Any way to get timestamps for upstream-downstream events?

[Ryan Burn]

Hello everyone,

I work on a module that provides distributed tracing for NGINX
(https://github.com/opentracing-contrib/nginx-opentracing). If
possible, I would like to include in the tracing data timestamps for
the following events:

* When the last byte from a downstream request was read
* When the first byte of an upstream request was sent
* When the last byte of an upstream request was sent
* When the first byte of an upstream response was read
* When the last byte of an upstream response was read
* When the first byte of a downstream response was sent
* When the last byte of a downstream response was sent

I recently added similar data to Envoy's tracing
(https://github.com/envoyproxy/envoy/pull/5915), but I'm having
trouble finding out how to access this data from an NGINX module.
Anyone know if it's possible?

Thanks,
Ryan