boto3 client region issue

[reikje]

Hi, I am into a strange issue. We are running a job that contains these steps:

      - name: Configure AWS Credentials for Region us-east-1         
        uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::<not shown>:role/GithubActionsFullAccess
          aws-region: us-east-1  

      - name: Set up Terraform
        uses: hashicorp/setup-terraform@v2
        with:
          terraform_version: "1.6.1"

      - name: Run Terraform Apply In Empty Environment 
        working-directory: ./infrastructure/test
        run: |
          terraform init
          terraform destroy -auto-approve 
          terraform apply -auto-approve

      - name: Run end-to-end tests
        run: poetry run python -m pytest -m e2e

Terraform correctly creates all resources in the us-east-1 region. We then use pytest to run some end to end tests against the environment. In the past this has worked fine for the two tests that we had. These tests only used s3 and created the client like this:

s3_client = boto3.client("s3")

Today I have added another test case which in addition to s3 also requires ssm and ec2:

ssm_client = boto3.client("ssm")
ec2_client = boto3.client("ec2")
s3_client = boto3.client("s3")

For both ssm and ec2 I am seeing unexpected exceptions indicating that the wrong region is being targeted. For instance I can see botocore.errorfactory.ParameterNotFound: An error occurred (ParameterNotFound) when calling the GetParameter operation while the parameter properly exists in us-east-1. I can work around this by setting the region when creating the client:

ssm_client = boto3.client("ssm", "us-east-1")
ec2_client = boto3.client("ec2", "us-east-1")
s3_client = boto3.client("s3")

I just don't understand why I have to do this?

• why does the s3 client work without the second parameter but not the ssm and ec2 client
• what environment variables is the configure-aws-credentials@v4 action setting in the job for the steps that follow (I think boto3 needs AWS_DEFAULT_REGION)