Expose Spring Integration global properties

[artembilan]

Spring Integration comes with some global properties
which can be configured via META-INF/spring.integration.properties.
The framework then provides an integrationGlobalProperties bean as an
org.springframework.integration.context.IntegrationProperties instance

• Expose those properties via an
  org.springframework.boot.autoconfigure.integration.IntegrationProperties
  for end-user convenience to have everything in a single application.properties
• Map respective org.springframework.boot.autoconfigure.integration.IntegrationProperties
  props into an org.springframework.integration.context.IntegrationProperties and
  expose the last one as an integrationGlobalProperties bean for further
  Spring Integration framework considerations

[snicoll]

@artembilan thanks for the PR but I am not sure I understood the migration path for users. Let's say they specify this file in their application with some customization. From a quick look at the code, given that they are defaults in the @ConfigurationProperties bean, these will be overwritten. Have I missed anything?

[artembilan]

Thanks, @snicoll , for heads up!

You are right: we definitely need to explain a migration path for end-users.
I was so concentrated how to implement this in Spring Boot and how to write test-cases to validate that I completely forgot the fact that this feature is really a breaking change for target applications 😄 .

Here is how it works right now:

• If there is no META-INF/spring.integration.properties file in classpath, Spring Integration creates an org.springframework.integration.context.IntegrationProperties bean with default values.
• If there are some META-INF/spring.integration.properties files, Spring Integration merges them in the order they are read from classpath and creates org.springframework.integration.context.IntegrationProperties bean based on properties with defaults for the rest.
• If there is an integrationGlobalProperties bean, the presence of META-INF/spring.integration.properties is fully ignored. I would say similar to "ConditionalOnMissingBean".

The idea with this fix is to let end-users to migrate from custom META-INF/spring.integration.properties to common application.properties. I believe my problem is that I have missed the presence of META-INF/spring.integration.properties in the target application fully falling back to default values. Breaking change as we call it for the current minor release.

So, let me play with something like "ConditionalOnMissingResource" to let the target application to stay stable after upgrading to Spring Boot 2.5. In the end we probably need to mention this feature for Spring Integration in the release notes to give end-users a chance to migrate their properties to Spring Boot style.

Thank you again for spotting the flaw in my PR!

[snicoll]

We discussed this one at the team meeting and we felt that making things a little bit more explicit would be better to let users debug where things are coming from. One thing that doesn't feel right is that one ways is winning over the other while we could do this on a property per property basis.

Our idea was to change this so that META-INF/spring.integration.properties is read by an EnvironmentPostProcessor and added in the Environment with the right precedence order. Then we'd have a single way of building the IntegrationProperties based on the content of the environment. This approach has several advantages:

• The rule of what wins on what is clearly defined in the environment and can be debugged with /actuator/env if necessary
• Rather than having the integration-specific file win over everything , we can still use application.properties if the property is not defined there
• Thanks to our Origin support, it is easier to know what contributed to a given setting.

@artembilan Would you have the time to update your PR in that direction?

[artembilan]

Thanks, @snicoll , for feedback!

Even if my preference would be do not encourage end-users to use META-INF/spring.integration.properties when they build Spring Boot application, I would say during the migration path, when they already have that file, it would be really beneficial to see those properties in the /actuator/env.

So, yeah, I will add respective EnvironmentPostProcessor today to re-map META-INF/spring.integration.properties to the appropriate IntegrationProperties entries to have a proper merged instance in the end.

[snicoll]

Even if my preference would be do not encourage end-users to use META-INF/spring.integration.properties when they build Spring Boot application.

This has my preference as well and the reason why we're trying to build some sort of middle ground solutions here. I would add this file with lowest precedence then, to encourage the use of the regular Environment. The problem here, I think, is that it'll be hard to deprecate it if Spring Integration doesn't do it. Food for thoughts.

[artembilan]

Please, see an update in the PR about an IntegrationEnvironmentPostProcessor.
I'm not fully sure that I understood an OriginLookup contract correctly.
Plus it is not clear how to test with EnvironmentPostProcessors in the ApplicationContextRunner.

Thanks

[artembilan]

Hi there!

Is there anything I need to do for this PR?
Looks like we are heading to RC1 in April, so would be great to have this merged.

Thank you!

[snicoll]

Is there anything I need to do for this PR?

I am not sure. We haven't got the chance to review the updated PR. Thanks for the follow-up.