Lambda Event Processing

Prerequisites

AWS account with appropriate permissions
Terraform >= 1.0

Step 1: Create the S3 Bucket

module "uploads_bucket" {
  source  = "registry.patterneddesigns.ca/essentials/s3-bucket/aws"
  version = "3.0.0"

  bucket_name        = "file-uploads"
  versioning_enabled = true
  encryption_type    = "aws:kms"
  kms_key_arn        = aws_kms_key.main.arn
}

Step 2: Create the Lambda Function

module "processor" {
  source  = "registry.patterneddesigns.ca/patterneddesigns/lambda-function/aws"
  version = "3.1.0"

  function_name = "s3-event-processor"
  runtime       = "python3.12"
  handler       = "main.handler"
  source_path   = "./src/processor"
  timeout       = 60

  environment_variables = {
    BUCKET_NAME = module.uploads_bucket.bucket_id
  }
}

Step 3: Configure S3 Event Notification

resource "aws_lambda_permission" "s3" {
  statement_id  = "AllowS3Invoke"
  action        = "lambda:InvokeFunction"
  function_name = module.processor.function_name
  principal     = "s3.amazonaws.com"
  source_arn    = module.uploads_bucket.bucket_arn
}

resource "aws_s3_bucket_notification" "uploads" {
  bucket = module.uploads_bucket.bucket_id

  lambda_function {
    lambda_function_arn = module.processor.function_arn
    events              = ["s3:ObjectCreated:*"]
    filter_prefix       = "uploads/"
    filter_suffix       = ".json"
  }

  depends_on = [aws_lambda_permission.s3]
}

Step 4: Grant Lambda Access to S3

resource "aws_iam_role_policy" "lambda_s3" {
  name = "lambda-s3-access"
  role = module.processor.role_arn

  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Effect = "Allow"
        Action = [
          "s3:GetObject",
          "s3:PutObject"
        ]
        Resource = "${module.uploads_bucket.bucket_arn}/*"
      }
    ]
  })
}

Step 5: Deploy and Test

Run terraform apply and test by uploading a file:

aws s3 cp test.json s3://file-uploads/uploads/test.json

Check CloudWatch Logs to verify the Lambda function processed the event.