KSQL

Control Center provides the convenience of running streaming queries on one or more KSQL clusters within its graphical user interface. The KSQL feature is enabled by default in Control Center.

Important

If RBAC is enabled, the ability to view and use KSQL in Control Center is determined by the assigned roles and associated privileges configured in both KSQL and Control Center.

For more information about KSQL, see KSQL.

Tip

Go through the Confluent Platform Local or Docker quick start guides for a fast set up of streams, tables, and persisted running queries in Control Center.

Configure Control Center for KSQL clusters

When you start a local Confluent Platform install using the confluent local start command from the Confluent CLI, a default KSQL cluster named KSQL is created for you.

To configure Control Center to communicate with your own multiple KSQL clusters in a production environment, set the following options in the appropriate control-center.properties files:

• confluent.controlcenter.ksql.<name of cluster>.url = <list of urls>
• confluent.controlcenter.ksql.<name of cluster>.advertised.url = <list of urls>

These options are required for connecting Control Center to your KSQL clusters. For more information, see the KSQL Settings options in the Control Center Configuration Reference.

Important

Be sure to review Integrate KSQL with Confluent Control Center for more information on configurations for both KSQL and Control Center.

Message displayed when KSQL is not configured for Control Center in a production environment

Click Learn More for information on Installing KSQL.

Links to comprehensive KSQL documentation are available throughout the Control Center KSQL web interface.

KSQL clusters page

To access the KSQL clusters page, click the cluster from the navigation bar and select KSQL from the cluster submenu.

Use the KSQL clusters page to:

• View a summary of all KSQL clusters connected to Control Center.
• Search for a KSQL cluster being managed by the Control Center instance.
• Browse topic messages.
• Navigate to the KSQL Editor, Streams, Tables, and Running Queries for each KSQL cluster. Click the KSQL cluster name link to navigate to the KSQL Editor and other pages.

KSQL clusters page

View the number of running queries, registered streams, and registered tables for each KSQL cluster.

KSQL Editor

To access the KSQL Editor page, click the KSQL cluster name in the KSQL clusters page.

Use the KSQL Editor page to run KSQL queries and browse messages.

KSQL Editor in Control Center

After creating streams and tables, the resizeable streams and tables pane becomes populated with the defined streams and tables for the cluster (beyond the default KSQL_PROCESSING_LOG):

• Streams are indicated with a blue St expandable node:
• Tables are indicated with an orange Tb expandable node:

Click a node to view the schema for a stream or table.

KSQL Editor search and browse streams and tables

A Search box is available for you to search for streams and tables.

Click the documentation links for more KSQL information.

Download selected messages

Download selected rows of messages in a JSON format. You can download messages from the Messages browser in Topics or KSQL Editor. Run a query in the KSQL Editor to activate the message browser area. After the messages area becomes populated with messages, you can select messages for download whether the query is running or stopped.

1. Select one or more contiguous or non-contiguous rows. The Download button becomes available and shows the number of selected messages.

   Tip

   Press the command key + click to select non-contiguous rows. Press shift + click on a beginning and ending row to select a contiguous range of messages.

   

2. Click Download (n). A file named selected_data_n.json that contains the selected messages in JSON format is downloaded into your downloads directory. The n represents the number of selected messages.

   Example filename: selected_data_1.json

   Example contents:

   [{"ROWTIME":1562939957397,"ROWKEY":"6578171","VIEWTIME":6578171,"USERID":"User_6","PAGEID":"Page_85"}]
   

Streams

To access the Streams page, click the KSQL cluster name in the KSQL clusters page and click the Streams tab.

Use the Streams page to:

• View a summary of streams for the KSQL cluster.
• Search for streams.
• Add a stream.
• View the Describe stream output (analogous to the DESCRIBE command in the KSQL CLI).
• Jump to the KSQL Editor page to query the stream.
• Drop a stream (analogous to the DROP command in the KSQL CLI).

KSQL Streams context menu in Control Center

View information such as the stream name, associated Kafka topic and its number of partitions and replicas, and the data format for existing streams.

Tables

To access the Tables page, click the KSQL cluster name in the KSQL clusters page and click the Tables tab.

Use the Tables page to:

• View a summary of tables for the KSQL cluster.
• Search for tables.
• Add a table.
• View the Describe table output (analogous to the DESCRIBE command in the KSQL CLI)
• Jump to the KSQL Editor page to query the table.
• Drop a table (analogous to the DROP command in the KSQL CLI).

Initial view

Click Learn More to view the KSQL recipes available in the Stream Processing Cookbook.

KSQL Streams context menu in Control Center

View information such as the table name, associated Kafka topic and its number of partitions and replicas, and the data format for existing tables.

Running Queries

To access the Running Queries page, click the KSQL cluster name in the KSQL clusters page and click the Running Queries tab.

Use the Running Queries page to:

• View the syntax and details of running queries.
• Search running queries.
• View the query execution plan by clicking Explain (analogous to the EXPLAIN command in the KSQL CLI).
• Terminate a running query.

Initial view

Click Persistent Query Examples to view the KSQL recipes available in the Stream Processing Cookbook.

Quick start queries

Tip

Go through the Confluent Platform Local or Docker quick start guides for a fast set up of streams, tables, and persisted running queries in Control Center.

Enable and disable the KSQL feature in Control Center

The KSQL feature is enabled by default. The feature can be disabled by setting the confluent.controlcenter.ksql.enable option in the Control Center properties file to false. After disabling the feature, the KSQL submenu in the Cluster navigation is no longer visible in the Control Center UI. You can disable the setting if you are not using RBAC in Control Center or KSQL, and you do not want anyone to access the KSQL feature.

Important

If RBAC is enabled for Control Center, it takes precedence over Access Control settings.

To disable the KSQL feature in Control Center:

1. Set the confluent.controlcenter.ksql.enable option in your control-center.properties file to false.

   ...
   confluent.controlcenter.ksql.enable=false
   ...
   

   Note

   Make the change in the appropriate Control Center properties files configured for your environments, including control-center-dev.properties or control-center-production.properties. The properties files are located in /path-to-confluent/etc/confluent-control-center/.

2. Restart Control Center and pass in the properties file for the configuration to take effect.

   • Local (dev) environment:

     Important

     Do not use confluent local for production use.

     confluent local stop --path <path-to-confluent>
     confluent local start --path <path-to-confluent> ../etc/confluent-control-center/control-center.properties
     

   • Production environment:

     ./bin/control-center-stop
     ./bin/control-center-start ../etc/confluent-control-center/control-center.properties
     

To enable the feature again, set the option back to true and restart Control Center with the updated properties file.

Next Steps

• Writing Streaming Queries Against Apache Kafka® Using KSQL and Confluent Control Center