What occurs when you run a hadoop job specifying output directory for job output which already exists in HDFS?

Question

Options

• Aan error will occur after the mappers have completed but before any reducers begin to run because the
• Bthe job will run successfully. Output from the reducers will override the contents of existing directory
• Cthe job will run successfully output from the reducers will be placed in a directory called job output -1
• DAn error will occur immediately because the output directory must not already exist.

• A
  10% (2)
• C
  5% (1)
• D
  85% (17)

Explanation

Class org.apache.hadoop.mapred include: * Interface OutputFormat<K,V> OutputFormat describes the output-specification for a Map-Reduce job. The Map-Reduce framework relies on the OutputFormat of the job to: / Validate the output-specification of the job. For e.g. check that the output directory doesn't / Provide the RecordWriter implementation to be used to write out the output files of the job. Output files are stored in a FileSystem. * checkOutputSpecs void checkOutputSpecs(FileSystem ignored, throws IOException Check for validity of the output-specification for the job. This is to validate the output specification for the job when it is a job is submitted. Typically checks that it does not already exist, throwing an exception when it already exists, so that output is not overwritten. job - job configuration. IOException - when output should not be attempted

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