API Mediation Layer

The API Mediation Layer provides a single point of access for mainframe service REST APIs. The layer offers enterprise, cloud-like features such as high-availability, scalability, dynamic API discovery, consistent security, a single sign-on experience, and documentation. The API Mediation Layer facilitates secure communication across loosely coupled microservices through the API Gateway. The API Mediation Layer includes an API Catalog that provides an interface to view all discovered microservices, their associated APIs, and Swagger documentation in a user-friendly manner. The Discovery Service makes it possible to determine the location and status of microservice instances running inside the ecosystem.

Key features

• High availability of services in which application instances on a failing node are distributed among surviving nodes
• Microservice UIs available through the API Gateway and API Catalog by means of reverse proxying
• Support for standardization and normalization of microservice URLs and routing to provide API Mediation Layer users with a consistent way of accessing microservices.
• Minimal effort to register a microservice with the gateway (configuration over code)
• Runs on Windows, Linux, and z/OS (target platform)
• Written in Java utilizing Spring Boot (2.x), Angular 5, and the Netflix CloudStack
• Supports multiple client types for discovery (including Spring Boot, Java, and NodeJS)
• Contains enablers that allow for easy discovery and exposure of REST APIs and Swagger documentation for each microservice

API Mediation Layer architecture

The following diagram illustrates the single point of access with the API Gateway and the interactions between the API Gateway, API Catalog, and the Discovery Service:


Components

The API Layer consists of the following key components:

API Gateway

The microservices that are contained within the ecosystem are located behind a reverse proxy. Clients interact with the gateway layer (reverse proxy). This layer forwards API requests to the appropriate corresponding service through the microservice endpoint UI. The gateway is built using Netflix Zuul and Spring Boot technology.

Discovery Service

The Discovery service is the central point in the API Gateway infrastructure that accepts "announcements of REST services" and serves as a repository of active services. Back-end microservices register with this service either directly by using a Eureka client. Non-Spring Boot applications register with the Discover Service indirectly through a Sidecar. The Discovery Service is built on Eureka and Spring Boot technology.

API Catalog

The API Catalog is the catalog of published APIs and their associated documentation that are discoverable or can be available if provisioned from the service catalog. The API documentation is visualized using the Swagger UI. The API Catalog contains APIs of services available as product versions. A service can be implemented by one or more service instances, which provide exactly the same service for high-availability or scalability.

Onboarding APIs

The most important part of the ecosystem are the real API services that provide useful APIs. Use the following topics to understand what options you have for adding new APIs to the Mediation Layer:

• Onboarding Overview