[Rust Server] Return kv_events from /server_info like Python

[haowu1234]

What changed

Rust server /server_info now returns the same kv_events discovery field that Python /server_info already returns (#25844).

Before this PR:

• Python workers exposed kv_events from /server_info
• Rust frontend workers did not expose that field
• KV-aware routers could not use the same discovery path for Rust workers

After this PR:

• Rust /server_info includes a structured kv_events descriptor when the configured publisher is safe to advertise
• Rust /server_info returns "kv_events": null when the config is disabled, malformed, non-TCP, has an invalid port, or lacks a positive page size
• Rust keeps its existing safe /server_info behavior: no raw server_args, no raw kv_events_config, and no secret fields are exposed

This is introspection-only. It does not implement KV-event publishing or move the scheduler-side publisher.

Code changes

• rust/sglang-server/src/runtime/config.rs

  • add typed ServerArgs fields for kv_events_config, page_size, and dp_size
  • add ServerArgs::describe_kv_events_publisher()
  • parse ZMQ-style TCP endpoints into endpoint_host and endpoint_port_base
  • validate publisher state, TCP scheme, port range, and positive page size

• rust/sglang-server/src/api_server/common.rs

  • include kv_events in the shaped Rust /server_info response
  • keep the response allowlisted instead of dumping raw server args
  • add tests for valid descriptors, invalid configs, and secret redaction

Example

Given these Rust server args:

{
  "kv_events_config": "{\"publisher\":\"zmq\",\"endpoint\":\"tcp://*:5557\",\"topic\":\"kv\"}",
  "page_size": 64,
  "dp_size": 2
}

Rust /server_info now includes:

{
  "kv_events": {
    "publisher": "zmq",
    "endpoint_host": "*",
    "endpoint_port_base": 5557,
    "topic": "kv",
    "block_size": 64,
    "dp_size": 2
  }
}

Validation

Local macOS:

• cargo fmt --manifest-path rust/Cargo.toml --package sglang-server --check
• cargo test --manifest-path rust/Cargo.toml -p sglang-server --lib api_server::common::tests::shape_server_info
  • 4 passed

Remote Linux/PyO3 validation on root@134.199.199.149, with heavy build paths on /mnt/lmcache-build/sglang-rust-server-kv-events:

• cargo fmt --manifest-path rust/Cargo.toml --package sglang-server --check
• cargo test --manifest-path rust/Cargo.toml -p sglang-server --lib api_server::common::tests::shape_server_info
  • 4 passed
• cargo test --manifest-path rust/Cargo.toml -p sglang-server
  • branch 1702c0aff: 135 passed; 3 failed
  • base fd28242b68: 132 passed; 3 failed
  • same pre-existing failures on both branch and base:
    • api_server::frame::tests::cumulative_frame_json_matches_serde
    • api_server::frame::tests::cumulative_frame_json_matches_serde_with_logprobs
    • message::egress::tests::chunk_event_frame_stays_small

Live Rust HTTP E2E:

• rebuilt the Rust server PyO3 extension from this branch
• started a real sglang.srt.server._core.Server with skip_tokenizer_init=true
• sent a real HTTP GET /server_info request to the Rust Axum listener
• decoded the ingress GetInternalStateReq and replied through push_result, simulating the scheduler control response
• verified HTTP 200
• verified the returned kv_events descriptor exactly matches the expected ZMQ host/port/topic/block-size/dp-size payload
• verified the serialized response does not contain api_key, admin_api_key, raw kv_events_config, or a nested test password

Result:

LIVE_E2E_PASS
commit 1702c0aff
kv_events {"block_size":64,"dp_size":2,"endpoint_host":"*","endpoint_port_base":5557,"publisher":"zmq","topic":"kv"}

Fixes #33055.
Part of #23206.
Related to #29799.
Follow-up to #25844.

---

CI States

Latest PR Test (Base): ✅ Run #30622023649
Latest PR Test (Extra): ❌ Run #30622023378

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