What does .share_key do in the backend definition


I’m wondering what “.share_key” does for me in the backend definition. e.g.:

backend F_mybackend {
  .share_key = "whatever65X57CQCRZ161843702706";

Does it allow for a global max_connections across different services that define backends with the same share_key? Does it allow Fastly to re-use backend connections across different services?

Please enlighten me!

Thank you


The share_key allows us to partition backends based on VCL. The only reason to change it is if you want to share a backend healthcheck between two different services/VCLs.

We have an ability to have parent/child services, and the share_key default to the service_id. If you were to have multiple services, and wanted to share the backends between them, then you would set the share key to the same thing and make sure that the definitions are identical.