---

title: Java API访问HDFS集群（HA）
date: 2021-06-23 17:06:11
tags:

• HDFS

---

hadoopV2版本及以后都是HA架构，active namenode和standby namenode, 当前active namenode 出现问题之后，zkfc会切换standby namenode 为active 状态保证hadoop集群正常运行，所以java api需要通过配置HA的方式来访问hdfs集群

对于namenode是HA高可用集群时，客户端远程访问hdfs有两种实现方法：
（1）将所有namenode ha相关的参数写入Configuration对象中.
（2）将配置文件core-site.xml和hdfs-site.xml文件复制到项目的目录下.

使用方式一：

import java.net.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
 
public class HADemo {
 
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://HACluster");
        conf.set("dfs.nameservices", "HACluster");
        conf.set("dfs.ha.namenodes.HACluster", "nn1,nn2");
        conf.set("dfs.namenode.rpc-address.HACluster.nn1", "namenode1_ip:8020");
        conf.set("dfs.namenode.rpc-address.HACluster.nn2", "namenode2_ip:8020");
        conf.set("dfs.client.failover.proxy.provider.HACluster",
                "org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider");
        try {
            FileSystem fs = FileSystem.get(new URI("hdfs://HACluster"), conf,"root");
            boolean b=fs.mkdirs(new Path("/tmp/a"));
            fs.copyFromLocalFile(new Path("D:\\test\\a.txt"), new Path("/tmp/a/a.txt"));
            fs.close();
        } catch (Exception e) {
            System.out.println(e);
        }
    }
}