This repository demonstrates an automated workflow for updating Docker image tags in k8s manifests. The workflow leverages the following tools:

• GitHub Actions
• Release Please: release-please creates a new version, and GitHub release with change log.
• GoReleaser: A release automation tool for Go projects, used here for building the application and its Docker image.
• Kustomization: build the k8s manifests and update the Docker image tag using the kustomize edit feature.

This repository also provides a simple HTTP and GRPC service to test various scenarios in the k8s. such as Istio, Service Mesh, etc.

The application exposes the following HTTP endpoints:

• /: Root endpoint that returns an HTML page with service information including:

  • Service name
  • Version
  • Instance hostname
  • Host
  • Color
  • Current timestamp

• /ping: Health check endpoint that returns a JSON response with:

  • "pong" message
  • Service name
  • Version
  • Instance hostname
  • Current timestamp

• /hello: Greeting endpoint that returns a text response

  • Returns a personalized greeting if NAME environment variable is set
  • Supports an optional wait query parameter (e.g., /hello?wait=5s or /hello?wait=5) to simulate delay
  • Includes instance hostname in the response
  • Example responses:
    • Basic: Hello, Instance: hostname
    • With name: Hello, John!, Instance: hostname
    • With wait: Hello, John!, waited 5s, Instance: hostname

• /health: Simple health check endpoint that returns "HEALTHY" when the service is running

The application uses the following environment variables:

• PORT: Specifies the port on which the server will listen. Defaults to 8080 if not set. The port is prefixed with 0.0.0.0: to ensure it listens on all network interfaces.

• PORT_2: Port number for the secondary web server

  • default is 3000
  • Must be different from PORT (primary server). Application will not start if PORT and PORT_2 have same port
  • Contains identical endpoints to the primary server
  • Used to simulate multiple servers in a single Kubernetes Pod

• GRPC_PORT: Port number for the GRPC server

  • default is 9090

• SERVICE: The name of the service. This is used in the response data for the root (/) and /ping endpoints.

• VERSION: The version of the service. This is also included in the response data for the root (/) and /ping endpoints.

• NAME: The name used in the /hello endpoint to personalize the greeting message. If not set, the message defaults to "Hello!".

• COLOR: Used in the response data for the root (/) endpoint to specify a color, which can be used for theming or display purposes.

These environment variables allow you to configure the behavior and responses of the application without modifying the code.

grpcurl -plaintext localhost:9090 describe api.HelloService

service HelloService {
  rpc Ping ( .api.PingRequest ) returns ( .api.PingResponse );
  rpc SayHello ( .api.HelloRequest ) returns ( .api.HelloReply );
}

grpcurl -plaintext localhost:9090 api.HelloService.Ping

result:

{
  "message": "pong",
  "instance": "your-host-name",
  "timestamp": "2024-12-23T14:22:38-05:00"
}

grpcurl -plaintext -d '{"name": "Darth Vader"}' \
  localhost:9090 api.HelloService.SayHello

result:

{
  "message": "Hello Darth Vader"
}