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Component family
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Big Data / HCatalog
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Function
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The tHCatalogInput component
reads data from the specified HCatalog managed database and sends
data in the data flow to the console or to a specified local file by
connecting this component to a proper component.
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Purpose
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This component allows you to read data from an HCatalog managed
Hive database and send data to the component that follows.
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Basic settings
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Property type
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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.
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Schema and Edit
Schema
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A schema is a row description. It defines the number of fields 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:
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View schema: choose this option to view the
schema only.
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Change to built-in property: choose this option
to change the schema to Built-in for local
changes.
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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.
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Built-in: The schema will be
created and stored locally for this component only. Related topic:
see Talend Studio User
Guide.
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Repository: The schema already
exists and is stored in the Repository, hence can be reused in
various projects and Job designs. Related topic: see
Talend Studio User
Guide.
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Version
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Distribution
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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:
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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
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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:
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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.
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Select Import from zip to import a custom
distribution zip that, for example, you can download from http://www.talendforge.org/exchange/index.php.
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 an step-by-step example about how to connect to a custom distribution and
share this connection, see Connecting to a custom Hadoop distribution.
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HCatalog version
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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:
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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:
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mapreduce.application.framework.path=/hdp/apps/2.2.0.0-2041/mapreduce/mapreduce.tar.gz#mr-framework |
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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
Talend Installation
and Upgrade Guide.
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Templeton Configuration
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Templeton hostname
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Fill this field with the URL of Templeton Webservice.
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Templeton port
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Fill this field with the port of URL of Templeton Webservice. By
default, this value is 50111.
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Use kerberos authentication
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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.
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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.
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HCatalog Configuration
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Database
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The database in which the HCatalog managed tables are placed. By
default, this database is the Hive one named default.
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Table
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Fill this field to operate on one or multiple tables in the
specified database.
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Partition
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Fill this field to specify one or more partitions for the
partition operation on a specified table. When you specify multiple
partitions, use commas to separate every two partitions and use
double quotation marks to quote the partition string.
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Username |
Fill this field with the username for the Hive database
authentication.
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Die on error
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This check box is cleared by default, meaning to skip the row on
error and to complete the process for error-free rows.
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| Advanced settings |
Row separator
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Enter the separator used to identify the end of a row.
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Field separator
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Enter character, string or regular expression to separate fields for the transferred
data.
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Custom encoding
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Select the encoding from the list or select Custom and
define it manually. This field is compulsory for database data handling.
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Hadoop properties
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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:
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Retrieve the HCatalog
logs |
Select this check box to retrieve log files generated
during HCatalog operations. |
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Standard Output
Folder |
Fill this field with the path to which log files are
stored.
Note
This field is enabled only when you selected Retrieve the HCatalog logs check
box.
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Error Output Folder
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Fill this field with the path to which error log files are stored.
Note
This field is enabled only when you selected Retrieve the HCatalog logs check
box.
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tStatCatcher Statistics
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Select this check box to gather the Job processing metadata at the
Job level as well as at each component level.
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Global Variables
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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.
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Usage
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This component is commonly used as the starting component in a
Job.
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’s documentation about HCatalog. For example, https://cwiki.apache.org/confluence/display/HCATALOG/Design+Document+-+Java+APIs+for+HCatalog+DDL+Commands.
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Prerequisites
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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.
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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
hadoophadoop-VERSIONlib
ative. For example, the library for
Windows is lib
ativeMapRClient.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.
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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. 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
set this argument, see the section describing how to view data of Talend Big Data Getting Started Guide.
For further information about how to install a Hadoop distribution, see the manuals
corresponding to the Hadoop distribution you are using.
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Log4j
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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.
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Limitation
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When Use kerberos authentication
is selected, the component cannot work with IBM JVM.
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