稳定性保障：升级、扩缩容与故障处理

在分布式文件存储平台的生命周期中，确保系统稳定运行是至关重要的。随着业务的发展和需求的变化，系统需要进行版本升级、容量扩缩容等操作，同时还要能够有效处理各种故障情况。一个成熟的分布式存储平台必须具备完善的稳定性保障机制，以确保在这些操作过程中业务不受影响，并能快速恢复。

10.1 平滑升级策略

系统升级是不可避免的，但如何在不影响业务的情况下进行平滑升级是一个重要课题。平滑升级策略需要考虑兼容性设计、滚动升级机制等多个方面。

10.1.1 版本兼容性设计

# 版本兼容性设计示例
from typing import Dict, Any, List, Optional
from enum import Enum
import json

class CompatibilityLevel(Enum):
    """兼容性级别"""
    FULL = "full"        # 完全兼容
    BACKWARD = "backward"  # 向后兼容
    FORWARD = "forward"   # 向前兼容
    NONE = "none"         # 不兼容

class Version:
    """版本信息"""
    
    def __init__(self, major: int, minor: int, patch: int, build: str = ""):
        self.major = major
        self.minor = minor
        self.patch = patch
        self.build = build
    
    def __str__(self):
        version_str = f"{self.major}.{self.minor}.{self.patch}"
        if self.build:
            version_str += f"-{self.build}"
        return version_str
    
    def __lt__(self, other):
        if self.major != other.major:
            return self.major < other.major
        if self.minor != other.minor:
            return self.minor < other.minor
        return self.patch < other.patch
    
    def __eq__(self, other):
        return (self.major == other.major and 
                self.minor == other.minor and 
                self.patch == other.patch)

class CompatibilityMatrix:
    """兼容性矩阵"""
    
    def __init__(self):
        self.matrix: Dict[str, Dict[str, CompatibilityLevel]] = {}
    
    def add_compatibility(self, version1: str, version2: str, 
                         level: CompatibilityLevel):
        """添加兼容性信息"""
        if version1 not in self.matrix:
            self.matrix[version1] = {}
        self.matrix[version1][version2] = level
        
        # 确保矩阵对称性（对于双向兼容性）
        if level == CompatibilityLevel.FULL:
            if version2 not in self.matrix:
                self.matrix[version2] = {}
            self.matrix[version2][version1] = level
    
    def check_compatibility(self, version1: str, version2: str) -> CompatibilityLevel:
        """检查两个版本的兼容性"""
        if version1 in self.matrix and version2 in self.matrix[version1]:
            return self.matrix[version1][version2]
        return CompatibilityLevel.NONE

class UpgradePlanner:
    """升级规划器"""
    
    def __init__(self, compatibility_matrix: CompatibilityMatrix):
        self.compatibility_matrix = compatibility_matrix
        self.current_versions: Dict[str, str] = {}  # component -> version
    
    def set_current_version(self, component: str, version: str):
        """设置当前版本"""
        self.current_versions[component] = version
    
    def plan_upgrade_path(self, target_version: str, 
                         components: List[str]) -> List[Dict[str, Any]]:
        """规划升级路径"""
        upgrade_steps = []
        
        for component in components:
            current_version = self.current_versions.get(component, "0.0.0")
            
            # 检查兼容性
            compatibility = self.compatibility_matrix.check_compatibility(
                current_version, target_version)
            
            if compatibility == CompatibilityLevel.NONE:
                # 需要中间版本
                intermediate_steps = self._find_intermediate_versions(
                    current_version, target_version)
                upgrade_steps.extend(intermediate_steps)
            else:
                # 可以直接升级
                upgrade_steps.append({
                    "component": component,
                    "from_version": current_version,
                    "to_version": target_version,
                    "compatibility": compatibility.value,
                    "direct_upgrade": True
                })
        
        return upgrade_steps
    
    def _find_intermediate_versions(self, from_version: str, 
                                  to_version: str) -> List[Dict[str, Any]]:
        """查找中间版本（简化实现）"""
        # 在实际实现中，这里会查询兼容性矩阵找到合适的中间版本
        # 这里简化为直接返回一个示例步骤
        return [{
            "component": "example",
            "from_version": from_version,
            "to_version": to_version,
            "compatibility": "需要中间版本",
            "direct_upgrade": False,
            "notes": "需要先升级到兼容的中间版本"
        }]

# 使用示例
def demonstrate_version_compatibility():
    """演示版本兼容性设计"""
    # 创建兼容性矩阵
    compat_matrix = CompatibilityMatrix()
    
    # 定义版本兼容性
    compat_matrix.add_compatibility("1.0.0", "1.1.0", CompatibilityLevel.FULL)
    compat_matrix.add_compatibility("1.1.0", "1.2.0", CompatibilityLevel.FULL)
    compat_matrix.add_compatibility("1.0.0", "1.2.0", CompatibilityLevel.BACKWARD)
    compat_matrix.add_compatibility("2.0.0", "2.1.0", CompatibilityLevel.FULL)
    
    # 创建升级规划器
    planner = UpgradePlanner(compat_matrix)
    
    # 设置当前版本
    planner.set_current_version("metadata-service", "1.0.0")
    planner.set_current_version("data-service", "1.1.0")
    planner.set_current_version("client-sdk", "1.0.0")
    
    # 规划升级到2.0.0
    upgrade_path = planner.plan_upgrade_path("2.0.0", 
                                           ["metadata-service", "data-service", "client-sdk"])
    
    print("升级路径规划:")
    for step in upgrade_path:
        print(f"  组件 {step['component']}: {step['from_version']} -> {step['to_version']}")
        print(f"    兼容性: {step['compatibility']}")
        if not step['direct_upgrade']:
            print(f"    注意: {step.get('notes', '需要特殊处理')}")

# 运行演示
# demonstrate_version_compatibility()

10.1.2 滚动升级实现

# 滚动升级实现
import time
import threading
from typing import List, Dict, Any, Callable, Optional
from datetime import datetime, timedelta
import random

class ServiceInstance:
    """服务实例"""
    
    def __init__(self, instance_id: str, service_name: str, version: str):
        self.instance_id = instance_id
        self.service_name = service_name
        self.version = version
        self.status = "running"  # running, upgrading, stopped, error
        self.health = "healthy"  # healthy, warning, error
        self.last_heartbeat = datetime.now()

class RollingUpgradeManager:
    """滚动升级管理器"""
    
    def __init__(self, health_check_interval: int = 30):
        self.instances: Dict[str, ServiceInstance] = {}
        self.upgrade_queue: List[str] = []
        self.upgrading = False