Hello App

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.

Usage

Web Endpoints

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

Environment Variables

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.

GRPC Endpoints

Describe the HelloService

grpcurl -plaintext localhost:9090 describe api.HelloService

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

Ping

grpcurl -plaintext localhost:9090 api.HelloService.Ping

result:

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

SayHello

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

result:

{
  "message": "Hello Darth Vader"
}