fLINK - Production-Ready URL Redirector

High-performance URL redirector with wildcard patterns, analytics integration, and QR code generation.
Battle-tested in production with minimal resource usage and excellent performance.

Designed as a simpler, more accessible alternative to Shlink, YOURLS, and Polr - no database, no complex setup, just a single binary or Docker container.

Docker Hub | GitHub | Website

Why fLINK?

Core Features

• Simple Deployment - Single static binary, no database required
• Hot Reload - Configuration changes detected automatically (file watch or HTTP polling)
• Wildcard Patterns - Bulk redirect entire directory structures with /* patterns
• Built-in QR Codes - Automatic QR code generation at /yourlink/qr endpoints
• Analytics Ready - Matomo integration with full UTM and click ID preservation
• High Performance - Optimized for speed with concurrent-safe operations
• Security - Path traversal protection, trusted proxy support, security headers

Quick Start

Docker (Recommended)

# Using environment variables for inline mappings
docker run -d \
  -p 8080:8080 \
  -e REDIRECT_MAPPINGS="store=https://shop.example.com;contact=https://example.com/contact" \
  funktionslust/flink:latest

Your redirects are ready:

• http://localhost:8080/store → https://shop.example.com
• http://localhost:8080/contact → https://example.com/contact

Using CLI Flags

# Build from source
go build -o flink .

# Run with inline mappings
./flink -mappings "store=https://shop.example.com;docs=https://docs.example.com" -port 8080

# Use a configuration file
./flink -mappings /etc/flink/redirects.txt

# Disable query parameter forwarding
./flink -mappings redirects.txt -forward-query-params=false

# With Matomo analytics tracking
./flink -mappings redirects.txt -matomo-url https://analytics.example.com -matomo-token your-api-token

# Custom trusted proxy configuration
./flink -mappings redirects.txt -trusted-proxies "10.0.0.0/8,192.168.1.0/24"

Using a Configuration File

Create redirects.txt:

# Marketing campaigns
summer-sale=https://shop.com/promotions/summer
black-friday=https://shop.com/deals/black-friday

# Support links  
help=https://docs.example.com
status=https://status.example.com

# Permanent redirects for SEO (using named aliases)
old-product=https://shop.com/products/new-name,permanent
legacy-api=https://api.v2.example.com,status=301

# Wildcard patterns for bulk redirects
blog/*=https://newsite.com/posts/*,permanent
old-docs/*=https://docs.example.com/archive/*

Run with Docker:

docker run -d \
  -p 8080:8080 \
  -v ./redirects.txt:/app/redirects.txt \
  -e REDIRECT_MAPPINGS=/app/redirects.txt \
  funktionslust/flink:latest

Using Remote Configuration (HTTP/HTTPS)

Load configuration from a web server - perfect for centralized management:

docker run -d \
  -p 8080:8080 \
  -e REDIRECT_MAPPINGS=https://config.example.com/redirects.txt \
  funktionslust/flink:latest

fLINK will fetch the configuration from the URL and refresh it every 10 minutes automatically.

Real-World Examples

Marketing Campaign Tracking

Problem: You need to advertise https://shop.example.com/products/category/summer-collection-2025?utm_source=radio&utm_medium=audio&utm_campaign=summer25 on a radio ad.

Solution: Create a short, memorable redirect:

# redirects.txt
summer=https://shop.example.com/products/category/summer-collection-2025

Now you can:

• Say "Visit link.co/summer" on radio (easy to remember)
• Use link.co/summer?utm_source=radio for radio ads
• Use link.co/summer?utm_source=billboard for outdoor ads
• Use link.co/summer?utm_source=tv for TV commercials
• Track all campaigns in your analytics while keeping URLs short and memorable

Dynamic QR Codes

# redirects.txt
menu=https://restaurant.com/current-menu.pdf
wifi=https://restaurant.com/wifi-instructions

Generate QR codes automatically:

• Menu QR: https://link.restaurant.com/menu/qr
• WiFi QR: https://link.restaurant.com/wifi/qr

Update the destination URLs anytime without reprinting QR codes!

SEO-Friendly Domain Migration

Preserve search rankings with permanent redirects:

# Use status codes or named aliases
old-blog=https://newsite.com/blog,permanent
legacy-api=https://api.v2.example.com,status=301
old-shop=https://newshop.com,301

# Bulk redirect with wildcards
docs/*=https://newdocs.com/archive/*,permanent
blog/*=https://newsite.com/articles/*,301

Production Deployment

Docker Compose with Traefik

services:
  flink:
    image: funktionslust/flink:latest
    volumes:
      - ./redirects.txt:/app/redirects.txt
    environment:
      - REDIRECT_MAPPINGS=/app/redirects.txt
      - TRUSTED_PROXIES=10.0.0.0/8,172.16.0.0/12,192.168.0.0/16
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.flink.rule=Host(`link.yourdomain.com`)"
      - "traefik.http.routers.flink.tls.certresolver=letsencrypt"
    restart: unless-stopped

With Matomo Analytics

services:
  flink:
    image: funktionslust/flink:latest
    environment:
      - REDIRECT_MAPPINGS=/app/redirects.txt
      - MATOMO_URL=https://analytics.example.com
      - MATOMO_TOKEN_FILE=/run/secrets/matomo_token
    secrets:
      - matomo_token
    restart: unless-stopped

Analytics Features:

• Automatic event tracking for all redirects
• Full UTM parameter preservation
• Click ID tracking (gclid, fbclid, msclkid)
• Respects visitor privacy settings

Configuration

Redirect Format

short-code=destination-url[,status=301|302|307|308|permanent|temporary]

• Default status: 302 (temporary)
• Use 301 or permanent for permanent redirects (SEO)
• Use 302 or temporary for temporary redirects
• Use 307 (temporary-strict) or 308 (permanent-strict) to preserve request method
• Use 303 (see-other) to change POST to GET

Wildcard Patterns

Handle bulk redirects with wildcard patterns:

# Redirect entire directory structures
blog/*=https://newsite.com/articles/*
docs/*=https://documentation.site/*

# API versioning
api/v1/*=https://v1.api.com/*
api/v2/*=https://v2.api.com/*

# Catch-all (lowest priority)
/*=https://default.com/*

Pattern Matching Rules:

• Wildcards (*) must be at the end of the path
• Longer prefixes match first (more specific wins)
• Exact matches always beat wildcard patterns
• The captured suffix is preserved in the destination URL
• Pattern: blog/* → https://new.com/posts/*
• Request: /blog/hello-world → https://new.com/posts/hello-world

CLI Flags

Flag	Description	Default
-mappings	File path, URL, or inline mappings	-
-port	Server port	8080
-forward-query-params	Forward query parameters to destination	true
-trusted-proxies	Comma-separated CIDR ranges of trusted proxies	Private networks
-matomo-url	Matomo analytics URL	-
-matomo-token	Matomo API token	-
-help	Show help message	-
-version	Show version information	-

Environment Variables

Variable	Description	Default
REDIRECT_MAPPINGS	File path, URL, or inline mappings	-
PORT	Server port	8080
FORWARD_QUERY_PARAMS	Forward query parameters to destination	true
TRUSTED_PROXIES	Comma-separated CIDR ranges of trusted proxies	Private networks
MATOMO_URL	Analytics server URL	-
MATOMO_TOKEN	Analytics API token	-

Notes:

• CLI flags take precedence over environment variables
• All environment variables support _FILE suffix for Docker secrets
• Private network ranges are trusted by default (can be overridden)

Security Features

Built-in Protections

• Path Traversal Prevention - Blocks ../, null bytes, and encoded attacks
• Security Headers - Automatic X-Content-Type-Options, X-Frame-Options
• Trusted Proxy Support - Configurable CIDR ranges for X-Forwarded-* headers
• Request Validation - Only GET/HEAD methods allowed
• URL Validation - Enforces http:// or https:// destinations

Performance

• Minimal Memory - Lightweight memory footprint
• Sub-millisecond Latency - 7-18 microseconds for redirects in production
• Zero Dependencies - Single static binary
• Instant Reload - Hot configuration updates without downtime
• Concurrent Safe - Thread-safe rule updates

Monitoring & Operations

Health Checks

# Simple health check
curl http://localhost:8080/health

# Check specific redirect
curl -I http://localhost:8080/your-link

Logging

All requests are logged with structured format:

[2025-01-15T10:30:45Z] 192.168.1.100 GET /campaign → https://shop.com (301) 1.2ms
[2025-01-15T10:30:46Z] 192.168.1.101 GET /menu/qr → QR:https://link.com/menu (200) 3.5ms

Planned Features

• Management API - REST API for dynamic rule management
• Google Analytics - Native GA4 integration
• Rule Validation - Pre-flight configuration testing

Support

• Issues: GitHub Issues
• Docker Hub: funktionslust/flink
• Support: Available from Funktionslust GmbH

License

MIT License - Use it freely in your projects!

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Built by Funktionslust GmbH
Enterprise software development and consulting.