Cloudformation DynamoDB-API Gateway Proxy - amazon-web-services

Question

I was trying to implement a dynamodb proxy using apigateway. But when invoking it, the api is returning error,
Fri Mar 19 20:30:27 UTC 2021 : Execution failed due to configuration
error: Unable to transform request
Fri Mar 19 20:30:27 UTC 2021 : Method completed with status: 500
To me it looks like the issue is not with the requestTemplates transformation(?), but what else, any idea?
Cloudformation template.
AWSTemplateFormatVersion: "2010-09-09"
Transform: "AWS::Serverless-2016-10-31"
Description: Feedback Store; A hypothetical example to test direct proxy to Dynamodb table from api gateway.
Metadata:
cfn-lint:
config:
ignore_checks:
# Not useful at all.
- I1022
Parameters:
Environment:
Type: String
Description: Current environment
Default: "dev"
Resources:
EventsTable:
Type: AWS::DynamoDB::Table
Properties:
TableName: feedback_events
AttributeDefinitions:
- AttributeName: UserID
AttributeType: S
- AttributeName: TimeUTC
AttributeType: S
KeySchema:
- AttributeName: UserID
KeyType: HASH
- AttributeName: TimeUTC
KeyType: RANGE
BillingMode: PAY_PER_REQUEST
Tags:
- Key: "Feedbacks"
Value: "true"
ApiGatewayDynamoRole:
Type: AWS::IAM::Role
Properties:
AssumeRolePolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: "Allow"
Principal:
Service: "apigateway.amazonaws.com"
Action:
- "sts:AssumeRole"
Policies:
- PolicyName: "ApiGatewayDynamoRolePolicy"
PolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: "Allow"
Action:
- "dynamodb:DescribeTable"
- "dynamodb:BatchWriteItem"
- "dynamodb:PutItem"
- "dynamodb:Query"
- "dynamodb:UpdateItem"
Resource:
- !GetAtt EventsTable.Arn
- Effect: "Allow"
Action:
- "dynamodb:ListTables"
Resource: "*"
ApiGatewayApi:
Type: AWS::Serverless::Api
Properties:
DefinitionBody:
swagger: 2.0
info:
title: !Sub "${AWS::StackName}-backend-api"
version: 2021-03-21T22:37:24Z
basePath: /prod
schemes:
- https
paths:
/feedback:
post:
summary: Creates a new feedback
description: |
Creates a new feedback object in the datastore
consumes:
- application/json
produces:
- application/json
parameters:
- name: NewFeedback
in: body
description: New feedback details.
schema:
$ref: "#/definitions/Feedbacks"
tags:
- Feedback Store
x-amazon-apigateway-integration:
type: aws
uri: !Sub arn:aws:apigateway:${AWS::Region}:dynamodb:action/BatchWriteItem
credentials: !GetAtt ApiGatewayDynamoRole.Arn
httpMethod: POST
requestTemplates:
application/json: |
#set($inputRoot = $input.path('$'))
{
"RequestItems": {
"${self:resources.Resources.EventsTable.Properties.TableName}": [
#foreach($event in $inputRoot.event)
{
"PutRequest": {
"Item": {
"UserID" : { "S": "$event.userid" },
"TimeUTC" : { "S": "$event.time" },
"Lat": { "S": "$event.lat" },
"Lng": { "S": "$event.lng" },
"UUID" : { "S": "$event.uuid"},
"Sensor" : { "S": "$event.sensor_name" },
"Reading" : { "S": "$event.reading_value" },
"Active" : { "S": "$event.is_active" },
}
}
}#if($foreach.hasNext),#end
#end
]
},
"ReturnValues": "UPDATED_NEW",
"ReturnConsumedCapacity": "NONE",
"ReturnItemCollectionMetrics": "NONE"
}
responses:
"default":
statusCode: "200"
SelectionPattern: "2\\d{2}"
responseParameters:
method.response.header.Access-Control-Allow-Methods: "'OPTIONS,POST'"
method.response.header.Access-Control-Allow-Headers: "'Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token'"
method.response.header.Access-Control-Allow-Origin: "'*'"
"BAD.*":
statusCode: "400"
SelectionPattern: "4\\d{2}"
responseParameters:
method.response.header.Access-Control-Allow-Methods: "'OPTIONS,POST'"
method.response.header.Access-Control-Allow-Headers: "'Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token'"
method.response.header.Access-Control-Allow-Origin: "'*'"
"INT.*":
statusCode: "500"
SelectionPattern: "5\\d{2}"
responseParameters:
method.response.header.Access-Control-Allow-Methods: "'OPTIONS,POST'"
method.response.header.Access-Control-Allow-Headers: "'Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token'"
method.response.header.Access-Control-Allow-Origin: "'*'"
responses:
"200":
description: The unique identifier of the new feedback
headers:
Access-Control-Allow-Origin:
type: "string"
Access-Control-Allow-Methods:
type: string
Access-Control-Allow-Headers:
type: string
schema:
$ref: "#/definitions/NewFeedbackResponse"
"400":
description: Bad request
headers:
Access-Control-Allow-Origin:
type: "string"
Access-Control-Allow-Methods:
type: string
Access-Control-Allow-Headers:
type: string
schema:
$ref: "#/definitions/Error"
"500":
description: Internal error
headers:
Access-Control-Allow-Origin:
type: "string"
Access-Control-Allow-Methods:
type: string
Access-Control-Allow-Headers:
type: string
schema:
$ref: "#/definitions/Error"
definitions:
Empty:
type: object
title: Empty Schema
Feedbacks:
type: array
items:
$ref: FeedbackItem
FeedbackItem:
properties:
userid:
type: string
description: UserID of the author
time:
type: string
description: Feedback time
lat:
type: string
description: Latitude
lng:
type: string
description: Longitude
uuid:
type: string
description: Globaly unique id for the feedback
sensor_name:
type: string
description: Device the feedback coming from
reading_value:
type: string
description: Current reading
is_active:
type: string
description: Device status
NewFeedbackResponse:
properties:
feedbackId:
type: string
description: The generated unique identifier for the new feedback
Error:
properties:
code:
type: integer
format: int32
message:
type: string
fields:
type: string
StageName: prod
Variables:
StageVariableName: "TestAPI"
Payload:
{
"event": [
{
"userid": "21d6523137f6",
"time": "2020-06-16T15:22:33Z",
"lng": "-122.03053391",
"lat": "37.33180957",
"uuid": "96a6f48c-fe67-4cad-be24-21d6523137f6",
"sensor_name": "CYT523",
"reading_value": "72.9",
"is_active": "true"
},
{
"userid": "4354069ba6e5",
"time": "2020-06-16T15:22:33Z",
"lng": "-122.03053391",
"lat": "37.33180957",
"uuid": "512f2543-a458-424c-a141-4354069ba6e5",
"sensor_name": "JQR928",
"reading_value": "41.3",
"is_active": "true"
}
]
}

Answer 1

Three things I noticed which needs corrections.
Dynamo table name is not replaced correctly. We need to use !Sub with tableName: !Ref EventsTable
There is a comma after "Active" : { "S": "$event.is_active" } which shouldn't be there.
The three additional parameters are not all valid at root level in batch-write-item api, I removed them temporarily, we can add as needed. "ReturnValues": "UPDATED_NEW", "ReturnConsumedCapacity": "NONE", and "ReturnItemCollectionMetrics": "NONE"
Updated request template:
requestTemplates:
application/json: !Sub
- |
#set($inputRoot = $input.path('$'))
{
"RequestItems": {
"${tableName}": [
#foreach($event in $inputRoot.event)
{
"PutRequest": {
"Item": {
"UserID" : { "S": "$event.userid" },
"TimeUTC" : { "S": "$event.time" },
"Lat": { "S": "$event.lat" },
"Lng": { "S": "$event.lng" },
"UUID" : { "S": "$event.uuid"},
"Sensor" : { "S": "$event.sensor_name" },
"Reading" : { "S": "$event.reading_value" },
"Active" : { "S": "$event.is_active" }
}
}
}#if($foreach.hasNext),#end
#end
]
},
"ReturnValues": "UPDATED_NEW",
"ReturnConsumedCapacity": "NONE",
"ReturnItemCollectionMetrics": "NONE"
}
- {
tableName: !Ref EventsTable
}

Answer 2

I think this line is the issue:
"${self:resources.Resources.EventsTable.Properties.TableName}"
I am not sure that works in API Gateway VTL. My recommendation is to get it working with static code, then add the refs back in.