= Kafka Health Check

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This library provides a kafka health check for spring boot actuator.

== Usage

Add the following dependency to your `pom.xml`

[source,xml]
....
<dependency>
    <groupId>com.deviceinsight.kafka</groupId>
    <artifactId>kafka-health-check</artifactId>
    <version>1.2.0</version>
</dependency>
....

In the same maven module you can configure the topic, poll timeouts, subscription timeouts and the receive timeouts
in the `application.yml`

An example for an `application.yaml` is:

[source,yaml]
....
kafka:
  health:
    topic: health-checks
    sendReceiveTimeout: 2.5s
    pollTimeout: 200ms
    subscriptionTimeout: 5s
....

The values shown are the defaults.

IMPORTANT: Make sure the configured health check topic exists!

[source,java]
....
@Bean
@ConfigurationProperties("kafka.health")
public KafkaHealthProperties kafkaHealthProperties() {
    return new KafkaHealthProperties();
}
....

[source,java]
....
@Bean
public KafkaConsumingHealthIndicator kafkaConsumingHealthIndicator(KafkaHealthProperties kafkaProperties,
        KafkaProperties processingProperties) {
    return new KafkaConsumingHealthIndicator(kafkaHealthProperties, processingProperties.buildConsumerProperties(),
            processingProperties.buildProducerProperties());
}
....

Now if you call the actuator endpoint `actuator/health` you should see the following output:

[source,json]
....
{
   "status" : "UP",
   "details" : {
      "kafkaConsuming" : {
         "status" : "UP"
      }
   }
}
....

== Configuration

|===
|Property |Default |Description

|kafka.health.topic |`health-checks` | Topic to subscribe to
|kafka.health.sendReceiveTimeout |2.5s | The maximum time, given as https://docs.spring.io/spring-boot/docs/2.1.9.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-conversion-duration[Duration], to wait for sending and receiving the message.
|kafka.health.pollTimeout |200ms | The time, given as https://docs.spring.io/spring-boot/docs/2.1.9.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-conversion-duration[Duration], spent fetching the data from the topic
|kafka.health.subscriptionTimeout |5s | The maximum time, given as https://docs.spring.io/spring-boot/docs/2.1.9.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-conversion-duration[Duration], to wait for subscribing to topic
|kafka.health.cache.maximumSize |200 | Specifies the maximum number of entries the cache may contain.

|===

== Releasing

Creating a new release involves the following steps:

. `./mvnw gitflow:release-start gitflow:release-finish`
. `git push origin master`
. `git push --tags`
. `git push origin develop`

In order to deploy the release to Maven Central, you need to create an account at https://issues.sonatype.org and
configure your account in `~/.m2/settings.xml`:

[source,xml]
....
<settings>
  <servers>
    <server>
      <id>ossrh</id>
      <username>your-jira-id</username>
      <password>your-jira-pwd</password>
    </server>
  </servers>
</settings>
....

The account also needs access to the project on Maven Central. This can be requested by another project member.

Then check out the release you want to deploy (`git checkout x.y.z`) and run `./mvnw deploy -Prelease`.