[rust-renderer] Standalone preprocessing (#36718)

Signed-off-by: Sage Ahrac <sagiahrak@gmail.com>
Co-authored-by: Shangming Cai <csmthu@gmail.com>
Co-authored-by: Liangsheng Yin <hnyls2002@gmail.com>
Co-authored-by: Rain Jiang <96632942+rainj-me@users.noreply.github.com>

rust/sglang-renderer/tests/render_only_cli.rs

@@ -0,0 +1,122 @@
+// Keep the inner attribute off the first line so shebang lint does not misclassify it.
+#![cfg(feature = "http")]
+
+use std::process::{Child, Command, Stdio};
+use std::time::{Duration, Instant};
+
+use reqwest::StatusCode;
+use serde_json::{Value, json};
+
+struct ChildGuard(Child);
+
+struct TestDirectory(std::path::PathBuf);
+
+impl Drop for ChildGuard {
+    fn drop(&mut self) {
+        let _ = self.0.kill();
+        let _ = self.0.wait();
+    }
+}
+
+impl Drop for TestDirectory {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.0);
+    }
+}
+
+fn available_port() -> u16 {
+    let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+    listener.local_addr().unwrap().port()
+}
+
+async fn wait_until_ready(child: &mut Child, client: &reqwest::Client, health_url: &str) {
+    let deadline = Instant::now() + Duration::from_secs(10);
+    loop {
+        if let Some(status) = child.try_wait().unwrap() {
+            panic!("render-only process exited during startup with {status}");
+        }
+        if client
+            .get(health_url)
+            .send()
+            .await
+            .is_ok_and(|response| response.status() == StatusCode::OK)
+        {
+            return;
+        }
+        assert!(
+            Instant::now() < deadline,
+            "render-only process did not start"
+        );
+        tokio::time::sleep(Duration::from_millis(25)).await;
+    }
+}
+
+#[tokio::test]
+async fn binary_starts_without_an_engine_and_serves_only_preprocessing() {
+    let source_tokenizer = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("../../experimental/sgl-router/tests/fixtures/tiny_tokenizer.json");
+    let model = TestDirectory(
+        std::env::temp_dir().join(format!("sglang-render-only-{}", uuid::Uuid::new_v4())),
+    );
+    std::fs::create_dir(&model.0).unwrap();
+    std::fs::copy(source_tokenizer, model.0.join("tokenizer.json")).unwrap();
+    let port = available_port();
+    let mut child = ChildGuard(
+        Command::new(env!("CARGO_BIN_EXE_sglang-renderer"))
+            .arg(&model.0)
+            .arg("--tokenizer-path")
+            .arg(&model.0)
+            .arg("--served-model-name")
+            .arg("model")
+            .arg("--resolved-sampling-params")
+            .arg("{}")
+            .arg("--context-length")
+            .arg("64")
+            .arg("--vocab-size")
+            .arg("512")
+            .arg("--host")
+            .arg("127.0.0.1")
+            .arg("--port")
+            .arg(port.to_string())
+            .stdout(Stdio::null())
+            .stderr(Stdio::inherit())
+            .spawn()
+            .unwrap(),
+    );
+    let client = reqwest::Client::builder().no_proxy().build().unwrap();
+    let origin = format!("http://127.0.0.1:{port}");
+    wait_until_ready(&mut child.0, &client, &format!("{origin}/health")).await;
+
+    let tokenized = client
+        .post(format!("{origin}/v1/tokenize"))
+        .json(&json!({"prompt": "hello"}))
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(tokenized.status(), StatusCode::OK);
+    let tokenized: Value = tokenized.json().await.unwrap();
+    assert!(tokenized["count"].as_u64().is_some_and(|count| count > 0));
+
+    let completion = json!({"model": "model", "prompt": "hello"});
+    let rendered = client
+        .post(format!("{origin}/v1/completions/render"))
+        .json(&completion)
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(rendered.status(), StatusCode::OK);
+    let rendered: Value = rendered.json().await.unwrap();
+    assert!(
+        rendered
+            .as_array()
+            .is_some_and(|requests| requests.len() == 1)
+    );
+
+    let inference = client
+        .post(format!("{origin}/v1/completions"))
+        .json(&completion)
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(inference.status(), StatusCode::NOT_FOUND);
+}