Serverless MongoDB Backup Automation using Event Triggers

Question

Pulumi · Accepted Answer

To create a serverless MongoDB backup automation using event triggers, you would typically use a combination of cloud services like AWS Lambda, Amazon S3, and AWS EventBridge or a similar setup in another cloud provider. However, since you're interested in using Pulumi to provision this infrastructure, I'll illustrate how you can achieve this using Pulumi and AWS resources.

This Pulumi program will create the following resources:

1. An Amazon S3 bucket to store the MongoDB backups.
2. An AWS IAM role and policy to give the necessary permissions to the Lambda function to access the S3 bucket and to perform the backup operation.
3. An AWS Lambda function, which is the serverless component that will execute the backup operation.
4. An AWS EventBridge (formerly CloudWatch Events) rule that triggers the Lambda function on a schedule you define (e.g., daily at midnight).

Below is the detailed Pulumi Python program that provisions this serverless MongoDB backup automation infrastructure:

```python
import pulumi
import pulumi_aws as aws

# Create an Amazon S3 bucket to store the MongoDB backups
backup_bucket = aws.s3.Bucket("mongoBackupBucket")

# Define an IAM role that AWS Lambda will assume
lambda_role = aws.iam.Role("lambdaRole",
    assume_role_policy="""{
      "Version": "2012-10-17",
      "Statement": [{
        "Action": "sts:AssumeRole",
        "Effect": "Allow",
        "Principal": {
          "Service": "lambda.amazonaws.com"
        }
      }]
    }""")

# Attach a policy to the IAM role with permissions to access the S3 bucket and perform the backup
backup_policy = aws.iam.RolePolicy("backupPolicy",
    role=lambda_role.id,
    policy=backup_bucket.arn.apply(lambda arn: f"""{{
      "Version": "2012-10-17",
      "Statement": [
        {{
          "Effect": "Allow",
          "Action": [
            "s3:PutObject",
            "s3:GetObject",
            "s3:ListBucket"
          ],
          "Resource": [
            "{arn}/*",
            "{arn}"
          ]
        }}
      ]
    }}"""))

# Define the AWS Lambda function
backup_lambda = aws.lambda_.Function("mongoBackupLambda",
    role=lambda_role.arn,
    handler="index.backup_handler",
    runtime="python3.8",
    code=pulumi.AssetArchive({
        '.': pulumi.FileArchive('./backup')
    }),
    timeout=900) # 15 min timeout - adjust as necessary for your backup operation

# Schedule the Lambda function using AWS EventBridge
backup_schedule = aws.cloudwatch.EventRule("backupSchedule",
    schedule_expression="cron(0 0 * * ? *)") # Daily at midnight UTC

# Define the target of the EventBridge rule as the Lambda function
backup_target = aws.cloudwatch.EventTarget("backupTarget",
    rule=backup_schedule.name,
    arn=backup_lambda.arn)

# Grant AWS EventBridge permission to invoke the Lambda function
event_permission = aws.lambda_.Permission("eventPermission",
    action="lambda:InvokeFunction",
    function=backup_lambda.name,
    principal="events.amazonaws.com",
    source_arn=backup_schedule.arn)

# Export the names and ARNs of the resources
pulumi.export("backup_bucket_name", backup_bucket.id)
pulumi.export("lambda_role_arn", lambda_role.arn)
pulumi.export("backup_lambda_arn", backup_lambda.arn)
pulumi.export("backup_schedule_arn", backup_schedule.arn)
```

This program does the following:

1. It defines an S3 bucket for storing backups.
2. It then creates an IAM role for the Lambda function, allowing it to assume the role, and attaches a policy to it that permits access to the S3 bucket.
3. A Lambda function is set up to execute a backup operation. The code for the Lambda function should be located in a directory named `backup`, and the `index.backup_handler` is the Python function that is invoked. The `code` parameter for the Lambda function is an archive of this directory, packaged by Pulumi.
4. An EventBridge rule is defined to schedule the backup operation. This uses a cron expression to execute the Lambda function daily at midnight UTC. The EventBridge target is connected to the Lambda function, and permissions are set to allow EventBridge to invoke the function.

Before deploying this program, you'll need to implement the actual backup logic in the Lambda function handler (i.e., `index.backup_handler` in the `backup` directory). Ensure that the code in your Lambda function obtains credentials securely, connects to MongoDB, performs the backup, and saves the backup file to the designated S3 bucket.

To provision this infrastructure, you would run the following Pulumi CLI commands after setting up your AWS credentials and Pulumi stack:

```bash
pulumi up # Preview and deploy changes
pulumi stack output # View stack outputs (e.g., bucket name)
```

Remember to replace any placeholders (like actual function code and correct MongoDB connection parameters) with real values suitable for your setup. This program example assumes you have AWS CLI configured with the necessary permissions to create these resources and that you have Pulumi installed and set up to manage your infrastructure-as-code.