Known Issues in Streams Replication Manager

Learn about the known issues in Streams Replication Manager, the impact or changes to the functionality, and the workaround.

Known Issues

CDPD-22089: 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-11079: Blacklisted topics appear in the list of replicated topics: If a topic was originally replicated but was later excluded for replication, it will still appear as a replicated topic under the /remote-topics REST API endpoint. As a result, if a call is made to this endpoint, this topic will be included in the response. Additionally, the excluded topic will also be visible in the SMM UI. However, it's Partitions and Consumer Groups will be 0, its Throughput, Replication Latency and Checkpoint Latency will show N/A.; None
OPSAPS-67772: SRM Service metrics processing fails when the noexec option is enabled for /tmp: The SRM Service role uses /tmp to extract RocksDB .so files, which are required for metrics processing to function. If the noexec option is enabled for the /tmp directory, the SRM Service role is not able load the required RocksDB files. This results in metrics processing failing.; In Cloudera Manager, select the SRM service and go to Configuration.

Add the following to SRM Service Environment Advanced Configuration Snippet (Safety Valve). Do this for all SRM Service role instances.
ROCKSDB_SHAREDLIB_DIR=[***PATH***]
Replace [***PATH***] with a directory that is not /tmp.
OPSAPS-67738: SRM Service role's Remote Querying feature does not work when the noexec option is enabled for /tmp: The SRM Service role puts the Netty native libraries into the /tmp directory. As a result, If the noexec option is enabled for the /tmp directory, the Remote Querying feature will fail to function.; In Cloudera Manager, select the SRM service and go to Configuration.

Add the following to SRM_JVM_PERF_OPTS.
-Dio.netty.native.workdir=[***PATH***]
Replace [***PATH***] with a directory that is not /tmp.
OPSAPS-67742: The SRM Service role fails to start if properties are added to Additional Configs For Streams Application Running Inside SRM Service: Configuring the SRM Service role's internal Kafka Streams application is not possible. If you add any properties to Using the Additional Configs For Streams Application Running Inside SRM Service, the SRM Service role fails to start. If you are affected by this issue, an exception similar to the following will be present in the SRM Service role's stderr.log:
o.dropwizard.configuration.ConfigurationParsingException: /var/run/cloudera-scm-agent/process/132-streams_replication_manager-STREAMS_REPLICATION_MANAGER_SERVICE/srm-service.yaml has an error: * Malformed YAML at line: 66, column: 49; mapping values are not allowed here in 'reader', line 65, column 48: . .; None
CDPD-60426: Configuration changes are lost following a rolling restart of the service: In certain cases, SRM might fail to apply configuration updates if the service is restarted with a rolling restart. In a case like this, configuration changes are ignored without any warning or indication. This issue also affects rolling upgrades.; When restarting the service, use Actions > > Restart instead of Actions > > Rolling Restart after making configuration changes. When upgrading a cluster, ensure that SRM is not restarted with a rolling restart.

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 [***CONFIG LEVEL PREFIX***].isolation.level=read_committed to the Streams Replication Manager's Replication Configs SRM service property in Cloudera Manger. The isolation.level property can be set on a global connector or replication level. For example:
#Global connector level connectors.consumer.isolation.level=read_committed #Replication level uswest->useast.consumer.isolation.level=read_committed
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.