Creates or updates an alarm and associates it with the specified metric, metric math expression, or anomaly detection model.
Alarms based on anomaly detection models cannot have Auto Scaling actions.
When this operation creates an alarm, the alarm state is immediately set to
INSUFFICIENT_DATA. The alarm is then evaluated and its state is set
appropriately. Any actions associated with the new state are then executed.
When you update an existing alarm, its state is left unchanged, but the update completely overwrites the previous configuration of the alarm.
If you are an IAM user, you must have Amazon EC2 permissions for some alarm operations:
iam:CreateServiceLinkedRole for all alarms with EC2 actions
iam:CreateServiceLinkedRole to create an alarm
with Systems Manager OpsItem actions.
The first time you create an alarm in the
Amazon Web Services Management Console, the CLI, or by using the PutMetricAlarm API, CloudWatch
creates the necessary service-linked role for you. The service-linked roles
For more information, see Amazon Web Services service-linked role.
You can set an alarm on metrics in the current account, or in another account. To create a cross-account alarm that watches a metric in a different account, you must have completed the following pre-requisites:
The account where the metrics are located (the sharing account) must already have a sharing role named CloudWatch-CrossAccountSharingRole. If it does not already have this role, you must create it using the instructions in Set up a sharing account in Cross-account cross-Region CloudWatch console. The policy for that role must grant access to the ID of the account where you are creating the alarm.
The account where you are creating the alarm (the monitoring account) must already have a service-linked role named AWSServiceRoleForCloudWatchCrossAccount to allow CloudWatch to assume the sharing role in the sharing account. If it does not, you must create it following the directions in Set up a monitoring account in Cross-account cross-Region CloudWatch console.