Alibaba Cloud Message Service (MNS) is a distributed messaging service that features scalability, high efficiency, reliability, security, and availability. This topic describes the precautions, configuration process, and message consumption of reliable MNS event notifications.

Background information

  • MNS provide queues to support a large number of concurrent access requests from multiple producers and consumers. After a message is pulled from a queue, the message cannot be pulled again for a specified duration of time. A message is invisible for a period of time after it is consumed. If you do not manually delete the message, it can be consumed again. For more information, see What is MNS?
  • ApsaraVideo VOD supports event notifications for multiple storage regions. You can configure the callback methods and callback URLs for event notifications for each region. You can upload videos to different storage regions. After a video is processed (for example, uploaded or transcoded), ApsaraVideo VOD notifies you of the processing results based on the callback configurations for the regions and pushes messages to your MNS queues.

Precautions

  • When the MNS callback method is used, if a message cannot be pushed to an MNS queue because ApsaraVideo VOD is not authorized to access MNS, if the MNS endpoint is not a public endpoint, or if the queue name is incorrect, ApsaraVideo VOD retries the push two more times. ApsaraVideo VOD attempts to push the message to the queue a maximum of three times. If the message still fails to be pushed to the queue, ApsaraVideo VOD discards the message.
  • Recommended regions for message queues:
    • If your video is stored in a mainland China region, we recommend that you push the message to a queue in the China (Shanghai) region. If you push the message to a queue in a region other than China (Shanghai), you may experience a short delay.
    • If your video is stored in a region such as Singapore or Indonesia that is outside mainland China, we recommend that you create or use a message queue in that region.

      For example, if your video is stored in the India (Mumbai) region, you must create or use a queue in the India (Mumbai) region.

Configure the reliable MNS event notification

  1. Log on to the Alibaba Cloud Management Console and go to the Cloud Resource Access Authorization page to authorize ApsaraVideo VOD to access your cloud resources. Click Confirm Authorization Policy in the lower part of the page.
    Cloud Resource Access Authorization
  2. Log on to the MNS console to create a queue or use an existing queue. For more information, see Manage queues in the console.
    Note If your video is stored in a mainland China region, we recommend that you select China (Shanghai) from the drop-down list.
  3. Call the SetMessageCallback operation to configure the event notification.
    • The MnsEndpoint parameter specifies the public endpoint of the queue. You can obtain the endpoint by clicking Get Endpoint in the upper-right corner of the Queues page.
    • The EventTypeList parameter specifies the event type. For more information, see the "Event types" section in Overview.
  4. After you complete the event notification configurations, log on to the ApsaraVideo VOD console and upload a video to trigger an event notification.
  5. When the conditions for generating a callback event are met, ApsaraVideo VOD pushes a callback message to the queue that you specified. In the MNS console, click Receive Message in the Action column corresponding to the queue and view the message in the Receive Message dialog box.

Message consumption

After you complete the configurations, you can use code to consume messages.

MNS queues support a large number of concurrent access requests from multiple producers and consumers. After a message is pulled from a queue, the message cannot be pulled again within a specified period of time. A message is invisible for a period of time after it is consumed. You must manually delete the message. Otherwise, the message can be consumed again.