Initial commit

Drone CI steps, Dockerfile for ENV arguments and README.md

.dockerignore

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+.git
+.gitignore
+.drone.yml
+docker-compose.yml
+README.md
+build-and-tag.sh
+build-and-tag.ps1

.drone.yml

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+kind: pipeline
+type: docker
+name: build-host-redirect-image
+
+steps:
+  - name: build-and-tag-host-image
+    image: docker:cli
+    volumes:
+      - name: dockersock
+        path: /var/run/docker.sock
+    commands:
+      - echo "Building redirect image on host Docker daemon..."
+      - docker build -t redirect:latest .
+      - |
+        if [ -n "$DRONE_COMMIT_SHA" ]; then
+          SHORT_SHA=$(echo $DRONE_COMMIT_SHA | cut -c1-7)
+          docker tag redirect:latest redirect:$SHORT_SHA
+          echo "Tagged redirect:$SHORT_SHA"
+        fi
+      - |
+        if [ -n "$DRONE_TAG" ]; then
+          docker tag redirect:latest redirect:$DRONE_TAG
+          echo "Tagged redirect:$DRONE_TAG"
+        fi
+      - echo "Build complete. Images registered on host Docker engine:"
+      - docker images | grep redirect || true
+
+volumes:
+  - name: dockersock
+    host:
+      path: /var/run/docker.sock
+
+trigger:
+  event:
+    - push
+    - tag
+

Dockerfile

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+FROM nginxinc/nginx-unprivileged:alpine-slim
+
+# Set default environment variables
+ENV REDIRECT_TARGET="https://example.com" \
+    REDIRECT_CODE="301" \
+    LISTEN_PORT="8080" \
+    NGINX_ENVSUBST_FILTER="REDIRECT_TARGET REDIRECT_CODE LISTEN_PORT"
+
+# Copy template for automatic envsubst rendering on startup
+COPY templates/default.conf.template /etc/nginx/templates/default.conf.template
+
+# Default unprivileged port
+EXPOSE 8080

README.md

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+# Unprivileged Nginx Redirect Docker Image
+
+A lightweight, secure, and reusable Docker image based on `nginxinc/nginx-unprivileged:alpine-slim` designed to redirect HTTP requests to any configurable target domain/path with customizable HTTP status codes.
+
+It is designed to be built via **Drone CI** directly onto the host server's Docker daemon, allowing multiple containers to run on the host system using the single tagged image.
+
+---
+
+## Features
+
+- **Ultra-Lightweight & Secure**: Based on `nginxinc/nginx-unprivileged:alpine-slim` (~12 MB), running as non-root user (UID 101).
+- **Environment Variable Configuration**: Leverages native Nginx startup template rendering (`envsubst`).
+- **Path & Query String Preservation**: Support for preserving request paths (e.g. `$request_uri`).
+- **Built-in Health Checks**:`/healthz` endpoint returns `200 OK` for orchestrator probe support without triggering a redirect.
+- **Drone CI Host Integration**: Pipeline builds directly onto the host machine's Docker engine via host Docker socket binding (`/var/run/docker.sock`).
+
+---
+
+## Environment Variables
+
+| Variable | Default Value | Description |
+| :--- | :--- | :--- |
+| `REDIRECT_TARGET` | `https://example.com` | Target URL or domain for redirection. Add `$request_uri` to preserve path & query parameters. |
+| `REDIRECT_CODE` | `301` | HTTP status code for redirection (e.g. `301`, `302`, `307`, `308`). |
+| `LISTEN_PORT` | `8080` | Internal HTTP listening port (unprivileged standard). |
+
+---
+
+## Drone CI Integration
+
+The included `.drone.yml` pipeline mounts the host Docker socket (`/var/run/docker.sock`) into a `docker:cli` container step. This builds and tags the image directly on the host host's Docker daemon.
+
+```yaml
+kind: pipeline
+type: docker
+name: build-host-redirect-image
+
+steps:
+  - name: build-and-tag-host-image
+    image: docker:cli
+    volumes:
+      - name: dockersock
+        path: /var/run/docker.sock
+    commands:
+      - docker build -t redirect:latest .
+      - |
+        if [ -n "$DRONE_COMMIT_SHA" ]; then
+          SHORT_SHA=$(echo $DRONE_COMMIT_SHA | cut -c1-7)
+          docker tag redirect:latest redirect:$SHORT_SHA
+        fi
+volumes:
+  - name: dockersock
+    host:
+      path: /var/run/docker.sock
+```
+
+> **Note**: Ensure your Drone runner environment allows mounting the host socket volume.
+
+### Tagging a Release with Git
+
+When you create and push a Git tag to your repository:
+
+```bash
+# Create a tag locally
+git tag v1.0.0
+
+# Push the tag to your git remote
+git push origin v1.0.0
+```
+
+1. Git sends a `tag` webhook event to Drone CI.
+2. Drone automatically populates `$DRONE_TAG` with the tag value (e.g. `v1.0.0`) and triggers the pipeline.
+3. The pipeline builds and tags the host image as `redirect:v1.0.0` (as well as `redirect:latest` and `redirect:<short_sha>`).
+
+---
+
+## Quick Start & Usage
+
+### 1. Manual Build (Local Testing)
+
+```bash
+# Bash
+./build-and-tag.sh redirect latest
+
+# PowerShell
+.\build-and-tag.ps1 -ImageName redirect -Tag latest
+```
+
+### 2. Run Single Containers
+
+**Basic Domain Redirect (301 Permanent Redirect)**
+```bash
+docker run -d \
+  --name redirect-domain \
+  -p 8080:8080 \
+  -e REDIRECT_TARGET="https://destination.com" \
+  -e REDIRECT_CODE="301" \
+  redirect:latest
+```
+
+**Path & Query Parameter Preserving Redirect (302 Found)**
+```bash
+docker run -d \
+  --name redirect-path \
+  -p 8081:8080 \
+  -e REDIRECT_TARGET="https://destination.com\$request_uri" \
+  -e REDIRECT_CODE="302" \
+  redirect:latest
+```
+
+### 3. Multi-Container Setup with Docker Compose
+
+To deploy multiple redirect services side-by-side using the host-tagged image:
+
+```yaml
+services:
+  site-a-redirect:
+    image: redirect:latest
+    container_name: site-a-redirect
+    ports:
+      - "8081:8080"
+    environment:
+      - REDIRECT_TARGET=https://site-a.com
+      - REDIRECT_CODE=301
+
+  site-b-redirect:
+    image: redirect:latest
+    container_name: site-b-redirect
+    ports:
+      - "8082:8080"
+    environment:
+      - REDIRECT_TARGET=https://site-b.com$request_uri
+      - REDIRECT_CODE=302
+```
+
+Run compose stack:
+```bash
+docker compose up -d
+```
+
+---
+
+## Health Check Endpoint
+
+All requests to `/healthz` bypass redirection and return an HTTP `200 OK` response with text body `OK`.
+
+```bash
+curl http://localhost:8080/healthz
+# Response: HTTP 200 OK -> "OK"
+```

build-and-tag.ps1

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+param (
+    [string]$ImageName = "redirect",
+    [string]$Tag = "latest"
+)
+
+$ErrorActionPreference = "Stop"
+
+Write-Host "Building Docker image: ${ImageName}:${Tag}"
+docker build -t "${ImageName}:${Tag}" .
+
+Write-Host "Build complete. Image ${ImageName}:${Tag} is registered on host Docker engine."

build-and-tag.sh

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+#!/usr/bin/env bash
+set -e
+
+IMAGE_NAME="${1:-redirect}"
+TAG="${2:-latest}"
+
+echo "Building Docker image: ${IMAGE_NAME}:${TAG}"
+docker build -t "${IMAGE_NAME}:${TAG}" .
+
+echo "Build complete. Image ${IMAGE_NAME}:${TAG} is registered on host Docker engine."

docker-compose.yml

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+services:
+  # Example 1: Simple domain redirect (301 Permanent Redirect)
+  redirect-example:
+    image: redirect:latest
+    container_name: redirect-example
+    ports:
+      - "8081:8080"
+    environment:
+      - REDIRECT_TARGET=https://example.com
+      - REDIRECT_CODE=301
+    restart: unless-stopped
+
+  # Example 2: Redirect preserving full request path and query string (302 Temporary Redirect)
+  redirect-with-path:
+    image: redirect:latest
+    container_name: redirect-with-path
+    ports:
+      - "8082:8080"
+    environment:
+      - REDIRECT_TARGET=https://newsite.com$request_uri
+      - REDIRECT_CODE=302
+    restart: unless-stopped
+
+  # Example 3: Redirect to a specific subpath (307 Temporary Redirect)
+  redirect-subpath:
+    image: redirect:latest
+    container_name: redirect-subpath
+    ports:
+      - "8083:8080"
+    environment:
+      - REDIRECT_TARGET=https://example.com/landing-page
+      - REDIRECT_CODE=307
+    restart: unless-stopped

templates/default.conf.template

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+server {
+    listen ${LISTEN_PORT};
+    server_name _;
+
+    # Health check endpoint for container orchestrator probes
+    location = /healthz {
+        access_log off;
+        default_type text/plain;
+        return 200 "OK\n";
+    }
+
+    # Redirect all other incoming traffic
+    location / {
+        return ${REDIRECT_CODE} ${REDIRECT_TARGET};
+    }
+}