AWS Cognito is a powerful tool for managing users on your website or mobile application. It handles user registration, sends confirmation codes, and assigns users to groups with distinct permissions.
However, a challenge arises when you need to synchronize users across multiple AWS Regions, such as from a Production environment to a Disaster Recovery (DR) environment. This synchronization is crucial because if one AWS Region becomes unavailable, users can still sign in through the DR Region without disruption, ensuring a seamless service experience.
To address this challenge, we can use AWS services like AWS DynamoDB and AWS Lambda to replicate user data from one region to another. This setup ensures that any new user created in the production environment is also created in the disaster recovery environment, allowing for uninterrupted service.
Here’s a detailed step-by-step guide to setting up this solution:
Step 1: Create a Lambda Function in Production Region (Region 1)
First, create a AWS Lambda function in the production region (Region 1). This function will be triggered whenever a new user is created in the AWS Cognito user pool of the production region (using the post-confirmation trigger).
The function’s code will extract the user’s email address and other relevant attributes, and then insert this data into a DynamoDB global table. This step ensures that the user data is captured and prepared for replication. Ensure the Lambda function’s role has appropriate permissions to access the DynamoDB table.
Steps:
Here’s the example code (python):
import boto3
def lambda_handler(event, context):
dynamodb = boto3.resource('dynamodb')
table = dynamodb.Table('UserTable')
user_data = {
'email': event['request']['userAttributes']['email'],
'sub': event['userName']
}
table.put_item(Item=user_data)
return event
Step 2: Create a Global Table (DynamoDB) with Replica in Disaster Region (Region 2)
Next, create a DynamoDB global table in the production region. A global table allows for automatic replication of data across multiple AWS Regions. Add a replica of this table in the disaster region (Region 2).
This setup ensures that any data inserted into the DynamoDB global table in the production region is automatically replicated to the disaster region.
Steps:
Step 3: Create a Lambda Function in Disaster Region (Region 2)
In the disaster region (Region 2), create another AWS Lambda function. This function will be responsible for creating users in the AWS Cognito user pool of the disaster region using the replicated data.
The function will handle the user creation process and ensure that the user attributes are correctly mapped and synchronized. Ensure the Lambda function’s role has appropriate permissions.
Steps:
Here’s the example code (python):
import boto3
def lambda_handler(event, context):
cognito = boto3.client('cognito-idp')
user_pool_id = 'your_user_pool_id'
for record in event['Records']:
if record['eventName'] == 'INSERT':
new_image = record['dynamodb']['NewImage']
email = new_image['email']['S']
sub = new_image['sub']['S']
cognito.admin_create_user(
UserPoolId=user_pool_id,
Username=sub,
UserAttributes=[
{'Name': 'email', 'Value': email},
{'Name': 'email_verified', 'Value': 'true'}
]
)
return 'User created'
Step 4: Add a DynamoDB Stream Trigger in Disaster Region (Region 2)
Enable DynamoDB Streams on the global table and add a trigger for the AWS Lambda function created in the disaster region.
This trigger will activate the Lambda function whenever a change is made to the DynamoDB global table in the disaster region. The Lambda function will then use the stream data (which includes the new user’s attributes) to create the user in the AWS Cognito user pool of the disaster region.
Steps:
When a new user is created in the AWS Cognito user pool of the production region, a post-confirmation Lambda function is triggered. This function inserts the user’s email address and other attributes into the DynamoDB global table.
The global table, with its replica in the disaster region, automatically replicates this data. The stream trigger on the DynamoDB global table in the disaster region activates the corresponding Lambda function, which processes the new data and creates a user in the AWS Cognito user pool of the disaster region. This seamless flow ensures that user data is consistently and reliably replicated across regions.
To optimize storage and ensure efficient data management, enable Time To Live (TTL) on the global DynamoDB table. Specify an attribute for TTL that will automatically delete data after a certain period. This prevents unnecessary data accumulation and helps reduce storage costs.
Steps:
By implementing this solution, you can achieve efficient and reliable user data replication across multiple AWS Regions, ensuring high availability and continuity of service for your application users.
This setup leverages AWS’s serverless and scalable services, offering a robust method to synchronize user data and maintain service availability across regions. The combination of AWS Lambda and AWS DynamoDB global tables provides a cost-effective and automated approach to handle user data replication, ensuring your application remains resilient in the face of regional outages.