Cloudera Docs

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-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 allowlist 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-11079: Blacklisted topics appear in the list of replicated topics
If a topic was originally replicated but was later disallowed (blacklisted), 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, the disallowed topic will be included in the response. Additionally, the disallowed 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
CDPD-60823: Configuring the SRM Client's secure storage is mandatory for unsecured environments
In an unsecured environment the srm-control tool should not need any additional configuration to run. However, due to an issue with the automatic generation of the default configuration, configuring the SRM Client's secure storage is mandatory for the srm-control tool. This is true even if none of the clusters that the tool connects to are secured.
If a secure storage is not configured, the tool will fail with the following NullPointerException:
java.lang.NullPointerException
at com.cloudera.dim.mirror.SecureConfigProvider.retrievePassword(SecureConfigProvider.java:99)
at com.cloudera.dim.mirror.SecureConfigProvider.configure(SecureConfigProvider.java:113)
at org.apache.kafka.common.config.AbstractConfig.instantiateConfigProviders(AbstractConfig.java:533)
at org.apache.kafka.common.config.AbstractConfig.resolveConfigVariables(AbstractConfig.java:477)
at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:107)
at org.apache.kafka.common.config.AbstractConfig.<init>(AbstractConfig.java:142)
at org.apache.kafka.connect.mirror.MirrorMakerConfig.<init>(MirrorMakerConfig.java:88)
at com.cloudera.dim.mirror.MirrorControlCommand$SourceTargetCommand.init(MirrorControlCommand.java:97)
at com.cloudera.dim.mirror.MirrorControlCommand.issueCommand(MirrorControlCommand.java:369)
at com.cloudera.dim.mirror.MirrorControlCommand.main(MirrorControlCommand.java:346)
Configure a secure storage password and set it as an environment variable in your CLI session before running the srm-control tool.
  1. In Cloudera Manager, select the Streams Replication Manager service.
  2. Go to Configuration.
  3. Find and configure the SRM Client's Secure Storage Password property.

    Take note of the password that you configure.

  4. Click Save changes.

  5. Restart the SRM service
  6. SSH into one of the SRM hosts in your cluster.
  7. Set the secure storage password as an environment variable.
    export [***SECURE STORAGE ENV VAR***]=”[***SECURE STORAGE PASSWORD***]”
    Replace [***SECURE STORAGE ENV VAR***] with the name of the environment variable you specified in Environment Variable Holding SRM Client's Secure Storage Password. Replace [***SRM SECURE STORAGE PASSWORD***] with the password you specified in SRM Client's Secure Storage Password. For example:
    export SECURESTOREPASS=”mypassword”
OPSAPS-61001: Saving configuration changes for SRM is not possible
Cloudera Manager incorrectly labels the SRM Client's Secure Storage Password property as mandatory. Moreover, it does not offer this property for configuration when SRM is installed with the Add Service Wizard.

As a result, it is possible to install and start SRM without configuring this property. However, in a case like this, making changes to SRM's configuration is not possible until the SRM Client's Secure Storage Password property is set.

Configure the SRM Client's Secure Storage Password property.
OPSAPS-61814: Using the service dependency method to configure Kerberos enabled co-located clusters is not supported
Using the Streams Replication Manager Co-located Kafka Cluster Alias property to auto-configure the connection to a Kerberos enabled co-located Kafka cluster is not supported. In a case like this, the generated JAAS configuration contains host-specific configuration. This causes SRM to fail to connect to the co-located Kafka cluster on other hosts.
Define your co-located Kafka clusters using Kafka credentials. For more information, see Defining co-located Kafka clusters using Kafka credentials. Alternatively, use the Streams Replication Manager's Replication Configs property to configure the connection to the co-located Kafka clusters.
OPSAPS-63992: Rolling restart unavailable for SRM
Initiating a rolling restart for the SRM service is not possible. Consequently, performing a rolling upgrade of the SRM service is also not possible.
None
CDPD-31745: SRM Control fails to configure internal topic when target is earlier than Kafka 2.3
When the target Kafka cluster of a replication is earlier than version 2.3, the srm-control internal topic is created with an incorrect configuration (cleanup.policy=compact). This causes the srm-control topic to lose the replication filter records, causing issues in the replication.
After a replication is enabled where the target Kafka cluster is earlier than 2.3, manually configure all srm-control.[***SOURCE CLUSTER ALIAS***].internal topics in the target cluster to use cleanup.policy=compact.
CDPD-31235: Negative consumer group lag when replicating groups through SRM

SRM checkpointing reads the offset-syncs topic to create offset mappings for committed consumer group offsets. In some corner cases, it is possible that a mapping is not available in offset-syncs. In a case like this SRM simply copies the source offset, which might not be a valid offset in the replica topic.

One possible situation is if there is an empty topic in the source cluster with a non-zero end offset (for example, retention already removed the records), and a consumer group which has a committed offset set to the end offset. If replication is configured to start replicating this topic, it will not have an offset mapping available in offset-syncs (as the topic is empty), causing SRM to copy the source offset.

This can cause issues when automatic offset synchronization is enabled, as the consumer group offset can be potentially set to a high number. SRM never rewinds these offsets, so even when there is a correct offset mapping available, the offset will not be updated correctly.

After offset mappings are created, stop the consumers of the group and set the committed offsets of the group to the end of the topic on the target cluster with this command:
kafka-consumer-groups --bootstrap-server [***HOST***]:[***PORT***] --group [***GROUP***] --topic [***SOURCE CLUSTER ALIAS***].[***TOPIC***] --reset-offsets --to-latest --execute
Alternatively, set it to the beginning of the topic with this command:
kafka-consumer-groups --bootstrap-server [***HOST***]:[***PORT***] --group <group> --topic [***SOURCE CLUSTER ALIAS***].[***TOPIC***] --reset-offsets --to-earliest --execute
OPSAPS-62546: Kafka External Account SSL keypassword configuration is used incorrectly by SRM
When a Kafka External Account specifies a keystore that uses an SSL key password, SRM uses it as the ssl.keystore.key configuration. Due to using the incorrect ssl.keystore.key configuration, SRM will fail to load the keystore in certain cases.
Workaround: For the keystores used by the Kafka External Accounts, the SSL key password should match the SSL keystore password, and the SSL keystore key password should not be provided. Alternatively, you can use the legacy connection configurations based on the streams.replication.manager.configs to specify the SSL key password.

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.
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.