This is a small server, written in GO, that returns GEO location for use in client-side apps.
At the moment, it relies on Fastly's GEO IP looking, but could someday include something like MaxMind internally.
There are no external dependencies, so checkout the project into your $GOPATH and:
go build cmd && PORT=8000 $GOPATH/bin/wtflocaleserver
I deploy this to Heroku on a Hobby dyno. It can handle a few thousand requests per second with a ~20ms response time.
In order to get the GEO information, we look for a series of headers set by Fastly. You can ask Fastly to set them using it's Headers feature or a custom VCL.
Here's a screenshot of setting up the headers feature:
If you'd prefer a custom VCL, add this to the vcl_recv section.:
set req.http.X-GEO-LATITUDE = geoip.latitude
set req.http.X-GEO-LONGITUDE = geoip.longitude
set req.http.X-GEO-CITY = geoip.city
set req.http.X-GEO-CONTINENT-CODE = geoip.continent_code
set req.http.X-GEO-COUNTRY-CODE = geoip.country_code
set req.http.X-GEO-COUNTRY-CODE3 = geoip.country_code3
set req.http.X-GEO-COUNTRY-NAME = geoip.country_name
set req.http.X-GEO-POSTAL-CODE = geoip.postal_code
set req.http.X-GEO-REGION = geoip.region
set req.http.X-GEO-AREA-CODE = geoip.area_code
set req.http.X-GEO-METRO-CODE = geoip.metro_code