# Create a load balancer latency alarm that sends email
<a name="US_AlarmAtThresholdELB"></a>

You can set up an Amazon SNS notification and configure an alarm that monitors latency exceeding 100 ms for your Classic Load Balancer.

## Setting up a latency alarm using the AWS Management Console
<a name="load-balancer-alarm-console"></a>

Use these steps to use the AWS Management Console to create a load balancer latency alarm.

**To create a load balancer latency alarm**

1. Open the CloudWatch console at [https://console.aws.amazon.com/cloudwatch/](https://console.aws.amazon.com/cloudwatch/).

1. In the navigation pane, choose **Alarms**, **All Alarms**.

1. Choose **Create alarm**.

1. Under **CloudWatch Metrics by Category**, choose the **ELB Metrics** category.

1. Select the row with the Classic Load Balancer and the **Latency** metric.

1. For the statistic, choose **Average**, choose one of the predefined percentiles, or specify a custom percentile (for example, **p95.45**).

1. For the period, choose **1 Minute**.

1. Choose **Next**.

1. Under **Alarm Threshold**, enter a unique name for the alarm (for example, **myHighCpuAlarm**) and a description of the alarm (for example, **Alarm when Latency exceeds 100s**). Alarm names must contain only UTF-8 characters, and can't contain ASCII control characters

   The name must contain only UTF-8 characters, and can't contain ASCII control characters. The description can include markdown formatting, which is displayed only in the alarm **Details** tab in the CloudWatch console. The markdown can be useful to add links to runbooks or other internal resources.

1. Under **Whenever**, for **is**, choose **>** and enter **0.1**. For **for**, enter **3**.

1. Under **Additional settings**, for **Treat missing data as**, choose **ignore (maintain alarm state)** so that missing data points don't trigger alarm state changes.

   For **Percentiles with low samples**, choose **ignore (maintain the alarm state)** so that the alarm evaluates only situations with adequate numbers of data samples. 

1. Under **Actions**, for **Whenever this alarm**, choose **State is ALARM**. For **Send notification to**, choose an existing SNS topic or create a new one.

   To create an SNS topic, choose **New list**. For **Send notification to**, enter a name for the SNS topic (for example, **myHighCpuAlarm**), and for **Email list**, enter a comma-separated list of email addresses to be notified when the alarm changes to the `ALARM` state. Each email address is sent a topic subscription confirmation email. You must confirm the subscription before notifications can be sent.

1. Choose **Create Alarm**.

## Setting up a latency alarm using the AWS CLI
<a name="load-balancer-alarm-cli"></a>

Use these steps to use the AWS CLI to create a load balancer latency alarm.

**To create a load balancer latency alarm**

1. Set up an SNS topic. For more information, see [Setting up Amazon SNS notifications](Notify_Users_Alarm_Changes.md#US_SetupSNS).

1. Create the alarm using the [put-metric-alarm](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/put-metric-alarm.html) command as follows:

   ```
   1. aws cloudwatch put-metric-alarm --alarm-name lb-mon --alarm-description "Alarm when Latency exceeds 100s" --metric-name Latency --namespace AWS/ELB --statistic Average --period 60 --threshold 100 --comparison-operator GreaterThanThreshold --dimensions Name=LoadBalancerName,Value=my-server --evaluation-periods 3 --alarm-actions arn:aws:sns:us-east-1:111122223333:my-topic --unit Seconds
   ```

1. Test the alarm by forcing an alarm state change using the [set-alarm-state](https://docs.aws.amazon.com/cli/latest/reference/cloudwatch/set-alarm-state.html) command.

   1. Change the alarm state from `INSUFFICIENT_DATA` to `OK`.

      ```
      1. aws cloudwatch set-alarm-state --alarm-name lb-mon --state-reason "initializing" --state-value OK
      ```

   1. Change the alarm state from `OK` to `ALARM`.

      ```
      1. aws cloudwatch set-alarm-state --alarm-name lb-mon --state-reason "initializing" --state-value ALARM
      ```

   1. Check that you have received an email notification about the alarm.