Hello. I encountered a problem building druid. *In short, `TestAWSCredentialsProvider` fails like the following*:
``` mvn -pl extensions-core/s3-extensions test ... testWithFileSessionCredentials(io.druid.storage.s3.TestAWSCredentialsProvider) Time elapsed: 6.615 sec <<< ERROR! com.amazonaws.SdkClientException: Unable to find a region via the region provider chain. Must provide an explicit region in the builder or setup environment to supply a region. at io.druid.storage.s3.TestAWSCredentialsProvider.testWithFileSessionCredentials(TestAWSCredentialsProvider.java:98) testWithFixedAWSKeys(io.druid.storage.s3.TestAWSCredentialsProvider) Time elapsed: 4.345 sec <<< ERROR! com.amazonaws.SdkClientException: Unable to find a region via the region provider chain. Must provide an explicit region in the builder or setup environment to supply a region. at io.druid.storage.s3.TestAWSCredentialsProvider.testWithFixedAWSKeys(TestAWSCredentialsProvider.java:67) ``` After digging the code, I found following: 1. `S3StorageDruidModule` does not provide a way to explictily set `Region`, but detects the region automatically with its default credential/region provider chain. `S3StorageDruidModule#getAmazonS3Client -> AmazonS3Client#builder -> AmazonS3ClientBuilder#standard;` 2. The default region provider chain[^1][^2] tries to determine region in following orders:[^1][^2] a. Environment Variable[^5] b. JVM property[^6] c. AWS Configuration[^7] d. EC2 instance metadata service[^8] If all of the above fails, it throws an Exception. *In short, there is a possibility that `S3StorageDruidModule` can't determine the Region. It would be better to provide a way to set Region explicitly.* How do you think? Best, Dongjin [^1]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/DefaultAwsRegionProviderChain.java [^2]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/AwsRegionProviderChain.java [^3]: https://docs.aws.amazon.com/sdk-for-java/v2/developer-guide/java-dg-region-selection.html [^4]: The example client in documentation is `AmazonEC2ClientBuilder` but it also applies to the other clients like `AmazonS3ClientBuilder`. [^5]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/AwsEnvVarOverrideRegionProvider.java [^6]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/AwsSystemPropertyRegionProvider.java [^7]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/AwsProfileRegionProvider.java [^8]: https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/regions/InstanceMetadataRegionProvider.java -- *Dongjin Lee* *A hitchhiker in the mathematical world.* *github: <http://goog_969573159/>github.com/dongjinleekr <http://github.com/dongjinleekr>linkedin: kr.linkedin.com/in/dongjinleekr <http://kr.linkedin.com/in/dongjinleekr>slideshare: www.slideshare.net/dongjinleekr <http://www.slideshare.net/dongjinleekr>*
