Message Queue for Apache Kafka regulates and sets constraints for some metrics. To avoid program exceptions when you use Message Queue for Apache Kafka, do not exceed the maximum limits. The following table describes the limits of relevant items.
|Auto creation of topics and consumer groups||Supported
Note To enable auto creation of topics and consumer groups, please submit a ticket.
|Auto creation of topics and consumer groups facilitates usage but increases the O&M difficulty and may cause system instability. In Message Queue for Apache Kafka, topics and consumer groups must be authenticated. We recommend that you create topics and consumer groups by using the following methods:|
|Total topic (partition) quantity limit||Supported||In Message Queue for Apache Kafka, messages are stored and scheduled by partition. If messages are stored in a large number of topics (partitions), storage fragmentation occurs, which reduces the cluster performance and stability.|
|Reduction in the number of partitions of a topic||Not supported||This is due to design constraints of Message Queue for Apache Kafka.|
|Exposed ZooKeeper||Not supported||ZooKeeper has been masked since Message Queue for Apache Kafka 0.9.0. Therefore, you do not need to access ZooKeeper to use the client. In Message Queue for Apache Kafka, ZooKeeper is partially shared. For security purposes, it is not exposed. You do not need to learn about ZooKeeper.|
|Topic-based authentication||Not supported||Topic-based authentication relies on ZooKeeper. Message Queue for Apache Kafka is deployed in virtual private clouds (VPCs) and provides sufficient security protection with the security group and whitelist features.|
|Logon to the machines on which Message Queue for Apache Kafka is deployed||Not supported||None|
|Consumer group count||The consumer group count is twice the topic count.||For example, if an instance has 50 topics, you can create up to 100 consumer groups in this instance. If you need to increase the number of consumer groups, you can increase the number of topics. The number of consumer groups is increased by two each time a topic is added. For more information, see Upgrade instance specifications.|
|Relationship between the topic count and partition count||1:16||In addition to the default number of partitions, 16 partitions are added for each additional topic. For example, if you purchased an instance with 50 topics, 20 Mbit/s peak traffic, and 400 partitions by default, after you add 10 topics, 160 partitions are added to this instance, and the total number of partitions becomes 560.|
|Number of topics of a Professional Edition instance||The number of topics of a Professional Edition instance is twice the number of purchased topics.||For example, if you purchase a Professional Edition instance with 50 topics, the actual number of topics you can create in the instance is 100.|
|Change of the region or network properties of an instance||Not supported||After you have purchased and deployed an instance, its region and network properties are closely integrated with its physical resources and cannot be changed. If you need to change the region or network properties of an instance, release the instance and purchase a new instance.|
|Message size||10 MB||The maximum size of a message is 10 MB. A message larger than 10 MB cannot be sent.|