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sglang/rust/sglang-server/src/api_server/native_api.rs
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2026-08-02 23:13:44 -07:00

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26 KiB
Rust

//! The native SGLang data-plane endpoints: `/generate` (submit a request, then
//! either fold egress frames to one unary JSON response or relay them as SSE
//! `data: {json}` … `[DONE]`, byte-compatible with Python
//! `http_server.generate_request`) and `/health` + `/health_generate` (which
//! round-trip a 1-token generate probe). Frame shaping (`meta_info`, logprob
//! tuples, cumulative vs incremental streams) lives here, as does
//! generate-request submission (`submit`); the shared `AppState` lives in the
//! parent `api_server` module.
use std::convert::Infallible;
use axum::{
Json, Router,
extract::State,
extract::rejection::JsonRejection,
http::StatusCode,
response::{
IntoResponse, Response,
sse::{Event, Sse},
},
routing::{get, post},
};
use tokio::sync::mpsc;
use super::AppState;
use super::frame::{
OutputAccumulator, cumulative_frame_string, error_value, frame_value, stream_frame_string,
tag_value,
};
use super::guard::AbortGuard;
use super::submit::{pre_submit_error, submit};
use crate::environ::env_bool;
use crate::ids::Rid;
use crate::message::{EgressItem, GenerateBody, GenerateRequest, RequestKind, SamplingParams};
/// The routes this module owns, mounted by `api_server::serve`.
pub(super) fn routes() -> Router<AppState> {
Router::new()
.route("/generate", post(generate))
.merge(health_routes())
}
/// `/health` + `/health_generate`. Both env knobs are resolved ONCE here, at
/// router build (server startup) — changing them on a live process needs a
/// restart. The deep-probe handler is built once with
/// `SGLANG_HEALTH_CHECK_TIMEOUT` frozen in and serves `/health_generate`
/// always; `SGLANG_ENABLE_HEALTH_ENDPOINT_GENERATION` (default true, mirroring
/// Python) decides whether `/health` shares it or is a plain 200 (routing the
/// request already proves the frontend is up).
fn health_routes() -> Router<AppState> {
let timeout =
std::time::Duration::from_secs(crate::environ::env_u64("SGLANG_HEALTH_CHECK_TIMEOUT", 20));
let probe = get(move |state: State<AppState>| health_generate(state, timeout));
let health = if env_bool("SGLANG_ENABLE_HEALTH_ENDPOINT_GENERATION", true) {
probe.clone()
} else {
get(|| async { StatusCode::OK.into_response() })
};
Router::new()
.route("/health", health)
.route("/health_generate", probe)
}
/// Sentinel host that makes the KV connector no-op. Parity with
/// `sglang.srt.disaggregation.utils.FAKE_BOOTSTRAP_HOST`.
const FAKE_BOOTSTRAP_HOST: &str = "2.2.2.2";
/// `GET /health_generate` — deep health: confirm the scheduler → detok path is
/// producing output. 200 iff the egress heartbeat advances within `timeout`
/// (from `SGLANG_HEALTH_CHECK_TIMEOUT`, frozen at router build), else 503.
/// (`/health` uses the same handler when its env gate is on.)
///
/// Fires a pre-tokenized 1-token probe (`input_ids = [0]`, skips the tokenizer) so
/// an idle pipeline produces a frame, then watches the *global*
/// [`AppState::egress_activity`] counter (not the probe's own rid) — so a busy
/// server passes immediately and a backlog never false-503s (the analogue of
/// Python's `last_receive_tstamp`). The `HEALTH_CHECK` skip + `http_worker_ipc`
/// ack are irrelevant here: this single-process server owns the egress ring.
async fn health_generate(State(state): State<AppState>, timeout: std::time::Duration) -> Response {
let baseline = state
.egress_activity
.load(std::sync::atomic::Ordering::Relaxed);
// Fire the probe (the heartbeat is the signal, not its own response). A busy
// scheduler skips it with no terminal frame, so its detok registration is
// cleaned up only by the `AbortGuard` below.
//
// On a PD node the scheduler 400-aborts room-less requests, so inject the
// same fake bootstrap pair Python uses (`FAKE_BOOTSTRAP_HOST` / room 0).
let pd = state.server_args.is_disaggregation();
let probe = GenerateRequest {
// The `HEALTH_CHECK_<uuid>` rid form
rid: Rid::new_health_check(),
input_ids: Some(vec![0]),
// One greedy token: the cheapest round-trip that still produces a frame.
sampling_params: SamplingParams {
max_new_tokens: Some(1),
temperature: 0.0,
..Default::default()
},
stream: false,
bootstrap_host: pd.then(|| FAKE_BOOTSTRAP_HOST.into()),
bootstrap_room: pd.then_some(0),
..Default::default()
};
let (rid, _keepalive) =
match submit(&state, RequestKind::Generate(Box::new(probe)), false).await {
// Hold the receiver so the probe's sink stays open until it completes.
Ok(v) => v,
Err(resp) => return resp,
};
// Deregister on drop (never disarmed): a busy-skipped probe has no terminal
// frame, so without this abort it leaks one detok entry per call.
let _abort_guard = AbortGuard::new(state.senders.clone(), rid);
// Watch the heartbeat advance (timeout frozen at router build, default 20s).
let deadline = tokio::time::Instant::now() + timeout;
loop {
if state
.egress_activity
.load(std::sync::atomic::Ordering::Relaxed)
!= baseline
{
return StatusCode::OK.into_response();
}
if tokio::time::Instant::now() >= deadline {
return StatusCode::SERVICE_UNAVAILABLE.into_response();
}
tokio::time::sleep(std::time::Duration::from_millis(50)).await;
}
}
/// `POST /generate` — the native generation endpoint. Splits the body
/// into per-request payloads (a scalar body → one, a list body → a batch) and
/// dispatches to the single or batch path; a malformed body is a 400 before
/// anything reaches the scheduler.
///
/// The body is extracted as a `Result` so a deserialization failure is answered
/// with **400** (Python's status for a bad request) carrying serde's field-level
/// message, instead of axum's default 422.
async fn generate(
State(state): State<AppState>,
body: Result<Json<GenerateBody>, JsonRejection>,
) -> Response {
let body = match body {
Ok(Json(body)) => body,
// A body that fails to parse has no readable `stream` flag, so this one
// can only answer unary — as Python's does (FastAPI rejects before its
// handler runs).
Err(rejection) => {
return pre_submit_error(StatusCode::BAD_REQUEST, &rejection.body_text(), false);
}
};
let stream = body.stream;
// Fan `text`/`input_ids`/`sampling_params` (scalar or list) into per-request
// payloads. `is_batch` = list form → the response is a JSON array.
let (payloads, is_batch) = match body.into_requests() {
Ok(v) => v,
// The error carries its own status (a bad batch is `Validation` → 400).
Err(e) => {
let code = StatusCode::from_u16(e.http_status()).unwrap_or(StatusCode::BAD_REQUEST);
return pre_submit_error(code, &e.to_string(), stream);
}
};
if !is_batch {
// `into_requests` guarantees exactly one payload for a non-batch body.
let payload = payloads
.into_iter()
.next()
.expect("into_requests yields >=1 payload");
generate_single(&state, payload, stream).await
} else {
generate_batch(&state, payloads, stream).await
}
}
/// Answer an error raised *before* anything was submitted, in the shape the client
/// asked for.
///
/// A single (non-batched) `/generate`: submit one request, then either stream its
/// SSE frames or fold to one unary response.
async fn generate_single(state: &AppState, req: GenerateRequest, stream: bool) -> Response {
// `return_text_in_logprobs` is decoded on the detok shard into `*_txt`, so
// `frame_value` just reads them — no tokenizer needed here.
let (rid_str, mut rx) = match submit(state, RequestKind::Generate(Box::new(req)), stream).await
{
Ok(v) => v,
Err(resp) => return resp,
};
// Abort on client disconnect: the guard fires when dropped before the request
// finishes (axum drops the handler/SSE stream). Disarmed on a natural terminal.
// `rid_str` is the response `meta_info.id`, reused for every frame.
let mut guard = AbortGuard::new(state.senders.clone(), rid_str.clone());
// Cumulative frames (SGLang default) vs per-step deltas.
let incremental = state.server_args.incremental_streaming_output;
if stream {
// A single request is a 1-element batch without the `index` field — reuse
// the same stream so the frame/abort/truncation logic lives in one place.
use futures::StreamExt;
let s = generation_event_stream(vec![(rid_str, rx)], guard, incremental, false)
.map(|data| Ok::<_, Infallible>(Event::default().data(data)));
Sse::new(s).into_response()
} else {
// Unary: fold to the terminal, respond once. Disarm only on a real terminal
// (a truncation leaves the guard armed so the scheduler work is aborted).
let (status, value, terminal) = drain_unary(&mut rx, rid_str.client_facing()).await;
if terminal {
guard.disarm(&rid_str);
}
(status, Json(value)).into_response()
}
}
/// Fold a unary request to its terminal → (HTTP status, result/`error` JSON, saw-terminal);
/// `false` = truncation, caller keeps the abort guard armed. Shared by single + batch.
async fn drain_unary(
rx: &mut mpsc::Receiver<EgressItem>,
rid_str: &str,
) -> (StatusCode, serde_json::Value, bool) {
let mut acc = OutputAccumulator::default();
while let Some(item) = rx.recv().await {
match item {
EgressItem::Frame(out) => acc.fold(&out),
EgressItem::Done(out) => {
acc.fold(&out);
let final_out = acc.into_output();
// A validation abort carries its own HTTP status + diagnostic.
if let Some((code, message)) = final_out
.finish_reason
.as_ref()
.and_then(|f| f.abort_status())
{
let status =
StatusCode::from_u16(code).unwrap_or(StatusCode::INTERNAL_SERVER_ERROR);
return (status, error_value(code, message), true);
}
return (StatusCode::OK, frame_value(&final_out, rid_str), true);
}
EgressItem::Error(e) => {
let code = e.http_status();
let status =
StatusCode::from_u16(code).unwrap_or(StatusCode::INTERNAL_SERVER_ERROR);
return (status, error_value(code, &e.to_string()), true);
}
EgressItem::Control(_) | EgressItem::Data(_) => continue, // never on `/generate`
}
}
// Sender dropped without a terminal item: the shard dropped this request (a
// truncation — a client disconnect would have dropped the handler future).
(
StatusCode::INTERNAL_SERVER_ERROR,
error_value(500, "response truncated before completion"),
false,
)
}
/// Batch `/generate`: submit all sub-requests first (scheduler runs them together),
/// then either (unary) drain each in order into a JSON array, or (streaming)
/// multiplex their streams into one SSE response, each frame carrying its `index`.
/// One [`AbortGuard`] covers the batch. A failed unary item is its own
/// `{ "error": … }` entry; the batch response is 200.
async fn generate_batch(
state: &AppState,
requests: Vec<GenerateRequest>,
stream: bool,
) -> Response {
// No cross-item rid collision to worry about: `into_requests` rejected duplicate
// rids within this batch, and `Rid::from_client` made each one unique against
// every other in-flight request.
let mut guard = AbortGuard::new_empty(state.senders.clone());
let mut receivers = Vec::with_capacity(requests.len());
for req in requests {
match submit(state, RequestKind::Generate(Box::new(req)), stream).await {
Ok((rid, rx)) => {
guard.arm(rid.clone());
receivers.push((rid, rx));
}
Err(resp) => return resp,
}
}
if stream {
// Multiplex the N streams (mirrors the Python `_handle_batch_request` path);
// `guard` moves into the stream so a disconnect aborts what's unfinished.
use futures::StreamExt;
let incremental = state.server_args.incremental_streaming_output;
let s = generation_event_stream(receivers, guard, incremental, true)
.map(|data| Ok::<_, Infallible>(Event::default().data(data)));
Sse::new(s).into_response()
} else {
// Unary: drain each in order (already all submitted, so they run together).
let mut results = Vec::with_capacity(receivers.len());
for (rid_str, mut rx) in receivers {
let (_status, value, terminal) = drain_unary(&mut rx, rid_str.client_facing()).await;
if terminal {
guard.disarm(&rid_str);
}
results.push(value);
}
(StatusCode::OK, Json(serde_json::Value::Array(results))).into_response()
}
}
/// Await the next item from `rx`, then drain whatever queued behind it (so the caller
/// can coalesce a backlog, as Python's `state.out_list` does), handing the receiver
/// back for `FuturesUnordered` to re-poll. Empty result = channel closed.
async fn recv_indexed(
index: usize,
mut rx: mpsc::Receiver<EgressItem>,
) -> (usize, mpsc::Receiver<EgressItem>, Vec<EgressItem>) {
let mut items = Vec::new();
match rx.recv().await {
Some(item) => items.push(item),
None => return (index, rx, items), // closed
}
while let Ok(item) = rx.try_recv() {
items.push(item);
}
(index, rx, items)
}
/// Multiplex `receivers` (one per request) into SSE `data` strings + a final `[DONE]`;
/// `with_index` tags each frame (batch only), `incremental` = delta vs cumulative,
/// `guard` aborts unfinished on drop.
fn generation_event_stream(
receivers: Vec<(Rid, mpsc::Receiver<EgressItem>)>,
mut guard: AbortGuard,
incremental: bool,
with_index: bool,
) -> impl futures::Stream<Item = String> {
async_stream::stream! {
use futures::StreamExt;
let n = receivers.len();
let rid_strs: Vec<Rid> = receivers.iter().map(|(rid, _)| rid.clone()).collect();
let mut accs: Vec<OutputAccumulator> =
(0..n).map(|_| OutputAccumulator::default()).collect();
// Batch position, tagged onto every frame (a single request omits it).
let idx = |i: usize| with_index.then_some(i);
// Poll all receivers concurrently; re-arm a receiver's future after each
// non-terminal frame so its stream keeps flowing.
let mut futs = futures::stream::FuturesUnordered::new();
for (i, (_, rx)) in receivers.into_iter().enumerate() {
futs.push(recv_indexed(i, rx));
}
while let Some((i, rx, items)) = futs.next().await {
if items.is_empty() {
// Channel closed with no terminal → truncation for this item;
// leave its rid armed so the scheduler work is aborted.
yield tag_value(error_value(500, "response truncated before completion"), idx(i));
continue;
}
// Cumulative frames supersede one another, so a drained backlog collapses
// to its last (Python's `out_list[-1]`); deltas can't be dropped.
let mut coalesced = false; // a cumulative frame is pending
let mut terminal = None; // (finish_reason) of a `Done` in this batch
let mut failed = None; // an `Error` in this batch
for item in items {
match item {
EgressItem::Frame(out) => {
accs[i].fold(&out);
if incremental {
yield stream_frame_string(out, &accs[i], true, rid_strs[i].client_facing(), idx(i));
} else {
coalesced = true;
}
}
EgressItem::Done(out) => {
accs[i].fold(&out);
terminal = Some(out);
}
EgressItem::Error(e) => failed = Some(e),
EgressItem::Control(_) | EgressItem::Data(_) => {} // never on /generate
}
}
if let Some(e) = failed {
yield tag_value(error_value(e.http_status(), &e.to_string()), idx(i));
guard.disarm(&rid_strs[i]);
} else if let Some(out) = terminal {
// A validation abort → an error object, not a frame. The final frame
// carries the full cumulative state, so any coalesced ones are moot.
yield match out.finish_reason.as_ref().and_then(|f| f.abort_status()) {
Some((code, message)) => tag_value(error_value(code, message), idx(i)),
None => stream_frame_string(out, &accs[i], incremental, rid_strs[i].client_facing(), idx(i)),
};
guard.disarm(&rid_strs[i]); // terminal → not re-pushed
} else {
if coalesced {
yield cumulative_frame_string(&accs[i], rid_strs[i].client_facing(), idx(i));
}
futs.push(recv_indexed(i, rx)); // keep this item flowing
}
}
yield "[DONE]".to_string();
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::message::ChunkEvent;
use crate::tokenizer_manager::Senders;
use futures::StreamExt;
fn senders() -> Senders {
Senders {
tm: flume::unbounded().0,
abort: flume::unbounded().0,
tok: flume::unbounded().0,
detok: vec![],
}
}
fn frame(rid: u64, text: &str) -> EgressItem {
EgressItem::Frame(ChunkEvent {
rid: Rid::from(rid.to_string()),
text: text.into(),
completion_tokens: 1,
..Default::default()
})
}
fn done(rid: u64, text: &str) -> EgressItem {
EgressItem::Done(ChunkEvent {
rid: Rid::from(rid.to_string()),
text: text.into(),
completion_tokens: 1,
// Parsed from the wire map Python emits, not a hand-built enum.
finish_reason: Some(
serde_json::from_value(serde_json::json!({"type": "length", "length": 1}))
.expect("finish reason must parse"),
),
..Default::default()
})
}
fn parse(s: &str) -> serde_json::Value {
serde_json::from_str(s).expect("frame is JSON")
}
/// Two sub-requests' frames interleave into one stream, each tagged with its
/// batch `index`; text accumulates per item; `[DONE]` comes only after both
/// terminate, then the stream ends.
#[tokio::test]
async fn interleaves_indexes_and_accumulates() {
let (tx0, rx0) = mpsc::channel(8);
let (tx1, rx1) = mpsc::channel(8);
let receivers = vec![("10".into(), rx0), ("11".into(), rx1)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), false, true);
futures::pin_mut!(stream);
// Drive deterministically: exactly one channel has data before each poll.
tx0.send(frame(10, "a")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 0);
assert_eq!(v["text"], "a");
tx1.send(frame(11, "b")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 1);
assert_eq!(v["text"], "b");
tx0.send(done(10, "!")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 0);
assert_eq!(v["text"], "a!", "cumulative per item");
assert_eq!(v["meta_info"]["finish_reason"]["type"], "length");
tx1.send(done(11, "?")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 1);
assert_eq!(v["text"], "b?");
assert_eq!(stream.next().await.unwrap(), "[DONE]");
assert!(stream.next().await.is_none());
}
/// A per-item error is surfaced with its `index` and doesn't end the batch;
/// `[DONE]` still waits for the other item.
#[tokio::test]
async fn per_item_error_carries_index() {
let (tx0, rx0) = mpsc::channel(8);
let (tx1, rx1) = mpsc::channel(8);
let receivers = vec![("10".into(), rx0), ("11".into(), rx1)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), false, true);
futures::pin_mut!(stream);
tx0.send(EgressItem::Error(crate::error::Error::Validation(
"bad".into(),
)))
.await
.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 0);
assert_eq!(v["error"]["code"], 400);
tx1.send(done(11, "ok")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["index"], 1);
assert_eq!(stream.next().await.unwrap(), "[DONE]");
}
/// `incremental=true`: each frame carries this step's **delta** text/output_ids,
/// but `meta_info.completion_tokens` stays cumulative (matching Python).
#[tokio::test]
async fn incremental_emits_deltas_with_cumulative_count() {
let (tx, rx) = mpsc::channel(8);
let receivers = vec![("10".into(), rx)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), true, true);
futures::pin_mut!(stream);
tx.send(frame(10, "Hello")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], "Hello");
assert_eq!(v["meta_info"]["completion_tokens"], 1);
tx.send(frame(10, " world")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], " world", "delta, not cumulative 'Hello world'");
assert_eq!(
v["meta_info"]["completion_tokens"], 2,
"count stays cumulative"
);
tx.send(done(10, "!")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], "!");
assert_eq!(v["meta_info"]["completion_tokens"], 3);
assert_eq!(v["meta_info"]["finish_reason"]["type"], "length");
assert_eq!(stream.next().await.unwrap(), "[DONE]");
}
/// The single-request shape (`with_index=false`, one receiver) omits the
/// `index` field entirely, and still terminates with `[DONE]`.
#[tokio::test]
async fn single_shape_omits_index() {
let (tx, rx) = mpsc::channel(8);
let receivers = vec![("10".into(), rx)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), false, false);
futures::pin_mut!(stream);
tx.send(done(10, "hi")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], "hi");
assert!(v.get("index").is_none(), "single response has no index");
assert_eq!(stream.next().await.unwrap(), "[DONE]");
}
/// A backlog of cumulative chunks collapses to a single frame carrying the latest
/// state — each cumulative frame supersedes the last, so emitting the intermediate
/// ones ships the full O(T) payload again for nothing. Mirrors the Python waiter's
/// `out = out_list[-1]`. This is the whole point of draining in `recv_indexed`.
#[tokio::test]
async fn cumulative_backlog_coalesces_to_latest() {
let (tx, rx) = mpsc::channel(8);
let receivers = vec![("10".into(), rx)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), false, false);
futures::pin_mut!(stream);
// Three chunks queued before the stream is ever polled (a client falling behind).
tx.send(frame(10, "a")).await.unwrap();
tx.send(frame(10, "b")).await.unwrap();
tx.send(frame(10, "c")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], "abc", "one frame, full cumulative text");
assert_eq!(v["meta_info"]["completion_tokens"], 3, "no tokens lost");
// The terminal frame still carries everything, and only then does [DONE] land.
tx.send(done(10, "!")).await.unwrap();
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], "abc!");
assert_eq!(v["meta_info"]["finish_reason"]["type"], "length");
assert_eq!(stream.next().await.unwrap(), "[DONE]");
}
/// Incremental frames are *deltas*, so a backlog must emit every one — dropping
/// any would silently lose tokens. Only the cumulative protocol may coalesce.
#[tokio::test]
async fn incremental_backlog_emits_every_delta() {
let (tx, rx) = mpsc::channel(8);
let receivers = vec![("10".into(), rx)];
let stream =
generation_event_stream(receivers, AbortGuard::new_empty(senders()), true, false);
futures::pin_mut!(stream);
tx.send(frame(10, "a")).await.unwrap();
tx.send(frame(10, "b")).await.unwrap();
tx.send(frame(10, "c")).await.unwrap();
for (n, expect) in [(1, "a"), (2, "b"), (3, "c")] {
let v = parse(&stream.next().await.unwrap());
assert_eq!(v["text"], expect, "delta {n} must not be dropped");
assert_eq!(
v["meta_info"]["completion_tokens"], n,
"count stays cumulative"
);
}
}
}