Added KafkaConsumerGroupOffsetHealthCheck

cohort-core/src/main/kotlin/com/sksamuel/cohort/cpu/FibWarmup.kt

@@ -1,6 +1,5 @@
 package com.sksamuel.cohort.cpu
 
-import com.sksamuel.cohort.Warmup
 import com.sksamuel.cohort.WarmupHealthCheck
 import kotlin.random.Random
 
@@ -22,22 +21,6 @@ class FibWarmup(
    }
 }
 
-class FibonacciWarmup(
-   private val depth: Int = 32,
-) : Warmup {
-
-   override val name: String = "fibonacci_warmup"
-
-   private fun fib(n: Int): Int = when (n) {
-      0, 1 -> 1
-      else -> fib(n - 1) + fib(n - 2)
-   }
-
-   override suspend fun warm(iteration: Int) {
-      fib(Random.nextInt(0, depth))
-   }
-}
-
 suspend fun main() {
    val w = FibonacciWarmup()
    repeat(1000) {

cohort-core/src/main/kotlin/com/sksamuel/cohort/cpu/FibonacciWarmup.kt

@@ -0,0 +1,20 @@
+package com.sksamuel.cohort.cpu
+
+import com.sksamuel.cohort.Warmup
+import kotlin.random.Random
+
+class FibonacciWarmup(
+   private val depth: Int = 32,
+) : Warmup {
+
+   override val name: String = "fibonacci_warmup"
+
+   private fun fib(n: Int): Int = when (n) {
+      0, 1 -> 1
+      else -> fib(n - 1) + fib(n - 2)
+   }
+
+   override suspend fun warm(iteration: Int) {
+      fib(Random.nextInt(0, depth))
+   }
+}

cohort-kafka/src/main/kotlin/com/sksamuel/cohort/kafka/KafkaConsumerGroupOffsetHealthCheck.kt

@@ -0,0 +1,52 @@
+package com.sksamuel.cohort.kafka
+
+import com.sksamuel.cohort.HealthCheck
+import com.sksamuel.cohort.HealthCheckResult
+import kotlinx.coroutines.future.await
+import org.apache.kafka.clients.admin.Admin
+import org.apache.kafka.clients.consumer.OffsetAndMetadata
+import org.apache.kafka.common.TopicPartition
+
+/**
+ * A Cohort [HealthCheck] that checks for stalled consumers by retrieving the committed offsets
+ * for a given consumer group. If the commited offset is the same, for all topics, between health
+ * check invocations, this check returns unhealthy.
+ *
+ * In other words, at least one partition must have an advancing offset for the given consumer group
+ * between health check invocations.
+ *
+ * This check can be useful to detect consumer groups which are making no progress.
+ */
+class KafkaConsumerGroupOffsetHealthCheck(
+   private val admin: Admin,
+   private val consumerGroupId: String,
+) : HealthCheck {
+
+   private var offsets = mapOf<TopicPartition, OffsetAndMetadata>()
+
+   override suspend fun check(): HealthCheckResult {
+
+      val groups = admin.listConsumerGroupOffsets(consumerGroupId).all().toCompletionStage().await()
+
+      val newOffsets = groups[consumerGroupId] ?: return HealthCheckResult.unhealthy(
+         "Offset metadata not available for consumer group $consumerGroupId",
+         null
+      )
+
+      // we are healthy, if for any partition, this is the first time we see the partition,
+      // or we have advanced the offset
+      val healthy = newOffsets.any { (tp, offset) ->
+         val currentOffset = offsets[tp]
+         currentOffset == null || currentOffset.offset() < offset.offset()
+      }
+
+      // replace all current offsets so next check uses new values
+      offsets = newOffsets
+
+      return if (healthy) {
+         HealthCheckResult.healthy("Kakfa consumer group is making progress")
+      } else {
+         HealthCheckResult.unhealthy("Kakfa consumer group has stalled", null)
+      }
+   }
+}