No messages emitted on start of smallrye-reactive-messaging-kafka codestart in dev mode

[rsvoboda]

Describe the bug

No messages emitted on start with smallrye-reactive-messaging-kafka codestart in dev mode.

I had to adjust JAX-RS endpoint to inject MyReactiveMessagingApplication and invoke the method with emitter as part of endpoint call. When I accessed the endpoint I finally saw the log messages with the upper-case text.

Application code: https://github.com/quarkusio/quarkus/blob/main/devtools/project-core-extension-codestarts/src/main/resources/codestarts/quarkus/extension-codestarts/reactive-messaging-codestart/java/src/main/java/org/acme/MyReactiveMessagingApplication.java#L19

In the log I noticed new lines just before the upper-case prints:

2022-01-19 16:55:03,870 INFO  [io.sma.rea.mes.kafka] (vert.x-eventloop-thread-0) SRMSG18256: Initialize record store for topic-partition 'word-0' at position -1.
2022-01-19 16:55:03,886 INFO  [io.sma.rea.mes.kafka] (vert.x-eventloop-thread-1) SRMSG18256: Initialize record store for topic-partition 'uppercase-word-0' at position -1.

Seems that kafka dev service is not fully or properly initialized to handle messages sent from onStart method

This behaviour is quite confusing and it took me some time to figure out that the code flow in MyReactiveMessagingApplication is correct and the problem is with message sending.

CC @cescoffier

Expected behavior

>> HELLO
>> WITH
>> SMALLRYE
>> REACTIVE
>> MESSAGE

gets printed on boot in dev mode

Actual behavior

Upper-case text is not printed

How to Reproduce?

• Select quarkus-resteasy-reactive and quarkus-smallrye-reactive-messaging-kafka on https://code.quarkus.io/
• Download the app and run mvn quarkus:dev

Output of uname -a or ver

macOS Monterey

Output of java -version

Java 17

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.6.2.Final and Quarkus main

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response

[quarkus-bot]

/cc @Ladicek, @cescoffier, @ia3andy, @jmartisk, @michalszynkiewicz, @ozangunalp, @phillip-kruger, @quarkusio/devtools, @radcortez

[cescoffier]

Ok... that's annoying...
The configuration generated with the codestart is incorrect. It cannot work, or really by accident when all planets are aligned. The problem is that Kafka default uses "latest" when subscribing to a topic, which means that only new messages are going to be consumed. The record previously sent are simply ignored.

Here is the working configuration:

mp.messaging.outgoing.source-out.topic=word


mp.messaging.incoming.source-in.topic=word
mp.messaging.incoming.source-in.auto.offset.reset=earliest

mp.messaging.incoming.uppercase-in.topic=uppercase-word

mp.messaging.outgoing.uppercase-out.topic=uppercase-word

I would also recommend using the topic as channel name to reduce the configuration to:

mp.messaging.incoming.source-in.auto.offset.reset=earliest

That would be so much better...

However, I don't know where this codestart is maintained. @maxandersen / @gastaldi any link?

[cescoffier]

We may want to rewrite the tests too, to use the dev service and not the in-memory connector.

[cescoffier]

I think I found where is it maintained... but I got some weird YAML-based config - do we generate the properties from that Yaml?

[gastaldi]

I think it's in https://github.com/quarkusio/quarkus/tree/main/devtools/project-core-extension-codestarts/src/main/resources/codestarts/quarkus/extension-codestarts/reactive-messaging-codestart

[gastaldi]

I think I found where is it maintained... but I got some weird YAML-based config - do we generate the properties from that Yaml?

Yes, I believe so

[cescoffier]

Ah, I got why it's done that way (with the topic set). While I believe I agreed with this, I think it is not OK. It shows what I would call an anti-pattern for simple applications (read/write to the same topic from the same application instead of using an in-memory stream). It can be useful when you want to implement checkpoints, but that's quite advanced and should not be covered by the code start.