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| import asyncio
from typing import Callable, Dict, Any, Optional
from enum import Enum
class RecoveryStrategy(Enum):
"""恢复策略"""
RETRY = "retry"
FALLBACK = "fallback"
CIRCUIT_BREAKER = "circuit_breaker"
GRACEFUL_DEGRADATION = "graceful_degradation"
class ErrorRecoveryManager:
"""错误恢复管理器"""
def __init__(self):
self.recovery_strategies: Dict[str, RecoveryStrategy] = {}
self.fallback_handlers: Dict[str, Callable] = {}
self.retry_policies: Dict[str, Dict] = {}
self.circuit_breakers: Dict[str, CircuitBreaker] = {}
def register_strategy(self, operation: str, strategy: RecoveryStrategy, **kwargs):
"""注册恢复策略"""
self.recovery_strategies[operation] = strategy
if strategy == RecoveryStrategy.RETRY:
self.retry_policies[operation] = {
'max_attempts': kwargs.get('max_attempts', 3),
'delay': kwargs.get('delay', 1.0),
'backoff_multiplier': kwargs.get('backoff_multiplier', 2.0),
'max_delay': kwargs.get('max_delay', 30.0)
}
elif strategy == RecoveryStrategy.CIRCUIT_BREAKER:
self.circuit_breakers[operation] = CircuitBreaker(
failure_threshold=kwargs.get('failure_threshold', 5),
timeout=kwargs.get('timeout', 60)
)
def register_fallback(self, operation: str, handler: Callable):
"""注册降级处理器"""
self.fallback_handlers[operation] = handler
async def execute_with_recovery(self, operation: str, func: Callable, *args, **kwargs):
"""带恢复机制的执行"""
strategy = self.recovery_strategies.get(operation, RecoveryStrategy.RETRY)
if strategy == RecoveryStrategy.RETRY:
return await self._execute_with_retry(operation, func, *args, **kwargs)
elif strategy == RecoveryStrategy.FALLBACK:
return await self._execute_with_fallback(operation, func, *args, **kwargs)
elif strategy == RecoveryStrategy.CIRCUIT_BREAKER:
return await self._execute_with_circuit_breaker(operation, func, *args, **kwargs)
elif strategy == RecoveryStrategy.GRACEFUL_DEGRADATION:
return await self._execute_with_degradation(operation, func, *args, **kwargs)
else:
return await func(*args, **kwargs)
async def _execute_with_retry(self, operation: str, func: Callable, *args, **kwargs):
"""重试执行"""
policy = self.retry_policies.get(operation, {})
max_attempts = policy.get('max_attempts', 3)
delay = policy.get('delay', 1.0)
backoff_multiplier = policy.get('backoff_multiplier', 2.0)
max_delay = policy.get('max_delay', 30.0)
last_exception = None
current_delay = delay
for attempt in range(max_attempts):
try:
return await func(*args, **kwargs)
except Exception as e:
last_exception = e
if attempt < max_attempts - 1:
await asyncio.sleep(current_delay)
current_delay = min(current_delay * backoff_multiplier, max_delay)
# 所有重试都失败，抛出最后一个异常
raise last_exception
async def _execute_with_fallback(self, operation: str, func: Callable, *args, **kwargs):
"""降级执行"""
try:
return await func(*args, **kwargs)
except Exception as e:
fallback_handler = self.fallback_handlers.get(operation)
if fallback_handler:
return await fallback_handler(*args, **kwargs)
raise e
async def _execute_with_circuit_breaker(self, operation: str, func: Callable, *args, **kwargs):
"""熔断器执行"""
circuit_breaker = self.circuit_breakers.get(operation)
if not circuit_breaker:
return await func(*args, **kwargs)
if circuit_breaker.is_open():
raise McpError(
code=ErrorCode.SERVICE_UNAVAILABLE,
message=f"服务 {operation} 熔断中"
)
try:
result = await func(*args, **kwargs)
circuit_breaker.record_success()
return result
except Exception as e:
circuit_breaker.record_failure()
raise e
async def _execute_with_degradation(self, operation: str, func: Callable, *args, **kwargs):
"""优雅降级执行"""
try:
return await func(*args, **kwargs)
except Exception as e:
# 记录错误但返回降级结果
fallback_handler = self.fallback_handlers.get(operation)
if fallback_handler:
try:
return await fallback_handler(*args, **kwargs)
except Exception:
# 降级也失败，返回默认值
return self._get_default_response(operation)
return self._get_default_response(operation)
def _get_default_response(self, operation: str):
"""获取默认响应"""
if operation.startswith('read_'):
return ""
elif operation.startswith('list_'):
return []
elif operation.startswith('call_'):
return ToolResult(
content=[TextContent(type="text", text="服务暂时不可用")],
isError=True
)
else:
return None
class ResilientMcpServer(McpServer):
"""具有错误恢复能力的MCP服务器"""
def __init__(self, name: str):
super().__init__(name)
self.recovery_manager = ErrorRecoveryManager()
self.setup_recovery_strategies()
def setup_recovery_strategies(self):
"""设置恢复策略"""
# 资源读取使用重试策略
self.recovery_manager.register_strategy(
'read_resource',
RecoveryStrategy.RETRY,
max_attempts=3,
delay=1.0,
backoff_multiplier=2.0
)
# 工具调用使用熔断器
self.recovery_manager.register_strategy(
'call_tool',
RecoveryStrategy.CIRCUIT_BREAKER,
failure_threshold=5,
timeout=60
)
# 注册降级处理器
self.recovery_manager.register_fallback(
'read_resource',
self.fallback_read_resource
)
self.recovery_manager.register_fallback(
'call_tool',
self.fallback_call_tool
)
async def read_resource(self, uri: str) -> str:
"""带恢复机制的资源读取"""
return await self.recovery_manager.execute_with_recovery(
'read_resource',
super().read_resource,
uri
)
async def call_tool(self, name: str, arguments: dict) -> ToolResult:
"""带恢复机制的工具调用"""
return await self.recovery_manager.execute_with_recovery(
'call_tool',
super().call_tool,
name,
arguments
)
async def fallback_read_resource(self, uri: str) -> str:
"""资源读取降级处理"""
return f"资源 {uri} 暂时不可用，请稍后重试"
async def fallback_call_tool(self, name: str, arguments: dict) -> ToolResult:
"""工具调用降级处理"""
return ToolResult(
content=[TextContent(
type="text",
text=f"工具 {name} 暂时不可用，请稍后重试"
)],
isError=True
)
|