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使用mysql号段方式生成唯一ID

news 2026/5/12 20:06:05

前言

之前项目中使用的唯一ID生成方式为雪花算法，但是该方式存在“需要动态分配机器标识”和”时钟回拨“的问题，且解决起来比较复杂，所以考虑切换实现方式为数据库号段，该方式参考美团开源的项目Leaf。具体原理为

每个服务实例第一次从数据库加载一个号段放到内存中，比如第一个实例1-1000，第二个实例1001-2000
下次先从内存加载，号段用完了再从数据库加载

代码实现

数据库初始化sql

CREATE TABLE `id_segment` (`biz_tag` int(11) NOT NULL COMMENT '业务标识',`max_id` bigint(20) NOT NULL COMMENT '当前最大ID',`step` int(11) NOT NULL COMMENT '步长',`description` varchar(256) NULL COMMENT '描述',`update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',PRIMARY KEY (`biz_tag`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='ID段表'
;
-- 初始化
INSERT INTO id_segment(`biz_tag`,`max_id`,`step`,`description`) VALUES (1,0,1000,'订单ID');

实体类

import lombok.Data;import java.sql.Timestamp;@Data
public class IdSegment {private Integer bizTag;private Long maxId;private Long step;private String description;private Timestamp updateTime;
}

号段包装类，使用线程安全的AtomicLong

import lombok.Data;import java.sql.Timestamp;
import java.util.concurrent.atomic.AtomicLong;@Data
public class IdSegmentWrapper {private IdSegment idSegment;private AtomicLong currentId;public IdSegmentWrapper(IdSegment idSegment) {this.idSegment = idSegment;this.currentId = new AtomicLong(idSegment.getMaxId() - idSegment.getStep());}public long getNextId() {return currentId.incrementAndGet();}public long getMaxId() {return idSegment.getMaxId();}
}

数据库层代码，注意要加事务注解

import com.alibaba.fastjson.JSON;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;@Slf4j
@Service
public class IdSegmentDao {@Autowiredprivate IdSegmentMapper idSegmentMapper;@Transactionalpublic IdSegmentWrapper getNext(int bizTag) {long startTime = System.nanoTime();;idSegmentMapper.updateMaxIdByBizTag(bizTag);IdSegment idSegment = idSegmentMapper.selectMaxIdByBizTag(bizTag);long endTime = System.nanoTime();log.info("获取到ID段：{}，耗时：{} ns", JSON.toJSONString(idSegment), endTime - startTime);return new IdSegmentWrapper(idSegment);}
}

服务层代码

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;@Service
public class IdGeneratorService {@Autowiredprivate IdSegmentDao idSegmentDao;private Map<Integer, IdSegmentWrapper> cache = new ConcurrentHashMap<>();/*** 获取下一个全局唯一ID，不同的业务标识起始ID不同，比如bizTag=1，则起始ID为72057594037927936** @param bizTag 业务标识*/public Long getNextId(Integer bizTag) {long id = generateIdByBizTag(bizTag);id |= Long.valueOf(bizTag) << 56; //其实就是相加return id;}/*** 同一个服务实例内生成递增的唯一ID** @param bizTag 业务标识*/private synchronized Long generateIdByBizTag(Integer bizTag) {{IdSegmentWrapper segment = cache.get(bizTag);if (Objects.isNull(segment)) {segment = idSegmentDao.getNext(bizTag);cache.put(bizTag, segment);}long id = segment.getNextId();if (id < segment.getMaxId()) {return id;} else {segment = idSegmentDao.getNext(bizTag);cache.put(bizTag, segment);return segment.getNextId();}}}
}

验证代码为

import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;import java.util.Set;
import java.util.concurrent.ConcurrentSkipListSet;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;@RestController
@RequestMapping("/id")
@Slf4j
public class IdSegmentController {@Autowiredprivate IdGeneratorService idGeneratorService;@GetMapping("/get")public String getId(@RequestParam(name = "count") Integer count) throws InterruptedException {ExecutorService executorService = Executors.newFixedThreadPool(100);Set<Long> ids = new ConcurrentSkipListSet<>();CountDownLatch latch = new CountDownLatch(count);long start = System.nanoTime();for (int i = 0; i < count; i++) {executorService.submit(() -> {try {Long id = idGeneratorService.getNextId(1);ids.add(id);} finally {latch.countDown();}});}// wait until all tasks finish or timeoutboolean completed = latch.await(30, TimeUnit.SECONDS);long end = System.nanoTime();executorService.shutdown();executorService.awaitTermination(5, TimeUnit.SECONDS);long elapsedMs = TimeUnit.NANOSECONDS.toMillis(end - start);log.info("生成ID数量：{}", ids.size());log.info("生成 {} 个ID耗时：{} ms{}", count, elapsedMs, completed ? "" : " (超时未全部完成)");return "ID生成任务已提交，耗时：" + elapsedMs + " ms";}
}