When I use logstash-integration-kafka at version 10.4.0, I find that the corresponding kafka-clients version is 2.4
but logstash-input-kafka and logstash-output-kafka of version 10.4.0 have kafka-clients of version 2.3.0
What's going on here?and which version shall prevail?
This is probably a documentation mistake as since Logstash 7.5 the Kafka input and output plugins are combined into the Kafka Integration Plugin.
If you check the documentation of the Kafka input on version 7.10 you will see that it now mentions that the plugin is a component of the kafka integration plugin.
The version of the Kafka Client used is the one described in the integration page, you can also check it by looking in the changelog of the integration.
Anyway, 7.9 is already EOL, if you want to use logstash 7.X you should use 7.17.