Is it possible from VCL to invoke a module function after a request has been processed?

Question

Ideally, I'd like to do something like this:

sub vcl_after_response_is_sent {
  mymod.f(req, resp);
}

But I don't see any builtin subroutine that could let you do this. Is there any other way it might be accomplished?

Answer 1

This can be done using PRIV_TASK with a free function.

In the module's VCC declare the function as follows:

$Function VOID f(PRIV_TASK)

Use something like the following for the function's definition:

void finish_request(void*) {
}

VCL_VOID vmod_trace_request(VRT_CTX, struct vmod_priv* priv_task) {
  priv_task->priv = /* Some non-null value */
  priv_task->free = finish_request;
}

If f is then called from vcl_recv

sub vcl_recv {
  mymod.f();
}

finish_request will be invoked when varnish is done with the request.