CloudWatch get-metric-data with Expression parameter fails with KeyError

warning

configurationUpdated Oct 1, 2024(via Exa)

Sources

bug: Cloudwatch get-metric-data using Expression fails and strangely looks for alternate field MetricStat · Issue #11618 · localstack/localstackgithub.com

Technologies:

LocalStacksubject

Amazon CloudWatchAmazon CloudWatch metrics correlate with this issue and help confirm diagnosis

How to detect:

CloudWatch get-metric-data API calls using Expression parameter (e.g., SEARCH queries with REMOVE_EMPTY) fail with HTTP 500 InternalError and KeyError: 'MetricStat'. LocalStack CloudWatch implementation only supports MetricStat parameter, not Expression-based metric math queries.

Recommended action:

Rewrite metric queries to use MetricStat parameter instead of Expression. Replace SEARCH/REMOVE_EMPTY expressions with explicit metric stat queries specifying namespace, metric name, dimensions, and statistic. Monitor localstack.service.errors for CloudWatch failures.