Lab 4 : Alerting

Alerting

Amazon ES has launched support for event monitoring and alerting. To use this feature, you work with monitors—scheduled jobs—that have triggers, which are specific conditions that you set, telling the monitor when it should send an alert. An *alert* is a notification that the triggering condition occurred. When a trigger fires, the monitor takes action, sending a message to your destination.

Step 1: Set up your destination

When you create alerts in Amazon ES, you assign one destination or multiple. A destination is a delivery channel, where your domain sends notifications when your alerts trigger. You can use Amazon SNS, your Slack channel, or Amazon Chime as your destination. Or, you can set up a custom webhook (a URL) to receive messages. You set up headers and the message body, and Amazon ES Alerts posts the message to the destination URL.

I use SNS to receive alerts from my Amazon ES domain in this example, but Amazon ES provides [many options for setting up your topic and subscription]{.underline}. I created the topic to receive notifications and subscribe to the topic for email delivery. Your SNS topic can have many subscriptions, supporting delivery via HTTP/S endpoint, email, Amazon SQS, AWS Lambda, and SMS.

To set up your destination, navigate to the AWS Management Console. Sign in and open the SNS console.

Choose Topics, Create Topic.

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In the Create topic page, fill out values for Name and Display name. I chose *aes-alerting* for both. Choose Create topic.

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Now subscribe to your topic. You can do this from the topic page, as the console automatically returns you there when you complete topic creation. You can also subscribe from the Subscriptions tab in the left navigation pane. From the topic page, choose Create subscription.

On the Create Subscription page, for Protocol, choose Email. Fill in your email address in the Endpoint box and choose Create subscription. Make a note of the Topic ARN here, as you refer to it again later.

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Finally, confirm your subscription by clicking the confirmation link in the email that SNS sends to you.

Step 2: Set up a role

To let Amazon ES publish alerts to your topic, create an IAM role with the proper permissions. Before you get started, copy the Topic ARN from the SNS topic page in Step 1.

Your role has two components: trusted entities and permissions for entities that assume the role. The console doesn’t support creating a role with Amazon ES as a trusted entity. Create a role with EC2 as the trusted entity and then edit the JSON trust document to change the entity.

In the AWS Management Console, open the IAM console and choose Roles, Create role.

On the Create role page, choose AWS Service and EC2. Choose Next: Permissions.

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On the permissions page, choose Create policy. This brings you to a new window to create the policy. Don’t close the old tab, as you return to it in a moment.

The policy that you create in this step defines the permissions for entities that assume the role. Add a policy document that allows various entities (Amazon ES in this case) to publish to your SNS topic.

On the Create policy page, choose the JSON tab and copy-paste to replace the JSON text with the following code. Replace the *sns-topic-arn* in the code with the ARN for the topic that you created earlier. After you have done this, choose Review policy.

{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Action": "sns:Publish",
    "Resource": <<sns-topic-arn>>
  }]
}

On the Review policy page, give your policy a name. I chose AES-Alerting-Policy in this example. Choose Create policy.

Return to the Create role window or tab. Use the refresh button to reload the policies and type the name of your policy in the search box. Select the check box next to your policy. Choose Next: Tags, then choose Next: Review. You can also add tags to make your role easier to search.

On the Review page, give your role a name. I used AES-Alerting-Role in this example. Choose Create role.

To change the trusted entity for the role to Amazon ES, in the IAM console, choose Roles. Type AES-Alerting-Role in the search box, and choose the link (not the check box) to view that role. Choose Trust relationships, Edit trust relationship.

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Edit the Policy Document code to replace ec2.amazonaws.com with es.amazonaws.com. Your completed policy document should look like the following code example:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "es.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Choose Update Trust Policy. Make a note of your role ARN, as you refer to it again.

Step 3: Set up Amazon ES alerting

In Kibana, choose Alerting in the left navigation pane. At the top of the window, choose Destinations, Add Destination.

In the Add Destination dialog, give your destination a name. For Type, choose SNS, and set the SNS topic ARN to the topic ARN that you created in Step 1. Set the IAM role ARN to the role ARN that you created in Step 2. Choose Create. You can set as many destinations as you like, allowing you to alert multiple people in the event of a problem.

Step 4: Set up a monitor

Monitors in Open Distro for Amazon ES allow you to specify a value to monitor. You can select the value either graphically or by specifying an Amazon ES query. You define a monitor first and then define triggers for the monitored value.

Navigate to the Alerting plugin.

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In Kibana, choose Monitors, Create Monitor.

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Give your monitor a name. I named my monitor cpu. You can set the frequency to one of the predefined intervals, or use a cron expression for more granular control. I chose Every 1 minute.

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Scroll to the Define Monitor section of the page. Use this set of controls to specify the value to monitor. You can enter a value for Index or Indexes, Time field, and a target value. Choose Define using visual graph from the How do you want to define your monitor? list. You can also enter information for Define using extraction query, allowing you to provide a query that produces a value to monitor. For simple thresholds, the visual interface is fast and easy.

Select the Index value to monitor from the list. The list contains individual indexes. To use a wildcard, you can also type in the text box. For the value to register, you must press Enter after typing the index name (for example, “metricbeat-*” <enter>).

Choose a value for Time field from the list. This reveals several selectors on top of a graph. Choose Count() and open the menu to see the aggregations for computing the value. Choose max(), then choose system.cpu.user.pct for Select a field. Finally, set FOR THE LAST to 2 minute(s). Choose Create.

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 Choose Create. This brings you to the Define Trigger page.

Step 5: Create a trigger

To create a trigger, specify the threshold value for the field that you’re monitoring. When the value of the field exceeds the threshold, the monitor enters an Active state. I created a trigger called cpu_90, with a threshold value of 90% and a severity level of 1.

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When you set the trigger conditions, set the action or actions that Amazon ES performs.

To add actions, scroll through the page. I added one action to send a message to my SNS topic—including the monitor name, trigger, severity, and the period over which the alarm has been active. You can use Mustache scripting to create a template for the message that you receive.

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After you finish adding actions, choose Create at the bottom of the page.

Wrap up

When you return to the Alerting Dashboard, your alert appears in the Completed state. Alerts can exist in a variety of states. Completed signals that the monitor successfully queried your target, and that the trigger is not engaged.

To send the alert into the Active state, you can generate load on the logstash or web server.