Using Multiple Spring Pulsar Clients in one application.

[chaitanya-guttula-collibra]

What is the best way to use spring-pulsar in an application, where different modules in the same application needs to connect to pulsar using different authentication credentials? Since, authentication is at the client spring.pulsar.client.authentication level I would assume that we would need separate pulsar client for each module but spring-pulsar does not seem to support it. Could you please help me on what would be the best way to handle this use-case. Please let me know if more info is needed.

[onobc]

Hello again @chaitanya-guttula-collibra ,

Great question. The Spring Boot autoconfiguration configures exactly 1 of each bean. This is how Spring Boot autoconfigures every technology - it does 1 set of the required components really well. It stops there though due to complexity and if you need 2 of anything, it is typically up to you to configure the 2nd set.

Here is an example of needing 2 datasources: https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#howto.data-access.configure-two-datasources

Option 1: Manually configure another client (and set of beans that use it)

This means that you will have to configure in your 2nd client.

Let's take a look at the autoconfigured PulsarClient bean

https://github.com/spring-projects/spring-boot/blob/62f922369d2714847f8e0f559e282f62d8eac63d/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/pulsar/PulsarConfiguration.java#L97-L101

If you provide the following 2 PC beans:

@Bean
@Primary
PulsarClient pulsarClient1(PulsarClientFactory clientFactory) throws PulsarClientException {
	return clientFactory.createClient();
}

@Bean
PulsarClient pulsarClient2() throws PulsarClientException {
	return PulsarClient.builder()....
}

The 1st one (marked as @Primary) will be used in the other AC'ed components (consumer + producer factory etc..).

The 2nd one will be ignored by other components but you can look it up from the app context. If you wanted to use a PulsarTemplate for that client you will need to configure another PulsarTemplate and therefore the PulsarProducerFactory that it requires. It gets messy quick.

Option 2: Use child application contexts.

In this case you would configure a child app context that AC another set of Spring Pulsar. This gets complicated though. Spring Cloud Stream and Spring Cloud Loadbalancer use this technique themselves.

I will take a deeper look and see if I can recommend something a bit softer than the 2 above options.

[chaitanya-guttula-collibra]

Thank you @onobc for your quick reply.