Cannot connect to remote HDFS from Windows

问题

i am trying to connect to a remote HDFS instance as

        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://hostName:8020");
        conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");
        FileSystem fs = FileSystem.get(conf);
        RemoteIterator<LocatedFileStatus> ri = fs.listFiles(fs.getHomeDirectory(), false);
        while (ri.hasNext()) {
            LocatedFileStatus lfs = ri.next();
            //log.debug(lfs.getPath().toString());
        }

        fs.close();

here are my Maven dependencies

<dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-mapreduce-client-core</artifactId>
        <version>2.7.1</version>
    </dependency>

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-client</artifactId>
        <version>2.7.1</version>
    </dependency>

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-examples</artifactId>
        <version>1.2.1</version>
    </dependency>

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>2.7.1</version>
    </dependency>

and here is the result of hadoop version command on my remote node

hadoop version
Hadoop 2.7.1.2.3.0.0-2557

but i get

Exception in thread "main" java.lang.UnsupportedOperationException: Not implemented by the DistributedFileSystem FileSystem implementation
at org.apache.hadoop.fs.FileSystem.getScheme(FileSystem.java:217)
at org.apache.hadoop.fs.FileSystem.loadFileSystems(FileSystem.java:2624)
at org.apache.hadoop.fs.FileSystem.getFileSystemClass(FileSystem.java:2634)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2651)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:92)
at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2687)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2669)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:371)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:170)
at filecheck.HdfsTest.main(HdfsTest.java:21)

and this is the line that causes the error

FileSystem fs = FileSystem.get(conf);

any idea why this might be happening?

After trying Manjunath's answer

here is what i get

ERROR util.Shell: Failed to locate the winutils binary in the hadoop binary path
java.io.IOException: Could not locate executable null\bin\winutils.exe in the Hadoop binaries.
    at org.apache.hadoop.util.Shell.getQualifiedBinPath(Shell.java:356)
    at org.apache.hadoop.util.Shell.getWinUtilsPath(Shell.java:371)
    at org.apache.hadoop.util.Shell.<clinit>(Shell.java:364)
    at org.apache.hadoop.util.StringUtils.<clinit>(StringUtils.java:80)
    at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2807)
    at org.apache.hadoop.fs.FileSystem$Cache$Key.<init>(FileSystem.java:2802)
    at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2668)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:371)
    at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:170)
    at filecheck.HdfsTest.main(HdfsTest.java:27)
15/11/16 09:48:23 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Exception in thread "main" java.lang.IllegalArgumentException: Pathname  from hdfs://hostName:8020 is not a valid DFS filename.
    at org.apache.hadoop.hdfs.DistributedFileSystem.getPathName(DistributedFileSystem.java:197)
    at org.apache.hadoop.hdfs.DistributedFileSystem.access$000(DistributedFileSystem.java:106)
    at org.apache.hadoop.hdfs.DistributedFileSystem$DirListingIterator.<init>(DistributedFileSystem.java:940)
    at org.apache.hadoop.hdfs.DistributedFileSystem$DirListingIterator.<init>(DistributedFileSystem.java:927)
    at org.apache.hadoop.hdfs.DistributedFileSystem$19.doCall(DistributedFileSystem.java:872)
    at org.apache.hadoop.hdfs.DistributedFileSystem$19.doCall(DistributedFileSystem.java:868)
    at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
    at org.apache.hadoop.hdfs.DistributedFileSystem.listLocatedStatus(DistributedFileSystem.java:886)
    at org.apache.hadoop.fs.FileSystem.listLocatedStatus(FileSystem.java:1694)
    at org.apache.hadoop.fs.FileSystem$6.<init>(FileSystem.java:1787)
    at org.apache.hadoop.fs.FileSystem.listFiles(FileSystem.java:1783)
    at filecheck.HdfsTest.main(HdfsTest.java:29)

回答1:

My HDFS client code code uses hadoop-hdfs also requires:

    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.7.1</version>
    </dependency>

and I use the Hortonworks repository:

    <repository>
        <id>repo.hortonworks.com</id>
        <name>Hortonworks HDP Maven Repository</name>
        <url>http://repo.hortonworks.com/content/repositories/releases/</url>
    </repository>

I think you're picking up the wrong version of FileSystem.

回答2:

The exception is occurring in FileSystem.java, in getScheme() method, which simply throws UnsupportedOperationException exception.

  public String getScheme() {
    throw new UnsupportedOperationException("Not implemented by the " + getClass().getSimpleName() + " FileSystem implementation");
  }

It is calling getScheme() method of FileSystem class, instead of calling getScheme() method from DistributedFileSystem class.

The getScheme() method of DistributedFileSystem class returns:

@Override
  public String getScheme() {
    return HdfsConstants.HDFS_URI_SCHEME;
  }

So, to overcome this problem, you need to change the "FileSystem.get(conf)" statement, as shown below:

DistributedFileSystem fs = (DistributedFileSystem) FileSystem.get(conf);

EDIT:

I tried out the program and it worked perfectly fine for me. In fact, it works with and without casting. Following is my code (only difference is, I am setting recursive listing to "true"):

package com.hadooptests;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocatedFileStatus;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.RemoteIterator;
import org.apache.hadoop.hdfs.DistributedFileSystem;

import java.io.IOException;

public class HDFSConnect {
    public static void main(String[] args)
    {
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://machine:8020");
        conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem");
        DistributedFileSystem fs = null;
        try {
            fs = (DistributedFileSystem) FileSystem.get(conf);
            RemoteIterator<LocatedFileStatus> ri;
            ri = fs.listFiles(new Path("hdfs://machine:8020/"), true);
            while (ri.hasNext()) {
                LocatedFileStatus lfs = ri.next();
                System.out.println(lfs.getPath().toString());
            }
            fs.close();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

My maven:

<dependencies>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-hdfs</artifactId>
        <version>2.7.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-common</artifactId>
        <version>2.7.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.hadoop</groupId>
        <artifactId>hadoop-core</artifactId>
        <version>1.2.1</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>2.6</version>
            <configuration>
                <archive>
                    <manifest> 
                      <mainClass>com.hadooptests.HDFSConnect
                    </mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

I ran the program as:

java -cp "%CLASSPATH%;hadooptests-1.0-SNAPSHOT.jar" com.hadooptests.HDFSConnect

where CLASSPATH is set to: .;%HADOOP_HOME%\etc\hadoop\;%HADOOP_HOME%\share\hadoop\common\*;%HADOOP_HOME%\share\hadoop\common\lib\*;%HADOOP_HOME%\share\hadoop\hdfs\*;%HADOOP_HOME%\share\hadoop\hdfs\lib\*;%HADOOP_HOME%\share\hadoop\mapreduce\*;%HADOOP_HOME%\share\hadoop\mapreduce\lib\*;%HADOOP_HOME%\share\hadoop\tools\*;%HADOOP_HOME%\share\hadoop\tools\lib\*;%HADOOP_HOME%\share\hadoop\yarn\*;%HADOOP_HOME%\share\hadoop\yarn\lib\*

Some of the output, I got:

hdfs://machine:8020/app-logs/machine/logs/application_1439815019232_0001/machine.corp.com_45454
hdfs://machine:8020/app-logs/machine/logs/application_1439815019232_0002/machine.corp.com_45454
hdfs://machine:8020/app-logs/machine/logs/application_1439817471006_0002/machine.corp.com_45454
hdfs://machine:8020/app-logs/machine/logs/application_1439817471006_0003/machine.corp.com_45454

EDIT 2:

My environment:

Hadoop 2.7.1 on Windows.

I installed HDP 2.3.0, which deploys Hadoop 2.7.1

来源：https://stackoverflow.com/questions/33681940/cannot-connect-to-remote-hdfs-from-windows