Add an example of multi-host inference using SGLang

[yankay]

What would you like to be added:

Add an example of multi-host inference using SGLang .

Why is this needed:

Recently, There have been some issues about how to run LWS with Sglang

• Set RANK environment variables for pods #368
• how get envs for multi node deploy like master addr、master port、rank？ #370

Completion requirements:

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[hwdef]

sglang has special advantages in reasoning about deepseek, it has a large throughput and supports MLA earlier.

[ahg-g]

@yankay @hwdef would you like to submit one?

[yankay]

@yankay @hwdef would you like to submit one?

/assign

[kerthcet]

If I remember correctly, SGLang doesn't support multi-host right now, PP support is still unfinished at 2024Q4. sgl-project/sglang#1487

[kerthcet]

Searched the document, they do support multi-host with TP.
see https://github.com/sgl-project/sglang/blob/637de9e8ce91fd3e92755eb2a842860925954ab1/docs/backend/backend.md?plain=1#L88-L95

[panpan0000]

TP -- yes, PP - not yeah

[ahg-g]

I think it is ok, it is useful to show case SGLang here!