Akamai Phased Release

At my day job I am migrating one of our websites to AWS. It is fronted by Akamai and we are using the Phased Release Cloudlet to split traffic between the on-premise instances and the AWS instances during our migration. One of the options in the configuration is to enable failover. If the new origin returns a error code, it stops sending traffic to the new origin for a configurable duration.

 The Phased Release Cloudlet configuration panel

The Phased Release Cloudlet configuration panel

But how do you know it is failing? It isn't immediately obvious through the Akamai control panel, but there is a way. The HTTP response headers hold the secret.

aka_cd_failover_INSTANCELABEL = 1

If you are using Chrome, you can find them with the Development Tools.