A toy example of a Kafka to OpenSearch / ElasticSearch pipeline for WikiMedia data written in pure FP Scala 3 with Cats Effect, fs2-kafka and opensearch-java client.

It consists of:

• producer: a Kafka producer that reads from the WikiMedia event stream and writes to a kafka topic
• consumer: a Kafka consumer that reads from a Kafka topic and writes to OpenSearch

1. Install scala-cli
2. Start VM (optional)

   # MacOS only, not needed if you have Docker Desktop or similar
   ./colima.sh

3. Run local infra.

   docker-compose -f ./docker-compose.yml up

4. Run the app

   # start producer process
   scala-cli ./sampler -- produce
   # start consumer process
   scala-cli ./sampler -- consume
   # run the producer & consumer processes concurrently
   scala-cli ./sampler -- produce-consume
   # for more options
   scala-cli ./sampler -- help

5. You can inspect processed data in:
   • Kafka UI available at http://localhost:8080
   • OpenSearch-Dashboards / Kibana console available at http://localhost:5601/app/dev_tools#/console

• parametrize more OpenSearch client options and move them to the CLI level
• use Avro or other format instead of JSON
• kafka consumer graceful shutdown
• use explicit mapping instead of dynamic one in OpenSearch
• create Grafana / Kibana dashboards
• add more tests