README.md

Readiness Probe Sidecar

This repository contains a small Go application used as a readiness probe, serving HTTP responses to signal readiness and termination status.

Features

• Serves a 200 OK response on /healthz by default.
• Responds with a 410 GONE status on /healthz upon receiving a SIGTERM signal or a manual shutdown request at /stop.
• Configurable port via command-line parameter.

Requirements

• Docker
• Go 1.23+ (if building manually)

Usage

Build and Run with Docker

1. Build the Docker Image

   docker build -t readiness-probe .

2. Run the Docker Container

   docker run -p 8000:8000 readiness-probe

   The application will listen on port 8000 by default. You can map this port or change it using -p.

Configuration Options

• -p : Sets the port for the server (default: 8000).
• -h : Displays help for available flags.

Example to run on a custom port:

readiness_probe -p 8080

Dockerfile Explanation

The Dockerfile is multi-stage:

1. Build Stage - Compiles the Go application.
2. Final Stage - Copies the built binary into a minimal Alpine image, creating a lightweight container.

The application runs as a non-root user for added security.

Endpoints

• /healthz: Returns 200 OK if healthy, 410 GONE if marked as terminated.
• /stop: Sets the application to return 410 GONE for /healthz, emulating a graceful shutdown.

Example Docker Commands

Retrieve the container ID and stop it with SIGTERM:

container_id=$(docker ps -qf "ancestor=readiness-probe")
docker kill -s SIGTERM "$container_id"