Alarm events and EventBridge - Amazon CloudWatch
Alarm State Change EventsAlarm Configuration Change Events

Alarm events and EventBridge

CloudWatch sends events to Amazon EventBridge whenever a CloudWatch alarm is created, updated, deleted, or 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?

CloudWatch guarantees the delivery of alarm state change events to EventBridge.

Alarm State Change Events

This section shows example events sent to EventBridge when an alarm's state changes. Select a tab to view different types of alarm state change events.

Single Metric Alarm

Events generated when a single metric alarm changes state. These events include state and previousState fields with the alarm's evaluation results.

{
    "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"
        }
    }
}
Metric Math Alarm

Events generated when a metric math alarm changes state. These events include the math expression details in the configuration field.

{
    "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"
        }
    }
}
Anomaly Detection Alarm

Events generated when an anomaly detection alarm changes state. These events include upper and lower threshold bounds in the reasonData field.

{
    "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
            }]
        }
    }
}
Composite Alarm

Events generated when a composite alarm changes state. These events include suppression information in the actionsSuppressedBy and actionsSuppressedReason fields.

{
    "version": "0",
    "id": "d3dfc86d-384d-24c8-0345-9f7986db0b80",
    "detail-type": "CloudWatch Alarm State Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-07-22T15:57:45Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServiceAggregatedAlarm"
    ],
    "detail": {
        "alarmName": "ServiceAggregatedAlarm",
        "state": {
            "actionsSuppressedBy": "WaitPeriod",
            "actionsSuppressedReason": "Actions suppressed by WaitPeriod",
            "value": "ALARM",
            "reason": "arn:aws:cloudwatch:us-east-1:123456789012:alarm:SuppressionDemo.EventBridge.FirstChild transitioned to ALARM at Friday 22 July, 2022 15:57:45 UTC",
            "reasonData": "{\"triggeringAlarms\":[{\"arn\":\"arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServerCpuTooHigh\",\"state\":{\"value\":\"ALARM\",\"timestamp\":\"2022-07-22T15:57:45.394+0000\"}}]}",
            "timestamp": "2022-07-22T15:57:45.394+0000"
        },
        "previousState": {
            "value": "OK",
            "reason": "arn:aws:cloudwatch:us-east-1:123456789012:alarm:SuppressionDemo.EventBridge.Main was created and its alarm rule evaluates to OK",
            "reasonData": "{\"triggeringAlarms\":[{\"arn\":\"arn:aws:cloudwatch:us-east-1:123456789012:alarm:TotalNetworkTrafficTooHigh\",\"state\":{\"value\":\"OK\",\"timestamp\":\"2022-07-14T16:28:57.770+0000\"}},{\"arn\":\"arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServerCpuTooHigh\",\"state\":{\"value\":\"OK\",\"timestamp\":\"2022-07-14T16:28:54.191+0000\"}}]}",
            "timestamp": "2022-07-22T15:56:14.552+0000"
        },
        "configuration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "actionsSuppressor": "ServiceMaintenanceAlarm",
            "actionsSuppressorWaitPeriod": 120,
            "actionsSuppressorExtensionPeriod": 180
        }
    }
}

Alarm Configuration Change Events

This section shows example events sent to EventBridge when an alarm's configuration changes. Configuration changes include creating, updating, or deleting alarms.

Creation Events

Events generated when new alarms are created. These events include the initial alarm configuration in the configuration field, with operation set to "create".

Composite Alarm Example

{
    "version": "0",
    "id": "91535fdd-1e9c-849d-624b-9a9f2b1d09d0",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-03-03T17:06:22Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServiceAggregatedAlarm"
    ],
    "detail": {
        "alarmName": "ServiceAggregatedAlarm",
        "operation": "create",
        "state": {
            "value": "INSUFFICIENT_DATA",
            "timestamp": "2022-03-03T17:06:22.289+0000"
        },
        "configuration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "alarmName": "ServiceAggregatedAlarm",
            "description": "Aggregated monitor for instance",
            "actionsEnabled": true,
            "timestamp": "2022-03-03T17:06:22.289+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}

Composite Alarm with Suppressor Example

{
    "version": "0",
    "id": "454773e1-09f7-945b-aa2c-590af1c3f8e0",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-07-14T13:59:46Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServiceAggregatedAlarm"
    ],
    "detail": {
        "alarmName": "ServiceAggregatedAlarm",
        "operation": "create",
        "state": {
            "value": "INSUFFICIENT_DATA",
            "timestamp": "2022-07-14T13:59:46.425+0000"
        },
        "configuration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "actionsSuppressor": "ServiceMaintenanceAlarm",
            "actionsSuppressorWaitPeriod": 120,
            "actionsSuppressorExtensionPeriod": 180,
            "alarmName": "ServiceAggregatedAlarm",
            "actionsEnabled": true,
            "timestamp": "2022-07-14T13:59:46.425+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}
Update Events

Events generated when existing alarms are modified. These events contain both configuration and previousConfiguration fields to show what changed.

Metric Alarm Example

{
    "version": "0",
    "id": "bc7d3391-47f8-ae47-f457-1b4d06118d50",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-03-03T17:06:34Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServerCpuTooHigh"
    ],
    "detail": {
        "alarmName": "ServerCpuTooHigh",
        "operation": "update",
        "state": {
            "value": "INSUFFICIENT_DATA",
            "timestamp": "2022-03-03T17:06:13.757+0000"
        },
        "configuration": {
            "evaluationPeriods": 1,
            "threshold": 80,
            "comparisonOperator": "GreaterThanThreshold",
            "treatMissingData": "ignore",
            "metrics": [
                {
                    "id": "86bfa85f-b14c-ebf7-8916-7da014ce23c0",
                    "metricStat": {
                        "metric": {
                            "namespace": "AWS/EC2",
                            "name": "CPUUtilization",
                            "dimensions": {
                                "InstanceId": "i-12345678901234567"
                            }
                        },
                        "period": 300,
                        "stat": "Average"
                    },
                    "returnData": true
                }
            ],
            "alarmName": "ServerCpuTooHigh",
            "description": "Goes into alarm when server CPU utilization is too high!",
            "actionsEnabled": true,
            "timestamp": "2022-03-03T17:06:34.267+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        },
        "previousConfiguration": {
            "evaluationPeriods": 1,
            "threshold": 70,
            "comparisonOperator": "GreaterThanThreshold",
            "treatMissingData": "ignore",
            "metrics": [
                {
                    "id": "d6bfa85f-893e-b052-a58b-4f9295c9111a",
                    "metricStat": {
                        "metric": {
                            "namespace": "AWS/EC2",
                            "name": "CPUUtilization",
                            "dimensions": {
                                "InstanceId": "i-12345678901234567"
                            }
                        },
                        "period": 300,
                        "stat": "Average"
                    },
                    "returnData": true
                }
            ],
            "alarmName": "ServerCpuTooHigh",
            "description": "Goes into alarm when server CPU utilization is too high!",
            "actionsEnabled": true,
            "timestamp": "2022-03-03T17:06:13.757+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}

Metric Alarm with Suppressor Example


    {
    "version": "0",
    "id": "4c6f4177-6bd5-c0ca-9f05-b4151c54568b",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-07-14T13:59:56Z",
    "region": "us-east-1",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServiceAggregatedAlarm"
    ],
    "detail": {
        "alarmName": "ServiceAggregatedAlarm",
        "operation": "update",
        "state": {
            "actionsSuppressedBy": "WaitPeriod",
            "value": "ALARM",
            "timestamp": "2022-07-14T13:59:46.425+0000"
        },
        "configuration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "actionsSuppressor": "ServiceMaintenanceAlarm",
            "actionsSuppressorWaitPeriod": 120,
            "actionsSuppressorExtensionPeriod": 360,
            "alarmName": "ServiceAggregatedAlarm",
            "actionsEnabled": true,
            "timestamp": "2022-07-14T13:59:56.290+0000",
            "okActions": [],
            "alarmActions": [], Remove 
            "insufficientDataActions": []
        },
        "previousConfiguration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "actionsSuppressor": "ServiceMaintenanceAlarm",
            "actionsSuppressorWaitPeriod": 120,
            "actionsSuppressorExtensionPeriod": 180,
            "alarmName": "ServiceAggregatedAlarm",
            "actionsEnabled": true,
            "timestamp": "2022-07-14T13:59:46.425+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}
Deletion Events

Events generated when alarms are deleted. These events include the final alarm configuration and set operation to "delete".

Metric Math Alarm Example

{
    "version": "0",
    "id": "f171d220-9e1c-c252-5042-2677347a83ed",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-03-03T17:07:13Z",
    "region": "us-east-*",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:TotalNetworkTrafficTooHigh"
    ],
    "detail": {
        "alarmName": "TotalNetworkTrafficTooHigh",
        "operation": "delete",
        "state": {
            "value": "INSUFFICIENT_DATA",
            "timestamp": "2022-03-03T17:06:17.672+0000"
        },
        "configuration": {
            "evaluationPeriods": 1,
            "threshold": 10000,
            "comparisonOperator": "GreaterThanThreshold",
            "treatMissingData": "ignore",
            "metrics": [{
                    "id": "m1",
                    "metricStat": {
                        "metric": {
                            "namespace": "AWS/EC2",
                            "name": "NetworkIn",
                            "dimensions": {
                                "InstanceId": "i-12345678901234567"
                            }
                        },
                        "period": 300,
                        "stat": "Maximum"
                    },
                    "returnData": false
                },
                {
                    "id": "m2",
                    "metricStat": {
                        "metric": {
                            "namespace": "AWS/EC2",
                            "name": "NetworkOut",
                            "dimensions": {
                                "InstanceId": "i-12345678901234567"
                            }
                        },
                        "period": 300,
                        "stat": "Maximum"
                    },
                    "returnData": false
                },
                {
                    "id": "e1",
                    "expression": "SUM(METRICS())",
                    "label": "Total Network Traffic",
                    "returnData": true
                }
            ],
            "alarmName": "TotalNetworkTrafficTooHigh",
            "description": "Goes into alarm if total network traffic exceeds 10Kb",
            "actionsEnabled": true,
            "timestamp": "2022-03-03T17:06:17.672+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}

Metric Math Alarm with Suppressor Example

{
    "version": "0",
    "id": "e34592a1-46c0-b316-f614-1b17a87be9dc",
    "detail-type": "CloudWatch Alarm Configuration Change",
    "source": "aws.cloudwatch",
    "account": "123456789012",
    "time": "2022-07-14T14:00:01Z",
    "region": "us-east-*",
    "resources": [
        "arn:aws:cloudwatch:us-east-1:123456789012:alarm:ServiceAggregatedAlarm"
    ],
    "detail": {
        "alarmName": "ServiceAggregatedAlarm",
        "operation": "delete",
        "state": {
            "actionsSuppressedBy": "WaitPeriod",
            "value": "ALARM",
            "timestamp": "2022-07-14T13:59:46.425+0000"
        },
        "configuration": {
            "alarmRule": "ALARM(ServerCpuTooHigh) OR ALARM(TotalNetworkTrafficTooHigh)",
            "actionsSuppressor": "ServiceMaintenanceAlarm",
            "actionsSuppressorWaitPeriod": 120,
            "actionsSuppressorExtensionPeriod": 360,
            "alarmName": "ServiceAggregatedAlarm",
            "actionsEnabled": true,
            "timestamp": "2022-07-14T13:59:56.290+0000",
            "okActions": [],
            "alarmActions": [],
            "insufficientDataActions": []
        }
    }
}