More detailed 5xx errors

[mlibbey]

Cloudflare has made some very useful 5xx errors for troubleshooting. From wikipedia:

• 520 Unknown Error: The 520 error is used as a "catch-all response for when the origin server returns something unexpected", listing connection resets, large headers, and empty or invalid responses as common triggers.
• 521 Web Server Is Down: The origin server has refused the connection from Cloudflare.
• 522 Connection Timed Out: Cloudflare could not negotiate a TCP handshake with the origin server.
• 523 Origin Is Unreachable: Cloudflare could not reach the origin server; for example, if the DNS records for the origin server are incorrect.
• 524 A Timeout Occurred:Cloudflare was able to complete a TCP connection to the origin server, but did not receive a timely HTTP response.
• 525 SSL Handshake Failed: Cloudflare could not negotiate a SSL/TLS handshake with the origin server.
• 526 Invalid SSL Certificate: Cloudflare could not validate the SSL/TLS certificate that the origin server presented.

[mlibbey]

Would also be nice to have codes for:

• DNS failures.
• Other SSL errors (post-handshake)

[maskit]

Probably, a possible approach to achieve the same thing will be that ATS core provides detail information to plugins (e.g. header_rewrite) so that they can modify status code as they like. I think we shouldn't have the unofficial status codes in ATS Core.

I'm going to start working on this but please create another issue if you need some standard specific status code. It could be done on ATS Core side while working on this.

List of HTTP status codes:
https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

IANA official registry:
https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml

[maskit]

It seems we already have an API for getting some of the information.

TSHttpTxnServerStateGet() returns one of these server state, it's undocumented though.
https://docs.trafficserver.apache.org/ja/latest/developer-guide/api/types/TSServerState.en.html

As for DNS and SSL, we need to introduce new APIs.

However, I'm not sure how much detail will be needed in general. Probably, the APIs should be proposed with some practical plugin.

[zwoop]

Yeh, that seems like a good idea (header_rewrite).

[mlibbey]

still hard to troubleshoot 502s. (users mailing list just had an example)

[masaori335]

"The Proxy-Status HTTP Header Field" might be what we're looking for. (It's just proposed)

https://tools.ietf.org/html/draft-nottingham-proxy-status-00

[mlibbey]

Looks promising!

[bryancall]

@mlibbey Can you please assign this to someone on your team if you are going to work on it?

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. Marking it stale to flag it for further consideration by the community.