Auto Scaling provides the event notification feature to help you monitor the scaling events that happen in your scaling group. After you create event notifications for your scaling group, Auto Scaling sends notifications to CloudMonitor or Message Service (MNS). This allows you to obtain dynamic information about your scaling group at the earliest opportunity, and your scaling group can be automatically managed.

Event notification methods

Auto Scaling allows you to create event notifications and configure notifications for your scaling group. After you create event notifications, the system intelligently manages the scaling events in your scaling group. If you configure notifications, you must manually manage the scaling events in your scaling group.

  • Create Event Notification: Auto Scaling sends notifications to CloudMonitor, MNS topics, or MNS queues after scaling activities are executed in the scaling group.
    • In CloudMonitor, you can query and view statistics on system events of various cloud services, including Auto Scaling. This allows you to obtain the status of your scaling group at the earliest opportunity. For more information about the event monitoring feature of CloudMonitor, see View cloud service events.
    • MNS provides two service models: MNS topic and MNS queue. MNS is a distributed message service that helps you transfer data and messages among distributed components, and build loosely coupled systems. For more information about the MNS topics and queues, see What is MNS?.
      • The MNS queue is a point-to-point messaging model that supports concurrent communications with high reliability. The MNS queue model is suitable when you need to send a message to only one message consumer.
      • The MNS topic is a publish/subscribe messaging model. The publisher produces messages to a topic, and then all subscribers that are subscribed to the topic receive and consume the messages. In the MNS topic model, messages can be pushed to subscribers by using various methods and to multiple servers. Subscribers can receive messages from various channels.
  • Configure Notification: Auto Scaling sends notifications by SMS, internal messages, and email after a scaling activity succeeds, fails, or is rejected in your scaling group. After you receive the messages, you must manually rectify issues if exceptions occur. For more information, see Set notification receiving.
    Note After you create event notifications for a scaling group, you cannot configure notifications in the scaling group. Before you configure notifications for the scaling group, you must delete all existing event notifications.

Event notification examples

The following section provides examples on event notifications. For information about how to create an event notification, see Create an event notification.

  • Event notifications by using CloudMonitor

    In this example, Notification Method is set to CloudMonitor, and Event Notification Type is set to Successful Scale-out Event and Start of Scale-out Event. After the scale-out activity is executed, CloudMonitor receives an event notification and displays the event. In the following figure, the events that a scale-out activity starts and the scale-out activity succeeds are displayed.

    Event notification overview - Event notifications by using CloudMonitor
    Note In the CloudMonitor console, you can obtain dynamic information about your scaling group. You can also create alert rules. This way, CloudMonitor sends alert notifications to contacts by SMS or email at the same time if alerts are reported, which improves O&M efficiency.
  • Event notifications by using MNS topics

    In this example, Notification Method is set to MNS Topic, the MNS topic that is created in the region in which the scaling group resides is selected, and Event Notification Type is set to Successful Scale-in Event and Start of Scale-in Event. After the scale-in activity is executed, Auto Scaling sends notifications to the MNS topic, and the MNS topic then pushes the messages to its subscribers. In the following figure, a scale-in activity is executed. In the figure, the number of messages that corresponds to the MNS topic increases. You can click View Subscriptions to view message details.

    The MNS topic does not support the direct consumption of messages. You must subscribe to the MNS topic through an MNS queue, HTTP request, or email. When the MNS topic receives a message, the MNS topic pushes the message to subscribers. This way, multiple subscribers separately consume messages from the same publisher, which increases the efficiency of automatic management.

    Event notification overview - Event notifications by using MNS topics
  • Event notifications by using MNS queues

    In this example, Notification Method is set to MNS Queue, the MNS queue that is created in the region in which the scaling group resides is selected, and Event Notification Type is set to Failed Scale-out Event and Start of Scale-out Event. After the scale-out activity fails, Auto Scaling sends notifications to the MNS queue and allows contacts to configure and consume the message. In the following figure, a scale-out activity fails to be executed. In the figure, the number of available messages that correspond to the MNS queue increases.

    You can consume, delay, activate, or delete the messages based on your business requirements. You can manage the messages in a flexible manner.

    Event notification overview - Event notifications by using MNS queues

Operations related to event notifications

The following table describes the operations related to event notifications in different scenarios.

Scenario References
If you want Auto Scaling to send notifications to CloudMonitor, MNS topics, and MNS queues after a scaling activity is executed in your scaling group, you can create an event notification. If you want Auto Scaling to send notifications to you by internal messages or email after a scaling activity is executed in your scaling group, and you want to manually rectify issues after you receive the messages, you can configure a notification.
If you want to view message details, you can switch from the Auto Scaling console to the CloudMonitor console or the MNS console. Manage event notifications
If the event notification type in your scaling group no longer meets your business requirements, you can simply change the event notification type. You do not need to create a new event notification.
Note You cannot change the notification method when you modify event notification settings.
Modify an event notification
If you no longer need an event notification that you created or configured, you can delete the event notification. Delete an event notification