Message Queue for Apache Kafka sets limits for some metrics. To avoid program exceptions when you use Message Queue for Apache Kafka, do not exceed the limits. The following table describes the limits.
|Automatic creation of topics and consumer groups||Supported
Note To enable automatic creation of topics and consumer groups, submit a ticket.
|Automatic 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 number of topics (partitions)||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. This reduces cluster performance and stability.|
|Reduction in the number of partitions of a topic||Not supported||This is due to the 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 by using security groups and whitelists.|
|Log on to the machines on which Message Queue for Apache Kafka is deployed||Not supported||None.|
|Number of consumer groups||The number of consumer groups can be twice the number of topics.||For example, if an instance has 50 topics, you can create up to 100 consumer groups in this instance. 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 the instance configuration.|
|Relationship between the number of topics and partitions||1:16||In addition to the default number of partitions, 16 partitions are added for each additional topic. For example, assume that you have purchased a Standard Edition (High Write) instance with 50 topics, 2xlarge traffic, and 400 partitions by default. If you purchase another 10 topics for this instance, 160 additional partitions are added to this instance. The total number of partitions becomes 560.|
|Number of topics of a Professional Edition instance||The number of topics of a Professional Edition instance can be twice the number of purchased topics.||For example, if you purchase a Professional Edition instance with 50 topics, you can create 100 topics in the instance.|
|Changes to the region or network properties of an instance||Not supported||After an instance is purchased and deployed, its region and network properties are closely associated 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.|
|Monitoring and alerting||Supported||The data latency is one minute.|