Notes and Constraints
This section describes the notes and constraints on DMS for Kafka.
Instance
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 |
|
Logging in to the VM where the Kafka brokers reside |
Not supported |
Storage |
|
Bandwidth or broker quantity |
The bandwidth and broker quantity can be increased but cannot be decreased. |
Broker flavor |
|
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 |
For instances purchased in July 2020 and later, each Kafka broker allows a maximum of 1000 connections from each IP address by default. For instances purchased before July 2020, each Kafka broker allows a maximum of 200 connections from each IP address by default. Excess connections will be rejected. |
Topic
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:
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:
|
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, 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
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, a number sign (#), monitoring data cannot be displayed. |
Broker faults |
When some instance brokers are faulty, consumer groups cannot be created, modified, or deleted, or consumption progress cannot be reset, but consumer groups can be queried. |
Message
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
Item |
Notes and Constraints |
---|---|
Number of users |
For Kafka instances created before July 15, 2023, a maximum of 20 users can be created for each instance. For Kafka instances created since July 15, 2023, a maximum of 500 users can be created for each instance. |
Broker faults |
When some instance brokers are faulty, users cannot be created, modified, or deleted, or password cannot be reset, but users can be queried. |
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