KAFKA-7838: Log leader and follower end offsets when shrinking ISR (#6168)

Reviewers: Jun Rao <junrao@gmail.com>

core/src/main/scala/kafka/cluster/Partition.scala

@@ -634,16 +634,25 @@ class Partition(val topicPartition: TopicPartition,
       leaderReplicaIfLocal match {
         case Some(leaderReplica) =>
           val outOfSyncReplicas = getOutOfSyncReplicas(leaderReplica, replicaMaxLagTimeMs)
-          if(outOfSyncReplicas.nonEmpty) {
+          if (outOfSyncReplicas.nonEmpty) {
             val newInSyncReplicas = inSyncReplicas -- outOfSyncReplicas
             assert(newInSyncReplicas.nonEmpty)
-            info("Shrinking ISR from %s to %s".format(inSyncReplicas.map(_.brokerId).mkString(","),
-              newInSyncReplicas.map(_.brokerId).mkString(",")))
+            info("Shrinking ISR from %s to %s. Leader: (highWatermark: %d, endOffset: %d). Out of sync replicas: %s."
+              .format(inSyncReplicas.map(_.brokerId).mkString(","),
+                newInSyncReplicas.map(_.brokerId).mkString(","),
+                leaderReplica.highWatermark.messageOffset,
+                leaderReplica.logEndOffset.messageOffset,
+                outOfSyncReplicas.map { replica =>
+                  s"(brokerId: ${replica.brokerId}, endOffset: ${replica.logEndOffset.messageOffset})"
+                }.mkString(" ")
+              )
+            )
+
             // update ISR in zk and in cache
             updateIsr(newInSyncReplicas)
-            // we may need to increment high watermark since ISR could be down to 1
-
             replicaManager.isrShrinkRate.mark()
+
+            // we may need to increment high watermark since ISR could be down to 1
             maybeIncrementLeaderHW(leaderReplica)
           } else {
             false