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.
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,
would have Traffic Server send a cache miss to
when the origin server in the remap rule returns a 401,
404, 410, or 502 error code.
This option sends the “pristine” Host: header (eg, the Host: header that the client sent) to the escalated request.
This plugin is considered stable and is included with Traffic Server by default. There are no special steps necessary for its installation.
With this line in
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
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