Notes and Constraints

Kafka ZooKeeper

Kafka clusters are managed using ZooKeeper. Opening ZooKeeper may cause misoperations and service losses. Currently, ZooKeeper is used only within Kafka clusters and does not provide services externally.

Version

• The service version can be 1.1.0, 2.3.0, or 2.7. Kafka instances cannot be upgraded once they are created.
• Clients later than version 0.10 are supported. Use a version that is consistent with the service version.

Logging in to the VM where the Kafka brokers reside

Not supported

VPC and subnet

After an instance is created, its VPC and subnet cannot be modified.

Kerberos authentication

Not supported

Total number of topic partitions

The total number of topic partitions is related to the instance specifications. For details, see Specifications.

Kafka manages messages by partition. If there are too many partitions, message creation, storage, and retrieval will be fragmented, affecting the performance and stability. If the total number of partitions of topics reaches the upper limit, you cannot create more topics.

Number of partitions in a topic

The number of partitions in a topic can be increased but cannot be decreased.

Topic quantity

The topic quantity is related to the total number of topic partitions and number of partitions in each topic. For details, see Specifications.

Automatic topic creation

Supported. If automatic topic creation is enabled, the system automatically creates a topic when a message is created in or retrieved from a topic that does not exist. This topic has the following default settings: 3 partitions, 3 replicas, aging time 72 hours, and synchronous replication and flushing disabled.

After you change the value of the log.retention.hours, default.replication.factor, or num.partitions parameter, automatically created topics later use the new value. For example, if num.partitions is set to 5, an automatically created topic will have the following settings: 5 partitions, 3 replicas, aging time 72 hours, and synchronous replication and flushing disabled.

Decreasing partition quantity

The partition quantity cannot be decreased due to the limitations of Apache Kafka.

Synchronous replication

If a topic has only one replica, synchronous replication cannot be enabled.

Replica quantity

Single-replica topics are not recommended. If an instance node is faulty, an internal service error may be reported when you query messages in a topic with only one replica. Therefore, you are not advised to use a topic with only one replica.

Aging time

The value of the log.retention.hours parameter takes effect only if the aging time has not been set for the topic.

For example, if the aging time of Topic01 is set to 60 hours and log.retention.hours is set to 72 hours, the actual aging time of Topic01 is 60 hours.

Batch importing and exporting topics

Batch export is supported, but batch import is not supported.

Topic name

If a topic name starts with a special character, for example, an underscore (_) or a number sign (#), monitoring data cannot be displayed.

Delay queues

Not supported

Creating consumer groups, consumers, and producers

Consumer groups, consumers, and producers are generated automatically when you use the instance.

Resetting the consumer offset

Messages may be retrieved more than once after the offset is reset.

Consumer group name

If a consumer group name starts with a special character, for example, an underscore (_) or a number sign (#), monitoring data cannot be displayed.

Message size

The maximum length of a message is 10 MB. If the length exceeds 10 MB, the production fails.