手写分布式id生成器

落日映苍穹つ 2022-11-20 02:59 169阅读 0赞

[https://github.com/wangchao550586585/common-sequence][https_github.com_wangchao550586585_common-sequence]

如何设计一个分布式id生成器  
设计目的  
解决目前公司订单目前采用UUID的问题  
方案选型  
技术抉择

设计草图

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70][]

目录结构

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 1][]

执行结果

500个线程同时创建二千万个id,步长设置为20,方便测试极端情况

![20210414145746454.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 2][]

![20210414145955153.png][]

核心代码

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 5][]

出现问题

当设置步长为100，并开启100线程时,在1这里返回-1,于是外层添加while循环,不断重试获取.

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 6][]

问题二:

这样设置表Name后,运行一段时间,数据库存在多条记录

![20201118005446445.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 7][]

分析class可得,每次运行时,LocalDateTime.now()获取的时间不一样造成的.

![20201118005541506.png][]

解决办法:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 8][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 9][]

问题三:程序执行完毕后,测试代码一直运行,发现不是这里代码的问题,

解决办法:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 10][]

下面是之前错误分析链路，还是挺有意思的。留着.

![20201117201331871.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 11][]

经过检测，发现没有死锁，线程都处于waiting状态

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 12][]

在此检测锁情况,也没问题

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 13][]

经过检测是线程池的问题,超时时间设置为1000秒,所以在此期间线程都处于等待状态,

![20201117201944589.png][]

java.util.concurrent.ThreadPoolExecutor\#getTask

参考地址:[https://blog.csdn.net/Nuan\_Feng/article/details/106388465][https_blog.csdn.net_Nuan_Feng_article_details_106388465]

这里实际上是，take()造成的阻塞,因为无界队列,所以造成核心线程永远>=wc,造成timed始终是false,所以只会走到take方法.进行无超时的阻塞.

这也好弄懂,如果wc>核心线程,那么就超时poll走,这是为了非核心线程的回收。

![20201118093052772.png][]

**从下面开始,分析的链路都是错误的.**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 14][]

java.util.concurrent.LinkedBlockingQueue\#poll(long, java.util.concurrent.TimeUnit)

参考地址:[https://blog.csdn.net/Nuan\_Feng/article/details/106971925][https_blog.csdn.net_Nuan_Feng_article_details_106971925]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 15][]

java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject\#awaitNanos

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 16][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70 17][]

[https_github.com_wangchao550586585_common-sequence]: https://github.com/wangchao550586585/common-sequence
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[20210414145955153.png]: https://img-blog.csdnimg.cn/20210414145955153.png
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[20201118005541506.png]: https://img-blog.csdnimg.cn/20201118005541506.png
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[20201117201331871.png]: https://img-blog.csdnimg.cn/20201117201331871.png
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[20201117201944589.png]: https://img-blog.csdnimg.cn/20201117201944589.png
[https_blog.csdn.net_Nuan_Feng_article_details_106388465]: https://blog.csdn.net/Nuan_Feng/article/details/106388465
[20201118093052772.png]: https://img-blog.csdnimg.cn/20201118093052772.png
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[https_blog.csdn.net_Nuan_Feng_article_details_106971925]: https://blog.csdn.net/Nuan_Feng/article/details/106971925
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