# How to configure Kafka?

With the exception of `KAFKA_BOOTSTRAP_SERVER` and `KAFKA_SCHEMAREGISTRY_URL`, Kafka is configured via [spring-boot](https://spring.io/projects/spring-boot), specifically with [KafkaProperties](https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/autoconfigure/kafka/KafkaProperties.html). See [Integration Properties](https://docs.spring.io/spring-boot/docs/current/reference/html/appendix-application-properties.html#integration-properties) prefixed with `spring.kafka`. 

Below is an example of how SASL/GSSAPI properties can be configured via environment variables:
```bash
export KAFKA_BOOTSTRAP_SERVER=broker:29092
export KAFKA_SCHEMAREGISTRY_URL=http://schema-registry:8081
export SPRING_KAFKA_PROPERTIES_SASL_KERBEROS_SERVICE_NAME=kafka
export SPRING_KAFKA_PROPERTIES_SECURITY_PROTOCOL=SASL_PLAINTEXT
export SPRING_KAFKA_PROPERTIES_SASL_JAAS_CONFIG=com.sun.security.auth.module.Krb5LoginModule required principal='principal@REALM' useKeyTab=true storeKey=true keyTab='/keytab';
```

These properties can be specified via `application.properties` or `application.yml` files, or as command line switches, or as environment variables. See Spring's [Externalized Configuration](https://docs.spring.io/spring-boot/docs/current/reference/html/spring-boot-features.html#boot-features-external-config) to see how this works.

See [Kafka Connect Security](https://docs.confluent.io/current/connect/security.html) for more ways to connect.

DataHub components that connect to Kafka are currently:
- mce-consumer-job
- mae-consumer-job
- gms