support for http/1.1 -> http2 client upgrade for outbound connections

[akshaychitneni]

Envoy only supports http2 connections to the upstream hosts with prior knowledge. Any upgrade request from http1.1 to http2 from the client is not supported.

Can this be supported?

Thanks!

[mattklein123]

This can be supported. There are two ways that I can see this being implemented functionality-wise.

1. Build functionality into the existing HTTP/2 connection pool that assumes that upgrade is required, but will always succeed. This is relatively simple to implement.

2. Support a new connection pool which can operate in both HTTP/1 and HTTP/2 modes depending on upgrade. If this is required I would implement an entirely new connection pool implementation. This is a lot more work.

[mandarjog]

/subscribe

[swift1911]

is any progress for this issue?