A Go Microservices Demo using Go kit And API Gateway Pattern

The article says go-kit is useful but its examples can be hard to follow, so the author combines stringsvc3 with the apigateway example to build a more practical microservices demo. The focus is on implementing the API gateway with Consul-based service discovery, then packaging the services with Docker and testing them through a client that routes requests to multiple service instances.

Reading notes

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• The author says he found go-kit interesting, but with unclear examples, and that the stringsvc tutorial and the stringsvc3 implementation confused him.
• He concludes that the original example only simulated an API gateway, which would be too impractical in the real world.
• To put together a more useful demo, he combines stringsvc3 with the apigateway example.
• The text says the implementation will focus on the API gateway, not on the basic concepts of endpoint, transport, or service.
• The architecture uses service discovery as a central part of the microservices solution.
• The example chooses Consul to perform simple client-side service discovery.
• In the registration, the stringsvc service is registered in Consul with a unique ID, service name, address, and port.
• The text mentions that it is necessary to provide the Consul address through an environment variable or configuration file.
• Before ending the program, the author highlights that it is important to call Deregister.
• To package the application, he creates a Docker image of stringsvc with Go modules and a two-stage build.
• The gateway is another Go modules project, called stringclient.
• In this client, the code creates a Consul instancer to obtain registered service instances.
• The author explains that the fourth parameter of consul.NewInstancer filters services by tags and the last one controls whether only healthy instances should be returned.
• The client creates endpoints for uppercase and count, uses round-robin load balancing, and applies retry.
• The serviceFactoryBuilder function builds a factory that turns an instance into an HTTP endpoint pointing to the correct path.
• The deployment uses Docker Compose with a Consul container, three stringsvc instances, and a stringclient exposed on port 8080.
• The tests show calls to uppercase and count, with FOO and 3 responses.
• In a sequence of calls, the logs show that the three service instances are called one by one.
• The text attributes this behavior to the round-robin policy used when creating the endpoint.