Notes and Constraints

DMS for Kafka has the following constraints, as listed in Table 1.

**Table 1** Kafka usage restrictions
Item	Constraint	Description
Kafka ZooKeeper	Not exposed externally	DMS ZooKeeper does not provide services externally. It is only used to serve Kafka instances.
Version	The service version can be 1.1.0, 2.3.0, or 2.7.	Clients later than version 0.10 are supported. Use a version that is consistent with the service version.
Message size	10 MB	The message size cannot exceed 10 MB. Otherwise, the message creation will fail.
Logging in to the VM where the Kafka brokers reside	No supported	N/A
Partition quantity	Limited	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.
Automatic topic creation	Supported	Configurable during instance creation. If it is enabled, a topic will be automatically created with 3 partitions and 3 replicas when a message is created in or retrieved from a topic that does not exist.
Creating consumer groups, consumers, and producers	Not required	Consumer groups, consumers, and producers are generated automatically when you use the instance.
Decreasing partition quantity	Not supported	The partition quantity cannot be decreased due to the limitations of Apache Kafka.