New feature: Shadow Traffic

[abraithwaite (Alan Braithwaite)]

I’ve been thinking about building a small Go proxy for shadowing traffic to a second upstream.

I’m curious if any of the Caddy developers have thought deeply about this or if there are any plans to implement something similar?

At a high level, I’d like to be able to specify a second host (or set of hosts) to be able to send a % of traffic to in which the response does not get proxied back to the client, but instead gets recorded (metrics) and discarded.

After briefly peeking at the code, I think it could involve some significant changes to the core proxy logic.

WDYT?

[matt (Matt Holt)]

I think this is a good case for a Caddy plugin, rather than a core feature. It can certainly be done as a plugin; Go makes it fairly easy to write proxies.

[Whitestrake (Matthew Fay)]

Might make a good extension to the existing proxy directive (as a subdirective that configures the proxy not to wait for or return the upstream response to the client but continue down the middleware chain as normal).