tHDFSOutput MapReduce properties (deprecated) - 7.3

Property type

Either Built-In or Repository.

Built-In: No property data stored centrally.

Repository: Select the repository file where the properties are stored.

The properties are stored centrally under the Hadoop Cluster node of the Repository tree.

For further information about the Hadoop Cluster node, see the Getting Started Guide.

Schema and Edit Schema

A schema is a row description. It defines the number of fields (columns) to be processed and passed on to the next component. When you create a Spark Job, avoid the reserved word line when naming the fields.

Built-In: You create and store the schema locally for this component only.

Repository: You have already created the schema and stored it in the Repository. You can reuse it in various projects and Job designs.

Folder

Browse to, or enter the path pointing to the data to be used in the file system.

This path must point to a folder rather than a file, because a Talend Map/Reduce Job need to write in its target folder not only the final result but also multiple part- files generated in performing Map/Reduce computations.

Note that you need to ensure you have properly configured the connection to the Hadoop distribution to be used in the Hadoop configuration tab in the Run view.

Type

Action

Select an operation in HDFS:

Create: Creates a file and write data in it.

Overwrite: Overwrites the file existing in the directory specified in the Folder field.

Row separator

The separator used to identify the end of a row.

This field is not available for a Sequence file.

Field separator

Enter a character, a string, or a regular expression to separate fields for the transferred data.

This field is not available for a Sequence file.

Include header

Select this check box to output the header of the data.

This option is not available for a Sequence file.

Custom encoding

You may encounter encoding issues when you process the stored data. In that situation, select this check box to display the Encoding list.

Select the encoding from the list or select Custom and define it manually. This field is compulsory for database data handling. The supported encodings depend on the JVM that you are using. For more information, see https://docs.oracle.com.

This option is not available for a Sequence file.

Compression

Select the Compress the data check box to compress the output data.

Hadoop provides different compression formats that help reduce the space needed for storing files and speed up data transfer. When reading a compressed file, the Studio needs to uncompress it before being able to feed it to the input flow.

Note that when the type of the file to be written is Sequence File, the compression algorithm is embedded within the container files (the part- files) of this sequence file. These files can be read by a Talend component such as tHDFSInput within MapReduce Jobs and other applications that understand the sequence file format. Alternatively, when the type is Text File, the output files can be accessed with standard compression utilities that understand the bzip2 or gzip container files.

Merge result to single file

Select this check box to merge the final part files into a single file and put that file in a specified directory.

Once selecting it, you need to enter the path to, or browse to the folder you want to store the merged file in. This directory is automatically created if it does not exist.

spark.sql.sources.commitProtocolClass org.apache.spark.sql.execution.datasources.SQLHadoopMapReduceCommitProtocol

This option is not available for a Sequence file.

Advanced separator (for number)

Select this check box to change the separator used for numbers. By default, the thousands separator is a comma (,) and the decimal separator is a period (.).

Global Variables

ERROR_MESSAGE: the error message generated by the component when an error occurs. This is an After variable and it returns a string. This variable functions only if the Die on error check box is cleared, if the component has this check box.

A Flow variable functions during the execution of a component while an After variable functions after the execution of the component.

To fill up a field or expression with a variable, press Ctrl + Space to access the variable list and choose the variable to use from it.

For further information about variables, see Talend Studio User Guide.

Usage rule

In a Talend Map/Reduce Job, it is used as an end component and requires a transformation component as input link. The other components used along with it must be Map/Reduce components, too. They generate native Map/Reduce code that can be executed directly in Hadoop.

Once a Map/Reduce Job is opened in the workspace, tHDFSOutput as well as the MapReduce family appears in the Palette of the Studio.

Note that in this documentation, unless otherwise explicitly stated, a scenario presents only Standard Jobs, that is to say traditional Talend data integration Jobs, and non Map/Reduce Jobs.

Hadoop Connection

You need to use the Hadoop Configuration tab in the Run view to define the connection to a given Hadoop distribution for the whole Job.

This connection is effective on a per-Job basis.