tHCatalogOutput Properties - 6.3

Talend Open Studio for Big Data Components Reference Guide
EnrichVersion
6.3
EnrichProdName
Talend Open Studio for Big Data
task
Data Governance
Data Quality and Preparation
Design and Development
EnrichPlatform
Talend Studio

Component family

Big Data / HCatalog

 

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.

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. The schema is either Built-In or stored remotely in the Repository.

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. Related topic: see Talend Studio User Guide.

 

 

Repository: You have already created the schema and stored it in the Repository. You can reuse it in various projects and Job designs. Related topic: see Talend Studio User Guide.

When the schema to be reused has default values that are integers or functions, ensure that these default values are not enclosed within quotation marks. If they are, you must remove the quotation marks manually.

For more details, see the article Verifying default values in a retrieved schema on Talend Help Center (https://help.talend.com).

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:

  • If available in this Distribution drop-down list, the Microsoft HD Insight option allows you to use a Microsoft HD Insight cluster. For this purpose, you need to configure the connections to the WebHCat service, the HD Insight service and the Windows Azure Storage service of that cluster in the areas that are displayed. A demonstration video about how to configure this connection is available in the following link: https://www.youtube.com/watch?v=A3QTT6VsNoM.

  • If you select Amazon EMR, see the article Amazon EMR - Getting Started on about how to configure the connection on Talend Help Center (https://help.talend.com).

  • The Custom option allows you to connect to a cluster different from any of the distributions given in this list, that is to say, to connect to a cluster not officially supported by Talend.

In order to connect to a custom distribution, once selecting Custom, click the button to display the dialog box in which you can alternatively:

  1. Select Import from existing version to import an officially supported distribution as base and then add other required jar files which the base distribution does not provide.

  2. Select Import from zip to import the configuration zip for the custom distribution to be used. This zip file should contain the libraries of the different Hadoop elements and the index file of these libraries.

    In Talend Exchange, members of Talend community have shared some ready-for-use configuration zip files which you can download from this Hadoop configuration list and directly use them in your connection accordingly. However, because of the ongoing evolution of the different Hadoop-related projects, you might not be able to find the configuration zip corresponding to your distribution from this list; then it is recommended to use the Import from existing version option to take an existing distribution as base to add the jars required by your distribution.

    Note that custom versions are not officially supported by Talend. Talend and its community provide you with the opportunity to connect to custom versions from the Studio but cannot guarantee that the configuration of whichever version you choose will be easy, due to the wide range of different Hadoop distributions and versions that are available. As such, you should only attempt to set up such a connection if you have sufficient Hadoop experience to handle any issues on your own.

    Note

    In this dialog box, the active check box must be kept selected so as to import the jar files pertinent to the connection to be created between the custom distribution and this component.

    For a step-by-step example about how to connect to a custom distribution and share this connection, see Connecting to a custom Hadoop distribution.

 

HCatalog 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:

  • If you use Hortonworks Data Platform V2.2, the configuration files of your cluster might be using environment variables such as ${hdp.version}. If this is your situation, you need to set the mapreduce.application.framework.path property in the Hadoop properties table of this component with the path value explicitly pointing to the MapReduce framework archive of your cluster. For example:

    mapreduce.application.framework.path=/hdp/apps/2.2.0.0-2041/mapreduce/mapreduce.tar.gz#mr-framework

  • If you use Hortonworks Data Platform V2.0.0, the type of the operating system for running the distribution and a Talend Job must be the same, such as Windows or Linux. Otherwise, you have to use Talend Jobserver to execute the Job in the same type of operating system in which the Hortonworks Data Platform V2.0.0 distribution you are using is run. For further information about Talend Jobserver, see the Talend Installation and Upgrade Guide.

 

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.

  • If this cluster is a MapR cluster of the version 4.0.1 or later, you can set the MapR ticket authentication configuration in addition or as an alternative by following the explanation in Connecting to a security-enabled MapR.

    Keep in mind that this configuration generates a new MapR security ticket for the username defined in the Job in each execution. If you need to reuse an existing ticket issued for the same username, leave both the Force MapR ticket authentication check box and the Use Kerberos authentication check box clear, and then MapR should be able to automatically find that ticket on the fly.

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

  Use a keytab to authenticate

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.

HDFS Configuration

NameNode URI

Type in the URI of the NameNode in HDFS.

 

File name

Browse to, or enter the location of the file which you write data to. This file is created automatically if it does not exist.

 

Action

Select a DB operation in HDFS:

Create: Creates a file with data using the file name defined in the File Name field.

Overwrite: Overwrites the data in the file specified in the File Name field.

Append: Inserts the data into the file specified in the File Name field. The specified file is created automatically if it does not exist.

Templeton Configuration

Templeton hostname

Fill this field with the URL of Templeton Webservice.

Note

Templeton is a webservice API for HCatalog. It has been renamed to WebHCat by the Apache community. This service facilitates the access to HCatalog and the related Hadoop elements such as Pig. For further information about Templeton (WebHCat), see https://cwiki.apache.org/confluence/display/Hive/WebHCat+UsingWebHCat.

 

Templeton port

Fill this field with the port of URL of Templeton Webservice. By default, this value is 50111.

Note

Templeton is a webservice API for HCatalog. It has been renamed to WebHCat by the Apache community. This service facilitates the access to HCatalog and the related Hadoop elements such as Pig. For further information about Templeton (WebHCat), see https://cwiki.apache.org/confluence/display/Hive/WebHCat+UsingWebHCat.

HCatalog Configuration

Database

Fill this field to specify an existing database in HDFS.

 

Table

Fill this field to specify an existing table in HDFS.

 

Partition

Fill this field to specify one or more partitions for the partition operation on the specified table. When you specify multiple partitions, use commas to separate every two partitions and use double quotation marks to quote the partition string.

If you are reading a non-partitioned table, leave this field empty.

Note

For further information about Partition, see https://cwiki.apache.org/Hive/.

  Username

Fill this field with the username for the DB authentication.

  File location

Fill this field with the path to which source data file is stored.

 

Die on error

This check box is cleared by default, meaning to skip the row on error and to complete the process for error-free rows.

Advanced settings

Row separator

Enter the separator used to identify the end of a row.

 

Field separator

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

 

Custom encoding

Select the encoding from the list or select Custom and define it manually. This field is compulsory for database data handling.

 

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 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:

  Retrieve the HCatalog logs Select this check box to retrieve log files generated during HCatalog operations.
  Standard Output Folder

Browse to, or enter the directory where the log files are stored.

Note

This field is enabled only when you selected Retrieve the HCatalog logs check box.

 

Error Output Folder

Browse to, or enter the directory where the error log files are stored.

Note

This field is enabled only when you selected Retrieve the HCatalog logs check box.

 

tStatCatcher Statistics

Select this check box to gather the Job processing metadata at the Job level as well as at each 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 commonly used together with an input component.

HCatalog is built on top of the Hive metastore to provide read and write interface for Pig and MapReduce, so that the latter systems can use the metadata of Hive to easily read and write data in HDFS.

For further information, see Apache documentation about HCatalog: https://cwiki.apache.org/confluence/display/Hive/HCatalog.

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 the 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. For further information, see the following link from MapR: http://www.mapr.com/blog/basic-notes-on-configuring-eclipse-as-a-hadoop-development-environment-for-mapr.

    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 the 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 the 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.

Limitation

n/a