Available inall subroutines.
The generation number of the currently executing VCL.
The generation number is an integer which is incorporated into the hash function Fastly uses to identify the cache location of requested objects. When a Fastly service is purged using a "purge all" operation, the generation number for that service is incremented, so that all subsequent hash calculations produce a new result. This makes existing cached objects unreachable and effectively clears the service cache.
Learn more about purging Fastly services in our purging guide.