Integrate KSQL with Confluent Control Center¶
You can develop event streaming applications by using the KSQL user interface provided by Confluent Control Center. In Control Center, you can create Apache Kafka® topics and develop persistent queries in the KSQL query editor. When you install Confluent Platform, KSQL Server is integrated with Control Center by default, and you can configure Control Center to interact with other KSQL Server instances that run on separate hosts.
Configuration Settings for KSQL and Confluent Control Center¶
Set up the integration between KSQL and Confluent Control Center by assigning properties in the KSQL Server and Control Center configuration files.
- By default, the KSQL Server configuration file is installed at
- By default, the Control Center configuration file is installed at
Secure Communication with KSQL Server¶
When you use Basic authentication in KSQL, Control Center allows passing credentials as part of the KSQL Server URL in Control Center configuration.
# KSQL cluster URL confluent.controlcenter.ksql.url=http://<username>:<password>@localhost:8088
You can set up KSQL Server to communicate securely with other components in Confluent Platform. For more information, see Configuring Security for KSQL.
Network Configuration for KSQL and Control Center¶
These are the configuration settings that you assign to set up network connectivity between KSQL and Control Center.
- In the KSQL Server configuration file, set the listeners property
to the IP address and port of the REST API endpoint for KSQL Server. Typical
- In the Control Center configuration file, set the
confluent.controlcenter.ksql.urlproperty to the URL of the KSQL Server host. This setting specifies how Control Center communicates with KSQL Server for regular HTTP requests. For more information, see KSQL Settings.
- If KSQL Server communicates over an internal DNS that is not externally
resolvable or routeable, set the
confluent.controlcenter.ksql.advertised.urlproperty In the Control Center configuration file. This setting specifies how the browser communicates with KSQL Server for websocket requests.
When KSQL Server and Confluent Control Center run on the same host, you can use the default configuration defined by Confluent Platform setup.
When KSQL and Confluent Control Center run on different hosts¶
If KSQL Server and Control Center run on different hosts, you must specify a configuration that ensures KSQL Server and Control Center can communicate. This is necessary when KSQL Server and Control Center are deployed in the following situations:
- KSQL Server and Control Center run in separate containers.
- They run in separate virtual machines.
- They communicate over a virtual private network (VPN).
- The KSQL Server host publishes a public URL that’s different from the private URL for KSQL Server.
When KSQL and Confluent Control Center communicate over a virtual private network (VPN),
Control Center proxies your queries, but query results stream directly
from KSQL Server back to your browser, without going through
Control Center. Over a VPN, the advertised URL isn’t
it’s the hostname of the remote server.
Assign the following configuration properties to integrate KSQL Server with Control Center when they run on separate hosts.
KSQL Server Configuration¶
In the KSQL Server configuration file, set
listeners to bind to all
Control Center Configuration¶
In the Control Center configuration file, set
to the URL of the KSQL Server host, which must be reachable from the host that
Control Center is installed on. Also, set
to the public IP address published by the KSQL Server host, which must be a URL
that the browser can resolve through externally available DNS.
You must specify the ports in the KSQL URL settings. For example, if the
public URL is
be sure to include port
80, or the Control Center connection to KSQL Server
Check Network Connectivity Between KSQL and Confluent Control Center¶
Use a web browser to check the configuration of an advertised URL. Make sure
that your browser can reach the
info endpoint at
If the configuration is wrong, and the browser can’t resolve the URL of the
KSQL Server host, you’ll receive an error:
Websocket error when communicating with <ksql.advertised.url>.
Check KSQL Server Network Binding¶
If Confluent Control Center doesn’t connect with your KSQL Server instance, check the network binding on the KSQL Server host:
sudo netstat -plnt|grep $(ps -ef|grep KsqlServerMain|grep -v grep|awk '')
If your KSQL server is bound to
localhost only, your output should
tcp6 0 0 127.0.0.1:8088 :::* LISTEN 64383/java tcp6 0 0 :::34791 :::* LISTEN 64383/java
0.0.0.0 isn’t listed, KSQL Server isn’t accepting external
connections. In the
ksql-server.properties file, set
listeners=http://0.0.0.0:8088 and restart KSQL Server.