Use PutMetricAlarm with an AWS SDK or CLI

    /// <summary>
    /// Add a metric alarm to send an email when the metric passes a threshold.
    /// </summary>
    /// <param name="alarmDescription">A description of the alarm.</param>
    /// <param name="alarmName">The name for the alarm.</param>
    /// <param name="comparison">The type of comparison to use.</param>
    /// <param name="metricName">The name of the metric for the alarm.</param>
    /// <param name="metricNamespace">The namespace of the metric.</param>
    /// <param name="threshold">The threshold value for the alarm.</param>
    /// <param name="alarmActions">Optional actions to execute when in an alarm state.</param>
    /// <returns>True if successful.</returns>
    public async Task<bool> PutMetricEmailAlarm(string alarmDescription, string alarmName, ComparisonOperator comparison,
        string metricName, string metricNamespace, double threshold, List<string> alarmActions = null!)
    {
        try
        {
            var putEmailAlarmResponse = await _amazonCloudWatch.PutMetricAlarmAsync(
                new PutMetricAlarmRequest()
                {
                    AlarmActions = alarmActions,
                    AlarmDescription = alarmDescription,
                    AlarmName = alarmName,
                    ComparisonOperator = comparison,
                    Threshold = threshold,
                    Namespace = metricNamespace,
                    MetricName = metricName,
                    EvaluationPeriods = 1,
                    Period = 10,
                    Statistic = new Statistic("Maximum"),
                    DatapointsToAlarm = 1,
                    TreatMissingData = "ignore"
                });
            return putEmailAlarmResponse.HttpStatusCode == HttpStatusCode.OK;
        }
        catch (LimitExceededException lex)
        {
            _logger.LogError(lex, $"Unable to add alarm {alarmName}. Alarm quota has already been reached.");
        }

        return false;
    }

    /// <summary>
    /// Add specific email actions to a list of action strings for a CloudWatch alarm.
    /// </summary>
    /// <param name="accountId">The AccountId for the alarm.</param>
    /// <param name="region">The region for the alarm.</param>
    /// <param name="emailTopicName">An Amazon Simple Notification Service (SNS) topic for the alarm email.</param>
    /// <param name="alarmActions">Optional list of existing alarm actions to append to.</param>
    /// <returns>A list of string actions for an alarm.</returns>
    public List<string> AddEmailAlarmAction(string accountId, string region,
        string emailTopicName, List<string>? alarmActions = null)
    {
        alarmActions ??= new List<string>();
        var snsAlarmAction = $"arn:aws:sns:{region}:{accountId}:{emailTopicName}";
        alarmActions.Add(snsAlarmAction);
        return alarmActions;
    }

Include the required files.

#include <aws/core/Aws.h>
#include <aws/monitoring/CloudWatchClient.h>
#include <aws/monitoring/model/PutMetricAlarmRequest.h>
#include <iostream>

Create the alarm to watch the metric.

        Aws::CloudWatch::CloudWatchClient cw;
        Aws::CloudWatch::Model::PutMetricAlarmRequest request;
        request.SetAlarmName(alarm_name);
        request.SetComparisonOperator(
            Aws::CloudWatch::Model::ComparisonOperator::GreaterThanThreshold);
        request.SetEvaluationPeriods(1);
        request.SetMetricName("CPUUtilization");
        request.SetNamespace("AWS/EC2");
        request.SetPeriod(60);
        request.SetStatistic(Aws::CloudWatch::Model::Statistic::Average);
        request.SetThreshold(70.0);
        request.SetActionsEnabled(false);
        request.SetAlarmDescription("Alarm when server CPU exceeds 70%");
        request.SetUnit(Aws::CloudWatch::Model::StandardUnit::Seconds);

        Aws::CloudWatch::Model::Dimension dimension;
        dimension.SetName("InstanceId");
        dimension.SetValue(instanceId);

        request.AddDimensions(dimension);

        auto outcome = cw.PutMetricAlarm(request);
        if (!outcome.IsSuccess())
        {
            std::cout << "Failed to create CloudWatch alarm:" <<
                outcome.GetError().GetMessage() << std::endl;
        }
        else
        {
            std::cout << "Successfully created CloudWatch alarm " << alarm_name
                << std::endl;
        }

To send an Amazon Simple Notification Service email message when CPU utilization exceeds 70 percent

The following example uses the put-metric-alarm command to send an Amazon Simple Notification Service email message when CPU utilization exceeds 70 percent:

aws cloudwatch put-metric-alarm --alarm-name cpu-mon --alarm-description "Alarm when CPU exceeds 70 percent" --metric-name CPUUtilization --namespace AWS/EC2 --statistic Average --period 300 --threshold 70 --comparison-operator GreaterThanThreshold  --dimensions "Name=InstanceId,Value=i-12345678" --evaluation-periods 2 --alarm-actions arn:aws:sns:us-east-1:111122223333:MyTopic --unit Percent

This command returns to the prompt if successful. If an alarm with the same name already exists, it will be overwritten by the new alarm.

To specify multiple dimensions

The following example illustrates how to specify multiple dimensions. Each dimension is specified as a Name/Value pair, with a comma between the name and the value. Multiple dimensions are separated by a space:

aws cloudwatch put-metric-alarm --alarm-name "Default_Test_Alarm3" --alarm-description "The default example alarm" --namespace "CW EXAMPLE METRICS" --metric-name Default_Test --statistic Average --period 60 --evaluation-periods 3 --threshold 50 --comparison-operator GreaterThanOrEqualToThreshold --dimensions Name=key1,Value=value1 Name=key2,Value=value2

    /**
     * Creates an alarm based on the configuration provided in a JSON file.
     *
     * @param fileName the name of the JSON file containing the alarm configuration
     * @return a CompletableFuture that represents the asynchronous operation of creating the alarm
     * @throws RuntimeException if an exception occurs while reading the JSON file or creating the alarm
     */
    public CompletableFuture<String> createAlarmAsync(String fileName) {
        com.fasterxml.jackson.databind.JsonNode rootNode;
        try {
            JsonParser parser = new JsonFactory().createParser(new File(fileName));
            rootNode = new ObjectMapper().readTree(parser);
        } catch (IOException e) {
            throw new RuntimeException("Failed to read the alarm configuration file", e);
        }

        // Extract values from the JSON node.
        String customMetricNamespace = rootNode.findValue("customMetricNamespace").asText();
        String customMetricName = rootNode.findValue("customMetricName").asText();
        String alarmName = rootNode.findValue("exampleAlarmName").asText();
        String emailTopic = rootNode.findValue("emailTopic").asText();
        String accountId = rootNode.findValue("accountId").asText();
        String region = rootNode.findValue("region").asText();

        // Create a List for alarm actions.
        List<String> alarmActions = new ArrayList<>();
        alarmActions.add("arn:aws:sns:" + region + ":" + accountId + ":" + emailTopic);

        PutMetricAlarmRequest alarmRequest = PutMetricAlarmRequest.builder()
            .alarmActions(alarmActions)
            .alarmDescription("Example metric alarm")
            .alarmName(alarmName)
            .comparisonOperator(ComparisonOperator.GREATER_THAN_OR_EQUAL_TO_THRESHOLD)
            .threshold(100.00)
            .metricName(customMetricName)
            .namespace(customMetricNamespace)
            .evaluationPeriods(1)
            .period(10)
            .statistic("Maximum")
            .datapointsToAlarm(1)
            .treatMissingData("ignore")
            .build();

        // Call the putMetricAlarm asynchronously and handle the result.
        return getAsyncClient().putMetricAlarm(alarmRequest)
            .handle((response, ex) -> {
                if (ex != null) {
                    logger.info("Failed to create alarm: {}", ex.getMessage());
                    throw new RuntimeException("Failed to create alarm", ex);
                } else {
                    logger.info("{} was successfully created!", alarmName);
                    return alarmName;
                }
            });
    }

Import the SDK and client modules and call the API.

import { PutMetricAlarmCommand } from "@aws-sdk/client-cloudwatch";
import { client } from "../libs/client.js";

const run = async () => {
  // This alarm triggers when CPUUtilization exceeds 70% for one minute.
  const command = new PutMetricAlarmCommand({
    AlarmName: process.env.CLOUDWATCH_ALARM_NAME, // Set the value of CLOUDWATCH_ALARM_NAME to the name of an existing alarm.
    ComparisonOperator: "GreaterThanThreshold",
    EvaluationPeriods: 1,
    MetricName: "CPUUtilization",
    Namespace: "AWS/EC2",
    Period: 60,
    Statistic: "Average",
    Threshold: 70.0,
    ActionsEnabled: false,
    AlarmDescription: "Alarm when server CPU exceeds 70%",
    Dimensions: [
      {
        Name: "InstanceId",
        Value: process.env.EC2_INSTANCE_ID, // Set the value of EC_INSTANCE_ID to the Id of an existing Amazon EC2 instance.
      },
    ],
    Unit: "Percent",
  });

  try {
    return await client.send(command);
  } catch (err) {
    console.error(err);
  }
};

export default run();

Create the client in a separate module and export it.

import { CloudWatchClient } from "@aws-sdk/client-cloudwatch";

export const client = new CloudWatchClient({});

// Load the AWS SDK for Node.js
var AWS = require("aws-sdk");
// Set the region
AWS.config.update({ region: "REGION" });

// Create CloudWatch service object
var cw = new AWS.CloudWatch({ apiVersion: "2010-08-01" });

var params = {
  AlarmName: "Web_Server_CPU_Utilization",
  ComparisonOperator: "GreaterThanThreshold",
  EvaluationPeriods: 1,
  MetricName: "CPUUtilization",
  Namespace: "AWS/EC2",
  Period: 60,
  Statistic: "Average",
  Threshold: 70.0,
  ActionsEnabled: false,
  AlarmDescription: "Alarm when server CPU exceeds 70%",
  Dimensions: [
    {
      Name: "InstanceId",
      Value: "INSTANCE_ID",
    },
  ],
  Unit: "Percent",
};

cw.putMetricAlarm(params, function (err, data) {
  if (err) {
    console.log("Error", err);
  } else {
    console.log("Success", data);
  }
});

suspend fun putMetricAlarm(
    alarmNameVal: String,
    instanceIdVal: String,
) {
    val dimensionOb =
        Dimension {
            name = "InstanceId"
            value = instanceIdVal
        }

    val request =
        PutMetricAlarmRequest {
            alarmName = alarmNameVal
            comparisonOperator = ComparisonOperator.GreaterThanThreshold
            evaluationPeriods = 1
            metricName = "CPUUtilization"
            namespace = "AWS/EC2"
            period = 60
            statistic = Statistic.fromValue("Average")
            threshold = 70.0
            actionsEnabled = false
            alarmDescription = "An Alarm created by the Kotlin SDK when server CPU utilization exceeds 70%"
            unit = StandardUnit.fromValue("Seconds")
            dimensions = listOf(dimensionOb)
        }

    CloudWatchClient { region = "us-east-1" }.use { cwClient ->
        cwClient.putMetricAlarm(request)
        println("Successfully created an alarm with name $alarmNameVal")
    }
}

class CloudWatchWrapper:
    """Encapsulates Amazon CloudWatch functions."""

    def __init__(self, cloudwatch_resource):
        """
        :param cloudwatch_resource: A Boto3 CloudWatch resource.
        """
        self.cloudwatch_resource = cloudwatch_resource


    def create_metric_alarm(
        self,
        metric_namespace,
        metric_name,
        alarm_name,
        stat_type,
        period,
        eval_periods,
        threshold,
        comparison_op,
    ):
        """
        Creates an alarm that watches a metric.

        :param metric_namespace: The namespace of the metric.
        :param metric_name: The name of the metric.
        :param alarm_name: The name of the alarm.
        :param stat_type: The type of statistic the alarm watches.
        :param period: The period in which metric data are grouped to calculate
                       statistics.
        :param eval_periods: The number of periods that the metric must be over the
                             alarm threshold before the alarm is set into an alarmed
                             state.
        :param threshold: The threshold value to compare against the metric statistic.
        :param comparison_op: The comparison operation used to compare the threshold
                              against the metric.
        :return: The newly created alarm.
        """
        try:
            metric = self.cloudwatch_resource.Metric(metric_namespace, metric_name)
            alarm = metric.put_alarm(
                AlarmName=alarm_name,
                Statistic=stat_type,
                Period=period,
                EvaluationPeriods=eval_periods,
                Threshold=threshold,
                ComparisonOperator=comparison_op,
            )
            logger.info(
                "Added alarm %s to track metric %s.%s.",
                alarm_name,
                metric_namespace,
                metric_name,
            )
        except ClientError:
            logger.exception(
                "Couldn't add alarm %s to metric %s.%s",
                alarm_name,
                metric_namespace,
                metric_name,
            )
            raise
        else:
            return alarm

# Creates or updates an alarm in Amazon CloudWatch.
#
# @param cloudwatch_client [Aws::CloudWatch::Client]
#   An initialized CloudWatch client.
# @param alarm_name [String] The name of the alarm.
# @param alarm_description [String] A description about the alarm.
# @param metric_name [String] The name of the metric associated with the alarm.
# @param alarm_actions [Array] A list of Strings representing the
#   Amazon Resource Names (ARNs) to execute when the alarm transitions to the
#   ALARM state.
# @param namespace [String] The namespace for the metric to alarm on.
# @param statistic [String] The statistic for the metric.
# @param dimensions [Array] A list of dimensions for the metric, specified as
#   Aws::CloudWatch::Types::Dimension.
# @param period [Integer] The number of seconds before re-evaluating the metric.
# @param unit [String] The unit of measure for the statistic.
# @param evaluation_periods [Integer] The number of periods over which data is
#   compared to the specified threshold.
# @param theshold [Float] The value against which the specified statistic is compared.
# @param comparison_operator [String] The arithmetic operation to use when
#   comparing the specified statistic and threshold.
# @return [Boolean] true if the alarm was created or updated; otherwise, false.
# @example
#   exit 1 unless alarm_created_or_updated?(
#     Aws::CloudWatch::Client.new(region: 'us-east-1'),
#     'ObjectsInBucket',
#     'Objects exist in this bucket for more than 1 day.',
#     'NumberOfObjects',
#     ['arn:aws:sns:us-east-1:111111111111:Default_CloudWatch_Alarms_Topic'],
#     'AWS/S3',
#     'Average',
#     [
#       {
#         name: 'BucketName',
#         value: 'amzn-s3-demo-bucket'
#       },
#       {
#         name: 'StorageType',
#         value: 'AllStorageTypes'
#       }
#     ],
#     86_400,
#     'Count',
#     1,
#     1,
#     'GreaterThanThreshold'
#   )
def alarm_created_or_updated?(
  cloudwatch_client,
  alarm_name,
  alarm_description,
  metric_name,
  alarm_actions,
  namespace,
  statistic,
  dimensions,
  period,
  unit,
  evaluation_periods,
  threshold,
  comparison_operator
)
  cloudwatch_client.put_metric_alarm(
    alarm_name: alarm_name,
    alarm_description: alarm_description,
    metric_name: metric_name,
    alarm_actions: alarm_actions,
    namespace: namespace,
    statistic: statistic,
    dimensions: dimensions,
    period: period,
    unit: unit,
    evaluation_periods: evaluation_periods,
    threshold: threshold,
    comparison_operator: comparison_operator
  )
  true
rescue StandardError => e
  puts "Error creating alarm: #{e.message}"
  false
end

    TRY.
        lo_cwt->putmetricalarm(
          iv_alarmname                 = iv_alarm_name
          iv_comparisonoperator        = iv_comparison_operator
          iv_evaluationperiods         = iv_evaluation_periods
          iv_metricname                = iv_metric_name
          iv_namespace                 = iv_namespace
          iv_statistic                 = iv_statistic
          iv_threshold                 = iv_threshold
          iv_actionsenabled            = iv_actions_enabled
          iv_alarmdescription          = iv_alarm_description
          iv_unit                      = iv_unit
          iv_period                    = iv_period
          it_dimensions                = it_dimensions ).
        MESSAGE 'Alarm created.' TYPE 'I'.
      CATCH /aws1/cx_cwtlimitexceededfault.
        MESSAGE 'The request processing has exceeded the limit' TYPE 'E'.
    ENDTRY.