高并发环境下生成订单唯一流水号方法:SnowFlake

╰+攻爆jí腚メ 2022-02-22 15:50 900阅读 0赞

关于订单号的生成，一些比较简单的方案：

1、数据库自增长ID

*  优势：无需编码
 *  缺陷：
    
     *  大表不能做水平分表，否则插入删除时容易出现问题
     *  高并发下插入数据需要加入事务机制
     *  在业务操作父、子表（关联表）插入时，先要插入父表，再插入子表

2、时间戳+随机数

*  优势：编码简单
 *  缺陷：随机数存在重复问题，即使在相同的时间戳下。每次插入数据库前需要校验下是否已经存在相同的数值。

3、时间戳+会员ID

*  优势：同一时间，一个用户不会存在两张订单
 *  缺陷：会员ID也会透露运营数据，鸡生蛋，蛋生鸡的问题

4、GUID/UUID

*  优势：简单
 *  劣势：用户不友好，索引关联效率较低。

今天要分享的方案：来自twitter的SnowFlake

Twitter-Snowflake算法产生的背景相当简单，为了满足Twitter每秒上万条消息的请求，每条消息都必须分配一条唯一的id，这些id还需要一些大致的顺序（方便客户端排序），并且在分布式系统中不同机器产生的id必须不同.Snowflake算法核心把时间戳，工作机器id，序列号(毫秒级时间41位+机器ID 10位+毫秒内序列12位)组合在一起。

![snowflake-64bit][]

在上面的字符串中，第一位为未使用（实际上也可作为long的符号位），接下来的41位为毫秒级时间，然后5位datacenter标识位，5位机器ID（并不算标识符，实际是为线程标识），然后12位该毫秒内的当前毫秒内的计数，加起来刚好64位，为一个Long型。

除了最高位bit标记为不可用以外，其余三组bit占位均可浮动，看具体的业务需求而定。默认情况下41bit的时间戳可以支持该算法使用到2082年，10bit的工作机器id可以支持1023台机器，序列号支持1毫秒产生4095个自增序列id。下文会具体分析。

Snowflake – 时间戳

这里时间戳的细度是毫秒级，具体代码如下，建议使用64位linux系统机器，因为有vdso，gettimeofday()在用户态就可以完成操作，减少了进入内核态的损耗。

<table> 
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      <span>uint64_t </span> 
      <span>generateStamp</span> 
      <span>(</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>timeval </span> 
      <span>tv</span> 
      <span>;</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>gettimeofday</span> 
      <span>(</span> 
      <span>&amp;</span> 
      <span>tv</span> 
      <span>,</span> 
      <span> </span> 
      <span>0</span> 
      <span>)</span> 
      <span>;</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>return</span> 
      <span> </span> 
      <span>(</span> 
      <span>uint64_t</span> 
      <span>)</span> 
      <span>tv</span> 
      <span>.</span> 
      <span>tv_sec *</span> 
      <span> </span> 
      <span>1000</span> 
      <span> </span> 
      <span>+</span> 
      <span> </span> 
      <span>(</span> 
      <span>uint64_t</span> 
      <span>)</span> 
      <span>tv</span> 
      <span>.</span> 
      <span>tv_usec</span> 
      <span> </span> 
      <span>/</span> 
      <span> </span> 
      <span>1000</span> 
      <span>;</span> 
     </div> 
     <div> 
      <span>}</span> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

默认情况下有41个bit可以供使用，那么一共有T（1llu << 41）毫秒供你使用分配，年份 = T / (3600 \* 24 \* 365 \* 1000) = 69.7年。如果你只给时间戳分配39个bit使用，那么根据同样的算法最后年份 = 17.4年。

Snowflake – 工作机器id

严格意义上来说这个bit段的使用可以是进程级，机器级的话你可以使用MAC地址来唯一标示工作机器，工作进程级可以使用IP+Path来区分工作进程。如果工作机器比较少，可以使用配置文件来设置这个id是一个不错的选择，如果机器过多配置文件的维护是一个灾难性的事情。

这里的解决方案是需要一个工作id分配的进程，可以使用自己编写一个简单进程来记录分配id，或者利用Mysql auto\_increment机制也可以达到效果。

![workid][]

工作进程与工作id分配器只是在工作进程启动的时候交互一次，然后工作进程可以自行将分配的id数据落文件，下一次启动直接读取文件里的id使用。这个工作机器id的bit段也可以进一步拆分，比如用前5个bit标记进程id，后5个bit标记线程id之类:D

Snowflake – 序列号

序列号就是一系列的自增id（多线程建议使用atomic），为了处理在同一毫秒内需要给多条消息分配id，若同一毫秒把序列号用完了，则“等待至下一毫秒”。

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      <span>uint64_t </span> 
      <span>waitNextMs</span> 
      <span>(</span> 
      <span>uint64_t </span> 
      <span>lastStamp</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>{ </span> 
     </div> 
     <div>
       &nbsp;&nbsp;&nbsp;&nbsp; 
      <span>uint64_t </span> 
      <span>cur</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>0</span> 
      <span>;</span> 
     </div> 
     <div>
       &nbsp;&nbsp;&nbsp;&nbsp; 
      <span>do</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div>
       &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
      <span>cur</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>generateStamp</span> 
      <span>(</span> 
      <span>)</span> 
      <span>;</span> 
     </div> 
     <div>
       &nbsp;&nbsp;&nbsp;&nbsp; 
      <span>}</span> 
      <span> </span> 
      <span>while</span> 
      <span> </span> 
      <span>(</span> 
      <span>cur</span> 
      <span> </span> 
      <span>&lt;=</span> 
      <span> </span> 
      <span>lastStamp</span> 
      <span>)</span> 
      <span>;</span> 
     </div> 
     <div>
       &nbsp;&nbsp;&nbsp;&nbsp; 
      <span>return</span> 
      <span> </span> 
      <span>cur</span> 
      <span>;</span> 
     </div> 
     <div> 
      <span>}</span> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

总体来说，是一个很高效很方便的GUID产生算法，一个int64\_t字段就可以胜任，不像现在主流128bit的GUID算法，即使无法保证严格的id序列性，但是对于特定的业务，比如用做游戏服务器端的GUID产生会很方便。另外，在多线程的环境下，序列号使用atomic可以在代码实现上有效减少锁的密度。

该项目地址为：[https://github.com/twitter/snowflake][https_github.com_twitter_snowflake] 是用Scala实现的。核心代码：

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      <span>/** Copyright 2010-2012 Twitter, Inc.*/</span> 
     </div> 
     <div> 
      <span>package</span> 
      <span> </span> 
      <span>com</span> 
      <span>.</span> 
      <span>twitter</span> 
      <span>.</span> 
      <span>service</span> 
      <span>.</span> 
      <span>snowflake</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>import </span> 
      <span>com</span> 
      <span>.</span> 
      <span>twitter</span> 
      <span>.</span> 
      <span>ostrich</span> 
      <span>.</span> 
      <span>stats</span> 
      <span>.</span> 
      <span>Stats</span> 
     </div> 
     <div> 
      <span>import </span> 
      <span>com</span> 
      <span>.</span> 
      <span>twitter</span> 
      <span>.</span> 
      <span>service</span> 
      <span>.</span> 
      <span>snowflake</span> 
      <span>.</span> 
      <span>gen</span> 
      <span>.</span> 
      <span>_</span> 
     </div> 
     <div> 
      <span>import </span> 
      <span>java</span> 
      <span>.</span> 
      <span>util</span> 
      <span>.</span> 
      <span>Random</span> 
     </div> 
     <div> 
      <span>import </span> 
      <span>com</span> 
      <span>.</span> 
      <span>twitter</span> 
      <span>.</span> 
      <span>logging</span> 
      <span>.</span> 
      <span>Logger</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>/**</span> 
     </div> 
     <div> 
      <span>* An object that generates IDs.</span> 
     </div> 
     <div> 
      <span>* This is broken into a separate class in case</span> 
     </div> 
     <div> 
      <span>* we ever want to support multiple worker threads</span> 
     </div> 
     <div> 
      <span>* per process</span> 
     </div> 
     <div> 
      <span>*/</span> 
     </div> 
     <div> 
      <span>class</span> 
      <span> </span> 
      <span>IdWorker</span> 
      <span>(</span> 
      <span>val </span> 
      <span>workerId</span> 
      <span>:</span> 
      <span> </span> 
      <span>Long</span> 
      <span>,</span> 
      <span> </span> 
      <span>val </span> 
      <span>datacenterId</span> 
      <span>:</span> 
      <span> </span> 
      <span>Long</span> 
      <span>,</span> 
      <span> </span> 
      <span>private</span> 
      <span> </span> 
      <span>val </span> 
      <span>reporter</span> 
      <span>:</span> 
      <span> </span> 
      <span>Reporter</span> 
      <span>,</span> 
      <span> </span> 
      <span>var</span> 
      <span> </span> 
      <span>sequence</span> 
      <span>:</span> 
      <span> </span> 
      <span>Long</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>0L</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>extends</span> 
      <span> </span> 
      <span>Snowflake</span> 
      <span>.</span> 
      <span>Iface</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>def </span> 
      <span>genCounter</span> 
      <span>(</span> 
      <span>agent</span> 
      <span>:</span> 
      <span> </span> 
      <span>String</span> 
      <span>)</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>Stats</span> 
      <span>.</span> 
      <span>incr</span> 
      <span>(</span> 
      <span>"ids_generated"</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>Stats</span> 
      <span>.</span> 
      <span>incr</span> 
      <span>(</span> 
      <span>"ids_generated_%s"</span> 
      <span>.</span> 
      <span>format</span> 
      <span>(</span> 
      <span>agent</span> 
      <span>)</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>}</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>exceptionCounter</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>Stats</span> 
      <span>.</span> 
      <span>getCounter</span> 
      <span>(</span> 
      <span>"exceptions"</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>log</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>Logger</span> 
      <span>.</span> 
      <span>get</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>rand</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>new</span> 
      <span> </span> 
      <span>Random</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>val </span> 
      <span>twepoch</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>1288834974657L</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>workerIdBits</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>5L</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>datacenterIdBits</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>5L</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>maxWorkerId</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>^</span> 
      <span> </span> 
      <span>(</span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>&lt;&lt;</span> 
      <span> </span> 
      <span>workerIdBits</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>maxDatacenterId</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>^</span> 
      <span> </span> 
      <span>(</span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>&lt;&lt;</span> 
      <span> </span> 
      <span>datacenterIdBits</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>sequenceBits</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>12L</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>workerIdShift</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>sequenceBits</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>datacenterIdShift</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>sequenceBits</span> 
      <span> </span> 
      <span>+</span> 
      <span> </span> 
      <span>workerIdBits</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>timestampLeftShift</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>sequenceBits</span> 
      <span> </span> 
      <span>+</span> 
      <span> </span> 
      <span>workerIdBits</span> 
      <span> </span> 
      <span>+</span> 
      <span> </span> 
      <span>datacenterIdBits</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>val </span> 
      <span>sequenceMask</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>^</span> 
      <span> </span> 
      <span>(</span> 
      <span>-</span> 
      <span>1L</span> 
      <span> </span> 
      <span>&lt;&lt;</span> 
      <span> </span> 
      <span>sequenceBits</span> 
      <span>)</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>private</span> 
      <span>[</span> 
      <span>this</span> 
      <span>]</span> 
      <span> </span> 
      <span>var</span> 
      <span> </span> 
      <span>lastTimestamp</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>-</span> 
      <span>1L</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>// sanity check for workerId</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>if</span> 
      <span> </span> 
      <span>(</span> 
      <span>workerId</span> 
      <span> </span> 
      <span>&gt;</span> 
      <span> </span> 
      <span>maxWorkerId</span> 
      <span> </span> 
      <span>||</span> 
      <span> </span> 
      <span>workerId</span> 
      <span> </span> 
      <span>&lt;</span> 
      <span> </span> 
      <span>0</span> 
      <span>)</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>exceptionCounter</span> 
      <span>.</span> 
      <span>incr</span> 
      <span>(</span> 
      <span>1</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>throw</span> 
      <span> </span> 
      <span>new</span> 
      <span> </span> 
      <span>IllegalArgumentException</span> 
      <span>(</span> 
      <span>"worker Id can't be greater than %d or less than 0"</span> 
      <span>.</span> 
      <span>format</span> 
      <span>(</span> 
      <span>maxWorkerId</span> 
      <span>)</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>}</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>if</span> 
      <span> </span> 
      <span>(</span> 
      <span>datacenterId</span> 
      <span> </span> 
      <span>&gt;</span> 
      <span> </span> 
      <span>maxDatacenterId</span> 
      <span> </span> 
      <span>||</span> 
      <span> </span> 
      <span>datacenterId</span> 
      <span> </span> 
      <span>&lt;</span> 
      <span> </span> 
      <span>0</span> 
      <span>)</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>exceptionCounter</span> 
      <span>.</span> 
      <span>incr</span> 
      <span>(</span> 
      <span>1</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>throw</span> 
      <span> </span> 
      <span>new</span> 
      <span> </span> 
      <span>IllegalArgumentException</span> 
      <span>(</span> 
      <span>"datacenter Id can't be greater than %d or less than 0"</span> 
      <span>.</span> 
      <span>format</span> 
      <span>(</span> 
      <span>maxDatacenterId</span> 
      <span>)</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>}</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>log</span> 
      <span>.</span> 
      <span>info</span> 
      <span>(</span> 
      <span>"worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d"</span> 
      <span>,</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>timestampLeftShift</span> 
      <span>,</span> 
      <span> </span> 
      <span>datacenterIdBits</span> 
      <span>,</span> 
      <span> </span> 
      <span>workerIdBits</span> 
      <span>,</span> 
      <span> </span> 
      <span>sequenceBits</span> 
      <span>,</span> 
      <span> </span> 
      <span>workerId</span> 
      <span>)</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;</span> 
      <span>def </span> 
      <span>get_id</span> 
      <span>(</span> 
      <span>useragent</span> 
      <span>:</span> 
      <span> </span> 
      <span>String</span> 
      <span>)</span> 
      <span>:</span> 
      <span> </span> 
      <span>Long</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>if</span> 
      <span> </span> 
      <span>(</span> 
      <span>!</span> 
      <span>validUseragent</span> 
      <span>(</span> 
      <span>useragent</span> 
      <span>)</span> 
      <span>)</span> 
      <span> </span> 
      <span>{ </span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>exceptionCounter</span> 
      <span>.</span> 
      <span>incr</span> 
      <span>(</span> 
      <span>1</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>throw</span> 
      <span> </span> 
      <span>new</span> 
      <span> </span> 
      <span>InvalidUserAgentError</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>}</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>val </span> 
      <span>id</span> 
      <span> </span> 
      <span>=</span> 
      <span> </span> 
      <span>nextId</span> 
      <span>(</span> 
      <span>)</span> 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>genCounter</span> 
      <span>(</span> 
      <span>useragent</span> 
      <span>)</span> 
     </div> 
     <div>
       &nbsp; 
     </div> 
     <div> 
      <span>&nbsp;&nbsp;&nbsp;&nbsp;</span> 
      <span>reporter</span> 
      <span>.</span> 
      <span>report</span> 
      <span>(</span> 
      <span>new</span> 
      <span> </span> 
      <span>AuditLogEntry</span> 
      <span>(</span> 
      <span>id</span> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

[snowflake-64bit]: /images/20220222/40177400988c43d49cca89ccd18d7215.png
[workid]: /images/20220222/5d5d74873ae44ec686969d3016f128fc.png
[https_github.com_twitter_snowflake]: https://github.com/twitter/snowflake