ISSUE-22: Make kafka health check cache size configurable

README.adoc

@@ -81,6 +81,7 @@ Now if you call the actuator endpoint `actuator/health` you should see the follo
 |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.maximum-size |200 | Specifies the maximum number of entries the cache may contain.
 
 |===
 

changelog.adoc

@@ -9,6 +9,8 @@
   (https://github.com/deviceinsight/kafka-health-check/issues/17[ISSUE-17])
 * As of now, cache metrics can be exposed. For this purpose, a corresponding MeterRegistry instance must be passed
   when instantiating the Kafka Health Check. (https://github.com/deviceinsight/kafka-health-check/issues/20[ISSUE-20])
+* The cache size can now be configure via the property `kafka.health.cache.maximum-size`.
+  The default value for the cache size is 200. (https://github.com/deviceinsight/kafka-health-check/issues/22[ISSUE-22])
 
 == Version 1.2.0
 

src/main/java/com/deviceinsight/kafka/health/KafkaConsumingHealthIndicator.java

@@ -92,7 +92,10 @@ public class KafkaConsumingHealthIndicator extends AbstractHealthIndicator {
 
 		this.executor = Executors.newSingleThreadExecutor();
 		this.running = new AtomicBoolean(true);
-		this.cache = Caffeine.newBuilder().expireAfterWrite(sendReceiveTimeout).build();
+		this.cache = Caffeine.newBuilder()
+				.expireAfterWrite(sendReceiveTimeout)
+				.maximumSize(kafkaHealthProperties.getCache().getMaximumSize())
+				.build();
 
 		enableCacheMetrics(cache, meterRegistry);
 

src/main/java/com/deviceinsight/kafka/health/KafkaHealthCheckCacheProperties.java

@@ -0,0 +1,19 @@
+package com.deviceinsight.kafka.health;
+
+public class KafkaHealthCheckCacheProperties {
+
+	private int maximumSize = 200;
+
+	public int getMaximumSize() {
+		return maximumSize;
+	}
+
+	public void setMaximumSize(int maximumSize) {
+		this.maximumSize = maximumSize;
+	}
+
+	@Override
+	public String toString() {
+		return "CacheProperties{" + "maximumSize=" + maximumSize + '}';
+	}
+}

src/main/java/com/deviceinsight/kafka/health/KafkaHealthProperties.java

@@ -8,6 +8,7 @@ public class KafkaHealthProperties {
 	private Duration sendReceiveTimeout = Duration.ofMillis(2500);
 	private Duration pollTimeout = Duration.ofMillis(200);
 	private Duration subscriptionTimeout = Duration.ofSeconds(5);
+	private KafkaHealthCheckCacheProperties cache = new KafkaHealthCheckCacheProperties();
 
 	public String getTopic() {
 		return topic;
@@ -56,9 +57,18 @@ public class KafkaHealthProperties {
 		setSubscriptionTimeout(Duration.ofMillis(subscriptionTimeoutMs));
 	}
 
+	public KafkaHealthCheckCacheProperties getCache() {
+		return cache;
+	}
+
+	public void setCache(KafkaHealthCheckCacheProperties cache) {
+		this.cache = cache;
+	}
+
 	@Override
 	public String toString() {
-		return "KafkaHealthProperties{topic='" + topic + "', sendReceiveTimeout=" + sendReceiveTimeout +
+		return "KafkaHealthProperties{" + "topic='" + topic + '\'' + ", sendReceiveTimeout=" + sendReceiveTimeout +
-				", pollTimeout=" + pollTimeout + ", subscriptionTimeout=" + subscriptionTimeout + '}';
+				", pollTimeout=" + pollTimeout + ", subscriptionTimeout=" + subscriptionTimeout + ", cacheProperties=" +
+				cache + '}';
 	}
 }

src/test/java/com/deviceinsight/kafka/health/KafkaHealthPropertiesTest.java

@@ -21,19 +21,22 @@ public class KafkaHealthPropertiesTest {
 			"kafka.health.topic", "custom-topic",
 			"kafka.health.send-receive-timeout", "1m",
 			"kafka.health.poll-timeout", "2s",
-			"kafka.health.subscription-timeout", "10s"
+			"kafka.health.subscription-timeout", "10s",
+			"kafka.health.cache.maximum-size", "42"
 	));
 
 	private static final ConfigurationPropertySource MILLISECONDS_PROPERTY_SOURCE = new MapConfigurationPropertySource(ImmutableMap.of(
 			"kafka.health.topic", "custom-topic",
 			"kafka.health.send-receive-timeout-ms", "60000",
 			"kafka.health.poll-timeout-ms", "2000",
-			"kafka.health.subscription-timeout-ms", "10000"
+			"kafka.health.subscription-timeout-ms", "10000",
+			"kafka.health.cache.maximum-size", "42"
 	));
 	// @formatter:on
 
 	@ParameterizedTest(name = "using {0} based setters")
 	@MethodSource("configurationPropertySources")
+	@SuppressWarnings("unused")
 	public void test_that_properties_bind_to_KafkaHealthProperties(String sourceName,
 			ConfigurationPropertySource propertySource) {
 
@@ -44,6 +47,7 @@ public class KafkaHealthPropertiesTest {
 		assertThat(kafkaHealthProperties.getSendReceiveTimeout()).isEqualTo(Duration.ofMinutes(1));
 		assertThat(kafkaHealthProperties.getPollTimeout()).isEqualTo(Duration.ofSeconds(2));
 		assertThat(kafkaHealthProperties.getSubscriptionTimeout()).isEqualTo(Duration.ofSeconds(10));
+		assertThat(kafkaHealthProperties.getCache().getMaximumSize()).isEqualTo(42);
 	}
 
 	static Stream<Arguments> configurationPropertySources() {