pingora-proxy examples don't support pipelining

[kenballus]

Describe the bug

The pingora-proxy examples don't support client-side HTTP pipelining.

Pingora info

Please include the following information about your environment:

Pingora version: e288bfe (built from source)
Rust version: cargo 1.79.0 (ffa9cf99a 2024-06-03)
Operating system version: Debian 12

Steps to reproduce

1. Build the pingora-proxy gateway example.
2. Test that it works:

printf 'GET / HTTP/1.1\r\nHost: one.one.one.one\r\n\r\n' \
  | ncat --no-shutdown localhost 6191 \
  | grep -oP 'HTTP/1.1 \d\d\d'

HTTP/1.1 200

3. Test that client-side connection reuse works when requests are not pipelined:

(printf 'GET / HTTP/1.1\r\nHost: one.one.one.one\r\n\r\n'; sleep 1; printf 'GET / HTTP/1.1\r\nHost: one.one.one.one\r\n\r\n') \
  | ncat --no-shutdown localhost 6191 \
  | grep -oP 'HTTP/1.1 \d\d\d'

HTTP/1.1 200
HTTP/1.1 200

4. Observe that connection reuse doesn't work when requests are pipelined:

printf 'GET / HTTP/1.1\r\nHost: one.one.one.one\r\n\r\nGET / HTTP/1.1\r\nHost: one.one.one.one\r\n\r\n' \
  | ncat --no-shutdown localhost 6191 \
  | grep -oP 'HTTP/1.1 \d\d\d'

HTTP/1.1 200

Expected results

I expect to get 2 responses when sending 2 pipelined requests.

Observed results

I only get 1 response.

[eaufavor]

Note that http pipelining is not supported by major browsers. Some also believe that it does more harm than good.

Ref
https://en.wikipedia.org/wiki/HTTP_pipelining
https://portswigger.net/research/browser-powered-desync-attacks
https://community.f5.com/kb/technicalarticles/http-pipelining-a-security-risk-without-real-performance-benefits/286621

[kenballus]

Note that http pipelining is not supported by major browsers. Some also believe that it does more harm than good.

Yep. For better or for worse, HTTP is filled with features that seem useless or confusing in hindsight. Some of my (least) favorites are

• chunk extensions,
• trailer fields,
• line folding,
• the fact that it takes this much text to explain how to parse a message body,

Here's a breakdown of how other HTTP reverse proxies handle pipelined requests:

Disallow request pipelining:

• Pingora (of course)
• OpenBSD relayd

Allow request pipelining, forward requests individually, then forward responses individually:

• Akamai GHost
• AWS CloudFront
• Google Cloud Classic Application Load Balancer
• Envoy
• Microsoft IIS

Allow request pipelining, forward requests individually, then forward responses pipelined:

• Apache httpd mod_proxy
• Apache Traffic Server
• AWS Elastic Load Balancer
• Cloudflare (which was unexpected, given that pingora is a cloudflare thing)
• Go net/http
• H2O
• HAProxy
• Lighttpd
• nghttpx
• Nginx
• OpenLiteSpeed
• Pound
• Squid
• Varnish

In summary, request pipelining is supported in nearly all reverse proxies, but requests are always un-pipelined before forwarding.