This topic describes how CloudMonitor automatically processes the status change events of Elastic Compute Service (ECS) instances by using Message Service (MNS) queues.


  • A queue is created in the MNS console, for example, ecs-cms-event.

    For more information, see Create a queue.

  • A system event-triggered alert rule is created in the CloudMonitor console.

    For more information, see Create a system event-triggered alert rule.

  • Python dependencies are installed.

    All the code in this topic is written in Python 3.6. You can also use other programming languages, such as Java and PHP.

    For more information, see Install Cloud Monitor SDK for Python.

Background information

In addition to the existing system events, CloudMonitor supports the status change events for ECS. The status change events include interruption notification events that are applied to preemptible instances. A status change event is triggered when the status of an ECS instance changes. The status changes can be caused by operations that you perform in the ECS console and by calling API operations or using SDKs, auto scaling, overdue payments, and system exceptions.

CloudMonitor provides the following notification methods for system events: MNS queues, Function Compute, callback URLs, and Log Service. This topic uses MNS queues as an example to describe three best practices about how CloudMonitor automatically processes the status change events of ECS instances.


CloudMonitor sends all status change events of ECS instances to MNS. MNS receives messages and handles the messages.

  • Practice 1: Record all creation and release events of ECS instances
    You cannot query ECS instances that have been released in the ECS console. If you need to query released ECS instances, you can store status change events of all ECS instances in a database or Log Service. When an ECS instance is created, CloudMonitor sends a Pending event. When an ECS instance is released, CloudMonitor sends a Deleted event.
    1. Create a Conf file.
      The Conf file must contain the following parameters: endpoint, access_key, access_key_secret, region_id (for example, cn-beijing), and queue_name.
      Note To obtain the endpoint, you can log on to the MNS console, go to the Queues page, and then click Get Endpoint.
      class Conf:
          endpoint = 'http://<id>.mns.<region>'
          access_key = '<access_key>'
          access_key_secret = '<access_key_secrect>'
          region_id = 'cn-beijing'
          queue_name = 'test'
          vsever_group_id = '<your_vserver_group_id>'
    2. Use the MNS SDK to develop an MNS client for receiving messages from MNS.
      # -*- coding: utf-8 -*-
      import json
      from mns.mns_exception import MNSExceptionBase
      import logging
      from mns.account import Account
      from . import Conf
      class MNSClient(object):
          def __init__(self):
              self.account =  Account(Conf.endpoint, Conf.access_key, Conf.access_key_secret)
              self.queue_name = Conf.queue_name
              self.listeners = dict()
          def regist_listener(self, listener, eventname='Instance:StateChange'):
              if eventname in self.listeners.keys():
                  self.listeners[eventname] = [listener]
          def run(self):
              queue = self.account.get_queue(self.queue_name)
              while True:
                      message = queue.receive_message(wait_seconds=5)
                      event = json.loads(message.message_body)
                      if event['name'] in self.listeners:
                          for listener in self.listeners.get(event['name']):
                  except MNSExceptionBase as e:
                      if e.type == 'QueueNotExist':
                          logging.error('Queue %s not exist, please create queue before receive message.', self.queue_name)
                          logging.error('No Message, continue waiting')
      class BasicListener(object):
          def process(self, event):

      The preceding code is used to receive messages from MNS and delete the messages after the listener is called to consume the messages.

    3. Register a listener to consume events. The following listener generates a log entry after it receives a Pending or Deleted event.
       # -*- coding: utf-8 -*-
      import logging
      from .mns_client import BasicListener
      class ListenerLog(BasicListener):
          def process(self, event):
              state = event['content']['state']
              resource_id = event['content']['resourceId']
              if state == 'Panding':
        'The instance {resource_id} state is {state}')
              elif state == 'Deleted':
        'The instance {resource_id} state is {state}')
      Add the following code to the Main function:
      mns_client = MNSClient()

      In the production environment, you can store the events in a database or Log Service for subsequent queries and audits.

  • Practice 2: Automatically restart ECS instances that are shut down

    In scenarios where ECS instances may be shut down unexpectedly, you may need to automatically restart the ECS instances.

    You can reuse the MNS client developed in Practice 1 and create another listener. When you receive a Stopped event for an ECS instance, you can run the start command on the ECS instance to start it.

    # -*- coding: utf-8 -*-
    import logging
    from aliyunsdkecs.request.v20140526 import StartInstanceRequest
    from aliyunsdkcore.client import AcsClient
    from .mns_client import BasicListener
    from .config import Conf
    class ECSClient(object):
        def __init__(self, acs_client):
            self.client = acs_client
        # Start the ECS instance.
        def start_instance(self, instance_id):
  'Start instance {instance_id} ...')
            request = StartInstanceRequest.StartInstanceRequest()
    class ListenerStart(BasicListener):
        def __init__(self):
            acs_client = AcsClient(Conf.access_key, Conf.access_key_secret, Conf.region_id)
            self.ecs_client = ECSClient(acs_client)
        def process(self, event):
            detail = event['content']
            instance_id = detail['resourceId']
            if detail['state'] == 'Stopped':

    In the production environment, you can listen to Starting, Running, or Stopped events after the start command is run. Then, you can perform further O&M by using a timer and a counter based on whether the ECS instance is started.

  • Practice 3: Automatically remove preemptible instances from SLB before they are released

    An interruption notification event is triggered about 5 minutes before a preemptible instance is released. During the 5 minutes, you can perform specific operations to prevent your services from being interrupted. For example, you can remove the preemptible instance from a Server Load Balancer (SLB) instance.

    You can reuse the MNS client developed in Practice 1 and create another listener. When the listener receives the interruption notification event for a preemptible instance, you can call the SLB SDK to remove the preemptible instance from an SLB instance.

    # -*- coding: utf-8 -*-
    from aliyunsdkcore.client import AcsClient
    from aliyunsdkcore.request import CommonRequest
    from .mns_client import BasicListener
    from .config import Conf
    class SLBClient(object):
        def __init__(self):
            self.client = AcsClient(Conf.access_key, Conf.access_key_secret, Conf.region_id)
            self.request = CommonRequest()
            self.request.add_query_param('RegionId', Conf.region_id)
        def remove_vserver_group_backend_servers(self, vserver_group_id, instance_id):
            self.request.add_query_param('VServerGroupId', vserver_group_id)
                                         "[{'ServerId':'" + instance_id + "','Port':'80','Weight':'100'}]")
            response = self.client.do_action_with_exception(self.request)
            return str(response, encoding='utf-8')
    class ListenerSLB(BasicListener):
        def __init__(self, vsever_group_id):
            self.slb_caller = SLBClient()
            self.vsever_group_id = Conf.vsever_group_id
        def process(self, event):
            detail = event['content']
            instance_id = detail['instanceId']
            if detail['action'] == 'delete':
                self.slb_caller.remove_vserver_group_backend_servers(self.vsever_group_id, instance_id)

    For interruption notification events, set the event name in the following way: mns_client.regist_listener(ListenerSLB(Conf.vsever_group_id), 'Instance:PreemptibleInstanceInterruption').

    In the production environment, you can apply for another preemptible instance and add it as a backend server to SLB to ensure the performance of your services.