爱威尔-quarkus下的分布式ID怎么实现

说是quarkus的分布式ID是一种错误的说法，目前在java普遍的框架使用的分布式ID都是ORM框架提供的比如hibernate，jpa，mybatis-plus等，是spring框架还是quarkus还是别的没关系。

所以在java领域的分布式ID实现方式基本都一样quarkus也不例外。

今天要说的就是基于hibernate的一个接口扩展实现的，这个接口就是
```java
org.hibernate.id.IdentifierGenerator;
```
那所以说jpa依赖的也是这个扩展而没有自己的扩展。

那有人说还区分hibernate和jpa么？是的。是有区分的：
```java
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import org.hibernate.annotations.GenericGenerator;
```
大家看这段引入就知道他们的分别。

好现在我们说下怎么实现分布式ID的，首先看扩展：
```java
package com.weir.quarkus.base.system.entity;

import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.IdentifierGenerator;

import com.weir.quarkus.base.system.utils.Sequence;

import java.io.Serializable;

public class MyIdGenerator implements IdentifierGenerator {
  private final Sequence sequence = new Sequence(null);
    @Override
    public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
        return sequence.nextId();
    }
}
```
这里依赖了Sequence：
```java
/*
 * Copyright (c) 2011-2022, baomidou (jobob@qq.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.weir.quarkus.base.system.utils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 分布式高效有序 ID 生产黑科技(sequence)
 *
 * 优化开源项目：https://gitee.com/yu120/sequence
 *

*/
public class Sequence {

/**
 * 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
 */
 private final long twepoch = 1288834974657L;
 /**
 * 机器标识位数
 */
 private final long workerIdBits = 5L;
 private final long datacenterIdBits = 5L;
 private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
 private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
 /**
 * 毫秒内自增位
 */
 private final long sequenceBits = 12L;
 private final long workerIdShift = sequenceBits;
 private final long datacenterIdShift = sequenceBits + workerIdBits;
 /**
 * 时间戳左移动位
 */
 private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
 private final long sequenceMask = -1L ^ (-1L << sequenceBits);

private final long workerId;

/**
     * 数据标识 ID 部分
     */
    private final long datacenterId;
    /**
     * 并发控制
     */
    private long sequence = 0L;
    /**
     * 上次生产 ID 时间戳
     */
    private long lastTimestamp = -1L;
    /**
     * IP 地址
     */
    private InetAddress inetAddress;

public Sequence(InetAddress inetAddress) {
        this.inetAddress = inetAddress;
        this.datacenterId = getDatacenterId(maxDatacenterId);
        this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
    }

/**
 * 有参构造器
 *
 * @param workerId 工作机器 ID
 * @param datacenterId 序列号
 */
 public Sequence(long workerId, long datacenterId) {
// Assert.isFalse(workerId > maxWorkerId || workerId < 0,
// String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
// Assert.isFalse(datacenterId > maxDatacenterId || datacenterId < 0,
// String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
 this.workerId = workerId;
 this.datacenterId = datacenterId;
 }

/**
     * 获取 maxWorkerId
     */
    protected long getMaxWorkerId(long datacenterId, long maxWorkerId) {
        StringBuilder mpid = new StringBuilder();
        mpid.append(datacenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (name != null) {
            /*
             * GET jvmPid
             */
            mpid.append(name.split("@")[0]);
        }
        /*
         * MAC + PID 的 hashcode 获取16个低位
         */
        return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

/**
 * 数据标识id部分
 */
 protected long getDatacenterId(long maxDatacenterId) {
 long id = 0L;
 try {
 if (null == this.inetAddress) {
 this.inetAddress = InetAddress.getLocalHost();
 }
 NetworkInterface network = NetworkInterface.getByInetAddress(this.inetAddress);
 if (null == network) {
 id = 1L;
 } else {
 byte[] mac = network.getHardwareAddress();
 if (null != mac) {
 id = ((0x000000FF & (long) mac[mac.length - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
 id = id % (maxDatacenterId + 1);
 }
 }
 } catch (Exception e) {
// logger.warn(" getDatacenterId: " + e.getMessage());
 }
 return id;
 }

/**
 * 获取下一个 ID
 *
 * @return 下一个 ID
 */
 public synchronized long nextId() {
 long timestamp = timeGen();
 //闰秒
 if (timestamp < lastTimestamp) {
 long offset = lastTimestamp - timestamp;
 if (offset <= 5) {
 try {
 wait(offset << 1);
 timestamp = timeGen();
 if (timestamp < lastTimestamp) {
 throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
 }
 } catch (Exception e) {
 throw new RuntimeException(e);
 }
 } else {
 throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
 }
 }

if (lastTimestamp == timestamp) {
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                // 同一毫秒的序列数已经达到最大
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            // 不同毫秒内，序列号置为 1 - 3 随机数
            sequence = ThreadLocalRandom.current().nextLong(1, 3);
        }

lastTimestamp = timestamp;

// 时间戳部分 | 数据中心部分 | 机器标识部分 | 序列号部分
 return ((timestamp - twepoch) << timestampLeftShift)
 | (datacenterId << datacenterIdShift)
 | (workerId << workerIdShift)
 | sequence;
 }

protected long tilNextMillis(long lastTimestamp) {
 long timestamp = timeGen();
 while (timestamp <= lastTimestamp) {
 timestamp = timeGen();
 }
 return timestamp;
 }

protected long timeGen() {
        return SystemClock.now();
    }

}
```
大家如果对它陌生可以自己去了解，这个分布式ID的实现在java领域用的比较普遍。
```java
/*
 * Copyright (c) 2011-2022, baomidou (jobob@qq.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.weir.quarkus.base.system.utils;

import java.sql.Timestamp;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

/**
 * 高并发场景下System.currentTimeMillis()的性能问题的优化
 *
 * System.currentTimeMillis()的调用比new一个普通对象要耗时的多（具体耗时高出多少我还没测试过，有人说是100倍左右）
 * System.currentTimeMillis()之所以慢是因为去跟系统打了一次交道
 * 后台定时更新时钟，JVM退出时，线程自动回收
 * 10亿：43410,206,210.72815533980582%
 * 1亿：4699,29,162.0344827586207%
 * 1000万：480,12,40.0%
 * 100万：50,10,5.0%
 *

*/
public class SystemClock {

private final long period;
    private final AtomicLong now;

private SystemClock(long period) {
        this.period = period;
        this.now = new AtomicLong(System.currentTimeMillis());
        scheduleClockUpdating();
    }

private static SystemClock instance() {
        return InstanceHolder.INSTANCE;
    }

public static long now() {
        return instance().currentTimeMillis();
    }

public static String nowDate() {
        return new Timestamp(instance().currentTimeMillis()).toString();
    }

private void scheduleClockUpdating() {
        ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor(runnable -> {
            Thread thread = new Thread(runnable, "System Clock");
            thread.setDaemon(true);
            return thread;
        });
        scheduler.scheduleAtFixedRate(() -> now.set(System.currentTimeMillis()), period, period, TimeUnit.MILLISECONDS);
    }

private long currentTimeMillis() {
        return now.get();
    }

private static class InstanceHolder {
        public static final SystemClock INSTANCE = new SystemClock(1);
    }
}

```
这个类解释的也比较明显。高并发下生成ID的一些优化。

有了上面的我们怎么使用呢？两个注解就搞定了：
```java
package com.weir.quarkus.base.system.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import org.hibernate.annotations.GenericGenerator;

@Entity
public class MumberUser extends BaseEntity {

private static final long serialVersionUID = 7653528299072640929L;
  
  @Id
  @GenericGenerator(name = "my_id", strategy = "com.weir.quarkus.base.system.entity.MyIdGenerator" )
    @GeneratedValue(generator = "my_id")
  public Long id;
  public String name;
  public void setId(Long id) {
    this.id = id;
  }
  
  
}
```
是不是比较简单，这样在quarkus框架下就可以拥有分布式ID了，大家好好消化下。