Geo based redirect Caddy Server module

This Caddy server module provides a latency-aware alternative to traditional latency-based DNS routing. It works by calculating the geographical distance between the client's IP address and a list of target domain IPs. It then redirects the client to the closest server, minimizing network latency and improving user experience.

Features:

• From a pool of domains, redirect users to the one with the closest geographical location to minimize latency
• For each domain it periodically check's if DNS A record changed
• For each domain it periodically check's health, slower service is better then dead service
• Ability to periodically sync geo ip database
• Designed with performance in mind, it caches everything it can

Make sure that module is used:

xcaddy build --with github.com/hmilkovi/caddy-geo-redirect

Example config:

{
    debug
    metrics
    order geo_based_redirect first
}

:8080 {
    geo_based_redirect {
        mmdb_uri https://git.io/GeoLite2-City.mmdb
        mmdb_path /usr/local/share/GeoIP/GeoLite2-City.mmdb
        mmdb_download_period_days 14
        domain_names example.com myapp.net
        max_cache_size 100000
        cache_ttl_seconds 3600
        health_uri /ping
    }
    respond "Hello from the server!"
}

• mmdb_uri optional uri from where we will download geo ip database, also supports gziped mmdb

• mmdb_download_period_days download interval in days to download mmdb geo ip database

• mmdb_path sets the file path for the GeoIP database.

• domain_names specifies a list of domain names ex. eu.example.com us.example.com.

• max_cache_size sets the maximum number of entries in the cache, default 100k

• cache_ttl_seconds defines the cache entry's time-to-live (TTL) in seconds, default 10 minutes

• health_uri health check http path ex. /ping with linear back-off 1,2,3,4 seconds

Limitations

• Currently supports only IPv4
• Has internal cache of Geo IP lookup so under big load it will start to miss cache and have bigget latency on first request
• Loads GeoIP database in memory so size of it should fit in ram
• Currently it doesn't support domains that resolve in multiple IP's (may add it in future)

Example download Geo IP city database from MaxMind's GeoLite2:

wget https://git.io/GeoLite2-City.mmdb