# tHDFSInput Extracts the data in a HDFS file for other components to process it. tHDFSInput reads a file located on a given Hadoop distributed file system (HDFS) and puts the data of interest from this file into a Talend schema. Then it passes the data to the component that follows. This component is not shipped with your Talend Studio by default. You need to install it using the Feature Manager. For more information, see [Installing features using the Feature Manager](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/install-features-to-talend-studio). ## tHDFSInput Standard properties These properties are used to configure tHDFSInput running in the Standard Job framework. The Standard tHDFSInput component belongs to the Big Data and the File families. The component in this framework is available in all Talend products with Big Data and in Talend Data Fabric. ## Basic settings | Properties | Description | | --- | --- | | Property Type | Select the way the connection details
will be set.

Built-In: The connection details will be set locally for this component. You need to specify the values for all related connection properties manually.
Repository: The connection details stored centrally in Repository > Metadata will be reused by this component.

You need to click the [...] button next to it and in the pop-up Repository Content dialog box, select the connection details to be reused, and all related connection properties will be automatically filled in.

| | 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.

Click Edit schema to make changes to the schema. If the current schema is of the Repository type, three options are available:
- View schema: choose this option to view the schema only.
- Change to built-in property: choose this option to change the schema to Built-in for local changes.
- Update repository connection: choose this option to change the schema stored in the repository and decide whether to propagate the changes to all the Jobs upon completion.
  
  If you just want to propagate the changes to the current Job, you can select No upon completion and choose this schema metadata again in the Repository Content window.
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.

| | *Use an existing connection* | Select this check box and in the Component List click the HDFS connection component from which
you want to reuse the connection details already defined.

Note that when a Job contains the parent Job and the child Job,
Component List presents only the
connection components in the same Job level. | | Hadoop version | Select the Hadoop version of the distribution you are using. | | Scheme | Select the URI scheme of the file system to be used from the
Scheme drop-down list. This scheme could be

HDFS
WebHDFS. WebHDFS with SSL is not supported yet.
ADLS. Only Azure Data Lake Storage Gen1 is supported.

The schemes present on this list vary depending on the distribution you
are using and only the scheme that appears on this list with a given
distribution is officially supported by Talend.

Once a scheme is
selected, the corresponding syntax such as
webhdfs://localhost:50070/ for WebHDFS is displayed in the
field for the NameNode location of your cluster.

If you have selected
ADLS, the connection parameters to be defined become:

In the Client ID and the Client key fields, enter, respectively, the authentication ID and the authentication key generated upon the registration of the application that the current Job you are developing uses to access Azure Data Lake Storage.

Ensure that the application to be used has appropriate permissions to access Azure Data Lake. You can check this on the Required permissions view of this application on Azure. For further information, see Azure documentation Assign the Azure AD application to the Azure Data Lake Storage account file or folder.
In the Token endpoint field, copy-paste the OAuth 2.0 token endpoint that you can obtain from the Endpoints list accessible on the App registrations page on your Azure portal.

For a
video demonstration, see [Configure and use Azure in a
Job](https://www.youtube.com/watch?v=Ww9-sp5Kd1o). | | NameNode URI | Type in the URI of the Hadoop NameNode, the master node of a
Hadoop system. For example, we assume that you have chosen a machine called *masternode* as the NameNode, then the location is
hdfs://masternode:portnumber. If you are using WebHDFS, the location should be
webhdfs://masternode:portnumber; WebHDFS with SSL is not
supported yet. | | Use kerberos authentication | If you are accessing the Hadoop cluster running with
Kerberos security, select this checkbox, then, enter the Kerberos principal name
for the NameNode in the field displayed. This enables you to use your username
to authenticate against the credentials stored in Kerberos.

This check box is available depending on the Hadoop distribution you are
connecting to. | | Use MapR Ticket authentication | Select this checkbox to authenticate using MapR Ticket, and enter the
following information:

User name: Enter your username.
Group: Enter the name of the group.
Password: Enter your password to authenticate to MapR Ticket.
Cluster name: Enter the name of the cluster you want to use.
Ticket duration: Enter the duration of the ticket in seconds. For example: 86400L, where L corresponds to a long integer.

| | Use a keytab to authenticate | Select the Use a keytab to authenticate
checkbox to log into a Kerberos-enabled system using a given keytab file. A keytab
file contains pairs of Kerberos principals and encrypted keys. You need to enter the
principal to be used in the Principal field and
the access path to the keytab file itself in the Keytab field. This keytab file must be stored in the machine in
which your Job actually runs, for example, on a Talend JobServer.

Note that the user that executes a keytab-enabled Job is not necessarily
the one a principal designates but must have the right to read the keytab file being
used. For example, the username you are using to execute a Job is *user1* and the principal to be used is *guest*; in this
situation, ensure that *user1* has the right to read the keytab
file to be used. | | User name | The User name field is available when you
are not using Kerberos to authenticate. In the User
name field, enter the login username for your distribution. If you leave
it empty, the username of the machine hosting Talend Studio will
be used. | | Group | Enter the membership including the authentication user under which the HDFS instances were
started. This field is available depending on the distribution you are using. | | File Name | Browse to, or enter the path pointing to the data to be used in the file system.

If the path you set points to a folder, this component will read all of the
files stored in that folder. Furthermore, if sub-folders exist in that folder
and you need to read files in the sub-folders, select the Include
sub-directories if path is directory check box in the
Advanced settings view. | | Type | Select the type of the file to be processed. The type of the file may be:

Text file.
Sequence file: a Hadoop sequence file consists of binary key/value pairs and is suitable for the Map/Reduce framework. For further information, see http://wiki.apache.org/hadoop/SequenceFile.

Once you select the Sequence file format, the Key column list and the Value column list appear to allow you to select the keys and the values of that Sequence file to be processed.

| | 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. | | Header | Set values to ignore the header of the transferred data. For example, enter
*0* to ignore no rows for the data without header and set *1* for the
data with header at the first row.

This field 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](https://docs.oracle.com/).

This option is not available for a Sequence file. | | Compression | Select the Uncompress the data check box to uncompress
the input 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, Talend Studio needs to
uncompress it before being able to feed it to the input flow.

This option is not available for a Sequence file. | ## Advanced settings | Properties | Description | | --- | --- | | Include sub-directories if path is directory | Select this check box to read not only the folder you have specified in the
File name field but also the sub-folders in that
folder. | | Hadoop properties | *Talend Studio* uses a default configuration for its engine to perform
operations in a Hadoop distribution. If you need to use a custom configuration in a specific
situation, complete this table with the property or properties to be customized. Then at
runtime, the customized property or properties will override those default ones.

Note that if you are using the centrally stored metadata from the Repository, this table automatically inherits the properties defined in that metadata and becomes uneditable unless you change the Property type from Repository to Built-in.

For further information about the properties required by Hadoop and its related
systems such as HDFS and Hive, see the documentation of the Hadoop distribution you are
using or see [Apache's Hadoop documentation](http://hadoop.apache.org/docs) and then select the version of the
documentation you want. For demonstration purposes, the links to some properties are listed
below:

Typically, the HDFS-related properties can be found in the hdfs-default.xml file of your distribution, such as http://hadoop.apache.org/docs/r2.6.0/hadoop-project-dist/hadoop-hdfs/hdfs-default.xml.
Apache also provides a page to list the Hive-related properties.

| | tStatCatcher Statistics | Select this check box to collect log data at the component level. Note that
this check box is not available in the Map/Reduce version of the
component. | ## Global Variables | Variables | Description | | --- | --- | | 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 checkbox is
cleared, if the component has this checkbox.

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 more information about variables, see [Using contexts and variables](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/contexts-and-variables). | ## Usage | Usage guidance | Description | | --- | --- | | **Usage rule** | This component needs an output link. | | Dynamic settings | Click the [+] button to add a row in the
table and fill the Code field with a context variable
to choose your HDFS connection dynamically from multiple connections planned in your
Job. This feature is useful when you need to access files in different HDFS systems or
different distributions, especially when you are working in an environment where you
cannot change your Job settings, for example, when your Job has to be deployed and
executed independent of *Talend Studio*.

The Dynamic settings table is
available only when the Use an existing
connection check box is selected in the Basic settings view. Once a dynamic parameter is
defined, the Component List box in the
Basic settings view becomes unusable.

For examples on using dynamic parameters, see [Reading data from databases through
context-based dynamic connections](https://help.qlik.com/talend/r/en-US/8.0/components/defining-context-groups/reading-data-from-databases-through-context-based-dynamic-connections) and [Reading data from different MySQL databases
using dynamically loaded connection parameters](https://help.qlik.com/talend/r/en-US/8.0/components/context/reading-data-from-different-mysql-databases-using-dynamically-loaded-connection-parameters). For more information on
Dynamic settings and context variables, see
[Dynamic schema](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/dynamic-schema) and [Creating a context group and define context
variables in it](https://help.qlik.com/talend/r/en-US/8.0/studio-user-guide/creating-context-group-and-define-context-variables-in-it). | | Prerequisites | The Hadoop distribution must be properly installed, so as to guarantee the interaction
with *Talend Studio*. The following list presents MapR related information for
example.

Ensure that you have installed the MapR client in the machine where Talend Studio is, and added the MapR client library to the PATH variable of that machine. According to MapR's documentation, the library or libraries of a MapR client corresponding to each OS version can be found under MAPR_INSTALL\ hadoop\hadoop-VERSION\lib\native. For example, the library for Windows is \lib\native\MapRClient.dll in the MapR client jar file.

Without adding the specified library or libraries, you may encounter the following error: no MapRClient in java.library.path.
Set the -Djava.library.path argument, for example, in the Job Run VM arguments area of the Run/Debug view in the Preferences dialog box in the Window menu. This argument provides to Talend Studio the path to the native library of that MapR client. This allows the subscription-based users to make full use of the Data viewer to view locally in Talend Studio the data stored in MapR.

For further information about how to install a Hadoop distribution, see the manuals
corresponding to the Hadoop distribution you are using. | | Limitations | JRE 1.6+ is required. | **Related concepts** * [Using HDFS components to work with Azure Data Lake Storage (ADLS)](https://help.qlik.com/talend/en-US/components/8.0/hdfs/thdfsinput-thdfsoutput-tlogrow-tfixedflowinput-using-hdfs-components-to-work-with-azure-data-lake-storage-adls "This scenario describes how to use the HDFS components to read data from and write data to Azure Data Lake Storage.")