Kafdrop 3

Kafdrop 3 is a UI for navigating and monitoring Apache Kafka brokers. The tool displays information such as brokers, topics, partitions, consumers and lets you view messages.

This project is a reboot of Kafdrop 2.x, dragged kicking and screaming into the world of JDK 11+, Kafka 2.x and Kubernetes. It's a lightweight application that runs on Spring Boot and requires very little configuration.

Requirements

• Java 11 or newer
• Kafka (version 0.10.0 or newer)

Optional, additional integration:

• Schema Registry

Getting Started

You can run the Kafdrop JAR directly, via Docker, or in Kubernetes.

Running from JAR

java --add-opens=java.base/sun.nio.ch=ALL-UNNAMED \
    -jar target/kafdrop-<version>.jar --zookeeper.connect=<host>:<port>,<host>:<port>,...

Open a browser and navigate to http://localhost:9000. The port can be overridden by adding the following config:

--server.port=<port>

Optionally, configure a schema registry connection with:

--schemaregistry.connect=http://localhost:8081

Finally, a default message format (e.g. to deserialize Avro messages) can optionally be configured as follows:

--message.format=AVRO

Valid format values are DEFAULT and AVRO. This can also be configured at the topic level via dropdown when viewing messages.

Running with Docker

Images are hosted at hub.docker.com/r/obsidiandynamics/kafdrop.

Launch container in background:

docker run -d --rm -p 9000:9000 \
    -e ZOOKEEPER_CONNECT=<host:port,host:port> \
    -e KAFKA_BROKERCONNECT=<host:port,host:port> \
    -e JVM_OPTS="-Xms32M -Xmx64M" \
    -e SERVER_SERVLET_CONTEXTPATH="/" \
    obsidiandynamics/kafdrop

Then access the UI at http://localhost:9000.

Running in Kubernetes (using a Helm Chart)

Clone the repository (if necessary):

git clone https://github.com/obsidiandynamics/kafdrop && cd kafdrop

Apply the chart:

helm upgrade -i kafdrop chart --set image.tag=3.0.0 \
    --set zkConnect=<host:port,host:port> \
    --set kafkaBrokerConnect=<host:port,host:port> \
    --set server.servlet.contextPath="/" \
    --set jvm.opts="-Xms32M -Xmx64M"

Replace 3.0.0 with the image tag of obsidiandynamics/kafdrop. Services will be bound on port 9000 by default (node port 30900).

Proxy to the Kubernetes cluster:

kubectl proxy

Navigate to http://localhost:8001/api/v1/namespaces/default/services/http:kafdrop:9000/proxy.

Building

After cloning the repository, building is just a matter of running a standard Maven build:

$ mvn clean package

The following command will generate a Docker image:

mvn assembly:single docker:build

Docker Compose

There is a docker-compose.yaml file that bundles a Kafka/ZooKeeper instance with Kafdrop:

cd docker-compose/kafka-kafdrop
docker-compose up

APIs

JSON endpoints

Starting with version 2.0.0, Kafdrop offers a set of Kafka APIs that mirror the existing HTML views. Any existing endpoint can be returned as JSON by simply setting the Accept: application/json header. Some endpoints are JSON only:

• /topic: Returns a list of all topics.

Swagger

To help document the Kafka APIs, Swagger has been included. The Swagger output is available by default at the following Kafdrop URL:

/v2/api-docs

This can be overridden with the following configuration:

springfox.documentation.swagger.v2.path=/new/swagger/path

Currently only the JSON endpoints are included in the Swagger output; the HTML views and Spring Boot debug endpoints are excluded.

You can disable Swagger output with the following configuration:

swagger.enabled=false

CORS Headers

Starting in version 2.0.0, Kafdrop sets CORS headers for all endpoints. You can control the CORS header values with the following configurations:

cors.allowOrigins (default is *)
cors.allowMethods (default is GET,POST,PUT,DELETE)
cors.maxAge (default is 3600)
cors.allowCredentials (default is true)
cors.allowHeaders (default is Origin,Accept,X-Requested-With,Content-Type,Access-Control-Request-Method,Access-Control-Request-Headers,Authorization)

You can also disable CORS entirely with the following configuration:

cors.enabled=false

Actuator

Health and info endpoints are available at the following path: /actuator

This can be overridden with the following configuration:

management.endpoints.web.base-path=<path>

Guides

Updating the Bootstrap theme

Edit the .scss files in the theme directory, then run theme/install.sh. This will overwrite src/main/resources/static/css/bootstrap.min.css. Then build as usual. (Requires npm.)

Securing Kafdrop

Kafdrop doesn't (yet) natively implement an authentication mechanism to restrict user access. Here's a quick workaround using NGINX using Basic Auth. The instructions below are for macOS and Homebrew.

Requirements

• NGINX: install using which nginx > /dev/null || brew install nginx
• Apache HTTP utilities: which htpasswd > /dev/null || brew install httpd

Setup

Set the admin password (you will be prompted):

htpasswd -c /usr/local/etc/nginx/.htpasswd admin

Add a logout page in /usr/local/opt/nginx/html/401.html:

<!DOCTYPE html>
<p>Not authorized. <a href="<!--# echo var="scheme" -->://<!--# echo var="http_host" -->/">Login</a>.</p>

Use the following snippet for /usr/local/etc/nginx/nginx.conf:

worker_processes 4;
  
events {
  worker_connections 1024;
}

http {
  upstream kafdrop {
    server 127.0.0.1:9000;
    keepalive 64;
  }

  server {
    listen *:8080;
    server_name _;
    access_log /usr/local/var/log/nginx/nginx.access.log;
    error_log /usr/local/var/log/nginx/nginx.error.log;
    auth_basic "Restricted Area";
    auth_basic_user_file /usr/local/etc/nginx/.htpasswd;

    location / {
      proxy_pass http://kafdrop;
    }

    location /logout {
      return 401;
    }

    error_page 401 /errors/401.html;

    location /errors {
      auth_basic off;
      ssi        on;
      alias /usr/local/opt/nginx/html;
    }
  }
}

Run NGINX:

nginx

Or reload its configuration if already running:

nginx -s reload

To logout, browse to /logout.