This topic describes the limits of ApsaraMQ for Kafka. To prevent the program from exiting unexpectedly when you use ApsaraMQ for Kafka, do not exceed the limits.
Important The service-level agreement (SLA) does not apply for instability that is caused due to the fact that your instance configurations exceed the limits.
The following table describes the limits of ApsaraMQ for Kafka.
| Item | Limit | Description |
|---|---|---|
| Maximum number of topics or partitions | Supported. | Messages are stored and scheduled based on partitions in ApsaraMQ for Kafka. Each topic consists of multiple partitions. If an excessive number of topics or partitions exist, storage fragmentation occurs. This reduces the performance and stability of your cluster. |
| Decrease in the number of partitions in a topic | Not supported. | This is due to the constraints in the design of Apache Kafka. |
| Exposed ZooKeeper | Not supported. | You do not need to access ZooKeeper on your client to use Apache Kafka V0.9.0 and later. In ApsaraMQ for Kafka, ZooKeeper is partially shared. For security purposes, it is not exposed. You do not need to understand how ZooKeeper works. |
| Logons to the machines on which ApsaraMQ for Kafka is deployed | Not supported. | None. |
| Supported versions | V0.10.x to V2.2.x. |
|
| Partition-to-topic ratio | 1:1. | The number of available topics equals the total number of partitions in an instance. For example, if your alikafka.hw.2xlarge instance provides 1,050 partitions (50 purchased and 1,000 provided free of charge), the number of available topics is 1,050. |
| Partition-to-consumer group ratio | 1:2. | The number of available consumer groups is closely related to the total number of partitions. For example, if your alikafka.hw.2xlarge instance provides 1,050 partitions (50 purchased and 1,000 provided free of charge), the number of available consumer groups is 2,100. |
| Change of the region for an instance | Not supported. | After an instance is purchased and deployed, its region is closely associated with the physical resources and cannot be changed. If you want to change the region of an instance, release the instance and purchase a new instance. |
| Change of the network properties for an instance | Supported. | You can modify the network properties of an instance based on your business requirements. For more information, see Upgrade instance specifications. |
| 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 has a latency of 1 minute. |
| Number of client connections to each broker | 1,000. | ApsaraMQ for Kafka clients must establish socket connections to brokers to send or consume messages. If the number of client connections to a broker exceeds 1,000, the broker occupies a large number of resources to maintain the connections. This can compromise the stability of the broker. We recommend that you establish no more than 1,000 client connections to each broker. |
| Endpoint | Determined by the edition purchased. |
|
| Setting of the cloud disk to one partition | Supported. However, this may cause service unavailability during broker downtime or service upgrade. | We recommend that you set more than one partition. If your application requires you to set only one partition, we recommend that you use local storage. Note You can set the Storage Engine parameter to Local Storage only when you create a topic for Professional Edition instances. |
Note The latest version of ApsaraMQ for Kafka does not allow you to purchase instances based on the number of topics. If your existing instances were purchased based on the number of topics, the number of available partitions is the number of topics multiplied by 16, and the number of consumer groups is twice the number of topics. For a Professional Edition instance purchased based on the number of topics, the number of available topics is twice the number of purchased topics.