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<a id="client-examples-kafka-connect-datagen"></a>

# Create a Kafka Client App for Kafka Connect Datagen for Use With Confluent Platform

In this tutorial, you will run a Kafka Connect Datagen source connector using
[Kafka Connect Datagen](https://www.confluent.io/hub/confluentinc/kafka-connect-datagen)
that produces messages to and consumes messages from an Apache Kafka® cluster.

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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

- Docker
- [Download](https://www.confluent.io/download/) Confluent Platform

### Kafka Cluster

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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. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   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 Kafka Connect Datagen.
   ```bash
   cd clients/cloud/kafka-connect-datagen/
   ```
3. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   Create a local file (for example, at `$HOME/.confluent/java.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.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username='{{ CLUSTER_API_KEY }}' password='{{ CLUSTER_API_SECRET }}';
     sasl.mechanism=PLAIN
     # Required for correctness in Apache Kafka clients prior to 2.6
     client.dns.lookup=use_all_dns_ips

     # Best practice for higher availability in Apache Kafka clients prior to 3.0
     session.timeout.ms=45000

     # Best practice for Kafka producer to prevent data loss 
     acks=all
     ```
   - Template configuration file for local host
     ```none
     # Kafka
     bootstrap.servers=localhost:9092
     ```

## Basic Producer and Consumer

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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. Create the topic in Confluent Cloud.
   ```bash
   kafka-topics --bootstrap-server `grep "^\s*bootstrap.server" $HOME/.confluent/java.config | tail -1` --command-config $HOME/.confluent/java.config --topic test1 --create --replication-factor 3 --partitions 6
   ```
2. Generate a file of `ENV` variables used by Docker to set the bootstrap
   servers and security configuration.
   ```bash
   ../../../ccloud/ccloud-generate-cp-configs.sh $HOME/.confluent/java.config
   ```
3. Source the generated file of `ENV` variables.
   ```bash
   source ./delta_configs/env.delta
   ```
4. Start Docker by running the following command:
   ```bash
   docker-compose up -d
   ```

   You should see:
   ```text
   Creating connect ... done
   ```
5. Wait for about 60 seconds, and then verify Connect is ready by running the following command:
   ```bash
   docker-compose logs -f connect | grep "Finished starting connectors and tasks"
   ```

   You should see:
   ```text
   connect    | [2019-05-30 14:43:53,799] INFO Finished starting connectors and tasks (org.apache.kafka.connect.runtime.distributed.DistributedHerder)
   ```
6. Verify the Connect Datagen connector plugin is available by running the following command:
   ```bash
   docker-compose logs connect | grep "DatagenConnector"
   ```

   You should see:
   ```text
   connect    | [2019-05-30 14:43:41,167] INFO Added plugin 'io.confluent.kafka.connect.datagen.DatagenConnector' (org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader)
   connect    | [2019-05-30 14:43:42,614] INFO Added aliases 'DatagenConnector' and 'Datagen' to plugin 'io.confluent.kafka.connect.datagen.DatagenConnector' (org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader)
   ```
7. Submit the `kafka-connect-datagen` connector.
   ```bash
   ./submit_datagen_orders_config.sh
   ```
8. View the [kafka-connect-datagen code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/kafka-connect-datagen/start-docker.sh).

### Consume Records

1. Consume from topic `test1` by doing the following:
   - Referencing a properties file
     ```bash
     docker-compose exec connect bash -c 'kafka-console-consumer --topic test1 --bootstrap-server $CONNECT_BOOTSTRAP_SERVERS --consumer.config /tmp/ak-tools-ccloud.delta --max-messages 5'
     ```
   - Referencing individual properties
     ```bash
     docker-compose exec connect bash -c 'kafka-console-consumer --topic test1 --bootstrap-server $CONNECT_BOOTSTRAP_SERVERS --consumer-property sasl.mechanism=PLAIN --consumer-property security.protocol=SASL_SSL --consumer-property sasl.jaas.config="$SASL_JAAS_CONFIG_PROPERTY_FORMAT" --max-messages 5'
     ```

   You should see messages as follows:
   ```text
   {"ordertime":1489322485717,"orderid":15,"itemid":"Item_352","orderunits":9.703502112840228,"address":{"city":"City_48","state":"State_21","zipcode":32731}}
   ```
2. When you are done, press `CTRL-C`.
3. View the [consumer code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/kafka-connect-datagen/start-docker.sh).

## Avro and Confluent Cloud Schema Registry

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This example is similar to the previous example, except the value is formatted
as Avro and integrates with the Confluent Cloud Schema Registry. Before using Confluent Cloud Schema Registry, check
its [availability and limits](https://docs.confluent.io/cloud/current/overview.html).

1. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   As described in the [Quick Start for Schema Management on Confluent Cloud](https://docs.confluent.io/cloud/current/get-started/schema-registry.html) in the Confluent Cloud Console, enable
   Confluent Cloud Schema Registry and create an API key and secret to connect
   to it.
2. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   Verify that your VPC can connect to the Confluent Cloud Schema Registry public internet endpoint.
3. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   Update your local configuration file (for example, at `$HOME/.confluent/java.config`) with parameters to connect to Schema Registry.
   - 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.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username='{{ CLUSTER_API_KEY }}' password='{{ CLUSTER_API_SECRET }}';
     sasl.mechanism=PLAIN
     # Required for correctness in Apache Kafka clients prior to 2.6
     client.dns.lookup=use_all_dns_ips

     # Best practice for higher availability in Apache Kafka clients prior to 3.0
     session.timeout.ms=45000

     # Best practice for Kafka producer to prevent data loss 
     acks=all

     # Required connection configs for Confluent Cloud Schema Registry
     schema.registry.url=https://{{ SR_ENDPOINT }}
     basic.auth.credentials.source=USER_INFO
     basic.auth.user.info={{ SR_API_KEY }}:{{ SR_API_SECRET }}
     ```
   - Template configuration file for local host
     ```none
     # Kafka
     bootstrap.servers=localhost:9092

     # Confluent Schema Registry
     schema.registry.url=http://localhost:8081
     ```
4. <!-- WARNING: THIS IS A SHARED FILE AND THE SOURCE IS LOCATED IN DOCS-COMMON. DO NOT ADD TO ANY OTHER REPO. -->

   Verify your Confluent Cloud Schema Registry credentials by listing the Schema Registry subjects.
   In the following example, substitute your values for `{{ SR_API_KEY }}`,
   `{{ SR_API_SECRET }}`, and `{{ SR_ENDPOINT }}`.
   ```text
   curl -u {{ SR_API_KEY }}:{{ SR_API_SECRET }} https://{{ SR_ENDPOINT }}/subjects
   ```

### Produce Avro Records

1. Create the topic in Confluent Cloud.
   ```bash
   kafka-topics --bootstrap-server `grep "^\s*bootstrap.server" $HOME/.confluent/java.config | tail -1` --command-config $HOME/.confluent/java.config --topic test2 --create --replication-factor 3 --partitions 6
   ```
2. Generate a file of ``ENV` variables used by Docker to set the bootstrap
   servers and security configuration.
   ```bash
   ../../../ccloud/ccloud-generate-cp-configs.sh $HOME/.confluent/java.config
   ```
3. Source the generated file of `ENV` variables.
   ```bash
   source ./delta_configs/env.delta
   ```
4. Start Docker by running the following command:
   ```bash
   docker-compose up -d
   ```

   You should see:
   ```text
   Creating connect ... done
   ```
5. Wait for about 60 seconds, and then verify Connect is ready by running the following command:
   ```bash
   docker-compose logs -f connect | grep "Finished starting connectors and tasks"
   ```

   You should see:
   ```text
   connect    | [2019-05-30 14:43:53,799] INFO Finished starting connectors and tasks (org.apache.kafka.connect.runtime.distributed.DistributedHerder)
   ```
6. Verify the Connect Datagen connector plugin is available by running the following command:
   ```bash
   docker-compose logs connect | grep "DatagenConnector"
   ```

   You should see:
   ```text
   connect    | [2019-05-30 14:43:41,167] INFO Added plugin 'io.confluent.kafka.connect.datagen.DatagenConnector' (org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader)
   connect    | [2019-05-30 14:43:42,614] INFO Added aliases 'DatagenConnector' and 'Datagen' to plugin 'io.confluent.kafka.connect.datagen.DatagenConnector' (org.apache.kafka.connect.runtime.isolation.DelegatingClassLoader)
   ```
7. Submit the `kafka-connect-datagen` connector.
   ```bash
   ./submit_datagen_orders_config_avro.sh
   ```
8. View the [kafka-connect-datagen Avro code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/kafka-connect-datagen/start-docker-avro.sh).

### Consume Avro Records

1. Consume from topic `test2` by doing the following:
   - Referencing a properties file
     ```bash
     docker-compose exec connect bash -c 'kafka-avro-console-consumer --topic test2 --bootstrap-server $CONNECT_BOOTSTRAP_SERVERS --consumer.config /tmp/ak-tools-ccloud.delta --property basic.auth.credentials.source=$CONNECT_VALUE_CONVERTER_BASIC_AUTH_CREDENTIALS_SOURCE --property schema.registry.basic.auth.user.info=$CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_BASIC_AUTH_USER_INFO --property schema.registry.url=$CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL --max-messages 5'
     ```
   - Referencing individual properties
     ```bash
     docker-compose exec connect bash -c 'kafka-avro-console-consumer --topic test2 --bootstrap-server $CONNECT_BOOTSTRAP_SERVERS --consumer-property sasl.mechanism=PLAIN --consumer-property security.protocol=SASL_SSL --consumer-property sasl.jaas.config="$SASL_JAAS_CONFIG_PROPERTY_FORMAT" --property basic.auth.credentials.source=$CONNECT_VALUE_CONVERTER_BASIC_AUTH_CREDENTIALS_SOURCE --property schema.registry.basic.auth.user.info=$CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_BASIC_AUTH_USER_INFO --property schema.registry.url=$CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL --max-messages 5'
     ```

   You should see the following messages:
   ```text
   {"ordertime":{"long":1494153923330},"orderid":{"int":25},"itemid":{"string":"Item_441"},"orderunits":{"double":0.9910185646928878},"address":{"io.confluent.ksql.avro_schemas.KsqlDataSourceSchema_address":{"city":{"string":"City_61"},"state":{"string":"State_41"},"zipcode":{"long":60468}}}}
   ```
2. When you are done, press `CTRL-C`.
3. View the [consumer Avro code](https://github.com/confluentinc/examples/tree/latest/clients/cloud/kafka-connect-datagen/start-docker-avro.sh).

### Confluent Cloud Schema Registry

1. View the schema subjects registered in Confluent Cloud Schema Registry. In the following output, substitute values for `<SR API KEY>`, `<SR API SECRET>`, and `<SR ENDPOINT>`.
   ```text
   curl -u <SR API KEY>:<SR API SECRET> https://<SR ENDPOINT>/subjects
   ```
2. Verify that the subject `test2-value` exists.
   ```text
   ["test2-value"]
   ```
3. View the schema information for subject test2-value. In the following output, substitute values for `<SR API KEY>`, `<SR API SECRET>`, and `<SR ENDPOINT>`.
   ```text
   curl -u <SR API KEY>:<SR API SECRET> https://<SR ENDPOINT>/subjects/test2-value/versions/1
   ```
4. Verify the schema information for subject `test2-value`.
   ```text
   {"subject":"test2-value","version":1,"id":100001,"schema":"{\"type\":\"record\",\"name\":\"KsqlDataSourceSchema\",\"namespace\":\"io.confluent.ksql.avro_schemas\",\"fields\":[{\"name\":\"ordertime\",\"type\":[\"null\",\"long\"],\"default\":null},{\"name\":\"orderid\",\"type\":[\"null\",\"int\"],\"default\":null},{\"name\":\"itemid\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"orderunits\",\"type\":[\"null\",\"double\"],\"default\":null},{\"name\":\"address\",\"type\":[\"null\",{\"type\":\"record\",\"name\":\"KsqlDataSourceSchema_address\",\"fields\":[{\"name\":\"city\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"state\",\"type\":[\"null\",\"string\"],\"default\":null},{\"name\":\"zipcode\",\"type\":[\"null\",\"long\"],\"default\":null}]}],\"default\":null}]}"}
   ```