Any way to invoke code from VCL after a request has been serviced?

[Dridi Boukelmoune]

> I'm looking into writing a module that enables Varnish for distributed
> tracing using the OpenTracing project [opentracing.io]. This requires
> invoking code at the beginning of a request to start a span and insert
> tracing context into the request's headers and invoking code after a
> request's been processed to finish the span and measure how long it
> took to process.

You can see this kind of tracing in action in the Zipnish [1] project.
It's Varnish's equivalent to Zipkin and if I'm not wrong was or is
compatible with the latter.

Dridi

[1] https://github.com/varnish/zipnish