Augment proxy rewrite

[waTeim]

Add to tycho the capability of setting the rewrite target to tycho while preserving backwards compatibility.

old:

proxy-rewrite-rule: boolean

new:

proxy-rewrite:
  enabled: boolean
  target: string

In the new implementation, proxy-rewrite-rule is still allowed, which is used to set proxy-rewrite.enabled in this instance target defaults to None. If a value of None is encountered, then the old rules apply. Both enabled and proxy-rewrite-rule default to False.

Additionally, if target is not None then an additional ambassador directive is included to recover the original URL.

add_response_headers:
    X-Original-Path: <same as the value of prefix>

[frostyfan109]

Do we know what proxy_rewrite_rule is supposed to do currently (like before this change)? I'm still unclear on its purpose.

[waTeim]

As am I, GPT claims all it did previously was set rewrite to the same value as prefix which accomplished nothing.

[frostyfan109]

I'm pretty sure you said that none of the apps currently (besides RStudio) are using this anyways? So I don't really think there's any reason to hold off on merging. But if that's wrong and apps are using this we should probably figure out what it does.

I know in the tycho code it appears like this rule is completely redundant, so I'm curious why enabling it changed the behavior of RStudio?

[waTeim]

It is on for Jupyter, and I did verify that its behavior is unchanged. I now half-suspect enabling proxy-rewrite-rule for R last week didn't actually fix R, but something else was going on (which I found out during testing).

[frostyfan109]

When I modified the service mapping for RStudio, it affected its behavior? So even if it didn't fix it a couple weeks ago, it still changed something about how Ambassador was proxying its requests, which puzzles me having looked at the Tycho code.

[waTeim]

Heisenbug (mild) is what I'm thinking currently.

[frostyfan109]

It's not because when I changed the service spec back the behavior went back to expected, so I think it must change something.