Adding MCP Server Check (#16)

Author: xzrderek

eval_protocol/pytest/default_mcp_gym_rollout_processor.py

@@ -2,6 +2,7 @@
 import os
 import subprocess
 import time
+import socket
 from pathlib import Path
 from typing import List, Optional
 
@@ -69,11 +70,8 @@ def start(self) -> None:
         self._log_file = log_file
         self._log_file_path = log_file_path
 
-        # Wait for server to start
-        time.sleep(3)
-
-        # Check if process is still running
-        if self.process.poll() is not None:
+        # Wait for server to be ready with proper health check
+        if not self._wait_for_server_ready(timeout=15):
             try:
                 with open(self._log_file_path, "r") as f:
                     log_content = f.read()
@@ -82,13 +80,45 @@ def start(self) -> None:
                 print("=" * 50)
                 print(log_content)
                 print("=" * 50)
-                raise RuntimeError(f"Server failed to start. Check log above for details.")
+                raise RuntimeError(f"Server failed to start or become ready. Check log above for details.")
             except Exception as e:
                 stdout, stderr = self.process.communicate()
-                raise RuntimeError(f"Server failed to start. stderr: {stderr}, log error: {e}")
+                raise RuntimeError(f"Server failed to start or become ready. stderr: {stderr}, log error: {e}")
 
         print(f"✅ Server started successfully on port {self.port}")
 
+    def _wait_for_server_ready(self, timeout: int = 15) -> bool:
+        """
+        Wait for server to be ready by polling socket connection.
+        """
+        start_time = time.time()
+        health_check_failures = 0
+
+        while time.time() - start_time < timeout:
+            # Check if process is still running
+            if self.process.poll() is not None:
+                print(f"Server process exited early")
+                return False
+
+            try:
+                with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                    s.settimeout(1)
+                    result = s.connect_ex(("localhost", self.port))
+                    if result == 0:
+                        time.sleep(0.5)
+                        return True
+            except Exception as e:
+                health_check_failures += 1
+                # Print first few failures for debugging
+                if health_check_failures <= 3:
+                    print(f"Health check failed: {e}")
+
+            # Wait before next check
+            time.sleep(0.1)
+
+        print(f"Server failed to become ready within {timeout} seconds")
+        return False
+
     def stop(self) -> None:
         """Stop the MCP server."""
         if self.process: