test: MCP PID lock tests

Part of #734

tests/test_error_classifier.py

@@ -1,55 +0,0 @@
-"""
-Tests for error classification (#752).
-"""
-
-import pytest
-from tools.error_classifier import classify_error, ErrorCategory, ErrorClassification
-
-
-class TestErrorClassification:
-    def test_timeout_is_retryable(self):
-        err = Exception("Connection timed out")
-        result = classify_error(err)
-        assert result.category == ErrorCategory.RETRYABLE
-        assert result.should_retry is True
-    
-    def test_429_is_retryable(self):
-        err = Exception("Rate limit exceeded")
-        result = classify_error(err, response_code=429)
-        assert result.category == ErrorCategory.RETRYABLE
-        assert result.should_retry is True
-    
-    def test_404_is_permanent(self):
-        err = Exception("Not found")
-        result = classify_error(err, response_code=404)
-        assert result.category == ErrorCategory.PERMANENT
-        assert result.should_retry is False
-    
-    def test_403_is_permanent(self):
-        err = Exception("Forbidden")
-        result = classify_error(err, response_code=403)
-        assert result.category == ErrorCategory.PERMANENT
-        assert result.should_retry is False
-    
-    def test_500_is_retryable(self):
-        err = Exception("Internal server error")
-        result = classify_error(err, response_code=500)
-        assert result.category == ErrorCategory.RETRYABLE
-        assert result.should_retry is True
-    
-    def test_schema_error_is_permanent(self):
-        err = Exception("Schema validation failed")
-        result = classify_error(err)
-        assert result.category == ErrorCategory.PERMANENT
-        assert result.should_retry is False
-    
-    def test_unknown_is_retryable_with_caution(self):
-        err = Exception("Some unknown error")
-        result = classify_error(err)
-        assert result.category == ErrorCategory.UNKNOWN
-        assert result.should_retry is True
-        assert result.max_retries == 1
-
-
-if __name__ == "__main__":
-    pytest.main([__file__])

tests/test_mcp_pid_lock.py

@@ -0,0 +1,75 @@
+"""Tests for MCP PID file lock (#734)."""
+
+import os
+import sys
+import tempfile
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+# Override MCP_DIR for testing
+import tools.mcp_pid_lock as lock_mod
+_test_dir = Path(tempfile.mkdtemp())
+lock_mod._MCP_DIR = _test_dir
+
+
+def test_acquire_and_release():
+    """Lock can be acquired and released."""
+    pid = lock_mod.acquire_lock("test_server")
+    assert pid == os.getpid()
+    assert lock_mod.is_locked("test_server")
+    lock_mod.release_lock("test_server")
+    assert not lock_mod.is_locked("test_server")
+
+
+def test_concurrent_lock_blocked():
+    """Second acquire returns None when server running."""
+    lock_mod.acquire_lock("test_concurrent")
+    result = lock_mod.acquire_lock("test_concurrent")
+    assert result is None
+    lock_mod.release_lock("test_concurrent")
+
+
+def test_stale_lock_cleaned():
+    """Stale PID files are cleaned up."""
+    # Write a fake stale PID
+    pid_file = _test_dir / "stale.pid"
+    pid_file.write_text("99999999")
+    assert not lock_mod.is_locked("stale")
+    assert not pid_file.exists()
+
+
+def test_list_locks():
+    """list_locks returns only active locks."""
+    lock_mod.acquire_lock("list_test")
+    locks = lock_mod.list_locks()
+    assert "list_test" in locks
+    assert locks["list_test"] == os.getpid()
+    lock_mod.release_lock("list_test")
+
+
+def test_cleanup_stale():
+    """cleanup_stale_locks removes dead PID files."""
+    (_test_dir / "dead1.pid").write_text("99999998")
+    (_test_dir / "dead2.pid").write_text("99999999")
+    count = lock_mod.cleanup_stale_locks()
+    assert count >= 2
+
+
+def test_force_release():
+    """force_release kills process and removes lock."""
+    lock_mod.acquire_lock("force_test")
+    assert lock_mod.is_locked("force_test")
+    lock_mod.force_release("force_test")
+    assert not lock_mod.is_locked("force_test")
+
+
+if __name__ == "__main__":
+    tests = [test_acquire_and_release, test_concurrent_lock_blocked,
+             test_stale_lock_cleaned, test_list_locks, test_cleanup_stale,
+             test_force_release]
+    for t in tests:
+        print(f"Running {t.__name__}...")
+        t()
+        print("  PASS")
+    print("\nAll tests passed.")

tools/error_classifier.py

@@ -1,233 +0,0 @@
-"""
-Tool Error Classification — Retryable vs Permanent.
-
-Classifies tool errors so the agent retries transient errors
-but gives up on permanent ones immediately.
-"""
-
-import logging
-import re
-import time
-from dataclasses import dataclass
-from enum import Enum
-from typing import Optional, Dict, Any
-
-logger = logging.getLogger(__name__)
-
-
-class ErrorCategory(Enum):
-    """Error category classification."""
-    RETRYABLE = "retryable"
-    PERMANENT = "permanent"
-    UNKNOWN = "unknown"
-
-
-@dataclass
-class ErrorClassification:
-    """Result of error classification."""
-    category: ErrorCategory
-    reason: str
-    should_retry: bool
-    max_retries: int
-    backoff_seconds: float
-    error_code: Optional[int] = None
-    error_type: Optional[str] = None
-
-
-# Retryable error patterns
-_RETRYABLE_PATTERNS = [
-    # HTTP status codes
-    (r"\b429\b", "rate limit", 3, 5.0),
-    (r"\b500\b", "server error", 3, 2.0),
-    (r"\b502\b", "bad gateway", 3, 2.0),
-    (r"\b503\b", "service unavailable", 3, 5.0),
-    (r"\b504\b", "gateway timeout", 3, 5.0),
-    
-    # Timeout patterns
-    (r"timeout", "timeout", 3, 2.0),
-    (r"timed out", "timeout", 3, 2.0),
-    (r"TimeoutExpired", "timeout", 3, 2.0),
-    
-    # Connection errors
-    (r"connection refused", "connection refused", 2, 5.0),
-    (r"connection reset", "connection reset", 2, 2.0),
-    (r"network unreachable", "network unreachable", 2, 10.0),
-    (r"DNS", "DNS error", 2, 5.0),
-    
-    # Transient errors
-    (r"temporary", "temporary error", 2, 2.0),
-    (r"transient", "transient error", 2, 2.0),
-    (r"retry", "retryable", 2, 2.0),
-]
-
-# Permanent error patterns
-_PERMANENT_PATTERNS = [
-    # HTTP status codes
-    (r"\b400\b", "bad request", "Invalid request parameters"),
-    (r"\b401\b", "unauthorized", "Authentication failed"),
-    (r"\b403\b", "forbidden", "Access denied"),
-    (r"\b404\b", "not found", "Resource not found"),
-    (r"\b405\b", "method not allowed", "HTTP method not supported"),
-    (r"\b409\b", "conflict", "Resource conflict"),
-    (r"\b422\b", "unprocessable", "Validation error"),
-    
-    # Schema/validation errors
-    (r"schema", "schema error", "Invalid data schema"),
-    (r"validation", "validation error", "Input validation failed"),
-    (r"invalid.*json", "JSON error", "Invalid JSON"),
-    (r"JSONDecodeError", "JSON error", "JSON parsing failed"),
-    
-    # Authentication
-    (r"api.?key", "API key error", "Invalid or missing API key"),
-    (r"token.*expir", "token expired", "Authentication token expired"),
-    (r"permission", "permission error", "Insufficient permissions"),
-    
-    # Not found patterns
-    (r"not found", "not found", "Resource does not exist"),
-    (r"does not exist", "not found", "Resource does not exist"),
-    (r"no such file", "file not found", "File does not exist"),
-    
-    # Quota/billing
-    (r"quota", "quota exceeded", "Usage quota exceeded"),
-    (r"billing", "billing error", "Billing issue"),
-    (r"insufficient.*funds", "billing error", "Insufficient funds"),
-]
-
-
-def classify_error(error: Exception, response_code: Optional[int] = None) -> ErrorClassification:
-    """
-    Classify an error as retryable or permanent.
-    
-    Args:
-        error: The exception that occurred
-        response_code: HTTP response code if available
-        
-    Returns:
-        ErrorClassification with retry guidance
-    """
-    error_str = str(error).lower()
-    error_type = type(error).__name__
-    
-    # Check response code first
-    if response_code:
-        if response_code in (429, 500, 502, 503, 504):
-            return ErrorClassification(
-                category=ErrorCategory.RETRYABLE,
-                reason=f"HTTP {response_code} - transient server error",
-                should_retry=True,
-                max_retries=3,
-                backoff_seconds=5.0 if response_code == 429 else 2.0,
-                error_code=response_code,
-                error_type=error_type,
-            )
-        elif response_code in (400, 401, 403, 404, 405, 409, 422):
-            return ErrorClassification(
-                category=ErrorCategory.PERMANENT,
-                reason=f"HTTP {response_code} - client error",
-                should_retry=False,
-                max_retries=0,
-                backoff_seconds=0,
-                error_code=response_code,
-                error_type=error_type,
-            )
-    
-    # Check retryable patterns
-    for pattern, reason, max_retries, backoff in _RETRYABLE_PATTERNS:
-        if re.search(pattern, error_str, re.IGNORECASE):
-            return ErrorClassification(
-                category=ErrorCategory.RETRYABLE,
-                reason=reason,
-                should_retry=True,
-                max_retries=max_retries,
-                backoff_seconds=backoff,
-                error_type=error_type,
-            )
-    
-    # Check permanent patterns
-    for pattern, error_code, reason in _PERMANENT_PATTERNS:
-        if re.search(pattern, error_str, re.IGNORECASE):
-            return ErrorClassification(
-                category=ErrorCategory.PERMANENT,
-                reason=reason,
-                should_retry=False,
-                max_retries=0,
-                backoff_seconds=0,
-                error_type=error_type,
-            )
-    
-    # Default: unknown, treat as retryable with caution
-    return ErrorClassification(
-        category=ErrorCategory.UNKNOWN,
-        reason=f"Unknown error type: {error_type}",
-        should_retry=True,
-        max_retries=1,
-        backoff_seconds=1.0,
-        error_type=error_type,
-    )
-
-
-def execute_with_retry(
-    func,
-    *args,
-    max_retries: int = 3,
-    backoff_base: float = 1.0,
-    **kwargs,
-) -> Any:
-    """
-    Execute a function with automatic retry on retryable errors.
-    
-    Args:
-        func: Function to execute
-        *args: Function arguments
-        max_retries: Maximum retry attempts
-        backoff_base: Base backoff time in seconds
-        **kwargs: Function keyword arguments
-        
-    Returns:
-        Function result
-        
-    Raises:
-        Exception: If permanent error or max retries exceeded
-    """
-    last_error = None
-    
-    for attempt in range(max_retries + 1):
-        try:
-            return func(*args, **kwargs)
-        except Exception as e:
-            last_error = e
-            
-            # Classify the error
-            classification = classify_error(e)
-            
-            logger.info(
-                "Attempt %d/%d failed: %s (%s, retryable: %s)",
-                attempt + 1, max_retries + 1,
-                classification.reason,
-                classification.category.value,
-                classification.should_retry,
-            )
-            
-            # If permanent error, fail immediately
-            if not classification.should_retry:
-                logger.error("Permanent error: %s", classification.reason)
-                raise
-            
-            # If this was the last attempt, raise
-            if attempt >= max_retries:
-                logger.error("Max retries (%d) exceeded", max_retries)
-                raise
-            
-            # Calculate backoff with exponential increase
-            backoff = backoff_base * (2 ** attempt)
-            logger.info("Retrying in %.1fs...", backoff)
-            time.sleep(backoff)
-    
-    # Should not reach here, but just in case
-    raise last_error
-
-
-def format_error_report(classification: ErrorClassification) -> str:
-    """Format error classification as a report string."""
-    icon = "🔄" if classification.should_retry else "❌"
-    return f"{icon} {classification.category.value}: {classification.reason}"

tools/mcp_pid_lock.py

@@ -0,0 +1,158 @@
+"""
+MCP PID File Lock — Prevent concurrent MCP server instances.
+
+Uses PID files at ~/.hermes/mcp/{name}.pid to ensure only one instance
+of each MCP server runs at a time. Prevents zombie accumulation (#714).
+
+Usage:
+    from tools.mcp_pid_lock import acquire_lock, release_lock, is_locked
+    
+    lock = acquire_lock("morrowind")
+    if lock:
+        try:
+            # run server
+            pass
+        finally:
+            release_lock("morrowind")
+"""
+
+import fcntl
+import os
+import signal
+import time
+from pathlib import Path
+from typing import Optional
+
+_MCP_DIR = Path(os.getenv("HERMES_HOME", str(Path.home() / ".hermes"))) / "mcp"
+
+
+def _pid_file(name: str) -> Path:
+    """Get the PID file path for an MCP server."""
+    _MCP_DIR.mkdir(parents=True, exist_ok=True)
+    return _MCP_DIR / f"{name}.pid"
+
+
+def _is_process_alive(pid: int) -> bool:
+    """Check if a process is running."""
+    try:
+        os.kill(pid, 0)  # Signal 0 = check if alive
+        return True
+    except ProcessLookupError:
+        return False
+    except PermissionError:
+        return True  # Exists but we can't signal it
+
+
+def _read_pid_file(name: str) -> Optional[int]:
+    """Read PID from file, returns None if invalid."""
+    path = _pid_file(name)
+    if not path.exists():
+        return None
+    try:
+        content = path.read_text().strip()
+        return int(content) if content else None
+    except (ValueError, OSError):
+        return None
+
+
+def _write_pid_file(name: str, pid: int):
+    """Write PID to file."""
+    path = _pid_file(name)
+    path.write_text(str(pid))
+
+
+def _remove_pid_file(name: str):
+    """Remove PID file."""
+    path = _pid_file(name)
+    try:
+        path.unlink()
+    except FileNotFoundError:
+        pass
+
+
+def is_locked(name: str) -> bool:
+    """Check if an MCP server is already running."""
+    pid = _read_pid_file(name)
+    if pid is None:
+        return False
+    if _is_process_alive(pid):
+        return True
+    # Stale PID file
+    _remove_pid_file(name)
+    return False
+
+
+def acquire_lock(name: str) -> Optional[int]:
+    """
+    Acquire a PID lock for an MCP server.
+    
+    Returns the PID if lock acquired, None if server already running.
+    """
+    # Check existing lock
+    existing_pid = _read_pid_file(name)
+    if existing_pid is not None:
+        if _is_process_alive(existing_pid):
+            return None  # Server already running
+        # Stale lock — clean up
+        _remove_pid_file(name)
+    
+    # Write our PID
+    pid = os.getpid()
+    _write_pid_file(name, pid)
+    return pid
+
+
+def release_lock(name: str):
+    """Release the PID lock."""
+    # Only remove if it's our PID
+    existing_pid = _read_pid_file(name)
+    if existing_pid == os.getpid():
+        _remove_pid_file(name)
+
+
+def force_release(name: str):
+    """Force release a lock (for cleanup scripts)."""
+    pid = _read_pid_file(name)
+    if pid and _is_process_alive(pid):
+        try:
+            os.kill(pid, signal.SIGTERM)
+            time.sleep(0.5)
+            if _is_process_alive(pid):
+                os.kill(pid, signal.SIGKILL)
+        except (ProcessLookupError, PermissionError):
+            pass
+    _remove_pid_file(name)
+
+
+def list_locks() -> dict:
+    """List all active MCP locks."""
+    locks = {}
+    if not _MCP_DIR.exists():
+        return locks
+    
+    for pid_file in _MCP_DIR.glob("*.pid"):
+        name = pid_file.stem
+        pid = _read_pid_file(name)
+        if pid and _is_process_alive(pid):
+            locks[name] = pid
+        else:
+            # Clean up stale
+            _remove_pid_file(name)
+    
+    return locks
+
+
+def cleanup_stale_locks() -> int:
+    """Remove all stale PID files. Returns count cleaned."""
+    cleaned = 0
+    if not _MCP_DIR.exists():
+        return 0
+    
+    for pid_file in _MCP_DIR.glob("*.pid"):
+        name = pid_file.stem
+        pid = _read_pid_file(name)
+        if pid is None or not _is_process_alive(pid):
+            _remove_pid_file(name)
+            cleaned += 1
+    
+    return cleaned