Document how to obtain URL host correctly during early hooks

[zhang15535135608]

A note should be added to the document, TSUrlHostGet only allows calls after TS_HTTP_POST_REMAP_HOOK。

In the TS_HTTP_READ_REQUEST_HDR_HOOK phase, you can call TSHttpHdrHostGet to get the host, if you want to get it.

https://docs.trafficserver.apache.org/en/latest/developer-guide/api/functions/TSUrlHostGet.en.html

[Sage-2001]

Hey, I made a pull request. @scw00 can you review it ?

[jpeach]

A note should be added to the document, TSUrlHostGet only allows calls after TS_HTTP_POST_REMAP_HOOK。

I'm not sure that is correct. TSUrlHostGet takes a URL from a marshal buffer, so as long as that buffer has the host portion set, it should be OK.

So you could do

    TSMBufferCreate(...)
    TSUrlParse(...)
    TSUrlHostGet(...)

[Sage-2001]

Can you check my pull request i did the needed changes @jpeach

[jpeach]

Can you check my pull request i did the needed changes @jpeach

What problem are you trying to fix here? I think that we need to understand that before we can think about what documentation change would help people who are using the API.

[JosiahWI]

@mmustafasenoglu Since you've taken up this issue (#13313), could you explain whether you have confirmed this is a real issue, and if so, explain why it is? The comments from @jpeach suggest this issue may be misunderstood.

[mmustafasenoglu]

Hi @JosiahWI, @jpeach

Thanks for the question. To be transparent, I haven't personally verified the exact hook behavior in the Traffic Server source code. The documentation change was based on the original issue reporter's experience (#5742) who stated that TSUrlHostGet only works after TS_HTTP_POST_REMAP_HOOK.

However, @jpeach's point is valid — TSUrlHostGet operates on a marshal buffer URL, so in theory it should work on any properly parsed URL regardless of hook phase.

I think the safest path forward is:

1. If the original issue reporter's use case was actually about the URL not being fully populated in earlier hooks (rather than the function itself failing), the note may be misleading
2. If there's a real difference in behavior between hook phases, we should document the specific reason why

I'm happy to update or close the PR based on the maintainers' consensus. If the function truly works at any point after URL parsing, we should probably close #5742 as well.

[bryancall]

I am closing this as not needed. The premise that TSUrlHostGet can only be called after TS_HTTP_POST_REMAP_HOOK is not correct. TSUrlHostGet reads the host from a marshal buffer, so it works at any point as long as that buffer has the host portion set (for example after TSMBufferCreate plus TSUrlParse), independent of which hook is running. The current documentation (doc/developer-guide/api/functions/TSUrlHostGet.en.rst) already describes the function as a marshal-buffer accessor with no hook-phase requirement, which is accurate, so adding a hook call condition would be misleading. This was raised by a maintainer on the issue and acknowledged on the related pull request, so no documentation change is warranted.