Event object is empty when received by the lambda function - amazon-web-services

I am calling a lambda function from my API Gateway with Lambda proxy integration enabled. But when I am receive the event object in the function it is an empty object i.e. '{}'. I have tested the function with a test input available on AWS Console with dummy request object and it works fine. I am using AWS Cognito Pool as authorizer for the API Gateway Method.
In the function I have made an object that returns me dummy data and event object itself. When I hit the API from Postman or my frontend application it returns me with the dummy data and the event object is empty.
I have looked at the following Stackoverflow questions but to no avail.
Event Object is empty in AWS Lambda nodejs function
Passing event from API gateway to Lambda
Event object is empty in api gateway call to lambda
Api Gateway sends empty parameters to AWS lambda
Lambda event returns empty object
This is a small thing and is really hindering my progress. Would really appreciate any help.

Just made whole another Lambda and API Gateway setup and it worked. Must have been bad API Gateway configuration

Related

How to call https endpoint when AWS Lambda throws error?

I have a node.js application where I am invoking a lambda function through AWS SDK and I'm trying to handle lambda's errors in such a way that when it fails it calls an https endpoint from my application.
My application flow is as follow:
Invoke lambda with object with data
Lambda receives the object in the "event" and run its processes.
if lambda fails either by runtime error, timeout, etc I need it to call an endpoint on my application, including the same object that I sent when invoking the lambda function.
I have thought of using CloudWatch alarms along with SNS to call my application endpoint, but I am not aware if that's entirely possible, specially if CloudWatch alarm can receive the lambda 'event' object.
How could I achieve calling an endpoint after Lambda has failed?

How does AWS lambda get triggered by an api request?

Im assuming lambda is like the missing piece of the puzzle for a complete api request. So you create the apigateway and then write the lambda function which bridges the gap between taking a request and returning the output of the lambda function as the http response.
I've successfully followed guides on how to set up an API gateway that triggers AWS lambda to do something, but I still don't really understand what is being done.
How is the function def handler(event, context): being called by the aws apigateway? How does it get triggered and how is the output of handler sent back?
You do not need a Lambda "in the middle". Using Lambda Proxy integration in the API Gateway you can receive the full information about the request (endpoint URL, query parameters, etc) in your targeted Lambda event.
Have a look at the following Tutorial how to setup Lambda Proxy integration with API Gateway.
The tricky thing you should care about is the structure of the response that you will return from your lambda_handler. See the requirements here.
Answering the question of "how this happens"... In short, when an HTTP request comes to your API endpoint it is automatically routed to the mapped Lambda function. Behind the scenes a new container for the Function is spawned and your request comes to the event of the lambda_handler. API Gateway by default also creates a CloudFront distribution in front of itself to serve your requests more efficiently. Once your Lambda returns the response, API Gateway parses it and constructs the HTTP response out of it. The nice thing is that all of this is managed by AWS.

API Gateway method integrates with lambda function but lambda function claims it has no triggers

I have a lambda function that I'd like to trigger via HTTP request.
When I click add trigger to a lambda function, I get an API Gateway API set up with:
method: ANY
Great. Now, when viewing this lambda function, I see a trigger has been configured.
However, I would like to restrict the trigger to only allow POST requests.
So I deleted the API Gateway method ANY, and created a new method POST, under the same resource, using an integration type of Lambda Function. I select my region, and sure enough, my existing lambda function is autocompleted.
However, when I view the triggers tab on the lambda function itself, it shows that there are no triggers.
What am I missing?
If you need flexible control of the API, I would suggest to use the API Gateway console to mange your API. Lambda triggers should only be used for simple use-cases - API methods configured through API Gateway will not show up in the Lambda triggers list.

Multiple AWS API Gateway APIs as trigger to the same Lambda function

I already had an API Gateway API as the trigger for my AWS Lambda function. However when I tried to add another API as a trigger to the same AWS Lambda, it threw an error saying that
There was an error creating the trigger: An integration is already present on this method.
Even when I delete the trigger already present from the configuration window of Lambda, it still shows that the trigger is present.
How can I add multiple API Gateway APIs as triggers for the same lambda function ?
You can setup it via API Gateway console.
Create the Lambda function via Lambda without providing a trigger
Go to API Gateway Console
Create an API.
Create a resource and method
Select the Lambda function you want to trigger by the method
Create an other API/method
Select the Lambda function you want to trigger by the method
Since you are creating the trigger/integration via API Gateway Console, API Gateway will setup the proper permission to allow API Gateway to invoke your Lambda function on multiple APIs/methods.
In the API Gateway, we cannot make entries with the same resource name. When you have created a trigger it's already created and again you are trying to create another one. So we have to clear the previous one and then try again or else we can update it going into the API Gateway interface.

Handing back a response to API Gateway from Lambda

I'm using API Gateway-to-Lambda for a few micro-services but in at least one case the service will take 20-30 seconds to complete so in cases like this I'd like to pass back an immediate response to the client, something like:
status: 200
message: {
progressId: 1234
}
and then allow the Lambda Function to continue on (and periodically updating the "processId" somewhere that is accessible to a client. The problem is that if you call context.succeed(), context.fail(), or context.done() that apparently stops the lambda function from further execution and yet it's the only way I know to flush the stdout buffer back to the API Gateway.
This has led me to a second approach which I haven't yet try to tackle (and for simplicity sake would love to avoid) which involves API Gateway calling a "Responder" Lambda function that then asynchronously fires off the Microservice and then immediately responds to the API Gateway.
I've tried to illustrate these two options in sketch format below. I'd love to hear how anyone's been able to solve this problem.
Currently API Gateway requires that the AWS Lambda integration is synchronous. If you desire asynchronous invocation of your Lambda function, you have 2 options:
Invoking the Lambda asynchrously, either with an AWS integration calling InvokeAsync on Lambda, or using an intermediate service such as SNS or Kinesis to trigger the Lambda function.
You're #2 diagram, using a synchronous Lambda invoke to initiate the asynchronous invoke.
As of Apr/2016 is it is possible to create async Lambda execution through API Gateway by using AWS Service Proxy. See http://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-lambda.html
You can send the X-Amz-Invocation-Type header, it supports async calls through the Event value
You can optionally request asynchronous execution by specifying Event as the InvocationType
http://docs.aws.amazon.com/lambda/latest/dg/API_Invoke.html#API_Invoke_RequestSyntax
Also, if you can't send it via your micro-service, you can configure this header to be passed by default through the Method Execution -> Integration Request -> HTTP Headers in your API Gateway Resource
This worked for me on a micro-service -> API Gateway -> Lambda scenario, like the mentioned on the question.