Notes and Constraints

This section describes the notes and constraints on DMS.

Instance

Table 1 Instance notes and constraints

Item	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 2.3.0, 2.7, or 3.x. 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
Storage	The storage space can be expanded but cannot be reduced. You can expand the storage space up to 20 times.
Broker quantity	The broker quantity can be increased but cannot be decreased.
Broker flavor	The broker flavor can be increased but cannot be decreased. Single-replica topics do not support message production during this period. Services will be interrupted. If a topic has multiple replicas, scaling up the broker flavor does not interrupt services, but may cause disorder of partition messages. Evaluate this impact and avoid peak hours. Broker rolling restarts will cause partition leader changes, interrupting connections for less than a minute when the network is stable. For multi-replica topics, configure the retry mechanism on the producer client.
VPC, subnet, and AZ	After an instance is created, its VPC, subnet, and AZ cannot be modified.
Kerberos authentication	Not supported
Client connections from each IP address	Each Kafka broker allows a maximum of 1000 connections from each IP address by default. Excess connections will be rejected.

Topic

Table 2 Topic notes and constraints

Item	Notes and Constraints
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	Based on the open-source Kafka constraints, 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 this option is enabled, a topic will be automatically created when a message is produced in or consumed from a topic that does not exist. By default, the topic has the following parameters: Partitions: 3 Replicas: 3 Aging Time: 72 Synchronous Replication and Synchronous Flushing disabled Message Timestamp: CreateTime Max.Message Size (bytes): 10,485,760 After you change the value of the log.retention.hours, default.replication.factor, or num.partitions parameter, the value will be used in later topics that are automatically created. For example, assume that num.partitions is changed to 5, an automatically created topic has the following parameters: Partitions: 5 Replicas: 3 Aging Time: 72 Synchronous Replication and Synchronous Flushing disabled Message Timestamp: CreateTime Max.Message Size (bytes): 10,485,760
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
Broker faults	When some brokers of an instance are faulty, topics cannot be created, modified, or deleted, but can be queried.

Consumer Group

Table 3 Consumer group notes and constraints

Item	Notes and Constraints
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.
Broker faults	When some instance brokers are faulty, consumer groups cannot be created or deleted, or consumption progress cannot be reset, but consumer groups can be queried.

Message

Table 4 Message notes and constraints

Item	Notes and Constraints
Message size	The maximum length of a message is 10 MB. If the length exceeds 10 MB, the production fails.

User

Table 5 User notes and constraints

Item	Notes and Constraints
Number of users	The maximum users that can be created for a Kafka instance is 20 or 500. Check the console for the actual limit.
Broker faults	When some instance brokers are faulty, users cannot be created or deleted, or password cannot be reset, but users can be queried.

last updated: 2024-11-13 14:47 UTC - commit: bab3492e4e325ec745b7b7fa1576930332ed8243