MQTT sessions Maximum client sessions per authentication name = 1, exceed in specific client

The “QuotaExceeded” error that the specific clients are experiencing could be due to the session overflow condition in the Azure Event Grid MQTT broker. When the maximum client sessions per authentication name is set to 1, if a client tries to connect while its previous session is still active, the connection request will be rejected. This can happen if the clients did not properly disconnect from their previous sessions or if they are still holding onto unacknowledged messages in their session queue.

Additionally, if the clients had previously connected with a session limit of 2 and are now trying to connect with the limit reverted to 1, they may still have an active session that is preventing them from establishing a new connection. The MQTT broker maintains a queue of messages for each active session, and if the session queue reaches its limit, it can lead to a termination of the session, which might also contribute to the issue.

To resolve this, ensure that the clients are properly disconnecting from their sessions and that there are no lingering active sessions that could be causing the quota to be exceeded. You may also want to check the session limits and ensure that they are configured correctly in the Azure portal.

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