Important

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Check the Health of a KSQL Server

Check a KSQL Server Running in a Native Deployment

If you installed KSQL server by using a package manager, like a DEB or RPM, or from an archive, like a TAR or ZIP file, you can check the health of your KSQL Server instances by using shell commands.

Use the ps command to check whether the KSQL server process is running:

ps -aux | grep ksql

Your output should resemble:

jim       2540  5.2  2.3 8923244 387388 tty2   Sl   07:48   0:33 /usr/lib/jvm/java-8-oracle/bin/java -cp /home/jim/confluent-4.1.0/share/java/monitoring-interceptors/* ...

If the process status of the JVM isn’t Sl or Ssl, the KSQL server may be down.

Check runtime stats for the KSQL server that you’re connected to.
  • Run ksql-print-metrics on a server host. The tool connects to a KSQL server that’s running on localhost and collects JMX metrics from the server process. Metrics include the number of messages, the total throughput, the throughput distribution, and the error rate. For more information, see ksql-monitoring-and-metrics
  • In the KSQL CLI or in Confluent Control Center, run SHOW STREAMS or SHOW TABLES, then run DESCRIBE EXTENDED <stream|table>.
  • In the KSQL CLI or in Confluent Control Center, run SHOW QUERIES, then run EXPLAIN <query>.

Check a KSQL Server by using the REST API

The KSQL REST API supports a “server info” request, which you access with a URL like http://<ksql-server-url>/info. The /info endpoint returns the KSQL Server version, the Apache Kafka® cluster ID, and the service ID of the KSQL Server. For more information, see KSQL REST API Reference.

curl -sX GET "http://localhost:8088/info"

Your output should resemble:

{
    "KsqlServerInfo":{
        "version":"4.1.0",
        "kafkaClusterId":"X5ZV2fjQR1u4zQDLlw62PQ",
        "ksqlServiceId":"default_"
    }
}

Note

This approach doesn’t work for non-interactive, or headless, deployments of KSQL Server, because a headless deployment doesn’t have a REST API server.