Creates or updates a metric filter and associates it with the specified log group. With metric filters, you can configure rules to extract metric data from log events ingested through PutLogEvents.

The maximum number of metric filters that can be associated with a log group is 100.

When you create a metric filter, you can also optionally assign a unit and dimensions to the metric that is created.

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 1,000 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.