be more conservative with external process i/o to prevent hung situations

ra_aid/proc/interactive.py

@@ -75,13 +75,15 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
 
     # Open a new pseudo-tty.
     master_fd, slave_fd = os.openpty()
+    # Set master_fd to non-blocking to avoid indefinite blocking.
+    os.set_blocking(master_fd, False)
 
     try:
         stdin_fd = sys.stdin.fileno()
     except (AttributeError, io.UnsupportedOperation):
         stdin_fd = None
 
-    # Set up environment variables for the subprocess using detected terminal size
+    # Set up environment variables for the subprocess using detected terminal size.
     env = os.environ.copy()
     env.update({
         'DEBIAN_FRONTEND': 'noninteractive',
@@ -106,7 +108,7 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
         bufsize=0,
         close_fds=True,
         env=env,
-        preexec_fn=os.setsid  # Create new process group for proper signal handling
+        preexec_fn=os.setsid  # Create new process group for proper signal handling.
     )
     os.close(slave_fd)  # Close slave end in the parent process.
 
@@ -117,16 +119,14 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
     def check_timeout():
         elapsed = time.time() - start_time
         if elapsed > 3 * expected_runtime_seconds:
-            # Force kill after 3x expected runtime
             os.killpg(os.getpgid(proc.pid), signal.SIGKILL)
             return True
         elif elapsed > 2 * expected_runtime_seconds:
-            # Graceful termination after 2x expected runtime
             os.killpg(os.getpgid(proc.pid), signal.SIGTERM)
             return True
         return False
 
-    # If we're in an interactive TTY, set raw mode and forward input.
+    # Interactive mode: forward input if running in a TTY.
     if stdin_fd is not None and sys.stdin.isatty():
         old_settings = termios.tcgetattr(stdin_fd)
         tty.setraw(stdin_fd)
@@ -135,7 +135,8 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
                 if check_timeout():
                     was_terminated = True
                     break
-                rlist, _, _ = select.select([master_fd, stdin_fd], [], [], 1.0)  # 1 second timeout for select
+                # Use a finite timeout to avoid indefinite blocking.
+                rlist, _, _ = select.select([master_fd, stdin_fd], [], [], 1.0)
                 if master_fd in rlist:
                     try:
                         data = os.read(master_fd, 1024)
@@ -144,12 +145,11 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
                             break
                         else:
                             raise
-                    if not data:
+                    if not data:  # EOF detected.
                         break
                     captured_data.append(data)
-                    # Update pyte's screen state.
-                    stream.feed(data.decode("utf-8", errors="ignore"))
-                    # Write to stdout for live output.
+                    decoded = data.decode("utf-8", errors="ignore")
+                    stream.feed(decoded)
                     os.write(1, data)
                 if stdin_fd in rlist:
                     try:
@@ -157,33 +157,33 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
                     except OSError:
                         input_data = b""
                     if input_data:
-                        # Forward raw keystrokes directly to the subprocess.
                         os.write(master_fd, input_data)
         except KeyboardInterrupt:
             proc.terminate()
         finally:
             termios.tcsetattr(stdin_fd, termios.TCSADRAIN, old_settings)
     else:
-        # Non-interactive mode (e.g., during unit tests).
+        # Non-interactive mode.
         try:
             while True:
                 if check_timeout():
                     was_terminated = True
                     break
+                rlist, _, _ = select.select([master_fd], [], [], 1.0)
+                if not rlist:
+                    continue
                 try:
-                    rlist, _, _ = select.select([master_fd], [], [], 1.0)  # 1 second timeout for select
-                    if not rlist:
-                        continue
                     data = os.read(master_fd, 1024)
                 except OSError as e:
                     if e.errno == errno.EIO:
                         break
                     else:
                         raise
-                if not data:
+                if not data:  # EOF detected.
                     break
                 captured_data.append(data)
-                stream.feed(data.decode("utf-8", errors="ignore"))
+                decoded = data.decode("utf-8", errors="ignore")
+                stream.feed(decoded)
                 os.write(1, data)
         except KeyboardInterrupt:
             proc.terminate()
@@ -201,12 +201,12 @@ def run_interactive_command(cmd: List[str], expected_runtime_seconds: int = 30)
     trimmed_lines = [line for line in all_lines if line.strip()]
     final_output = "\n".join(trimmed_lines)
     
-    # Add timeout message if process was terminated
+    # Add timeout message if process was terminated due to timeout.
     if was_terminated:
         timeout_msg = f"\n[Process exceeded timeout ({expected_runtime_seconds} seconds expected)]"
         final_output += timeout_msg
     
-    # Limit output to last 8000 bytes
+    # Limit output to the last 8000 bytes.
     final_output = final_output[-8000:]
     
     return final_output.encode("utf-8"), proc.returncode