Thread:Extension talk:CentralNotice/Caching Overhaul - Frontend Proxy/Node.js as frontend proxy

I mostly like this proposal, and think it's the right way to go at it. I do however disagree with the idea of choosing Node.js as the frontend proxy. I would much rather like to see Varnish be the frontend proxy, with the CentralNotice banner selection code be a backend or plugin to that - even if it means that every request needs to pass through it anyway.

From an Operations management perspective, using Node.js as frontend proxy instead of one of our existing solutions is not a great idea:
 * Even though its performance and scalability is not bad, it's not as good as the existing solutions we use (Varnish, nginx)
 * Having an additional piece of software as a frontend proxy means that we need to integrate it into our solutions for logging, analytics, statistics, alerting, configuration management, IP ACLs & banning, etc, which is quite a lot of work on top of developing just this proxy
 * We have far less expertise dealing with performance and reliability problems of Node.js
 * Node.js would also need to work with whatever solution we use for SSL termination - e.g. X-Forwarded-For and X-Forwarded-Proto handling with nginx now, possibly stud with the PROXY protocol in the future
 * We would be unable to serve these banners from the same servers/clusters (e.g. bits or text), which may be good to reduce hostname lookups, and save hardware resources. For each additional cluster, we're normally talking about 4 servers per datacenter. Today we have 4 data centers, with more planned for the future. Therefore, the option to consolidate is always nice.

In short, I think there's more to it than simply selecting node.js because it's a popular and nice choice to put a little bit of logic into.

I don't necessarily think putting it in Varnish VCL is such a great idea, however. Perhaps an integrated LUA implementation (as has been talked about for Varnish, and for which a VMOD exists) could be nice, but may not be very realistic at this point. I think Varnish pass'ing all requests to a Node.js backend would be reasonable, along with ESI.