Passing a path parameter to Google's Endpoint for Cloud Function - aws-lambda

Question

I am following Google's tutorial on setting up Google Cloud endpoint (not AWS API Gateway) in front of my Cloud Function. I am triggering my Cloud Function to trigger an AWS lambda function, AND I am trying to pass a path parameter from my Endpoint as defined by OpenAPI spec.
Path parameters are variable parts of a URL path. They are typically used to point to a specific resource within a collection, such as a user identified by ID. A URL can have several path parameters, each denoted with curly braces { }.
paths: /users/{id}:
get:
parameters:
- in: path
name: id # Note the name is the same as in the path
required: true
schema:
type: integer
GET /users/{id}
My openapi.yaml
swagger: '2.0'
info:
title: Cloud Endpoints + GCF
description: Sample API on Cloud Endpoints with a Google Cloud Functions backend
version: 1.0.0
host: HOST
x-google-endpoints:
- name: "HOST"
allowCors: "true
schemes:
- https
produces:
- application/json
paths:
/function1/{pathParameters}:
get:
operationId: function1
parameters:
- in: path
name: pathParameters
required: true
type: string
x-google-backend:
address: https://REGION-FUNCTIONS_PROJECT_ID.cloudfunctions.net/function1
responses:
'200':
description: A successful response
schema:
type: string
The error I get when I use Endpoint URL https://REGION-FUNCTIONS_PROJECT_ID.cloudfunctions.net/function1/conversations is a TypeError from my AWS lambda function
StatusCode:200, FunctionError: "Unhandled", ExecutedVersion: "$LATEST". Payload: "errorType":"TypeError", errorMessage:"Cannot read property 'startsWith' of undefined..."
It is saying that on line
var path = event.pathParameters;
...
...
if (path.startsWith('conversations/'){...};
my path var is undefined.
I initially thought my Google Function was not correctly passing pathParameters but when I tested my Google function using triggering event {"pathParameters":"conversations"}, my Lambda returns the payload successfully.
My Google Cloud Function:
let AWS = require('aws-sdk');
AWS.config.update({
accessKeyId: 'key',
secretAccessKey: 'secret',
region: 'region'
})
let lambda = new AWS.Lambda();
exports.helloWorld = async(req,res) => {
let params = {
FunctionName:'lambdafunction',
InvocationType: "RequestRespone",
Payload: JSON.stringify(req.body)
};
res.status(200).send(await lambda.invoke(params, function(err,data){
if(err){throw err}
else{
return data.Payload
}
}).promise());
}
EDIT 1:
Seeing this Google Group post, I tried adding to my openapi.yaml file path_translation: APPEND_PATH_TO_ADDRESS, yet still I'm having no luck.
...
paths:
/{pathParameters}:
get:
...
x-google-backend:
address: https://tomy.cloudfunctions.net/function-Name
path_translation: APPEND_PATH_TO_ADDRESS
#Arunmainthan Kamalanathan mentioned in the comments that testing in AWS and Google Cloud directly with trigger event {"pathParameters":"conversations"} is not equivalent to passing req.body from my Google function to AWS lambda. I think this is where my error is occurring -- I'm not correctly passing my path parameter in the payload.
EDIT 2:
There is this Stackoverflow post concerning passing route parameters to Cloud Functions using req.path. When I console.log(req.path) I get / and console.log(req.params) I get {'0': '' }, so for some reason my path parameter is not getting passed correctly from Cloud Endpoint URL to my Google function.

Answer 1

I was running into the same issue when specifying multiple paths/routes within my openapi.yaml. It all depends on where you place the x-google-backend (top-level versus operation-level). This has implications on the behaviour of the path_translation. You could also overwrite path_translation yourself, as the documentation clearly describes:
path_translation: [ APPEND_PATH_TO_ADDRESS | CONSTANT_ADDRESS ]
Optional. Sets the path translation strategy used by ESP when making
target backend requests.
Note: When x-google-backend is used at the top level of the OpenAPI
specification, path_translation defaults to APPEND_PATH_TO_ADDRESS,
and when x-google-backend is used at the operation level of the
OpenAPI specification, path_translation defaults to CONSTANT_ADDRESS.
For more details on path translation, please see the Understanding
path translation section.
This means that if you want the path to be appended as a path parameter instead of a query parameter in your backend, you should adhere to the following scenario's:
Scenario 1: Do you have one cloud function in the x-google-backend.address that handles all of your paths in the openapi specification? Put x-google-backend at the top-level.
Scenario 2: Do you have multiple cloud functions corresponding to different paths? Put x-google-backend at the operation-level and set x-google-backend.path_translation to APPEND_PATH_TO_ADDRESS.

Answer 2

When your invocation type is RequestRespone, you can access the payload directly from the event parameter of lambda.
Look at the `Payload' parameter of the Google function:
let params = {
FunctionName:'lambdafunction',
InvocationType: "RequestRespone",
Payload: JSON.stringify({ name: 'Arun'})
};
res.status(200).send(await lambda.invoke(params)...)
Also the Lambda part:
exports.handler = function(event, context) {
context.succeed('Hello ' + event.name);
};
I hope this helps.