Spring Event Hubs: dedicated builder in one section pollutes shared section's EventHubClientBuilder injection

[j7nw4r]

Follow-up to #49076.

Problem

In spring-cloud-azure-starter-eventhubs, AzureEventHubsClientBuilderConfiguration#eventHubClientBuilder is @ConditionalOnMissingBean(EventHubClientBuilder.class) (type-based). Whenever either AzureEventHubsConsumerClientConfiguration.DedicatedConsumerConnectionConfiguration or AzureEventHubsProducerClientConfiguration.DedicatedProducerConnectionConfiguration activates, it registers a named-but-EventHubClientBuilder-typed bean (springCloudAzureEventHubsConsumerClientBuilder / springCloudAzureEventHubsProducerClientBuilder). That suppresses the root builder.

If the other section has no sub-level override, its SharedConsumer/SharedProducerConnectionConfiguration still activates (its @ConditionalOnBean(EventHubClientBuilder.class) is now satisfied by the dedicated builder from the opposite section) and Spring resolves the unqualified EventHubClientBuilder parameter to that one bean. Result: the shared client targets the other section's event hub.

Repro (after #49076)

spring:
  cloud:
    azure:
      eventhubs:
        namespace: evhns-sample
        event-hub-name: base-hub
        consumer:
          consumer-group: $Default
          event-hub-name: override-hub

• Dedicated consumer activates against override-hub (correct, fixed by Fix Spring sub-level event-hub-name override and EventContext checkpoint offsetString propagation #49076).
• Producer has no sub-level override, so shared producer activates and injects the consumer-dedicated builder, producing against override-hub instead of base-hub.

The same flaw triggers today (without #49076) when a user sets consumer.connection-string or consumer.namespace without a producer override (or vice versa); #49076 only extends the trigger to event-hub-name.

Scope

Out of scope for #49076 because the wiring flaw predates that PR. Plausible fixes:

• Name the root builder and switch @ConditionalOnMissingBean(EventHubClientBuilder.class) to a name-based check so dedicated builders no longer suppress it.
• Or mark the root @Primary (after the above) and add @Qualifier to the shared EventHubClientBuilder injection points.
• Add regression coverage in AzureEventHubsConsumer/ProducerClientConfigurationTests for the asymmetric (one-side dedicated, one-side shared) configuration.

Unaffected: the Spring Messaging template path (AzureEventHubsMessagingAutoConfiguration → NamespaceProperties → DefaultEventHubsNamespaceProducerFactory) does not depend on these client builder beans.

cc @rujche

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @axisc @hmlam @sjkwak.