前提条件 使用Kafka客户端时：已安装客户端，例如安装目录为“/opt/client”，以下操作的客户端目录只是举例，请根据实际安装目录修改。 使用KafkaUI操作时：已创建具有KafkaUI页面访问权限的用户，如需在页面上进行相关操作，例如创建Topic，需同时授予用户相关权限，请参考Kafka用户权限说明。 第一次访问Manager和KafkaUI，需要在浏览器中添加站点信任以继续访问KafkaUI。

前提条件 使用Kafka客户端时：已安装客户端，例如安装目录为“/opt/client”，以下操作的客户端目录只是举例，请根据实际安装目录修改。 使用KafkaUI时：已创建具有KafkaUI页面访问权限的用户，如需在页面上进行相关操作，例如创建Topic，需同时授予用户相关权限，请参考Kafka用户权限说明。 第一次访问Manager和KafkaUI，需要在浏览器中添加站点信任以继续访问KafkaUI。

原因分析 查看Kerberos日志“/var/log/Bigdata/kerberos/krb5kdc.log”，发现有集群外的IP使用Kafka用户连接，导致多次认证失败，最终导致Kafka账号被锁定。 Jul 11 02:49:16 192-168-1-91 krb5kdc[1863](info): AS_REQ (2 etypes {18 17}) 192.168.1.93: NEEDED_PREAUTH: kafka/hadoop.hadoop.com@HADOOP.COM for krbtgt/HADOOP.COM@HADOOP.COM, Additional pre-authentication required Jul 11 02:49:16 192-168-1-91 krb5kdc[1863](info): preauth (encrypted_timestamp) verify failure: Decrypt integrity check failed Jul 11 02:49:16 192-168-1-91 krb5kdc[1863](info): AS_REQ (2 etypes {18 17}) 192.168.1.93: PREAUTH_FAILED: kafka/hadoop.hadoop.com@HADOOP.COM for krbtgt/HADOOP.COM@HADOOP.COM, Decrypt integrity check failed

原因分析 原因：由于参数设置不当，数据量大时数据处理时间过长，导致频繁发生balance，此时offset无法正常提交，导致重复消费数据。 原理：每次poll的数据处理完后才提交offset，如果poll数据后的处理时长超出了session.timeout.ms的设置时长，此时发生rebalance导致本次消费失败，已经消费数据的offset无法正常提交，所以下次重新消费时还是在旧的offset消费数据，从而导致消费数据重复。

解决办法 建议用户在Manager页面调整以下服务参数： request.timeout.ms=100000 session.timeout.ms=90000 max.poll.records=50 heartbeat.interval.ms=3000 其中： request.timeout.ms要比session.timeout.ms大10s。 session.timeout.ms的大小设置要在服务端参数group.min.session.timeout.ms和group.max.session.timeout.ms之间。 以上参数可以根据实际情况进行适当的调整，特别是max.poll.records，这个参数是为了控制每次poll数据的records量，保证每次的处理时长尽量保持稳定。目的是为了保证poll数据以后的处理时间不要超过session.timeout.ms的时间。

问题背景与现象 当数据量较大时会频繁地发生rebalance导致出现重复消费的情况，关键日志如下： 2018-05-12 10:58:42,561 | INFO | [kafka-request-handler-3] | [GroupCoordinator 2]: Preparing to restabilize group DemoConsumer with old generation 118 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:58:43,245 | INFO | [kafka-request-handler-5] | [GroupCoordinator 2]: Stabilized group DemoConsumer generation 119 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:58:43,560 | INFO | [kafka-request-handler-7] | [GroupCoordinator 2]: Assignment received from leader for group DemoConsumer for generation 119 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:59:13,562 | INFO | [executor-Heartbeat] | [GroupCoordinator 2]: Preparing to restabilize group DemoConsumer with old generation 119 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:59:13,790 | INFO | [kafka-request-handler-3] | [GroupCoordinator 2]: Stabilized group DemoConsumer generation 120 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:59:13,791 | INFO | [kafka-request-handler-0] | [GroupCoordinator 2]: Assignment received from leader for group DemoConsumer for generation 120 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 10:59:43,802 | INFO | [kafka-request-handler-2] | Rolled new log segment for '__consumer_offsets-17' in 2 ms. | kafka.log.Log (Logging.scala:68) 2018-05-12 10:59:52,456 | INFO | [group-metadata-manager-0] | [Group Metadata Manager on Broker 2]: Removed 0 expired offsets in 0 milliseconds. | kafka.coordinator.GroupMetadataManager (Logging.scala:68) 2018-05-12 11:00:49,772 | INFO | [kafka-scheduler-6] | Deleting segment 0 from log __consumer_offsets-17. | kafka.log.Log (Logging.scala:68) 2018-05-12 11:00:49,773 | INFO | [kafka-scheduler-6] | Deleting index /srv/BigData/kafka/data4/kafka-logs/__consumer_offsets-17/00000000000000000000.index.deleted | kafka.log.OffsetIndex (Logging.scala:68) 2018-05-12 11:00:49,773 | INFO | [kafka-scheduler-2] | Deleting segment 2147948547 from log __consumer_offsets-17. | kafka.log.Log (Logging.scala:68) 2018-05-12 11:00:49,773 | INFO | [kafka-scheduler-4] | Deleting segment 4282404355 from log __consumer_offsets-17. | kafka.log.Log (Logging.scala:68) 2018-05-12 11:00:49,775 | INFO | [kafka-scheduler-2] | Deleting index /srv/BigData/kafka/data4/kafka-logs/__consumer_offsets-17/00000000002147948547.index.deleted | kafka.log.OffsetIndex (Logging.scala:68) 2018-05-12 11:00:49,775 | INFO | [kafka-scheduler-4] | Deleting index /srv/BigData/kafka/data4/kafka-logs/__consumer_offsets-17/00000000004282404355.index.deleted | kafka.log.OffsetIndex (Logging.scala:68) 2018-05-12 11:00:50,533 | INFO | [kafka-scheduler-6] | Deleting segment 4283544095 from log __consumer_offsets-17. | kafka.log.Log (Logging.scala:68) 2018-05-12 11:00:50,569 | INFO | [kafka-scheduler-6] | Deleting index /srv/BigData/kafka/data4/kafka-logs/__consumer_offsets-17/00000000004283544095.index.deleted | kafka.log.OffsetIndex (Logging.scala:68) 2018-05-12 11:02:21,178 | INFO | [kafka-request-handler-2] | [GroupCoordinator 2]: Preparing to restabilize group DemoConsumer with old generation 120 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 11:02:22,839 | INFO | [kafka-request-handler-4] | [GroupCoordinator 2]: Stabilized group DemoConsumer generation 121 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 11:02:23,169 | INFO | [kafka-request-handler-1] | [GroupCoordinator 2]: Assignment received from leader for group DemoConsumer for generation 121 | kafka.coordinator.GroupCoordinator (Logging.scala:68) 2018-05-12 11:02:49,913 | INFO | [kafka-request-handler-6] | Rolled new log segment for '__consumer_offsets-17' in 2 ms. | kafka.log.Log (Logging.scala:68) 其中Preparing to restabilize group DemoConsumer with old generation表示正在发生rebalance。

解决办法 配置自定义配置“allow.everyone.if.no.acl.found”参数为“true”，重启Kafka服务。 采用具有权限用户登录。 例如： kinit test_user 或者赋予用户相关权限。 需要使用Kafka管理员用户（属于kafkaadmin组）操作。 例如： kafka-acls.sh --authorizer-properties zookeeper.connect=10.5.144.2:2181/kafka --topic topic_acl --producer --add --allow-principal User:test [root@10-10-144-2 client]# kafka-acls.sh --authorizer-properties zookeeper.connect=8.5.144.2:2181/kafka --list --topic topic_acl Current ACLs for resource `Topic:topic_acl`: User:test_user has Allow permission for operations: Describe from hosts: * User:test_user has Allow permission for operations: Write from hosts: * User:test has Allow permission for operations: Describe from hosts: * User:test has Allow permission for operations: Write from hosts: * 用户加入Kafka组或者Kafkaadmin组。

参数调优 修改服务配置参数，请参考修改集群服务配置参数。调优参数请参考表1。 表1 调优参数 配置参数 缺省值 调优场景 num.recovery.threads.per.data.dir 10 在Kafka启动过程中，数据量较大情况下，可调大此参数，可以提升启动速度。 background.threads 10 Broker后台任务处理的线程数目。数据量较大的情况下，可适当调大此参数，以提升Broker处理能力。 num.replica.fetchers 1 副本向Leader请求同步数据的线程数，增大这个数值会增加副本的I/O并发度。 num.io.threads 8 Broker用来处理磁盘I/O的线程数目，这个线程数目建议至少等于硬盘的个数。 KAFKA_HEAP_OPTS -Xmx6G -Xms6G Kafka JVM堆内存设置。当Broker上数据量较大时，应适当调整堆内存大小。