From de89ef49da9314da0395287ff2e4ee2e9a94ccc2 Mon Sep 17 00:00:00 2001
From: Liangsheng Yin <hnyls2002@gmail.com>
Date: Fri, 3 Oct 2025 12:31:13 +0800
Subject: [PATCH] [CI]] Tee server logs to both file and stdout/stderr using
 PIPE (#11185)

---
 python/sglang/test/test_utils.py | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/python/sglang/test/test_utils.py b/python/sglang/test/test_utils.py
index ddab8bbf6..060a41c13 100644
--- a/python/sglang/test/test_utils.py
+++ b/python/sglang/test/test_utils.py
@@ -9,6 +9,7 @@ import os
 import random
 import re
 import subprocess
+import sys
 import threading
 import time
 import unittest
@@ -566,11 +567,30 @@ def popen_launch_server(
     if return_stdout_stderr:
         process = subprocess.Popen(
             command,
-            stdout=return_stdout_stderr[0],
-            stderr=return_stdout_stderr[1],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
             env=env,
             text=True,
+            bufsize=1,
         )
+
+        def _dump(src, sinks):
+            for line in iter(src.readline, ""):
+                for sink in sinks:
+                    sink.write(line)
+                    sink.flush()
+            src.close()
+
+        threading.Thread(
+            target=_dump,
+            args=(process.stdout, [return_stdout_stderr[0], sys.stdout]),
+            daemon=True,
+        ).start()
+        threading.Thread(
+            target=_dump,
+            args=(process.stderr, [return_stdout_stderr[1], sys.stderr]),
+            daemon=True,
+        ).start()
     else:
         process = subprocess.Popen(command, stdout=None, stderr=None, env=env)