using amazon s3 as input,output and to store intermediate results in EMR map reduce job

Question

I am trying to use Amazon s3 storage with EMR. However, when I currently run my code I get multiple errors like

java.lang.IllegalArgumentException: This file system object (hdfs://10.254.37.109:9000)    does not support access to the request path 's3n://energydata/input/centers_200_10k_norm.csv' You possibly called FileSystem.get(conf) when you should have called FileSystem.get(uri, conf) to obtain a file system supporting your path.
at org.apache.hadoop.fs.FileSystem.checkPath(FileSystem.java:384)
at org.apache.hadoop.hdfs.DistributedFileSystem.getPathName(DistributedFileSystem.java:129)
at org.apache.hadoop.hdfs.DistributedFileSystem.open(DistributedFileSystem.java:154)
at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:429)
at edu.stanford.cs246.hw2.KMeans$CentroidMapper.setup(KMeans.java:112)
at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:142)
at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:771)
at org.apache.hadoop.mapred.MapTask.run(MapTask.java:375)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1132)
at org.apache.hadoop.mapred.Child.main(Child.java:249)

In main I set my input and output paths like this and I put s3n://energydata/input/centers_200_10k_norm.csv in configuration CFILE that I retrieve in the mapper and reducer:

FileSystem fs = FileSystem.get(conf);
conf.set(CFILE, inPath); //inPath in this case is s3n://energydata/input/centers_200_10k_norm.csv
FileInputFormat.addInputPath(job, new Path(inputDir));
FileOutputFormat.setOutputPath(job, new Path(outputDir));

The specific example where the error above occurs in my mapper and reducer where I try to access CFILE (s3n://energydata/input/centers_200_10k_norm.csv). This is how I try to get the path:

FileSystem fs = FileSystem.get(context.getConfiguration());
Path cFile = new Path(context.getConfiguration().get(CFILE));
DataInputStream d = new DataInputStream(fs.open(cFile));  ---->Error

s3n://energydata/input/centers_200_10k_norm.csv is one of the input arguments to the program and when I launched my EMR job I specified my input and output directories to be s3n://energydata/input and s3n://energydata/output

I tried doing what was suggested in file path in hdfs but I'm still getting the error. Any help would be appreciated.

thanks!

Answer 1

try instead:

Path cFile = new Path(context.getConfiguration().get(CFILE));
FileSystem fs = cFile.getFileSystem(context.getConfiguration());
DataInputStream d = new DataInputStream(fs.open(cFile));

Answer 2

thanks. I actually fixed it by using the following code:

String uriStr =  "s3n://energydata/centroid/";
URI uri = URI.create(uriStr);
FileSystem fs = FileSystem.get(uri, context.getConfiguration());    
Path cFile = new Path(context.getConfiguration().get(CFILE));  
DataInputStream d = new DataInputStream(fs.open(cFile));