Java API访问HA方式的HDFS

￡神魔★判官ぃ 2022-05-17 07:19 199阅读 0赞

### 1、介绍 ###

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）将所有关于namenode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src目录下

### 2、方式一 ###

（1）样例代码

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://my");
            conf.set("dfs.nameservices", "my");
            conf.set("dfs.ha.namenodes.my", "nn1,nn2");
            conf.set("dfs.namenode.rpc-address.my.nn1", "192.168.12.156:8020");
            conf.set("dfs.namenode.rpc-address.my.nn2", "192.168.157:8020");
            conf.set("dfs.client.failover.proxy.provider.my",
                    "org.apache.hadoop.hdfs.server.namenode.ha.ConfiguredFailoverProxyProvider");
            try {
                FileSystem fs = FileSystem.get(new URI("hdfs://my"), conf,"root");
                boolean b=fs.mkdirs(new Path("/a"));
                System.out.println(b);
                fs.copyFromLocalFile(new Path("D:\\a.txt"), new Path("/a/a.txt"));
                fs.close();
            } catch (Exception e) {
                System.out.println(e);
            }
    
        }
    
    }

（2）运行结果

log4j:WARN No appenders could be found for logger (org.apache.hadoop.metrics2.lib.MutableMetricsFactory).
    log4j:WARN Please initialize the log4j system properly.
    log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
    true

（3）HDFS命令验证

[root@node1 ~]# hdfs dfs -ls /a
    Found 2 items
    -rw-r--r--   3 root supergroup         13 2018-08-08 09:11 /a/a.txt
    [root@node1 ~]# hdfs dfs -cat /a/a.txt
    Hello,Hadoop!
    [root@node1 ~]#