How to Set Up Cross-Account Access from a Java Lambda Function to an AWS SQS Queue

How to Set Up Cross-Account Access from a Java Lambda Function to an AWS SQS Queue

This article provides a comprehensive guide on enabling a Java Lambda function in one AWS account (Account A) to access and read messages from an SQS queue in another account (Account B). We'll cover the necessary configurations for both accounts and address potential challenges.

Prerequisites

Before diving in, ensure you have the following:

• AWS Accounts: Two separate AWS accounts (Account A and Account B).
• AWS CLI: Version 2 installed and configured with named profiles for each account.
• Java Development Environment: Set up for Lambda function development.

Steps in Account A (Lambda Function Account)

1. Create an Execution Role:

• Go to the IAM console and create a new role.
• Choose "AWS Lambda" as the trusted entity.
• Attach the AWSLambdaSQSQueueExecutionRole managed policy. This grants basic permissions for Lambda to interact with SQS and CloudWatch Logs.
• Give the role a descriptive name like cross-account-lambda-sqs-role.

2. Create the Lambda Function:

• Develop your Java code to process SQS messages. You can use the AWS SDK for Java to interact with the SQS queue.
• Package your code and dependencies into a deployment package (e.g., JAR file).
• Create the Lambda function using the AWS CLI or console, specifying the execution role created in step 1.

3. Test the Lambda Function:

• Use a sample SQS event to manually invoke the Lambda function and verify its functionality.

Steps in Account B (SQS Queue Account)

1. Create an SQS Queue:

• Go to the SQS console and create a new queue. Choose the appropriate queue type (standard or FIFO) based on your needs.
• Give the queue a descriptive name like LambdaCrossAccountQueue.

2. Configure the Queue Policy:

• In the queue's configuration, navigate to the "Access policy" section.
• Choose "Advanced" and paste a policy granting the Lambda execution role in Account A access to perform actions on the queue.
• Make sure to replace <AccountA_ID> and <AccountB_ID> with the actual account IDs.

{
  "Version": "2012-10-17",
  "Id": "Queue1_Policy_UUID",
  "Statement": [{
    "Sid": "Queue1_AllActions",
    "Effect": "Allow",
    "Principal": {
      "AWS": [
        "arn:aws:iam::<AccountA_ID>:role/cross-account-lambda-sqs-role"
      ]
    },
    "Action": "sqs:*",
    "Resource": "arn:aws:sqs:us-east-1:<AccountB_ID>:LambdaCrossAccountQueue"
  }]
}

3. Configure the Event Source (Account A):

• In Account A, create an event source mapping between the SQS queue in Account B and your Lambda function. You can use the AWS CLI or console for this.

Additional Considerations

• Cross-Region Access: If the Lambda function and SQS queue reside in different regions, ensure your Lambda execution role has appropriate permissions for cross-region SQS access.
• SQS Encryption: If the SQS queue uses encryption, grant the Lambda execution role necessary KMS permissions to access the encryption key.

Conclusion

By following these steps, you can successfully set up cross-account access from a Java Lambda function to an SQS queue. Remember to adjust the configurations based on your specific environment and security requirements.