tCassandraOutput properties in Spark Streaming Jobs - 6.3

Talend Components Reference Guide

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6.3
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Talend Big Data
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Data Governance
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Talend Studio

Component family

Databases / Cassandra

 

Basic settings

Property type

Either Built-In or Repository.

Built-In: No property data stored centrally.

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

 

Sync columns

Click this button to retrieve schema from the previous component connected in the Job.

 

Keyspace

Type in the name of the keyspace into which you want to write data.

 

Action on keyspace

Select the operation you want to perform on the keyspace to be used:

  • None: No operation is carried out.

  • Drop and create keyspace: The keyspace is removed and created again.

  • Create keyspace: The keyspace does not exist and gets created.

  • Create keyspace if not exists: A keyspace gets created if it does not exist.

  • Drop keyspace if exists and create: The keyspace is removed if it already exists and created again.

 

Column family

Type in the name of the keyspace into which you want to write data.

 

Action on column family

Select the operation you want to perform on the column family to be used:

  • None: no operation is carried out.

  • Create column family if not exists: a column family gets created if it does not exist.

  • Drop column family if exists and create: the column family is removed if it already exists and created again.

  • Truncate column family: all data from the column family is permanently removed.

This list is available only when you have selected Update, Upsert or Insert from the Action on data drop-down list.

 

Action on data

On the data of the table defined, you can perform:

  • Upsert: insert the columns if they do not exist or update the existing columns.

    With this action, the columns to be defined in the schema must use lower case in their names, while the names you put in the DB column column of the schema must be identical with their equivalents in the target table, including the letter cases.

  • Insert: insert the columns if they do not exist. This action also updates the existing ones.

  • Update: update the existing columns or add the columns that do not exist. This action does not support the Counter Cassandra data type.

  • Delete: remove columns corresponding to the input flow.

For more advanced actions, use the Advanced settings view.

 

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.

The schema of this component does not support the Object type and the List type.

 

 

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).

Advanced settings

Configuration

Add the Cassandra properties you need to customize in upserting data into Cassandra.

  • For example, if you need to define the Cassandra consistency level for writing, select the output_consistency_level property in the Property name column and enter the numeric level value in the Value column.

The following list presents the numerical values you can put and the consistency levels they signify:

  • 0: ANY,

  • 1: ONE,

  • 2: TWO,

  • 3: THREE,

  • 4: QUORUM,

  • 5: ALL,

  • 6: LOCAL_QUORUM,

  • 7: EACH_QUORUM,

  • 8: SERIAL,

  • 9: LOCAL_SERIAL,

  • 10: LOCAL_ONE

For further details about each of the consistency policies, see Datastax documentation about Cassandra.

When a row is added to the table, you need to click the new row in the Property name column to display the list of the available properties and select the property or properties to be customized. For further information about each of these properties, see the Tuning section in the following link: https://github.com/datastax/spark-cassandra-connector/blob/master/doc/5_saving.md.

 

Use unlogged batch

Select this check box to handle data in batch but with Cassandra's UNLOGGED approach. This feature is available to the following three actions: Insert, Update and Delete.

Then you need to configure how the batch mode works:

  • Batch size: enter the number of lines in each batch to be processed.

  • Group batch method: select how to group rows into batches:

    1. Partition: rows sharing the same partition keys are grouped.

    2. Replica: rows to be written to the same replica are grouped.

    3. None: rows are grouped randomly. This option is suitable for a single node Cassandra.

  • Cache batch group: select this check box to load rows into memory before grouping them. This way, grouping is not impacted by the order of the rows.

    If you leave this check box clear, only successive rows that meet the same criteria are grouped.

  • Async execute: select this check box if you want tCassandraOutput to send batches in parallel. If you leave it clear, tCassandraOutput waits for the result of a batch before sending another batch to Cassandra.

  • Maximum number of batches executed in parallel: once you have selected Async execute, enter the number of batches to be sent in parallel to Cassandra.

    This number should not be a negative number or 0 and it is also recommended not to use too large a value.

The ideal situation to use batches with Cassandra is when a small number of tables must synchronize the data to be inserted or updated.

In this UNLOGGED approach, the Job does not write batches into Cassandra's batchlog system and thus avoids the performance issue incurred by this writing. For further information about Cassandra's BATCH statement and UNLOGGED approach, see Batches and Using unlogged batches.

 

Insert if not exists

Select this check box to insert rows. This row insertion takes place only when they do not exist in the target table.

This feature is available to the Insert action only.

 

Delete if exists

Select this check box to remove from the target table only the rows that have the same records in the incoming flow.

This feature is available only to the Delete action.

 

Use TTL

Select this check box to write the TTL data in the target table. In the column list that is displayed, you need to select the column to be used as the TTL column. The DB type of this column must be Int.

This feature is available to the Insert action and the Update action only.

 

Use Timestamp

Select this check box to write the timestamp data in the target table. In the column list that is displayed, you need to select the column to be used to store the timestamp data. The DB type of this column must be BigInt.

This feature is available to the following actions: Insert, Update and Delete.

 

IF condition

Add the condition to be met for the Update or the Delete action to take place. This condition allows you to be more precise about the columns to be updated or deleted.

 

Special assignment operation

Complete this table to construct advanced SET commands of Cassandra to make the Update action more specific. For example, add a record to the beginning or a particular position of a given column.

In the Update column column of this table, you need to select the column to be updated and then select the operations to be used from the Operation column. The following operations are available:

  • Append: it adds incoming records to the end of the column to be updated. The Cassandra data types it can handle are Counter, List, Set and Map.

  • Prepend: it adds incoming records to the beginning of the column to be updated. The only Cassandra data type it can handle is List.

  • Remove: it removes records from the target table when the same records exist in the incoming flow. The Cassandra data types it can handle are Counter, List, Set and Map.

  • Assign based on position/key: it adds records to a particular position of the column to be updated. The Cassandra data types it can handle are List and Map.

    Once you select this operation, the Map key/list position column becomes editable. From this column, you need to select the column to be used as reference to locate the position to be updated.

For more details about these operations, see Datastax's related documentation in http://docs.datastax.com/en/cql/3.1/cql/cql_reference/update_r.html?scroll=reference_ds_g4h_qzq_xj__description_unique_34.

 

Row key in the List type

Select the column to be used to construct the WHERE clause of Cassandra to perform the Update or the Delete action on only selected rows. The column(s) to be used in this table should be from the set of the Primary key columns of the Cassandra table.

 

Delete collection column based on postion/key

Select the column to be used as reference to locate the particular row(s) to be removed.

This feature is available only to the Delete action.

Usage in Spark Batch Jobs

This component is used as an end component and requires an input link.

This component should use one and only one tCassandraConfiguration component present in the same Job to connect to Cassandra. More than one tCassandraConfiguration components present in the same Job fail the execution of the Job.

This component, along with the Spark Batch component Palette it belongs to, appears only when you are creating a Spark Batch Job.

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

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.

Spark Connection

You need to use the Spark Configuration tab in the Run view to define the connection to a given Spark cluster for the whole Job. In addition, since the Job expects its dependent jar files for execution, one and only one file system related component from the Storage family is required in the same Job so that Spark can use this component to connect to the file system to which the jar files dependent on the Job are transferred:

This connection is effective on a per-Job basis.