What is MapReduce Output Format?

For writing to local or HDFS files, outputFormat instances are utilised. During the execution of a MapReduce task, the output format is used.

The output directory is verified by the Hadoop MapReduce job to ensure it is not already there.

The RecordWriter implementation is provided by OutputFormat in a MapReduce job and is used to write the job’s output files. After that, a FileSystem is used to store the output files.

In the MapReduce programming model, the OutputFormat is a class that defines how the output data produced by the reduce function is written to storage. The OutputFormat class is responsible for creating OutputCommitters, which are responsible for committing the output of a MapReduce job to storage.

There are several different OutputFormat classes available in the MapReduce framework, including:

• TextOutputFormat: This is the default OutputFormat for MapReduce jobs. It writes the output data to plain text files, with each key-value pair written to a separate line in the output file.
• KeyValueTextOutputFormat: This OutputFormat is similar to TextOutputFormat, but it writes the output data in the form of key-value pairs separated by a separator character (e.g., a tab).
• SequenceFileOutputFormat: This OutputFormat is used to write data to Hadoop SequenceFiles. A SequenceFile is a binary file format that stores a sequence of binary key-value pairs.
• MultipleOutputs: This OutputFormat allows the developer to specify multiple output files for a MapReduce job, each with its own OutputFormat. This is useful when the output data needs to be written to multiple locations or in multiple formats.

OutputFormat is an important part of the MapReduce programming model because it determines how the output data is written to storage. By choosing the appropriate OutputFormat for the output data, the developer can ensure that the MapReduce job is able to write the data efficiently and correctly. Depending on the situation, various OutputFormats are employed.