基于zookeeper的分布式主键生成

         <dependency>
                <groupId>org.apache.curatorgroupId>
                <artifactId>curator-recipesartifactId>
                <version>4.2.0version>
            dependency>
			<dependency>
			    <groupId>org.apache.curatorgroupId>
			    <artifactId>curator-frameworkartifactId>
			      <version>4.2.0version>
			dependency>

添加配置文件

# zk host地址
zk.host=note01:2181,note02:2181,note03:2181
# zk自增存储node
zk.sequence-path=/leadnews/sequence/

定义枚举类,枚举表名

public enum ZkSequenceEnum {
    AP_LIKES,AP_READ_BEHAVIOR,AP_COLLECTION,AP_USER_FOLLOW,AP_USER_FAN
}

分布式原子自增类（DistributedAtomicLong）实现，注意每500毫秒重试3次后仍然生成失败则返回null，

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.atomic.AtomicValue;
import org.apache.curator.framework.recipes.atomic.DistributedAtomicLong;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class ZkSequence {
    //
  RetryPolicy retryPolicy = new ExponentialBackoffRetry(500,3);
    DistributedAtomicLong distAtomicLong;
    public ZkSequence(CuratorFramework client, String counterPath){
        this.distAtomicLong = distAtomicLong = new DistributedAtomicLong(client,counterPath,retryPolicy);
    }

    /**
     * 生成序列
     * @return
     * @throws Exception
     */
    public Long sequence() throws Exception {
        AtomicValue<Long> increment = distAtomicLong.increment();
        if(increment.succeeded()){
            return increment.postValue();
        }else{
            return null;
        }
    }
}

构建zookeeper client,通过PostConstruct注解在内构器之后调用init方法初始化客户端连接，并调用initZkSequence方法初始项目所定义的ZkSequence，并存储在zkSequence的Map集合中，最终提供sequence方法来查询对应zkSequence获取自增ID

被@PostConstruct修饰的方法会在服务器加载Servlet的时候运行，并且只会被服务器调用一次，类似于Serclet的inti()方法。被@PostConstruct修饰的方法会在构造函数之后，init()方法之前运行。

package com.heima.common.zookeeper;

import com.google.common.collect.Maps;
import com.heima.common.zookeeper.sequence.ZkSequence;
import com.heima.common.zookeeper.sequence.ZkSequenceEnum;
import lombok.Getter;
import lombok.Setter;
import lombok.extern.slf4j.Slf4j;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;

import javax.annotation.PostConstruct;
import java.util.Map;

@Getter
@Setter
@Slf4j
public class ZookeeperClient {
    private String host;
    private String sequencePath;

    // 重试休眠时间
    private final int SLEEP_TIME_MS = 1000;
    // 最大重试1000次
    private final int MAX_RETRIES = 1000;
    //会话超时时间
    private final int SESSION_TIMEOUT = 30 * 1000;
    //连接超时时间
    private final int CONNECTION_TIMEOUT = 3 * 1000;
    //创建连接实例
    private CuratorFramework client = null;
    // 序列化集合
    private Map<String, ZkSequence> zkSequence = Maps.newConcurrentMap();

    public ZookeeperClient(String host, String sequencePath) {
        this.host = host;
        this.sequencePath = sequencePath;
    }

    @PostConstruct
    public void init() throws Exception {
        CuratorFrameworkFactory.builder()
                .connectString(this.getHost())
                .connectionTimeoutMs(CONNECTION_TIMEOUT)
                .sessionTimeoutMs(SESSION_TIMEOUT)
                .retryPolicy(new ExponentialBackoffRetry(SLEEP_TIME_MS, MAX_RETRIES)).build();
        this.client.start();
        this.initZkSequence();
    }

    private void initZkSequence() {
        ZkSequenceEnum[] list = ZkSequenceEnum.values();
        for (int i = 0; i < list.length; i++) {
            String name = list[i].name();
            String path = this.sequencePath + name;
            ZkSequence zep = new ZkSequence(this.client, path);
            zkSequence.put(name,zep);
        }
    }

    public Long sequence(ZkSequenceEnum name){
        try{
            ZkSequence seq = zkSequence.get(name.name());
            if (seq != null){
                return seq.sequence();
            }

        }catch (Exception e){
            log.error("获取[{}]Sequence错误:{}",name,e);
        }
        return null;
    }


}

配置管理

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;

@Setter
@Getter
@Configuration
@ConfigurationProperties(prefix="zk")
@PropertySource("classpath:zookeeper.properties")
public class ZkConfig {
    String host;
    String sequencePath;

    @Bean
    public ZookeeperClient zookeeperClient(){
        return new ZookeeperClient(this.host,this.sequencePath);
    }

}

为便于程序中调用，以及对自增生成失败的统一处理,暴露生成自增主键的功能

@Component
public class Sequences {

    @Autowired
    private ZookeeperClient client;

    public Long sequenceApLikes(){
        return this.client.sequence(ZkSequenceEnum.AP_LIKES);
    }

    public Long sequenceApReadBehavior(){
        return this.client.sequence(ZkSequenceEnum.AP_READ_BEHAVIOR);
    }

    public Long sequenceApCollection(){
        return this.client.sequence(ZkSequenceEnum.AP_COLLECTION);
    }

    public Long sequenceApUserFollow(){return this.client.sequence(ZkSequenceEnum.AP_USER_FOLLOW);}

    public Long sequenceApUserFan(){return this.client.sequence(ZkSequenceEnum.AP_USER_FAN);}


}

使用

// 第一步，注入Sequences
@Autowired
private Sequences sequences;

// 第二步，在方法中调用生成
alb.setId(sequences.sequenceApCollection());