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GH-698 Fix routing function support in AWS

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Introduce auto-fallback to routing function if more then one function is present and no definition is provided.
Add explicit routing sample

Add documentation
This commit is contained in:
Oleg Zhurakousky
2021-05-19 15:22:57 +02:00
parent 86e141c199
commit 039387d9c6
19 changed files with 721 additions and 10 deletions
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docs/src/main/asciidoc/adapters/aws-intro.adoc
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@@ -69,6 +69,27 @@ property or environment variable. The functions are extracted from the Spring Cl
the framework will attempt to find a default following the search order where it searches first for `Function` then `Consumer` and finally `Supplier`).
==== AWS Function Routing
One of the core features of Spring Cloud Function is https://docs.spring.io/spring-cloud-function/docs/{project-version}/reference/html/spring-cloud-function.html#_function_routing_and_filtering[routing]
- an ability to have one special function to delegate to other functions based on the user provided routing instructions.
In AWS Lambda environment this feature provides one additional benefit, as it allows you to bind a single function (Routing Function)
as AWS Lambda and thus a single HTTP endpoint for API Gateway. So in the end you only manage one function and one endpoint, while benefiting
from many function that can be part of your application.
More details are available in the provided https://github.com/spring-cloud/spring-cloud-function/tree/main/spring-cloud-function-samples/function-sample-aws-routing[sample],
yet few general things worth mentioning.
Routing capabilities will be enabled by default whenever there is more then one function in your application as `org.springframework.cloud.function.adapter.aws.FunctionInvoker`
can not determine which function to bind as AWS Lambda, so it defaults to `RoutingFunction`.
This means that all you need to do is provide routing instructions which you can do https://docs.spring.io/spring-cloud-function/docs/{project-version}/reference/html/spring-cloud-function.html#_function_routing_and_filtering[using several mechanisms]
(see https://github.com/spring-cloud/spring-cloud-function/tree/main/spring-cloud-function-samples/function-sample-aws-routing[sample] for more details).
Also, note that since AWS does not allow dots `.` and/or hyphens`-` in the name of the environment variable, you can benefit from boot support and simply substitute
dots with underscores and hyphens with camel case. So for example `spring.cloud.function.definition` becomes `spring_cloud_function_definition`
and `spring.cloud.function.routing-expression` becomes `spring_cloud_function_routingExpression`.
==== Notes on JAR Layout