Skip to main content

Kafka Modules — Troubleshooting

Kafka UI Not Launching or Continuously Loading/Crashing​

Symptoms: Kafka UI fails to launch, keeps loading indefinitely, or crashes repeatedly. Common indicators include "Sync Replicas are set to 0" errors or schema registry issues.

Solution:

  1. Stop all Docker containers: 
    make stop
  2. Delete the /data folder located at the root of the docker-compose folder.
  3. Restart the docker containers: 
    make start

This process will clear persistent data and typically resolves initialization issues.

This should fix the issue.

JDBC Connector Not Creating Topics​

Symptoms: JDBC connector runs but fails to create expected Kafka topics.

Potential Causes & Solutions:

  • Incorrect SQL Query: Verify your query syntax and test it directly against your database
  • Incrementing Mode Configuration: When using "mode": "incrementing", the connector automatically appends:
WHERE "version" > ? ORDER BY "version" ASC

The ? parameter is automatically handled for incremental loading. Ensure your main query is compatible with this appended clause.

Resolution Steps:

  1. Fix any query issues identified

  2. Stop containers: make stop

  3. Delete the /data folder

  4. Restart containers: make start

  5. Allow several minutes for topic creation before attempting to create streams

KSQLDB Alert common error​

Symptoms: URLs generated in alerts are not clickable or functional due to special characters.

  • # needs encoding as %23 (URL fragment identifier)
  • Spaces need encoding as %20
  • Other special characters may also require encoding

Solution: Since KSQLDB lacks built-in URL encoding functions, manually chain REPLACE statements for each special character:

-- Example encoding for # and space characters
REPLACE(REPLACE(case_id, '#', '%23'), ' ', '%20')

Add additional REPLACE calls for other special characters your data may contain.