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Indicates how to transform ingested log events to metric data in a CloudWatch metric.


  • MetricTransformation


defaultValue?: number

(Optional) The value to emit when a filter pattern does not match a log event. This value can be null.

dimensions?: Record<string, string>

The fields to use as dimensions for the metric. One metric filter can include as many as three dimensions.

Metrics extracted from log events are charged as custom metrics. To prevent unexpected high charges, do not specify high-cardinality fields such as IPAddress or requestID as dimensions. Each different value found for a dimension is treated as a separate metric and accrues charges as a separate custom metric.

CloudWatch Logs disables a metric filter if it generates 1000 different name/value pairs for your specified dimensions within a certain amount of time. This helps to prevent accidental high charges.

You can also set up a billing alarm to alert you if your charges are higher than expected. For more information, see Creating a Billing Alarm to Monitor Your Estimated Amazon Web Services Charges.

metricName: undefined | string

The name of the CloudWatch metric.

metricNamespace: undefined | string

A custom namespace to contain your metric in CloudWatch. Use namespaces to group together metrics that are similar. For more information, see Namespaces.

metricValue: undefined | string

The value to publish to the CloudWatch metric when a filter pattern matches a log event.

unit?: string

The unit to assign to the metric. If you omit this, the unit is set as None.