Axon4 - kafka ext: Query event not invoked - apache-kafka

Question

Command side events are getting processed but query (projector) is not invoked.
Using axon kafka extension 4.0-RC2.
Please check below code reference.
AxonConfig
import org.springframework.context.annotation.Configuration;
#Configuration
public class AxonConfig {
}
application.yml
server:
port: 9001
spring:
application:
name: Query Application
datasource:
url: jdbc:postgresql://localhost:5441/orderdemo
username: orderdemo
password: secret
driver-class-name: org.postgresql.Driver
jpa:
properties:
hibernate:
dialect: org.hibernate.dialect.PostgreSQL95Dialect
jdbc:
lob:
non_contextual_creation: true
hbm2ddl.auto: update
implicit_naming_strategy: org.springframework.boot.orm.jpa.hibernate.SpringImplicitNamingStrategy
physical_naming_strategy: org.springframework.boot.orm.jpa.hibernate.SpringPhysicalNamingStrategy
axon:
eventhandling:
processors:
query:
mode: tracking
source: kafkaMessageSource
kafka:
default-topic: axon-events
consumer:
group-id: query-group
bootstrap-servers: localhost:9092

Answer 1

For this configuration to work, the classes which contain the #EventHandler annotated functions you want to be called for handling the events from Kafka, needs to be part of the processing group query.
This requirement follows from the configuration pattern you've chosen, where "axon. eventhandling.processors.query" defines the Processing Group you want to configure. To specify the Processing Group, I think the easiest approach is to add the #ProcessingGroup annotation to your Event Handling Class. In the annotation, you have to provide the name of the Processing Group, which needs to correspond with what you've set int he configuration file.
Lastly, I would suggest to use a different name than query for your Processing Group. Something more specific to the query model that Event Handler updates would seem more in place to me.
Hope this helps!