Installing ksqlDB¶

ksqlDB is available as a component of Confluent Platform and Confluent Cloud. For Confluent Platform the ksqlDB binaries are located at https://www.confluent.io/download/ as a part of the Confluent Platform bundle.

ksqlDB must have access to a running Apache Kafka® cluster, which can be in your data center, in a public cloud, Confluent Cloud, etc.

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Docker support: You can deploy ksqlDB by using Docker containers. Starting with Confluent Platform 4.1.2, Confluent maintains images at Docker Hub. To start ksqlDB containers in configurations like “ksqlDB Headless Server” and “Interactive Server with Interceptors”, see Docker Configuration Parameters.

Watch the screencast of Installing and Running KSQL on YouTube.

Supported Versions and Interoperability¶

You can use Confluent Platform ksqlDB with compatible Confluent Platform and Kafka versions.

Starting with version 5.4.x, Confluent Platform ksqlDB is compatible with:

Confluent Platform 3.3.0 and later;
Kafka 0.11.0 and later.

Installation Instructions¶

Follow the instructions at Quick Start for Confluent Platform.

Also, you can install ksqlDB individually by using the confluent-ksql package. For more information, see Confluent Platform Packages.

Scale Your ksqlDB Server Deployment¶

You can scale ksqlDB by adding more capacity per server (vertically) or by adding more servers (horizontally). Also, you can scale ksqlDB clusters during live operations without loss of data. For more information, see Scaling ksqlDB.

Starting the ksqlDB Server¶

The ksqlDB servers are run separately from the ksqlDB CLI client and Kafka brokers. You can deploy servers on remote machines, VMs, or containers and then the CLI connects to these remote servers.

You can add or remove servers from the same resource pool during live operations, to elastically scale query processing. You can use different resource pools to support workload isolation. For example, you could deploy separate pools for production and for testing.

You can only connect to one ksqlDB server at a time. The ksqlDB CLI does not support automatic failover to another ksqlDB server.

Follow these instructions to start ksqlDB server using the ksql-server-start script.

Tip

These instructions are based on the assumption that you are installing Confluent Platform by using ZIP or TAR archives. For more information, see Install Confluent Platform On-Premises.

Specify your ksqlDB server configuration parameters. You can also set any property for the Kafka Streams API, the Kafka producer, or the Kafka consumer. The required parameters are bootstrap.servers and listeners. You can specify the parameters in the ksqlDB properties file or the KSQL_OPTS environment variable. Properties set with KSQL_OPTS take precedence over those specified in the properties file.

A recommended approach is to configure a common set of properties using the ksqlDB configuration file and override specific properties as needed, using the KSQL_OPTS environment variable.

Here are the default settings:
```
bootstrap.servers=localhost:9092
listeners=http://0.0.0.0:8088
```
For more information, see Configure ksqlDB Server.

Start a server node with this command:

<path-to-confluent>/bin/ksql-server-start <path-to-confluent>/etc/ksqldb/ksql-server.properties

Tip

You can view the ksqlDB server help text by running <path-to-confluent>/bin/ksql-server-start --help.

NAME
        server - KSQL Cluster

SYNOPSIS
        server [ {-h | --help} ] [ --queries-file <queriesFile> ] [--]
                <config-file>

OPTIONS
        -h, --help
            Display help information

        --queries-file <queriesFile>
            Path to the query file on the local machine.

        --
            This option can be used to separate command-line options from the
            list of arguments (useful when arguments might be mistaken for
            command-line options)

        <config-file>
            A file specifying configs for the KSQL Server, KSQL, and its
            underlying Kafka Streams instance(s). Refer to KSQL documentation
            for a list of available configs.

            This option may occur a maximum of 1 times

Have a look at this page for instructions on running ksqlDB in non-interactive (aka headless) mode.

Starting the ksqlDB CLI¶

The ksqlDB CLI is a client that connects to the ksqlDB servers.

You can start the ksqlDB CLI by providing the connection information to the ksqlDB server.

LOG_DIR=./ksql_logs <path-to-confluent>/bin/ksql http://localhost:8088

Important

By default ksqlDB attempts to store its logs in a directory called logs that is relative to the location of the ksql executable. For example, if ksql is installed at /usr/local/bin/ksql, then it would attempt to store its logs in /usr/local/logs. If you are running ksql from the default Confluent Platform location, $CONFLUENT_HOME/bin, you must override this default behavior by using the LOG_DIR variable.

After ksqlDB is started, your terminal should resemble this.

                  ===========================================
                  =       _              _ ____  ____       =
                  =      | | _____  __ _| |  _ \| __ )      =
                  =      | |/ / __|/ _` | | | | |  _ \      =
                  =      |   <\__ \ (_| | | |_| | |_) |     =
                  =      |_|\_\___/\__, |_|____/|____/      =
                  =                   |_|                   =
                  =        The Database purpose-built       =
                  =        for stream processing apps       =
                  ===========================================

Copyright 2017-2022 Confluent Inc.

CLI v7.4.7, Server v7.4.7 located at http://localhost:8088
Server Status: RUNNING

Having trouble? Type 'help' (case-insensitive) for a rundown of how things work!

ksql>

Tip

You can view the ksqlDB CLI help text by running <path-to-confluent>/bin/ksql --help.

NAME
        ksql - KSQL CLI

SYNOPSIS
        ksql [ --config-file <configFile> ]
                [ --confluent-api-key <ccloudApiKey> ]
                [ --confluent-api-secret <ccloudApiSecret> ]
                [ {--define | -d} <definedVars>... ]
                [ {--execute | -e} <execute> ] [ {--file | -f} <scriptFile> ]
                [ {-h | --help} ] [ --output <outputFormat> ]
                [ {--password | -p} <password> ]
                [ --query-row-limit <streamedQueryRowLimit> ]
                [ --query-timeout <streamedQueryTimeoutMs> ]
                [ {--user | -u} <userName> ] [--] [ <server> ]

OPTIONS
        --config-file <configFile>
            A file specifying configs for Ksql and its underlying Kafka Streams
            instance(s). Refer to KSQL documentation for a list of available
            configs.

        --confluent-api-key <ccloudApiKey>
            If you're connecting to a Confluent Cloud ksqlDB server and would
            like to use ksqlDB's connector management capabilities, then
            provide your Confluent Cloud API key here. The API key secret must
            be specified separately with the --confluent-api-secret flag

        --confluent-api-secret <ccloudApiSecret>
            If you're connecting to a Confluent Cloud ksqlDB server and would
            like to use ksqlDB's connector management capabilities, then
            provide your Confluent Cloud API key secret here. The API key
            itself must be specified separately with the --confluent-api-key
            flag

        --define <definedVars>, -d <definedVars>
            Define variables for the CLI session (equivalent to the DEFINE
            statement).

        --execute <execute>, -e <execute>
            Execute one or more SQL statements and quit.

        --file <scriptFile>, -f <scriptFile>
            Execute commands from a file and exit.

        -h, --help
            Display help information

        --output <outputFormat>
            The output format to use (either 'JSON' or 'TABULAR'; can be
            changed during REPL as well; defaults to TABULAR)

        --password <password>, -p <password>
            If your KSQL server is configured for authentication, then provide
            your password here. The username must be specified separately with
            the -u/--user flag

        --query-row-limit <streamedQueryRowLimit>
            An optional maximum number of rows to read from streamed queries

            This options value must fall in the following range: value >= 1


        --query-timeout <streamedQueryTimeoutMs>
            An optional time limit (in milliseconds) for streamed queries

            This options value must fall in the following range: value >= 1


        --user <userName>, -u <userName>
            If your KSQL server is configured for authentication, then provide
            your user name here. The password must be specified separately with
            the -p/--password flag

        --
            This option can be used to separate command-line options from the
            list of arguments (useful when arguments might be mistaken for
            command-line options)

        <server>
            The address of the Ksql server to connect to (ex:
            http://confluent.io:9098)

            This option may occur a maximum of 1 times

Configuring ksqlDB for Confluent Cloud¶

You can use ksqlDB with a Kafka cluster in Confluent Cloud. For more information, see Connecting ksqlDB to Confluent Cloud.