Keep-alive connections over http

[brian-mann]

Problem

HTTP requests through the proxy layer seem to be not taking advantage of HTTP keep-alive to re-use the same connection for multiple requests. Some requests were getting Connection: close instead of taking advantage of Connection: keep-alive, here's what I found when looking at the headers sent and received by Chrome:

	Connection in request	Connection in response
HTTPS, intercepted	keep-alive	keep-alive
HTTPS, non-intercepted	keep-alive	keep-alive
HTTP, non-intercepted	none (is keep-alive in Chrome)	close (should be none)

I think that Chrome is omitting the Connection: keep-alive because it's connected to a proxy, and it expects the proxy to negotiate the Keep-Alive part of the connection. That would explain why HTTP has it and HTTPS does not (HTTPS is not interceptable).

Solution

When an HTTP request is received by the proxy layer, by default, send it with a Connection: keep-alive header so that the connection will be reused if possible.

Commit: 8839177

PR comment discussing before and after: #3531 (comment)

[brian-mann]

Fixed by #3531

[cypress-bot]

Released in 3.3.0.