Known Issues in Streams Messaging

Learn about the known issues Streams Messaging, the impact or changes to the functionality, and the workaround.

Kafka

Learn about the known issues and limitations in Kafka in this release:

Known Issues

Topics created with the kafka-topics tool are only accessible by the user who created them when the deprecated --zookeeper option is used: By default all created topics are secured. However, when topic creation and deletion is done with the kafka-topics tool using the --zookeeperoption, the tool talks directly to Zookeeper. Because security is the responsibility of ZooKeeper authorization and authentication, Kafka cannot prevent users from making ZooKeeper changes. As a result, if the --zookeeper option is used, only the user who created the topic will be able to carry out administrative actions on it. In this scenario Kafka will not have permissions to perform tasks on topics created this way.; Use kafka-topics with the --bootstrap-server option that does not require direct access to Zookeeper.
Certain Kafka command line tools require direct access to Zookeeper: The following command line tools talk directly to ZooKeeper and therefore are not secured via Kafka:

kafka-reassign-partitions; None
The offsets.topic.replication.factor property must be less than or equal to the number of live brokers: The offsets.topic.replication.factor broker configuration is now enforced upon auto topic creation. Internal auto topic creation will fail with a GROUP_COORDINATOR_NOT_AVAILABLE error until the cluster size meets this replication factor requirement.; None
Requests fail when sending to a nonexistent topic with auto.create.topics.enable set to true: The first few produce requests fail when sending to a nonexistent topic with auto.create.topics.enable set to true.; Increase the number of retries in the producer configuration setting retries.
Custom Kerberos principal names cannot be used for kerberized ZooKeeper and Kafka instances: When using ZooKeeper authentication and a custom Kerberos principal, Kerberos-enabled Kafka does not start. You must disable ZooKeeper authentication for Kafka or use the default Kerberos principals for ZooKeeper and Kafka.; None
KAFKA-2561: Performance degradation when SSL Is enabled: In some configuration scenarios, significant performance degradation can occur when SSL is enabled. The impact varies depending on your CPU, JVM version, Kafka configuration, and message size. Consumers are typically more affected than producers.; Configure brokers and clients with ssl.secure.random.implementation = SHA1PRNG. It often reduces this degradation drastically, but its effect is CPU and JVM dependent.
OPSAPS-43236: Kafka garbage collection logs are written to the process directory: By default Kafka garbage collection logs are written to the agent process directory. Changing the default path for these log files is currently unsupported.; None

Limitations

Collection of Partition Level Metrics May Cause Cloudera Manager’s Performance to Degrade: If the Kafka service operates with a large number of partitions, collection of partition level metrics may cause Cloudera Manager's performance to degrade.

If you are observing performance degradation and your cluster is operating with a high number of partitions, you can choose to disable the collection of partition level metrics.
important
If you are using SMM to monitor Kafka or Cruise Control for rebalancing Kafka partitions, be aware that both SMM and Cruise Control rely on partition level metrics. If partition level metric collection is disabled, SMM will not be able to display information about partitions. In addition, Cruise Control will not operate properly.

Complete the following steps to turn off the collection of partition level metrics:

Obtain the Kafka service name:

In Cloudera Manager, Select the Kafka service.

Select any available chart, and select Open in Chart Builder from the configuration icon drop-down.

Find $SERVICENAME= near the top of the display.
The Kafka service name is the value of $SERVICENAME.

Turn off the collection of partition level metrics:

Go to Hosts > Hosts Configuration.

Find and configure the Cloudera Manager Agent Monitoring Advanced Configuration Snippet (Safety Valve) configuration property.
Enter the following to turn off the collection of partition level metrics:
[KAFKA_SERVICE_NAME]_feature_send_broker_topic_partition_entity_update_enabled=false
Replace [KAFKA_SERVICE_NAME] with the service name of Kafka obtained in step 1. The service name should always be in lower case.

Click Save Changes.

Schema Registry

There are no known issues in Schema Registry in this release.

Streams Messaging Manager

Learn about the known issues in Streams Messaging Manager in this release:

CDPD-19495: SMM UI does not show producer data on topics page

In the SMM UI, the topics page, the topic profile pages, and the broker profile pages consistently show 0 for producer messages.

Workaround: For the real producer metrics, check the aggregated REST API responses. The real producer metrics are within the producerIdToOutMessagesCount field.

Streams Replication Manager

Learn about the known issues and limitations in Streams Replication Manager in this release:

Known Issues

MM2-163: SRM does not sync re-created source topics until the offsets have caught up with target topic: Messages written to topics that were deleted and re-created are not replicated until the source topic reaches the same offset as the target topic. For example, if at the time of deletion and re-creation there are a 100 messages on the source and target clusters, new messages will only get replicated once the re-created source topic has 100 messages. This leads to messages being lost.; None
CDPD-14019: SRM may automatically re-create deleted topics: If auto.create.topics.enable is enabled, deleted topics are automatically recreated on source clusters.; Prior to deletion, remove the topic from the topic whitelist with the srm-control tool. This prevents topics from being re-created.
srm-control topics --source [SOURCE_CLUSTER] --target [TARGET_CLUSTER] --remove [TOPIC1][TOPIC2]
CDPD-13864 and CDPD-15327: Replication stops after the network configuration of a source or target cluster is changed: If the network configuration of a cluster which is taking part in a replication flow is changed, for example, port numbers are changed as a result of enabling or disabling TLS, SRM will not update its internal configuration even if SRM is reconfigured and restarted. From SRM’s perspective, it is the cluster identity that has changed. SRM cannot determine whether the new identity corresponds to the same cluster or not, only the owner or administrator of that cluster can know. In this case, SRM tries to use the last known configuration of that cluster which might not be valid, resulting in the halt of replication.; The internal topic storing the configuration of SRM can be deleted. After a restart SRM will re-create and re-populate it with the configuration data loaded from its property file. The topic is hosted on the target cluster of the replication flow. The topic name is: mm2-configs.[SOURCE_ALIAS].internal. However, changing a replicated cluster's identity is generally not recommended.
CDPD-22094: The SRM service role displays as healthy, but no metrics are processed: The SRM service role might encounter errors that make metrics processing impossible. An example of this is when the target Kafka cluster is not reachable. The SRM service role does not automatically stop or recover if such an error is encountered. It continues to run and displays as healthy in Cloudera Manager. Metrics, however, are not processed. In addition, no new data is displayed in SMM for the replications.; Ensure that all clusters are available and are in a healthy state.

Restart SRM.
CDPD-22389: The SRM driver role displays as healthy, but replication fails: During startup, the SRM driver role might encounter errors that make data replication impossible. An example of this is when one of the clusters added for replication is not reachable. The SRM driver role does not automatically stop or recover if such an error is encountered. It will start up, continue to run, and display as healthy in Cloudera Manager. Replication, however, will not happen.; Ensure that all clusters are available and are in a healthy state.

Restart SRM.
CDPD-23683: The replication status reported by the SRM service role for healthy replications is flaky: The replication status reported by the SRM service role is flaky. The replication status might change between active and inactive frequently even if the replication is healthy. This status is also reflected in SMM on the replications tab.; None

Limitations

SRM cannot replicate Ranger authorization policies to or from Kafka clusters: Due to a limitation in the Kafka-Ranger plugin, SRM cannot replicate Ranger policies to or from clusters that are configured to use Ranger for authorization. If you are using SRM to replicate data to or from a cluster that uses Ranger, disable authorization policy synchronization in SRM. This can be achieved by clearing the Sync Topic Acls Enabled (sync.topic.acls.enabled) checkbox.
SRM cannot ensure the exactly-once semantics of transactional source topics: SRM data replication uses at-least-once guarantees, and as a result cannot ensure the exactly-once semantics (EOS) of transactional topics in the backup/target cluster.
note
Even though EOS is not guaranteed, you can still replicate the data of a transactional source, but you must set isolation.level to read_committed for SRM's internal consumers. This can be done by adding [***SOURCE CLUSTER ALIAS***]->[***TARGET CLUSTER ALIAS***].consumer.isolation.level=read_committed to the Streams Replication Manager's Replication Configs SRM service property in Cloudera Manger.
SRM checkpointing is not supported for transactional source topics: SRM does not correctly translate checkpoints (committed consumer group offsets) for transactional topics. Checkpointing assumes that the offset mapping function is always increasing, but with transactional source topics this is violated. Transactional topics have control messages in them, which take up an offset in the log, but they are never returned on the consumer API. This causes the mappings to decrease, causing issues in the checkpointing feature. As a result of this limitation, consumer failover operations for transactional topics is not possible.