从java中删除hdfs文件夹

Question

In a java app running on an edge node, I need to delete a hdfs folder, if it exists. I need to do that before running a mapreduce job (with spark) that output in the folder.

I found I could use the method

org.apache.hadoop.fs.FileUtil.fullyDelete(new File(url))

However, I can only make it work with local folder (ie file url on the running computer). I tried to use something like:

url = "hdfs://hdfshost:port/the/folder/to/delete";

with hdfs://hdfshost:port being the hdfs namenode IPC. I use it for the mapreduce, so it is correct. However it doesn't do anything.

So, what url should I use, or is there another method?

Note: here is the simple project in question.

Answer 1

This works for me.

Just add the following codes in my WordCount program will do:

import org.apache.hadoop.fs.*;

...
Configuration conf = new Configuration();

Path output = new Path("/the/folder/to/delete");
FileSystem hdfs = FileSystem.get(URI.create("hdfs://namenode:port"),conf);

// delete existing directory
if (hdfs.exists(output)) {
    hdfs.delete(output, true);
}

Job job = Job.getInstance(conf, "word count");
...

You need to add hdfs://hdfshost:port explicitly to get distributed file system. Else the code will work for local file system only.

Answer 2

I do it this way:

    Configuration conf = new Configuration();
    conf.set("fs.hdfs.impl",org.apache.hadoop.hdfs.DistributedFileSystem.class.getName());
    conf.set("fs.file.impl",org.apache.hadoop.fs.LocalFileSystem.class.getName());
    FileSystem  hdfs = FileSystem.get(URI.create("hdfs://<namenode-hostname>:<port>"), conf);
    hdfs.delete("/path/to/your/file", isRecursive);

you don't need hdfs://hdfshost:port/ in your file path

Answer 3

if you need to delete all files in the directory:

1) check how many files are there in your directory.

2) later delete all of them

     public void delete_archivos_dedirectorio() throws IOException {

//namenode= hdfs://ip + ":" + puerto 

            Path directorio = new Path(namenode + "//test//"); //nos situamos en la ruta//
            FileStatus[] fileStatus = hdfsFileSystem.listStatus(directorio); //listamos los archivos que hay actualmente en ese directorio antes de hacer nada
            int archivos_basura =  fileStatus.length; //vemos cuandoarchivos hay en el directorio antes de hacer nada, y luego iteramos hasta el nuemro de archivos que haya y llos vamos borrando para luego ir crandolos de nuevo en el writte.


            for (int numero = 0; numero <= archivos_basura ; numero++) {

                Path archivo = new Path(namenode + "//test//" + numero + ".txt");

                try {

                    if(hdfsFileSystem.exists(archivo)) {

                        try {
                            hdfsFileSystem.delete(archivo, true);
                        } catch (IOException ex) {
                            System.out.println(ex.getMessage());
                        }
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

good luck :)