Escalate Plugin

The Escalate plugin allows Traffic Server to try an alternate origin when the origin server in the remap rule is either unavailable or returns specific HTTP error codes. Some services call this failover or fail-action.

Plugin Configuration

The escalate plugin is a remap plugin (not global) and takes a parameter with two delimitated fields: comma-separated-error-codes:secondary-origin-server. For instance,

@pparam=401,404,410,502:second-origin.example.com

would have Traffic Server send a cache miss to second-origin.example.com when the origin server in the remap rule returns a 401, 404, 410, or 502 error code.

@pparam=–pristine

This option sends the “pristine” Host: header (eg, the Host: header that the client sent) to the escalated request.

Installation

This plugin is only built if the configure option

--enable-experimental-plugins

is given at build time.

Example

With this line in remap.config

map cdn.example.com origin.example.com
  @plugin=escalate.so @pparam=401,404,410,502:second-origin.example.com @pparam=--pristine

Traffic Server would accept a request for cdn.example.com and, on a cache miss, proxy the request to origin.example.com. If the response code from that server is a 401, 404, 410, or 502, then Traffic Server would proxy the request to second-origin.example.com, using a Host: header of cdn.example.com.