fix: Final round of improvements

HIGH PRIORITY:
1. Pool allocation race condition
   - Add file locking around entire pool allocation in haproxy_add_domain
   - Prevents concurrent calls from getting same pool

2. haproxy_remove_server - disk-first pattern
   - Remove from config FIRST, then update HAProxy
   - Rollback config on HAProxy failure

3. Wildcard domain prefix validation
   - Reject domains starting with '.'
   - Prevents double-prefix like '..domain.com'

MEDIUM PRIORITY:
4. Variable shadowing fix
   - Rename state_output to servers_state in haproxy_set_domain_state

5. JSON size limit
   - Add MAX_SERVERS_JSON_SIZE = 10000 limit for haproxy_add_servers

6. Remove get_server_suffixes
   - Delete unused abstraction layer
   - Inline logic in restore_servers_from_config and haproxy_add_domain

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mcp/server.py

@@ -82,6 +82,7 @@ STATE_MIN_COLUMNS = 19  # Minimum columns in HAProxy server state output
 SOCKET_TIMEOUT = 5  # seconds for HAProxy socket connection
 SOCKET_RECV_TIMEOUT = 30  # seconds for HAProxy socket recv loop
 MAX_BULK_SERVERS = 10  # Max servers per bulk add call
+MAX_SERVERS_JSON_SIZE = 10000  # Max size of servers JSON in haproxy_add_servers
 
 
 class HaproxyError(Exception):
@@ -577,16 +578,6 @@ def remove_domain_from_config(domain: str) -> None:
             fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
 
 
-def get_server_suffixes(http_port: int) -> List[Tuple[str, int]]:
-    """Get server suffixes and ports based on port configuration.
-
-    Args:
-        http_port: HTTP port for backend
-
-    Returns:
-        List of (suffix, port) tuples - always HTTP only
-    """
-    return [("", http_port)]
 
 
 def configure_server_slot(backend: str, server_prefix: str, slot: int, ip: str, http_port: int) -> str:
@@ -667,13 +658,12 @@ def restore_servers_from_config() -> int:
                 continue
 
             try:
-                http_port = int(server_info.get("http_port", 80))
+                port = int(server_info.get("http_port", 80))
             except (ValueError, TypeError):
                 logger.warning("Invalid port for %s slot %d, skipping", domain, slot)
                 continue
 
-            for suffix, port in get_server_suffixes(http_port):
+            server = f"{server_prefix}_{slot}"
-                server = f"{server_prefix}{suffix}_{slot}"
             try:
                 haproxy_cmd_checked(f"set server {backend}/{server} addr {ip} port {port}")
                 haproxy_cmd_checked(f"set server {backend}/{server} state ready")
@@ -769,6 +759,8 @@ def haproxy_add_domain(domain: str, ip: str = "", http_port: int = 80) -> str:
         haproxy_add_domain("api.example.com", ip="10.0.0.1", http_port=8080)
     """
     # Validate inputs
+    if domain.startswith("."):
+        return "Error: Domain cannot start with '.' (wildcard entries are added automatically)"
     if not validate_domain(domain):
         return "Error: Invalid domain format"
     if not validate_ip(ip, allow_empty=True):
@@ -776,6 +768,11 @@ def haproxy_add_domain(domain: str, ip: str = "", http_port: int = 80) -> str:
     if not (1 <= http_port <= 65535):
         return "Error: Port must be between 1 and 65535"
 
+    # Use file locking for the entire pool allocation operation
+    lock_path = f"{MAP_FILE}.lock"
+    with open(lock_path, 'w') as lock_file:
+        fcntl.flock(lock_file.fileno(), fcntl.LOCK_EX)
+        try:
             # Read map contents once for both existence check and pool lookup
             entries = get_map_contents()
 
@@ -829,9 +826,8 @@ def haproxy_add_domain(domain: str, ip: str = "", http_port: int = 80) -> str:
                     add_server_to_config(domain, 1, ip, http_port)
 
                     try:
-                for suffix, port in get_server_suffixes(http_port):
+                        server = f"{pool}_1"
-                    server = f"{pool}{suffix}_1"
+                        haproxy_cmd(f"set server {pool}/{server} addr {ip} port {http_port}")
-                    haproxy_cmd(f"set server {pool}/{server} addr {ip} port {port}")
                         haproxy_cmd(f"set server {pool}/{server} state ready")
                     except HaproxyError as e:
                         # Rollback server config on failure
@@ -844,6 +840,8 @@ def haproxy_add_domain(domain: str, ip: str = "", http_port: int = 80) -> str:
 
             except HaproxyError as e:
                 return f"Error: {e}"
+        finally:
+            fcntl.flock(lock_file.fileno(), fcntl.LOCK_UN)
 
 
 @mcp.tool()
@@ -1053,6 +1051,10 @@ def haproxy_add_servers(domain: str, servers: str) -> str:
     if not validate_domain(domain):
         return "Error: Invalid domain format"
 
+    # Check JSON size before parsing
+    if len(servers) > MAX_SERVERS_JSON_SIZE:
+        return f"Error: servers JSON exceeds maximum size ({MAX_SERVERS_JSON_SIZE} bytes)"
+
     # Parse JSON array
     try:
         server_list = json.loads(servers)
@@ -1199,16 +1201,25 @@ def haproxy_remove_server(domain: str, slot: int) -> str:
     try:
         backend, server_prefix = get_backend_and_prefix(domain)
 
+        # Get current server info for potential rollback
+        config = load_servers_config()
+        old_config = config.get(domain, {}).get(str(slot), {})
+
+        # Remove from persistent config FIRST (disk-first pattern)
+        remove_server_from_config(domain, slot)
+
+        try:
             # HTTP only - single server per slot
             server = f"{server_prefix}_{slot}"
             haproxy_cmd_checked(f"set server {backend}/{server} state maint")
             haproxy_cmd_checked(f"set server {backend}/{server} addr 0.0.0.0 port 0")
-
-        # Remove from persistent config
-        remove_server_from_config(domain, slot)
-
             return f"Removed server at slot {slot} from {domain} ({backend})"
-    except (HaproxyError, ValueError, IOError) as e:
+        except HaproxyError as e:
+            # Rollback: re-add config if HAProxy command failed
+            if old_config:
+                add_server_to_config(domain, slot, old_config.get("ip", ""), old_config.get("http_port", 80))
+            return f"Error: {e}"
+    except (ValueError, IOError) as e:
         return f"Error: {e}"
 
 
@@ -1245,14 +1256,14 @@ def haproxy_set_domain_state(domain: str, state: str) -> str:
 
     # Get active servers for this domain
     try:
-        state_output = haproxy_cmd("show servers state")
+        servers_state = haproxy_cmd("show servers state")
     except HaproxyError as e:
         return f"Error: {e}"
 
     changed = []
     errors = []
 
-    for line in state_output.split("\n"):
+    for line in servers_state.split("\n"):
         parts = line.split()
         if len(parts) >= STATE_MIN_COLUMNS and parts[StateField.BE_NAME] == backend:
             server_name = parts[StateField.SRV_NAME]