OpenSearchIngestion CreatePipeline fails with UnknownError in ap-northeast-1 but works in ap-northeast-2

This issue appears to be related to a region-specific problem with the OpenSearch Ingestion service in ap-northeast-1.

When creating an OpenSearch Ingestion pipeline using AWS CDK's CfnPipeline construct, the service requires several configurations including pipeline configuration body, minimum and maximum units, and potentially other options like buffer configurations and encryption settings. The fact that the same code works in ap-northeast-2 but fails in ap-northeast-1 with an "UnknownError" suggests this could be:

1. A temporary service availability issue in the ap-northeast-1 region
2. A configuration that's valid in ap-northeast-2 but not properly supported in ap-northeast-1
3. A regression in the service as you mentioned, since it previously worked

For OpenSearch Ingestion pipelines, there are specific requirements like properly configured IAM roles and an OpenSearch Service domain or OpenSearch Serverless collection as the sink. It's possible that one of these dependencies is causing issues in the specific region.

To troubleshoot this issue:

1. Verify that all required services and features for OpenSearch Ingestion are fully available in ap-northeast-1
2. Check if there are any service quotas or limits that might be different between regions
3. Ensure that the IAM permissions are correctly set up for the ap-northeast-1 region
4. Consider reaching out to AWS Support with the CloudTrail logs, as "UnknownError" typically indicates an internal service issue that might require their investigation

Since this worked previously in ap-northeast-1, it's likely a temporary service issue or a recent change in the service behavior specific to that region.
Sources
class CfnPipeline (construct) · AWS CDK
Creating Amazon OpenSearch Ingestion pipelines - Amazon OpenSearch Service