Python Lambda with Dependency Layer Terraform

README.md

Python Lambda with Dependency Layer Terraform

.
├── lambda.tf
└── function/
    ├── requirements.txt
    └── src/
        └── handler.py

Remember to .gitignore .dist/!

lambda.tf

locals {
  prefix         = "prod"
  lambda_runtime = "python3.12"
  lambda_timeout = 30
}

# Placeholder for lambda execution role
data "aws_iam_role" "lambda_execution_role" {
  name = "lambda-role"
}

# Placeholder for lambda cloudwatch log group
data "aws_iam_role" "lambda_log_group" {
  name = "lambda-log-group"
}

resource "null_resource" "install_layer_dependencies" {
  provisioner "local-exec" {
    command = "mkdir -p .dist/ && pip install -r function/requirements.txt -t .dist/layer/python/lib/python3.9/site-packages"
  }
  triggers = {
    trigger = filesha256("function/requirements.txt")
  }
}

data "archive_file" "layer_zip" {
  type        = "zip"
  source_dir  = ".dist/layer"
  output_path = ".dist/layer.zip"
  depends_on = [
    null_resource.install_layer_dependencies
  ]
}

resource "aws_lambda_layer_version" "lambda_layer" {
  filename         = ".dist/layer.zip"
  source_code_hash = data.archive_file.layer_zip.output_base64sha256
  layer_name       = "${local.prefix}-dependency-layer"

  compatible_runtimes = [local.lambda_runtime]
  depends_on = [
    data.archive_file.layer_zip
  ]
}

data "archive_file" "function_zip" {
  type        = "zip"
  source_dir  = "function/src"
  output_path = ".dist/function.zip"
}

resource "aws_lambda_function" "lambda" {
  function_name    = local.prefix
  filename         = ".dist/function.zip"
  handler          = "handler.handler"
  source_code_hash = data.archive_file.function_zip.output_base64sha256
  runtime          = local.lambda_runtime
  timeout          = local.lambda_timeout
  role             = data.aws_iam_role.lambda_execution_role.arn

  logging_config {
    log_group  = data.aws_cloudwatch_log_group.lambda_log_group.name
    log_format = "Text"
  }

  layers = [
    aws_lambda_layer_version.lambda_layer.arn
  ]
  depends_on = [
    data.archive_file.function_zip,
    aws_lambda_layer_version.lambda_layer
  ]
}