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andmarios docker: make the docker image capable to run under any user
Signed-off-by: Marios Andreopoulos <>
Latest commit 1dce2f8 Oct 15, 2018

Kafka Topics UI

This is a small docker image for Landoop's kafka-topics-ui. It serves the kafka-topics-ui from port 8000 by default. A live version can be found at

The software is stateless and the only necessary option is your Kafka REST Proxy URL:

docker run --rm -it -p 8000:8000 \
           -e "KAFKA_REST_PROXY_URL=" \

Visit http://localhost:8000 to see the UI.

Proxying Kafka REST Proxy

If you have CORS issues or want to pass through firewalls and maybe share your server, we added the PROXY option. Run the container with -e PROXY=true and Caddy server will proxy the traffic to the REST Proxy:

docker run --rm -it -p 8000:8000 \
           -e "KAFKA_REST_PROXY_URL=" \
           -e "PROXY=true" \

Important: When proxying, for the KAFKA_REST_PROXY_URL you have to use an IP address or a domain that can be resolved to it. You can't use localhost even if you serve Kafka REST port from your localhost. The reason for this is that a docker container has its own network, so your localhost is different from the container's localhost. As an example, if you are in your home network and have an IP address of and run Kafka REST from your computer, instead of http://127.0.1:8082 you must use

If your REST Proxy uses self-signed SSL certificates, you can use the PROXY_SKIP_VERIFY=true environment variable to instruct the proxy to not verify the backend TLS certificate.

Configuration options

Kafka Topics UI

You can control most of Kafka Topics UI settings via environment variables:

  • MAX_BYTES (default 50000)
  • RECORD_POLL_TIMEOUT (default 2000)
  • DEBUG_LOGS_ENABLED (default true).

Docker Options

  • PROXY=[true|false]

    Whether to proxy REST Proxy endpoint via the internal webserver

  • PROXY_SKIP_VERIFY=[true|false]

    Whether to accept self-signed certificates when proxying REST Proxy via https


    The port number to use for kafka-topics-ui. The default is 8000. Usually the main reason for using this is when you run the container with --net=host, where you can't use docker's publish flag (-p HOST_PORT:8000).


    The webserver that powers the image is Caddy. Via this variable you can add options that will be appended to its configuration (Caddyfile). Variables than span multiple lines are supported.

    As an example, you can set Caddy to not apply timeouts via:

    -e "CADDY_OPTIONS=timeouts none"

    Or you can set basic authentication via:

    -e "CADDY_OPTIONS=basicauth / [USER] [PASS]"

Kafka REST Proxy Configuration

For Kafka REST Proxy 3.2.x you should set Without this option, Kafka REST Proxy will fail to return messages for large topics. Although the default value is 1000, a bug in the Kafka REST code prevents you from manually setting (depending on some other consumer options) a value lower than 30000. It is also a good idea to set to a lower value than as per Kafka's docs.

If you don't wish to proxy REST Proxy's api, you should permit CORS via setting access.control.allow.methods=GET,POST,PUT,DELETE,OPTIONS and access.control.allow.origin=*.


In the latest iterations, the container will print informational messages during startup at stderr and web server logs at stdout. This way you may sent the logs (stdout) to your favorite log management solution.