aws api gateway return Could not parse payload into json Unrecognized token

Question

Iam trying to send a post request to aws lambda function throuth api gateway.

but when i send it by postman it return a error "Could not parse payload into json". Unrecognized token like the picture below(i remove some useless info):

next i try to send the same request through "Test Method" on the webpage of api gateway: it successed! (iam pretty sure use the same request body)

extra info:

1. not choose "Use Lambda Proxy integration" in Api gateway Integration Request.
2. try to set "Mapping Templates" but not solved my problem.
3. i create that reource for api through serverless freamwork.
4. request header Content-Type have been set to "application/json".
5. i have check the CloudWatch of my lambda function, and nothing find ,it proved that the problem is limited in api gateway.

here is the code of my lambda:

def handle(event, context):
  res = {'code': 200}
  bad_res = {'code': 400}
  if event['operation'] == 'JoinCluster':
    # verify user by aws cognito
    is_allowed, user = is_joining_allowed(event)
    if is_allowed:
        # add a item in dynamodb
        client_info = client_table.add_requested_client(user, event["metadata"])
        # get a available token from another table
        token = token_table.get_valid_token()
        res = {'owner': user, 'id': client_info['id'], **token, **res}
        # Send a message to SQS to indicate that a node is ready to join
        aws.send_message({'id': client_info['id']}, queue_name="netmind-node-join-queue")
        return res
    else:
        bad_res["message"] = "You are not allowed to join this cluster, check your access token before retrying."
        return bad_res

  bad_res["message"] = "unknown operation."
  return bad_res

Answer 1

I try your lambda with api-gateway from postman site, it works well.

Something you not mentioned above cause the problem.

In my postman page, Body tab with green dot at right hand. I also choose raw and JSON follow your screen capture.

But for Params and Authorization tab, I dont know what to set, and keep them without green lights. I guess something there make things wrong.

Following is my test api-gateway definition which works in my site. You shoud change ARN_FOR_YOUR_LAMBDA to your real lambda-arn before you can import into your api-gateway.

---
swagger: "2.0"
info:
  description: "test"
  version: "2022-04-02T15:18:02Z"
  title: "PetStore"
host: "HOST_OF_YOUR_API"
basePath: "/test"
schemes:
- "https"
paths:
  /mao:
    post:
      produces:
      - "application/json"
      responses:
        "200":
          description: "200 response"
          schema:
            $ref: "#/definitions/Empty"
      x-amazon-apigateway-integration:
        httpMethod: "POST"
        uri: "arn:aws:apigateway:ap-northeast-1:lambda:path/2015-03-31/functions/ARN_FOR_YOUR_LAMBDA/invocations"
        responses:
          default:
            statusCode: "200"
        passthroughBehavior: "when_no_match"
        contentHandling: "CONVERT_TO_TEXT"
        type: "aws"
    options:
      consumes:
      - "application/json"
      produces:
      - "application/json"
      responses:
        "200":
          description: "200 response"
          schema:
            $ref: "#/definitions/Empty"
          headers:
            Access-Control-Allow-Origin:
              type: "string"
            Access-Control-Allow-Methods:
              type: "string"
            Access-Control-Allow-Headers:
              type: "string"
      x-amazon-apigateway-integration:
        responses:
          default:
            statusCode: "200"
            responseParameters:
              method.response.header.Access-Control-Allow-Methods: "'DELETE,GET,HEAD,OPTIONS,PATCH,POST,PUT'"
              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: "'*'"
        requestTemplates:
          application/json: "{\"statusCode\": 200}"
        passthroughBehavior: "when_no_match"
        type: "mock"
definitions:
  Empty:
    type: "object"

Wish this help.