tHDFSConnection - 6.3

Component family

Big Data / Hadoop

Basic settings

Property type

Either Built-in or Repository

Built-in: No property data stored centrally.

Repository: Select the repository file in which the properties are stored. The fields that follow are completed automatically using the data retrieved.

Version

Distribution

Select the cluster you are using from the drop-down list. The options in the list vary depending on the component you are using. Among these options, the following ones requires specific configuration:

Hadoop version

Select the version of the Hadoop distribution you are using. The available options vary depending on the component you are using. Along with the evolution of Hadoop, please note the following changes:

Inspect the classpath for configurations

Select this check box to allow the component to check the configuration files in the directory you have set with the $HADOOP_CONF_DIR variable and directly read parameters from these files in this directory. This feature allows you to easily change the Hadoop configuration for the component to switch between different environments, for example, from a test environment to a production environment.

In this situation, the fields or options used to configure Hadoop connection and/or Kerberos security are hidden.

If you want to use certain parameters such as the Kerberos parameters but these parameters are not included in these Hadoop configuration files, you need to create a file called talend-site.xml and put this file into the same directory defined with $HADOOP_CONF_DIR. This talend-site.xml file should read as follows:

<!-- Put site-specific property overrides in this file. --> 
<configuration> 
    <property> 
        <name>talend.kerberos.authentication </name> 
        <value>kinit </value>
         <description> Set the Kerberos authentication method to use. Valid values are: kinit or keytab.  </description> 
    </property> 
    <property> 
        <name>talend.kerberos.keytab.principal </name>
        <value>user@BIGDATA.COM </value>
        <description> Set the keytab's principal name.  </description>
    </property> 
    <property>   
        <name>talend.kerberos.keytab.path </name> 
        <value>/kdc/user.keytab </value> 
        <description> Set the keytab's path.  </description> 
    </property> 
    <property> 
        <name>talend.encryption </name> 
        <value>none </value> 
        <description> Set the encryption method to use. Valid values are: none or ssl.  </description> 
    </property> 
    <property> 
        <name>talend.ssl.trustStore.path </name> 
        <value>ssl </value> 
        <description> Set SSL trust store path.  </description> 
    </property> 
    <property> 
        <name>talend.ssl.trustStore.password </name> 
        <value>ssl </value> 
        <description> Set SSL trust store password.  </description> 
    </property> 
</configuration>

The parameters read from these configuration files override the default ones used by the Studio. When a parameter does not exist in these configuration files, the default one is used.

 Authentication

Use kerberos authentication

If you are accessing the Hadoop cluster running with Kerberos security, select this check box, then, enter the Kerberos principal name for the NameNode in the field displayed. This enables you to use your user name to authenticate against the credentials stored in Kerberos.

This check box is available depending on the Hadoop distribution you are connecting to.

Select the Use a keytab to authenticate check box to log into a Kerberos-enabled Hadoop 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.

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 user name 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.

NameNode URI

Type in the URI of the Hadoop NameNode.

User name

User authentication name of HDFS.

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.

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.

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 on 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:

Use datanode hostname

Select the Use datanode hostname check box to allow the Job to access datanodes via their hostnames. This actually sets the dfs.client.use.datanode.hostname property to true.

Setup HDFS encryption configurations

If the HDFS transparent encryption has been enabled in your cluster, select the Setup HDFS encryption configurations check box and in the HDFS encryption key provider field that is displayed, enter the location of the KMS proxy.

For further information about the HDFS transparent encryption and its KMS proxy, see Transparent Encryption in HDFS.

Advanced settings

tStatCatcher Statistics

Select this check box to collect log data at the component level.

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

This component is generally used with other Hadoop components.

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.

For further information about how to install a Hadoop distribution, see the manuals corresponding to the Hadoop distribution you are using.

Log4j

If you are using a subscription-based version of the Studio, the activity of this component can be logged using the log4j feature. For more information on this feature, see Talend Studio User Guide.

For more information on the log4j logging levels, see the Apache documentation at http://logging.apache.org/log4j/1.2/apidocs/org/apache/log4j/Level.html.

Limitations

JRE 1.6+ is required.