This topic describes the limits that are set on server-side subscriptions.
Limits on AMQP subscriptions
|Authentication timeout||An authentication request is sent immediately after a connection is established. If the authentication fails within 15 seconds, the server ends the connection.|
|Data timeout||When a server establishes a connection with IoT Platform, the heartbeat timeout period
(the idle-timeout parameter in AMQP) must be specified. The timeout period ranges
from 30 to 300 seconds. If no frame is transmitted over the connection after the heartbeat
timeout period expires, IoT Platform ends the connection.
After the connection is established, the server must send ping packets within the heartbeat timeout period to maintain the connection. If no ping packet is sent within the heartbeat time, IoT Platform ends the connection.
Note If the connection is established by using an Alibaba Cloud SDK, the server does not need to send ping packets to maintain the connection. During the keep-alive time that is provided by the SDK, make sure that the main process does not exit.
|Policy for message pushing retries||
Messages may not be consumed in real time due to some issues. In this case, these messages are accumulated. These issues include that consumers disconnect from IoT Platform and the speed at which these messages are consumed is slow.
|Maximum number of saved messages||A consumer group can retain a maximum of 100 million messages.|
|Message retention period||One day.|
|Maximum push rate for real-time messages||A consumer group can process a maximum of 1,000 queries per second (QPS).|
|Maximum push rate for accumulated messages||A consumer group can process a maximum of 200 QPS.
Note To prevent a large number of accumulated messages, make sure that consumers are connected to IoT Platform. You must also make sure that these consumers send ACK responses to messages that are pushed by IoT Platform in a timely manner.
|Maximum number of consumer groups with which a product can be associated||10.|
|Maximum number of products with which a consumer group can be associated||1,000.|
|Maximum number of consumer groups||An account can create a maximum of 1,000 consumer groups.|
|Maximum number of consumers||A consumer group can have a maximum of 64 consumers.|
|Maximum connection requests||A consumer can issue a maximum of 100 connection requests within 1 minute.
Note Consumers correspond to AMQP clients that are used to receive IoT Platform messages. These consumers are not devices.
Limits on MNS subscriptions
For more information about the limits of Message Service (MNS) server-side subscriptions, see the limits of MNS queues in the MNS limits topic.
- After you create an MNS server-side subscription, you are charged for the usage of MNS queues regardless of whether IoT Platform forwards messages to MNS queues.
- The maximum size of a message that can be received by an MNS queue is 64 KB. If the size of a message exceeds the limit, the message is discarded.