How to detect bucket region

[paleloser]

Describe the issue

Reading the documentation on how to use the SDK, I find that in order to initialize the client I previously must know which region am I going to talk to.

Let's say I have a program whose job is receiving a bucket URL,S3://bucket-name, plus the credentials to write objects on it (AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY). With that info. my program writes an object in the bucket. Currently my program doesn't accept more parameters.

Thus, it would try to instantiate an S3Client the following way:

final String bucket = "bucket-name";
final String awsAccessKeyId = "...";
final String awsSecretAccessKey = "..."

final S3ClientBuilder clientBuilder = S3Client.builder();

// Configures the credentials
final AwsCredentials credentials = AwsBasicCredentials.create(awsAccessKeyId, awsSecretAccessKey);
final AwsCredentialsProvider credentialsProvider = StaticCredentialsProvider.create(credentials);
clientBuilder.credentialsProvider(credentialsProvider);

// Configures the region
try (final S3Client client = clientBuilder.build()) {
  final GetBucketLocationResponse response = client.getBucketLocation(GetBucketLocationRequest.builder().bucket(bucket).build());
  clientBuilder.region(Region.of(response.locationConstraintAsString()));
}

// Builds the client
this.client = clientBuilder.build()

However, when the program attempts so detect the region, it throws with the following exception:

Unable to load region from any of the providers in the chain software.amazon.awssdk.regions.providers.DefaultAwsRegionProviderChain@353efdbf: [software.amazon.awssdk.regions.providers.SystemSettingsRegionProvider@4c0884e8: Unable to load region from system settings. Region must be specified either via environment variable (AWS_REGION) or system property (aws.region)., software.amazon.awssdk.regions.providers.AwsProfileRegionProvider@7b208b45: No region provided in profile: default, software.amazon.awssdk.regions.providers.InstanceProfileRegionProvider@2fc07784: Unable to contact EC2 metadata service.]

Which in theory says that again, either the program must know previously in which region the bucket is located, or it won't be able to detect it dynamically.

Is that the expected behavior? Should I change my program input parameters to accept the bucket region as well? I find this very weird, since the URL S3:// is the suggested way in the docs, and it doesn't contain all of the info about the target bucket.

Thanks in advance.

Links

https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/home.html
https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/region-selection.html
https://docs.aws.amazon.com/AmazonS3/latest/userguide/access-bucket-intro.html

[yasminetalby]

Hello @paleloser ,

Thank you very much for your submission.

The exception Unable to load region from any of the providers in the chain software.amazon.awssdk.regions.providers.DefaultAwsRegionProviderChain@353efdbf: [software.amazon.awssdk.regions.providers.SystemSettingsRegionProvider@4c0884e8: Unable to load region from system settings. Region must be specified either via environment variable (AWS_REGION) or system property (aws.region)., software.amazon.awssdk.regions.providers.AwsProfileRegionProvider@7b208b45: No region provided in profile: default, software.amazon.awssdk.regions.providers.InstanceProfileRegionProvider@2fc07784: Unable to contact EC2 metadata service.] underlines that that the DefaultAwsRegionProviderChain wasn't able to load region from any of the following region provider:

1. Check the 'aws.region' system property for the region.
2. Check the 'AWS_REGION' environment variable for the region.
3. Check the {user.home}/.aws/credentials and {user.home}/.aws/config files for the region.
4. If running in EC2, check the EC2 metadata service for the region.
   see

In the following sample:

S3ClientBuilder clientBuilder = S3Client.builder();
[...]
clientBuilder.credentialsProvider(credentialsProvider);
   try (final S3Client client = clientBuilder.build()) {
        final GetBucketLocationResponse response = client.getBucketLocation(GetBucketLocationRequest.builder().bucket("test-bucket-for-customer").build());
        clientBuilder.region(Region.of(response.locationConstraintAsString()));
    }

You attempt to build an S3 client without any specified region to retrieve a bucket's location. This is unfortunately not possible in the AWS Java SDK V2.
You would have to specify the region to be able to use getBucketLocation (note that this does not have to be the region of the specified bucket, that is a client inUS_EAST_2 can retrieve the region of a bucket located in US_WEST_2, the only special case that showcase limitation is US_EAST_1 : *S3 client making Get Bucket Location fail on calls for buckets in other regions only when the client is configured for us-east-1 *see).

Example: The following modification to your sample should work to use getBucketLocation:

try (final S3Client client = clientBuilder.region(`US_EAST_2`).build()) {
  final GetBucketLocationResponse response = client.getBucketLocation(GetBucketLocationRequest.builder().bucket(bucket).build());
  clientBuilder.region(Region.of(response.locationConstraintAsString()));
}
S3Client client = clientBuilder.build();

I have tested this out using my own account and bucket located in US_WEST_2, you should be able to make this work with any region (except US_EAST_1) which is a bit of a special case.

---

As a side note, we do have an open feature request in the AWS Java SDK V2 to support S3 client automatically routing requests to the correct bucket region: #52
You can add a thumbs up to showcase your interest in this feature!

I will transfer this issue submission to the AWS Java SDK V2 repository as this is in issue with the use of the AWS Java SDK V2 rather than V1.

I would love to have your feedback on potential documentation improvement for the AWS Java SDK V2.
Let me know if you have any further questions or feedback.

Sincerely,

Yasmine

[paleloser]

First of all, thank you for such quick and detailed response. It looks like your proposal does the job for me, unless for us-east-1 as you mentioned, in which case I get a 403. I'll just fallback to that region by default in case the detection failed.

I've also 👍🏼 -ed the feature request.

Regarding to possible documentation improvements on the AWS Java SDK v2, it'd be nice to have a section dedicated to this part in the S3 site. I mean, by reading the docs, I supposed that unless I already knew the region of the bucket, I couldn't perform any operation. But after this conversation I found out that some operations (like GetBucketLocationRequest here) don't really have that constraint; they just need a random region to work.

On the other side, having this restriction seems very weird to me (maybe I'm not enough familiar with how does the AWS API work). Because I've been able to connect to MinIO instances locally with the client, where the region didn't made any sense at all. So it would be also good to have some references on that.

Again thank you.

[yasminetalby]

Hello @paleloser ,

Thank you very much for your detailed feedback.
I am glad to hear this work around worked for you.

I will bring up the documentation improvement for the S3 portion of the developer guide to the docs team. I agree that this behavior should be documented for better visibility.
I also will look into improving our current documentation of GetBucketLocation with more details.

Thank you very much again for your feedback and contribution.

Sincerely,

Yasmine

[paleloser]

Great to hear that. From my side, we can close this issue now.

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