java分布式定时任务实现细节

public class RedisDistributedLock {
    private final RedisTemplate<String, String> redisTemplate;
    private final String lockKey;
    private final String lockValue; // 用于标识锁持有者（支持可重入）
    private final long expireMillis; // 锁过期时间（避免死锁）
    // 构造函数：初始化锁参数
    public RedisDistributedLock(RedisTemplate<String, String> redisTemplate, 
                               String lockKey, String requestId, long expireMillis) {
        this.redisTemplate = redisTemplate;
        this.lockKey = lockKey;
        this.lockValue = requestId; // 建议使用UUID+线程ID
        this.expireMillis = expireMillis;
    }
    // 尝试获取锁（原子操作）
    public boolean tryLock() {
        // 使用Redis的SET命令实现：NX（不存在则设置）+ PX（毫秒过期）
        return redisTemplate.opsForValue().setIfAbsent(lockKey, lockValue, expireMillis, TimeUnit.MILLISECONDS);
    }
    // 释放锁（需校验持有者，避免误释放）
    public boolean unlock() {
        // 使用Lua脚本保证删除操作的原子性
        String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
        Long result = (Long) redisTemplate.execute(
            new DefaultRedisScript<>(script, Long.class),
            Collections.singletonList(lockKey),
            lockValue
        );
        return result != null && result > 0;
    }
    // 带超时等待的获取锁（轮询重试）
    public boolean tryLock(long waitTime, TimeUnit unit) throws InterruptedException {
        long timeout = unit.toMillis(waitTime);
        long start = System.currentTimeMillis();
        while (true) {
            if (tryLock()) {
                return true;
            }
            // 等待重试（避免自旋过于频繁）
            long remaining = timeout - (System.currentTimeMillis() - start);
            if (remaining <= 0) {
                return false; // 超时未获取到锁
            }
            Thread.sleep(Math.min(remaining, 100)); // 最多等待100ms重试
        }
    }
}

@XxlJob("shardingTask")
public ReturnT<String> shardingHandler(String param) {
    // 获取分片参数（由调度中心分配）
    ShardingUtil.ShardingVO shardingVO = ShardingUtil.getShardingVo();
    int shardIndex = shardingVO.getIndex(); // 当前分片索引（0-4）
    int shardTotal = shardingVO.getTotal(); // 总分片数（5）
    // 按分片处理数据（如按ID取模：id % shardTotal == shardIndex）
    List<Data> dataList = dataService.queryBySharding(shardIndex, shardTotal);
    for (Data data : dataList) {
        processData(data);
    }
    return ReturnT.SUCCESS;
}

// 自定义任务执行指标（使用Micrometer）
@Component
public class TaskMetrics {
    private final MeterRegistry meterRegistry;
    public TaskMetrics(MeterRegistry meterRegistry) {
        this.meterRegistry = meterRegistry;
    }
    // 记录任务执行耗时
    public void recordTaskDuration(String taskName, long durationMs) {
        Timer.builder("task.execution.duration")
             .tag("task", taskName)
             .register(meterRegistry)
             .record(durationMs, TimeUnit.MILLISECONDS);
    }
    // 记录任务失败次数
    public void incrementFailCount(String taskName) {
        Counter.builder("task.execution.fail")
               .tag("task", taskName)
               .register(meterRegistry)
               .increment();
    }
}

@XxlJob("orderTimeoutTask")
public ReturnT<String> orderTimeoutHandler(String param) {
    long start = System.currentTimeMillis();
    try {
        // 任务逻辑...
        metrics.recordTaskDuration("orderTimeoutTask", System.currentTimeMillis() - start);
        return ReturnT.SUCCESS;
    } catch (Exception e) {
        metrics.incrementFailCount("orderTimeoutTask");
        return ReturnT.FAIL;
    }
}

// 钉钉告警示例
public class DingTalkAlarm {
    private final String webhook;
    public void sendAlarm(String message) {
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        Map<String, Object> body = new HashMap<>();
        body.put("msgtype", "text");
        body.put("text", Map.of("content", "定时任务告警：" + message));
        new RestTemplate().postForObject(webhook, new HttpEntity<>(body, headers), String.class);
    }
}

@Component
public class RedisScheduledTask {
    @Autowired
    private RedisTemplate<String, String> redisTemplate;
    @Autowired
    private TaskService taskService;
    // 初始化定时任务（每分钟执行一次）
    @PostConstruct
    public void init() {
        ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
        executor.scheduleAtFixedRate(this::executeTask, 0, 1, TimeUnit.MINUTES);
    }
    // 执行任务（加分布式锁）
    private void executeTask() {
        String lockKey = "task:order:timeout";
        String requestId = UUID.randomUUID().toString();
        RedisDistributedLock lock = new RedisDistributedLock(redisTemplate, lockKey, requestId, 60000);
        try {
            if (lock.tryLock()) {
                // 执行核心逻辑
                taskService.processTimeoutOrders();
            } else {
                log.info("任务被其他节点执行，当前节点跳过");
            }
        } finally {
            lock.unlock(); // 释放锁
        }
    }
}