Konstantin created MAHOUT-1487:
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Summary: More understandable error message when attempt to use
wrong FileSystem
Key: MAHOUT-1487
URL: https://issues.apache.org/jira/browse/MAHOUT-1487
Project: Mahout
Issue Type: Improvement
Components: Clustering
Affects Versions: 0.9
Environment: Amazon S3, Amazon EMR, Local file system
Reporter: Konstantin
Priority: Trivial
Fix For: 1.0
RandomSeedGenerator has following code:
FileSystem fs = FileSystem.get(output.toUri(), conf);
...
fs.getFileStatus(input).isDir()
If specify output path correctly and input path not correctly, Mahout throws
not well understandable error message. "Exception in thread "main"
java.lang.IllegalArgumentException: This file system object
(hdfs://172.31.41.65:9000) does not support access to the request path
's3://by.kslisenko.bigdata/stackovweflow-small/out_new/sparse/tfidf-vectors'
You possibly called FileSystem.get(conf) when you should have called
FileSystem.get(uri, conf) to obtain a file system supporting your path"
This happens because FileSystem object was created from output path, and
getFileStatus has parameter for input path. This caused misunderstanding when
try to understand what error message means.
To prevent this misunderstanding, I propose to improve error message adding
following details:
1. Specify which filesystem type used (DistributedFileSystem,
NativeS3FileSystem, etc. using fs.getClass().getName())
2. Then specify which path can not be processed correctly.
This can be done by validation utility which can be applied to many places in
Mahout. When we use Mahout we need to specify many paths and we also can use
many types of file systems: local for debugging, distributed on Hadoop, and s3
on Amazon. In this case better error messages can save much time.
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