > > > > > > > > > > > > > > > listeners so that they are not blocking each > > other. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > One downside of the async ones is that event > > order > > > > > isn't > > > > > > > > > > > deterministic. > > > > > > > > > > > > > > > For example, event listeners of Spark need the > > > order to > > > > > > > > > understand > > > > > > > > > > > the > > > > > > > > > > > > > > > execution semantics. I think Polaris is fine > with > > > that, > > > > > > > given > > > > > > > > > the > > > > > > > > > > > ts of > > > > > > > > > > > > > > > each event is generated by Polaris. The > > downstream > > > can > > > > > > > still > > > > > > > > > > > figure out > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > order. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks Pierre for sharing, I think any > I/O-bound > > or > > > > > > > potentially > > > > > > > > > > > slow > > > > > > > > > > > > > > > listener should be annotated with @Blocking. > That > > > > > ensures > > > > > > > we > > > > > > > > > keep > > > > > > > > > > > the > > > > > > > > > > > > > > event > > > > > > > > > > > > > > > loop responsive and avoid impacting REST > latency. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Yufei > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Nov 10, 2025 at 9:43 AM Alexandre > Dutra < > > > > > > > > > [email protected] > > > > > > > > > > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Answering the questions above: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > However, we can easily make sure that we > use > > > > > > Quarkus's > > > > > > > > > SmallRye > > > > > > > > > > > > > Fault > > > > > > > > > > > > > > > > Tolerance > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Yes, that was my idea. It's not so much the > bus > > > > > itself > > > > > > > that > > > > > > > > > > > needs to > > > > > > > > > > > > > > > > be fault tolerant, but the receiving end, > that > > > is, > > > > > the > > > > > > > > > > > listeners. A > > > > > > > > > > > > > > > > listener can fail for a variety of reasons > > (e.g. > > > > > remote > > > > > > > > > broker > > > > > > > > > > > > > > > > unavailable), it would be nice to be able to > > > backoff > > > > > > and > > > > > > > > > retry > > > > > > > > > > > > > > > > automatically. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Since the Vert.x event bus runs on > event-loop > > > > > threads > > > > > > > [...] > > > > > > > > > > > could > > > > > > > > > > > > > > > > blocking or slow event listeners potentially > > > stall > > > > > REST > > > > > > > > > requests > > > > > > > > > > > and > > > > > > > > > > > > > > > impact > > > > > > > > > > > > > > > > latency? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > What Pierre said: this could indeed happen, > but > > > it's > > > > > > > > > possible to > > > > > > > > > > > > > > > > annotate the receiving end with @Blocking, in > > > which > > > > > > > case, the > > > > > > > > > > > > > listener > > > > > > > > > > > > > > > > will be invoked in a separate pool. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > With asynchronous event listeners, is > there a > > > > > > > guarantee of > > > > > > > > > > > delivery > > > > > > > > > > > > > > to > > > > > > > > > > > > > > > > all listeners for a given event? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > If I understand the question correctly: with > > > > > > asynchronous > > > > > > > > > > > delivery, a > > > > > > > > > > > > > > > > slow or failing listener wouldn't impact the > > > delivery > > > > > > of > > > > > > > the > > > > > > > > > same > > > > > > > > > > > > > > > > event to other listeners. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > Alex > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Nov 10, 2025 at 10:12 AM Pierre > > Laporte < > > > > > > > > > > > > > [email protected] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks for the proposal, Alex. This sounds > > > like a > > > > > > > great > > > > > > > > > > > > > improvement. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > @Yufei As per Quarkus documentation, slow > > event > > > > > > > listeners > > > > > > > > > > > should be > > > > > > > > > > > > > > > > marked > > > > > > > > > > > > > > > > > with @Blocking so that they are not run on > > the > > > > > event > > > > > > > loop > > > > > > > > > > > threads. > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Pierre > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Sat, Nov 8, 2025 at 2:14 AM Michael > > Collado > > > < > > > > > > > > > > > > > > [email protected] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > With asynchronous event listeners, is > > there a > > > > > > > guarantee > > > > > > > > > of > > > > > > > > > > > > > delivery > > > > > > > > > > > > > > > to > > > > > > > > > > > > > > > > all > > > > > > > > > > > > > > > > > > listeners for a given event? The downside > > of > > > > > > > synchronous > > > > > > > > > > > > > listeners > > > > > > > > > > > > > > is > > > > > > > > > > > > > > > > that > > > > > > > > > > > > > > > > > > everything is serial, but also if > something > > > > > fails, > > > > > > > > > processing > > > > > > > > > > > > > > stops. > > > > > > > > > > > > > > > > This > > > > > > > > > > > > > > > > > > feels important for auditing purposes, > > though > > > > > less > > > > > > > > > important > > > > > > > > > > > for > > > > > > > > > > > > > > > other > > > > > > > > > > > > > > > > > > cases. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Mike > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Nov 7, 2025 at 2:28 PM Yufei Gu < > > > > > > > > > > > [email protected]> > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, Alex and Adam. One concern I > have > > > is > > > > > > about > > > > > > > the > > > > > > > > > > > shared > > > > > > > > > > > > > > > runtime > > > > > > > > > > > > > > > > > > > thread pool. > > > > > > > > > > > > > > > > > > > Since the Vert.x event bus runs on > > > event-loop > > > > > > > threads > > > > > > > > > that > > > > > > > > > > > are > > > > > > > > > > > > > > also > > > > > > > > > > > > > > > > used > > > > > > > > > > > > > > > > > > by > > > > > > > > > > > > > > > > > > > Quarkus’ reactive REST endpoints, could > > > > > blocking > > > > > > or > > > > > > > > > slow > > > > > > > > > > > event > > > > > > > > > > > > > > > > listeners > > > > > > > > > > > > > > > > > > > potentially stall REST requests and > > impact > > > > > > latency? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Yufei > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Nov 7, 2025 at 11:25 AM Adam > > > Christian > > > > > < > > > > > > > > > > > > > > > > > > > [email protected]> > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I think that this would be a great > > > > > enhancement. > > > > > > > > > Thanks > > > > > > > > > > > for > > > > > > > > > > > > > > > > proposing > > > > > > > > > > > > > > > > > > it! > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > The only concern I would have is > around > > > > > > > > > fault-tolerance. > > > > > > > > > > > From > > > > > > > > > > > > > > > what > > > > > > > > > > > > > > > > I > > > > > > > > > > > > > > > > > > can > > > > > > > > > > > > > > > > > > > > tell, from the Quarkus documentation, > > the > > > > > > Quarkus > > > > > > > > > event > > > > > > > > > > > bus > > > > > > > > > > > > > > uses > > > > > > > > > > > > > > > > Vert.x > > > > > > > > > > > > > > > > > > > > EventBus which does not guarantee > > message > > > > > > > delivery if > > > > > > > > > > > failure > > > > > > > > > > > > > > of > > > > > > > > > > > > > > > > part > > > > > > > > > > > > > > > > > > of > > > > > > > > > > > > > > > > > > > > the event bus occurs [1]. However, we > > can > > > > > > easily > > > > > > > make > > > > > > > > > > > sure > > > > > > > > > > > > > that > > > > > > > > > > > > > > > we > > > > > > > > > > > > > > > > use > > > > > > > > > > > > > > > > > > > > Quarkus's SmallRye Fault Tolerance > [2]. > > > Is my > > > > > > > rough > > > > > > > > > > > > > > understanding > > > > > > > > > > > > > > > > > > inline > > > > > > > > > > > > > > > > > > > > with your proposal? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Go community, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Adam > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [1]: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://vertx.io/docs/apidocs/io/vertx/core/eventbus/EventBus.html > > > > > > > > > > > > > > > > > > > > [2]: > > > > > > > > > https://quarkus.io/guides/smallrye-fault-tolerance > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Nov 7, 2025 at 11:49 AM > > Alexandre > > > > > > Dutra < > > > > > > > > > > > > > > > [email protected] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I'd like to propose an enhancement > to > > > our > > > > > > > existing > > > > > > > > > > > events > > > > > > > > > > > > > > > > feature: > > > > > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > > > > > > > ability to support multiple > > listeners. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Currently, only a single listener > can > > > be > > > > > > > active at > > > > > > > > > a > > > > > > > > > > > time, > > > > > > > > > > > > > > > which > > > > > > > > > > > > > > > > is > > > > > > > > > > > > > > > > > > > > > quite limiting. For example, we > might > > > need > > > > > to > > > > > > > > > persist > > > > > > > > > > > > > events > > > > > > > > > > > > > > > for > > > > > > > > > > > > > > > > > > audit > > > > > > > > > > > > > > > > > > > > > purposes and simultaneously send > them > > > to a > > > > > > > message > > > > > > > > > > > queue > > > > > > > > > > > > > for > > > > > > > > > > > > > > > > > > > > > optimization. With the current > setup, > > > this > > > > > > > isn't > > > > > > > > > easily > > > > > > > > > > > > > > > > achievable. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > While a composite listener could be > > > > > created, > > > > > > it > > > > > > > > > feels > > > > > > > > > > > like > > > > > > > > > > > > > a > > > > > > > > > > > > > > > less > > > > > > > > > > > > > > > > > > > > > elegant solution, and the delivery > > > would be > > > > > > > > > strictly > > > > > > > > > > > > > serial, > > > > > > > > > > > > > > > > > > > > > processing one listener after > > another. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > My suggestion is to leverage > Quarkus > > > > > internal > > > > > > > > > event bus > > > > > > > > > > > > > [1]: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 1) There will be one central event > > > emitter > > > > > > > > > responsible > > > > > > > > > > > for > > > > > > > > > > > > > > > > publishing > > > > > > > > > > > > > > > > > > > > > events to the bus. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 2) We will have zero to N > listeners, > > > each > > > > > > > > > independently > > > > > > > > > > > > > > > watching > > > > > > > > > > > > > > > > the > > > > > > > > > > > > > > > > > > > > > event bus for relevant events. They > > > will be > > > > > > > > > discovered > > > > > > > > > > > by > > > > > > > > > > > > > > CDI. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 3) We could apply filters to each > > > listener, > > > > > > > e.g. > > > > > > > > > > > listener A > > > > > > > > > > > > > > > > listens > > > > > > > > > > > > > > > > > > > > > for event types X and Y, listener B > > > only > > > > > > > listens to > > > > > > > > > > > event > > > > > > > > > > > > > > type > > > > > > > > > > > > > > > Y. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 4) This approach would ensure fully > > > > > > > asynchronous > > > > > > > > > > > delivery > > > > > > > > > > > > > of > > > > > > > > > > > > > > > > events > > > > > > > > > > > > > > > > > > to > > > > > > > > > > > > > > > > > > > > > all interested listeners. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 5) Fault-tolerance could also be > > easily > > > > > > > implemented > > > > > > > > > > > (event > > > > > > > > > > > > > > > > delivery > > > > > > > > > > > > > > > > > > > > > retries, timeouts, etc.). > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > What do you all think? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > Alex > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [1]: > > > > > > > https://quarkus.io/guides/reactive-event-bus > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
