# Create a Kafka Client App for Ruby for Use With Confluent Platform In this tutorial, you will run a Ruby client application using the [rdkafka](https://github.com/appsignal/rdkafka-ruby) gem that produces messages to and consumes messages from an Apache Kafka® cluster. After you run the tutorial, use the provided [source code](https://github.com/confluentinc/examples/tree/latest/clients/cloud) as a reference to develop your own Kafka client application. ## Prerequisites ### Client - [Bundler](https://bundler.io/) installed on your machine. Install using `gem install bundler`. ### Kafka Cluster The easiest way to follow this tutorial is with [Confluent Cloud](https://www.confluent.io/confluent-cloud/tryfree/) because you don’t have to run a local Kafka cluster. From the Console, click on [LEARN](https://confluent.cloud/learn) to provision a cluster and click on `Clients` to get the cluster-specific configurations and credentials to set for your client application. You can alternatively use the supported [CLI](https://docs.confluent.io/confluent-cli/current/) or [REST API](https://docs.confluent.io/cloud/current/client-apps/kafka-rest/krest-qs.html), or the community-supported [ccloud-stack utility for Confluent Cloud](/cloud/current/examples/ccloud/docs/ccloud-stack.html). If you don’t want to use Confluent Cloud, you can also use this tutorial with a Kafka cluster running on your [local host](/platform/current/platform-quickstart.html) or any other remote server. ## Setup 1. Clone the [confluentinc/examples](https://github.com/confluentinc/examples) GitHub repository and check out the `latest` branch. ```bash git clone https://github.com/confluentinc/examples cd examples git checkout latest ``` 2. Change directory to the example for Ruby. ```bash cd clients/cloud/ruby/ ``` 3. Create a local file (for example, at `$HOME/.confluent/librdkafka.config`) with configuration parameters to connect to your Kafka cluster. Starting with one of the templates below, customize the file with connection information to your cluster. Substitute your values for `{{ BROKER_ENDPOINT }}`, `{{CLUSTER_API_KEY }}`, and `{{ CLUSTER_API_SECRET }}` (see [Configure Confluent Cloud Clients](https://docs.confluent.io/cloud/current/client-apps/config-client.html) for instructions on how to manually find these values, or use the [ccloud-stack utility for Confluent Cloud](/cloud/current/examples/ccloud/docs/ccloud-stack.html) to automatically create them). - Template configuration file for Confluent Cloud ```none # Required connection configs for Kafka producer, consumer, and admin bootstrap.servers={{ BROKER_ENDPOINT }} security.protocol=SASL_SSL sasl.mechanisms=PLAIN sasl.username={{ CLUSTER_API_KEY }} sasl.password={{ CLUSTER_API_SECRET }} # Best practice for higher availability in librdkafka clients prior to 1.7 session.timeout.ms=45000 ``` - Template configuration file for local host ```none # Kafka bootstrap.servers=localhost:9092 ``` ## Basic Producer and Consumer In this example, the producer application writes Kafka data to a topic in your Kafka cluster. If the topic does not already exist in your Kafka cluster, the producer application will use the Kafka Admin Client API to create the topic. Each record written to Kafka has a key representing a username (for example, `alice`) and a value of a count, formatted as json (for example, `{"count": 0}`). The consumer application reads the same Kafka topic and keeps a rolling sum of the count as it processes each record. ### Produce Records 1. Install gems: ```bash bundle install ``` 2. Run the producer, passing in arguments for: - the local file with configuration parameters to connect to your Kafka cluster - the topic name ```bash ruby producer.rb -f $HOME/.confluent/librdkafka.config --topic test1 ``` 3. Verify the producer sent all the messages. You should see: ```text Creating topic test1 Producing record: alice {"count":0} Producing record: alice {"count":1} Producing record: alice {"count":2} Producing record: alice {"count":3} Producing record: alice {"count":4} Producing record: alice {"count":5} Producing record: alice {"count":6} Producing record: alice {"count":7} Producing record: alice {"count":8} Producing record: alice {"count":9} 10 messages were successfully produced to topic test1! ``` 4. View the [producer code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/ruby/producer.rb). ### Consume Records 1. Run the consumer, passing in arguments for: - the local file with configuration parameters to connect to your Kafka cluster - the topic name you used earlier ```bash ruby consumer.rb -f $HOME/.confluent/librdkafka.config --topic test1 ``` 2. Verify the consumer received all the messages: ```text Consuming messages from test1 Consumed record with key alice and value {"count":0}, and updated total count 0 Consumed record with key alice and value {"count":1}, and updated total count 1 Consumed record with key alice and value {"count":2}, and updated total count 3 Consumed record with key alice and value {"count":3}, and updated total count 6 Consumed record with key alice and value {"count":4}, and updated total count 10 Consumed record with key alice and value {"count":5}, and updated total count 15 Consumed record with key alice and value {"count":6}, and updated total count 21 Consumed record with key alice and value {"count":7}, and updated total count 28 Consumed record with key alice and value {"count":8}, and updated total count 36 Consumed record with key alice and value {"count":9}, and updated total count 45 ... ``` 3. View the [consumer code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/ruby/consumer.rb).