Terraform API Gateway for use with Lambda Proxy Integration - aws-lambda

Question

I've spent the day fighting with API Gateway and AWS Serverless Express to no avail. My goal is to deploy an API Gateway, via Terraform (v0.12), that proxies all requests to an AWS Serverless Express based lambda. The connection between API Gateway and Lambda seems to exist, but tenuous, as any invocation (from API Gateway console or Postman) respond with 502 Bad Gateway, apparently due to timeout (so states the lambda CloudWatch logs). It does not appear that the lambda code actually runs, only that it spins up ineffectually.
The API Gateway and Lambda should support path parameters and query strings:
GET /some/path/:id get by id
GET /some/path?query=param get
collection
POST /some/path create resource
PATCH /some/path/:id update resource
DELETE /some/path/:id remove resource
After several false starts, I've tried to make the API Gateway Terraform module as flexible as possible:
resource "aws_api_gateway_rest_api" "rest_api" {
name = "${var.application_name} API"
description = var.description
}
resource "aws_api_gateway_resource" "proxy" {
rest_api_id = aws_api_gateway_rest_api.rest_api.id
parent_id = aws_api_gateway_rest_api.rest_api.root_resource_id # aws_api_gateway_resource.version.id
path_part = "{proxy+}"
}
resource "aws_api_gateway_method" "method" {
rest_api_id = aws_api_gateway_rest_api.rest_api.id
resource_id = aws_api_gateway_resource.proxy.id
http_method = "ANY"
authorization = "NONE"
request_parameters = {
"method.request.path.proxy" = true
}
}
resource "aws_api_gateway_integration" "integration" {
rest_api_id = aws_api_gateway_rest_api.rest_api.id
resource_id = aws_api_gateway_resource.proxy.id
http_method = aws_api_gateway_method.method.http_method
integration_http_method = "POST"
type = "AWS_PROXY"
uri = "arn:aws:apigateway:${local.region}:lambda:path/2015-03-31/functions/${var.lambda_arn}/invocations"
}
resource "aws_api_gateway_deployment" "apig_deployment" {
depends_on = [
"aws_api_gateway_resource.proxy",
"aws_api_gateway_method.method",
"aws_api_gateway_integration.integration"
]
rest_api_id = aws_api_gateway_rest_api.rest_api.id
stage_name = var.api_stage_name
lifecycle {
create_before_destroy = true
}
}
resource "aws_lambda_permission" "apig_to_lambda" {
statement_id = "AllowExecutionFromAPIGateway"
action = "lambda:InvokeFunction"
function_name = var.function_name
principal = "apigateway.amazonaws.com"
source_arn = "arn:aws:execute-api:${local.region}:${local.account_id}:${aws_api_gateway_rest_api.rest_api.id}/*/*/*" # TODO: lock this down
}

Answer 1

You are getting 502 error that indicates that the response received by api gateway is not proper.
Having said that your application seems to return json response. Can you try below/confirm the settings?
Add the correct binary mime types in your lambda configuration. See here for more details.
Allow the same mime types or wildcard on api gateway side as below.
resource "aws_api_gateway_rest_api" "rest_api" {
name = "${var.application_name} API"
description = var.description
// Wildcard mimes, accept any
binary_media_types = ["*/*"]
}