Edge Proxy

Every section.io application proxy stack implicitly begins with the Edge proxy. The Edge proxy is the endpoint to which the User-Agent (eg web browser) connects and it has a few responsibilities:

  • Performing the TLS handshake for HTTPS connections
  • Routing requests to the corresponding application proxy stack
  • Implementing the HTTP/2 protocol
  • Request correlation
  • Serving custom error pages

This enables a consistent experience on the section.io platform regardless of which proxies are in your application’s stack or in which sequence they appear.

IP geolocation

For each incoming request, the Edge proxy attempts to resolve the client’s connecting IP address to a geographic location. The results of the lookup are then exposed to the other proxies in the proxy stack and to the origin web server as HTTP request headers. These headers are:

  • section-io-geo-country - the ISO 3166-1 alpha-2 country code such as US for the United States, or AU for Australia.
  • section-io-geo-region - examples include California and Virginia for US IPs or New South Wales for Australian IPs.
  • section-io-geo-city - examples include New York, Mountain View, Sydney, and Drummoyne.
  • section-io-geo-latlon - the approximate latitude and longitude in the format -33.8696,151.2099.

Not all headers are populated for all IP addresses.

These geolocation values are also available in the access logs.

Request correlation

When the Edge proxy handles each incoming request, a unique identifier is generated and is added to the request via a section-io-id HTTP request header.

This request header then propagates through to each proxy in your application’s proxy stack and ultimately to your application’s configured origin web server. When the final response is returned from your application, via the proxy stack, to the User-Agent, the Edge proxy also inserts the same identifier as a section-io-id HTTP response header.

The section-io-id value is available in all the proxy logs provided by Aperture to enable easy correlation of log entries across the different proxies in the stack. You can also choose to log the section-io-id request header on your origin server to aid with diagnostics.

By providing the identifier as a request header, its value can be consumed in your chosen proxies. For example, Varnish can refer to req.http.section-io-id in the VCL.

The format of the section-io-id identifier is subject to change without notice so it should be treated as an opaque string and no meaning should be inferred from its value.