Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Work with CloudWatch alarms

Create an alarm

To create an alarm based on a CloudWatch metric, call the CloudWatchClient’s putMetricAlarm method with a PutMetricAlarmRequest filled with the alarm conditions.

Imports

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.cloudwatch.CloudWatchClient;
import software.amazon.awssdk.services.cloudwatch.model.Dimension;
import software.amazon.awssdk.services.cloudwatch.model.PutMetricAlarmRequest;
import software.amazon.awssdk.services.cloudwatch.model.ComparisonOperator;
import software.amazon.awssdk.services.cloudwatch.model.Statistic;
import software.amazon.awssdk.services.cloudwatch.model.StandardUnit;
import software.amazon.awssdk.services.cloudwatch.model.CloudWatchException;

Code

    public static void putMetricAlarm(CloudWatchClient cw, String alarmName, String instanceId) {

        try {
            Dimension dimension = Dimension.builder()
                .name("InstanceId")
                .value(instanceId).build();

            PutMetricAlarmRequest request = PutMetricAlarmRequest.builder()
                .alarmName(alarmName)
                .comparisonOperator(
                        ComparisonOperator.GREATER_THAN_THRESHOLD)
                .evaluationPeriods(1)
                .metricName("CPUUtilization")
                .namespace("AWS/EC2")
                .period(60)
                .statistic(Statistic.AVERAGE)
                .threshold(70.0)
                .actionsEnabled(false)
                .alarmDescription(
                        "Alarm when server CPU utilization exceeds 70%")
                .unit(StandardUnit.SECONDS)
                .dimensions(dimension)
                .build();

            cw.putMetricAlarm(request);
            System.out.printf(
                    "Successfully created alarm with name %s", alarmName);

        } catch (CloudWatchException e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
    }

See the complete example on GitHub.

List alarms

To list the CloudWatch alarms that you have created, call the CloudWatchClient’s describeAlarms method with a DescribeAlarmsRequest that you can use to set options for the result.

Imports

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.cloudwatch.CloudWatchClient;
import software.amazon.awssdk.services.cloudwatch.model.CloudWatchException;
import software.amazon.awssdk.services.cloudwatch.model.DescribeAlarmsRequest;
import software.amazon.awssdk.services.cloudwatch.model.DescribeAlarmsResponse;
import software.amazon.awssdk.services.cloudwatch.model.MetricAlarm;

Code

    public static void desCWAlarms( CloudWatchClient cw) {

        try {

            boolean done = false;
            String newToken = null;

            while(!done) {
                DescribeAlarmsResponse response;

                if (newToken == null) {
                    DescribeAlarmsRequest request = DescribeAlarmsRequest.builder().build();
                    response = cw.describeAlarms(request);
                } else {
                    DescribeAlarmsRequest request = DescribeAlarmsRequest.builder()
                        .nextToken(newToken)
                        .build();
                    response = cw.describeAlarms(request);
                }

                for(MetricAlarm alarm : response.metricAlarms()) {
                    System.out.printf("\n Retrieved alarm %s", alarm.alarmName());
                }

                if(response.nextToken() == null) {
                    done = true;
                } else {
                    newToken = response.nextToken();
                }
            }

        } catch (CloudWatchException e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
        System.out.printf("Done");
    }

The list of alarms can be obtained by calling MetricAlarms on the DescribeAlarmsResponse that is returned by describeAlarms.

The results may be paged. To retrieve the next batch of results, call nextToken on the response object and use the token value to build a new request object. Then call the describeAlarms method again with the new request.

See the complete example on GitHub.

Delete alarms

To delete CloudWatch alarms, call the CloudWatchClient’s deleteAlarms method with a DeleteAlarmsRequest containing one or more names of alarms that you want to delete.

Imports

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.cloudwatch.CloudWatchClient;
import software.amazon.awssdk.services.cloudwatch.model.CloudWatchException;
import software.amazon.awssdk.services.cloudwatch.model.DeleteAlarmsRequest;

Code

    public static void deleteCWAlarm(CloudWatchClient cw, String alarmName) {

        try {
            DeleteAlarmsRequest request = DeleteAlarmsRequest.builder()
                    .alarmNames(alarmName)
                    .build();

            cw.deleteAlarms(request);
            System.out.printf("Successfully deleted alarm %s", alarmName);

        } catch (CloudWatchException e) {
            System.err.println(e.awsErrorDetails().errorMessage());
            System.exit(1);
        }
    }

See the complete example on GitHub.

More information