AWS API Gateway Integration and Terraform

I’m struggling to translate my API Gateway Integration request into Terraform code, I’m trying to pass a multipart/form-data request to a Lambda for storage.

I’ve been able to set up the API gateway manually from scratch, but when I try the terraform I receive an Internal server error and Cloudwatch tells me the gateway has been unable to transform the request.

Execution failed due to configuration error: Unable to transform request

The problem seems to be in the Integration request, because if I do the terraform deployment I can get the whole thing to work by changing the Integration Type in the UI to Lambda Proxy, changing it back again and adding re-adding the Mapping Template.

Terraform block for the Integration;

  • My aws_api_gateway_integration
  resource "aws_api_gateway_integration" "docuemnt-api-method-integration" {
    rest_api_id =
    resource_id =
    http_method = aws_api_gateway_method.document-post-method.http_method
    type = "AWS"
    uri = aws_lambda_function.document_function.invoke_arn
    integration_http_method = "POST"
    passthrough_behavior = "WHEN_NO_TEMPLATES"
    request_templates = {
      "multipart/form-data" = file("${path.module}/mapping/mapping_template.json")
  • The Mapping template
  "content-type": "$util.escapeJavaScript($input.params().header.get('Content-Type'))"

I finally fix it and here is the solution.

On the AWS console you are NOT able to set the Integration Request’s content_handling and it is only an Optional parameter in terraform as well. When you are changing the Integration Type in the UI to Lambda Proxy, the integration request’s content_handling will be set to CONVERT_TO_TEXT.

So you need to add this row to the aws_api_gateway_integration: