Amazon CloudWatch
User Guide

Alarm Events and EventBridge

CloudWatch sends events to Amazon EventBridge whenever a CloudWatch alarm changes alarm state. You can use EventBridge and these events to write rules that take actions, such as notifying you, when an alarm changes state. For more information, see What is Amazon EventBridge?

Currently, there is a requirement to use the AWS Management Console to create a rule based on an event from CloudWatch. You must use the Custom Event Pattern option for the event text that the rule is to watch for. You can also use the AWS SDKs or AWS APIs to create a rule based on an event from CloudWatch.

Sample Events from CloudWatch

This section includes example events from CloudWatch.

State Change for a Single-Metric Alarm

{ "version": "0", "id": "c4c1c1c9-6542-e61b-6ef0-8c4d36933a92", "detail-type": "CloudWatch Alarm State Change", "source": "aws.cloudwatch", "account": "123456789012", "time": "2019-10-02T17:04:40Z", "region": "us-east-1", "resources": [ "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServerCpuTooHigh" ], "detail": { "alarmName": "ServerCpuTooHigh", "configuration": { "description": "Goes into alarm when server CPU utilization is too high!", "metrics": [ { "id": "30b6c6b2-a864-43a2-4877-c09a1afc3b87", "metricStat": { "metric": { "dimensions": { "InstanceId": "i-12345678901234567" }, "name": "CPUUtilization", "namespace": "AWS/EC2" }, "period": 300, "stat": "Average" }, "returnData": true } ] }, "previousState": { "reason": "Threshold Crossed: 1 out of the last 1 datapoints [0.0666851903306472 (01/10/19 13:46:00)] was not greater than the threshold (50.0) (minimum 1 datapoint for ALARM -> OK transition).", "reasonData": "{\"version\":\"1.0\",\"queryDate\":\"2019-10-01T13:56:40.985+0000\",\"startDate\":\"2019-10-01T13:46:00.000+0000\",\"statistic\":\"Average\",\"period\":300,\"recentDatapoints\":[0.0666851903306472],\"threshold\":50.0}", "timestamp": "2019-10-01T13:56:40.987+0000", "value": "OK" }, "state": { "reason": "Threshold Crossed: 1 out of the last 1 datapoints [99.50160229693434 (02/10/19 16:59:00)] was greater than the threshold (50.0) (minimum 1 datapoint for OK -> ALARM transition).", "reasonData": "{\"version\":\"1.0\",\"queryDate\":\"2019-10-02T17:04:40.985+0000\",\"startDate\":\"2019-10-02T16:59:00.000+0000\",\"statistic\":\"Average\",\"period\":300,\"recentDatapoints\":[99.50160229693434],\"threshold\":50.0}", "timestamp": "2019-10-02T17:04:40.989+0000", "value": "ALARM" } } }

State Change for a Metric Math Alarm

{ "version": "0", "id": "2dde0eb1-528b-d2d5-9ca6-6d590caf2329", "detail-type": "CloudWatch Alarm State Change", "source": "aws.cloudwatch", "account": "123456789012", "time": "2019-10-02T17:20:48Z", "region": "us-east-1", "resources": [ "arn:aws:cloudwatch:us-east-1:123456789012:alarm:TotalNetworkTrafficTooHigh" ], "detail": { "alarmName": "TotalNetworkTrafficTooHigh", "configuration": { "description": "Goes into alarm if total network traffic exceeds 10Kb", "metrics": [ { "expression": "SUM(METRICS())", "id": "e1", "label": "Total Network Traffic", "returnData": true }, { "id": "m1", "metricStat": { "metric": { "dimensions": { "InstanceId": "i-12345678901234567" }, "name": "NetworkIn", "namespace": "AWS/EC2" }, "period": 300, "stat": "Maximum" }, "returnData": false }, { "id": "m2", "metricStat": { "metric": { "dimensions": { "InstanceId": "i-12345678901234567" }, "name": "NetworkOut", "namespace": "AWS/EC2" }, "period": 300, "stat": "Maximum" }, "returnData": false } ] }, "previousState": { "reason": "Unchecked: Initial alarm creation", "timestamp": "2019-10-02T17:20:03.642+0000", "value": "INSUFFICIENT_DATA" }, "state": { "reason": "Threshold Crossed: 1 out of the last 1 datapoints [45628.0 (02/10/19 17:10:00)] was greater than the threshold (10000.0) (minimum 1 datapoint for OK -> ALARM transition).", "reasonData": "{\"version\":\"1.0\",\"queryDate\":\"2019-10-02T17:20:48.551+0000\",\"startDate\":\"2019-10-02T17:10:00.000+0000\",\"period\":300,\"recentDatapoints\":[45628.0],\"threshold\":10000.0}", "timestamp": "2019-10-02T17:20:48.554+0000", "value": "ALARM" } } }

State Change for an Anomaly Detection Alarm

{ "version": "0", "id": "daafc9f1-bddd-c6c9-83af-74971fcfc4ef", "detail-type": "CloudWatch Alarm State Change", "source": "aws.cloudwatch", "account": "123456789012", "time": "2019-10-03T16:00:04Z", "region": "us-east-1", "resources": ["arn:aws:cloudwatch:us-east-1:123456789012:alarm:EC2 CPU Utilization Anomaly"], "detail": { "alarmName": "EC2 CPU Utilization Anomaly", "state": { "value": "ALARM", "reason": "Thresholds Crossed: 1 out of the last 1 datapoints [0.0 (03/10/19 15:58:00)] was less than the lower thresholds [0.020599444741798756] or greater than the upper thresholds [0.3006915352732461] (minimum 1 datapoint for OK -> ALARM transition).", "reasonData": "{\"version\":\"1.0\",\"queryDate\":\"2019-10-03T16:00:04.650+0000\",\"startDate\":\"2019-10-03T15:58:00.000+0000\",\"period\":60,\"recentDatapoints\":[0.0],\"recentLowerThresholds\":[0.020599444741798756],\"recentUpperThresholds\":[0.3006915352732461]}", "timestamp": "2019-10-03T16:00:04.653+0000" }, "previousState": { "value": "OK", "reason": "Thresholds Crossed: 1 out of the last 1 datapoints [0.166666666664241 (03/10/19 15:57:00)] was not less than the lower thresholds [0.0206719426210418] or not greater than the upper thresholds [0.30076870222143803] (minimum 1 datapoint for ALARM -> OK transition).", "reasonData": "{\"version\":\"1.0\",\"queryDate\":\"2019-10-03T15:59:04.670+0000\",\"startDate\":\"2019-10-03T15:57:00.000+0000\",\"period\":60,\"recentDatapoints\":[0.166666666664241],\"recentLowerThresholds\":[0.0206719426210418],\"recentUpperThresholds\":[0.30076870222143803]}", "timestamp": "2019-10-03T15:59:04.672+0000" }, "configuration": { "description": "Goes into alarm if CPU Utilization is out of band", "metrics": [{ "id": "m1", "metricStat": { "metric": { "namespace": "AWS/EC2", "name": "CPUUtilization", "dimensions": { "InstanceId": "i-12345678901234567" } }, "period": 60, "stat": "Average" }, "returnData": true }, { "id": "ad1", "expression": "ANOMALY_DETECTION_BAND(m1, 0.8)", "label": "CPUUtilization (expected)", "returnData": true }] } } }