| Tracking Headers | Description |
|---|---|
| X-Varnish | This header is automatically picked up from the Varnish Shared Memory log. |
| X-Varnish-Parent | Parent of a request. Each RPC call must have a X-Varnish-Parent. It is a copy of X-Varnish header at the parent RPC call level. |
| X-Varnish-Trace | It is used to connect a Request / RPC call to a trace. Each RPC call except the root RPC call will have a X-Varnish-Trace header. |
| X-Varnish-Debug | 0 or 1. For now value doesn't signify anything special. It needs to comply with ZipKin, but we'll probably look int this later. |
Request
When a RPC call makes a call to another RPC call down the chain. These headers are passed along X-Varnish-Trace and X-Varnish-Parent.
Response
When a RPC call responds. It needs to respond back with X-Varnish-Trace and X-Varnish-Parent headers, which it received from it's parent call.