refactor(e2e_test): fix smg ci e2e test code quality (#16664)

sgl-model-gateway/e2e_test/benchmarks/conftest.py

@@ -152,13 +152,20 @@ def genai_bench_runner():
         )
         timeout = timeout_sec or int(os.environ.get("GENAI_BENCH_TEST_TIMEOUT", "120"))
 
-        proc = subprocess.Popen(
-            cmd,
-            env=os.environ.copy(),
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-            text=True,
-        )
+        try:
+            proc = subprocess.Popen(
+                cmd,
+                env=os.environ.copy(),
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                text=True,
+            )
+        except FileNotFoundError:
+            pytest.fail(f"genai-bench executable not found at {cli}")
+        except PermissionError:
+            pytest.fail(f"Permission denied executing {cli}")
+        except OSError as e:
+            pytest.fail(f"Failed to start genai-bench: {e}")
 
         # Start GPU monitor if needed
         gpu_monitor: GPUMonitor | None = None
@@ -172,6 +179,16 @@ def genai_bench_runner():
         except subprocess.TimeoutExpired:
             proc.kill()
             stdout, stderr = proc.communicate()
+            logger.error("genai-bench timed out after %ds", timeout)
+
+        # Log output if process failed or for debugging
+        if proc.returncode != 0:
+            logger.error(
+                "genai-bench exited with code %d\nstdout:\n%s\nstderr:\n%s",
+                proc.returncode,
+                stdout or "(empty)",
+                stderr or "(empty)",
+            )
 
         try:
             # Parse and validate results
@@ -187,6 +204,16 @@ def genai_bench_runner():
                 gpu_monitor.log_summary()
                 gpu_monitor.assert_thresholds(thresholds)
 
+        except AssertionError:
+            # Log genai-bench output when results not found
+            logger.error(
+                "genai-bench output (returncode=%d):\nstdout:\n%s\nstderr:\n%s",
+                proc.returncode,
+                stdout or "(empty)",
+                stderr or "(empty)",
+            )
+            raise
+
         finally:
             _cleanup_procs(kill_procs, drain_delay_sec)
             if gpu_monitor: