AWS API Gateway 401 Unauthorized when lambda fails - amazon-web-services

Question

Im using Serverless framework to deploy a set of API's running on API Gateway using cognito as authorizer. Everything seemed to work but i found an issue that when lambda crashes for some reason (maybe time out or some unhandled exception), API Gateway returns 401 Unauthorized.
I added some gateway responses and I can handle some of the errors but even if I get the initial error, I keep receiving the 401 Unauthorized in Frontend.
This is part of my serverless.yml file:
getSimulationStatus:
handler: getSimulationStatus.handler
events:
- http:
path: /simulation/status
method: post
cors: true
authorizer:
arn: arn:aws:cognito-idp:us-east-1:${self:custom.settings.COGNITO_ARN}
resources:
Resources:
GatewayResponseDefault5XX:
Type: 'AWS::ApiGateway::GatewayResponse'
Properties:
ResponseParameters:
gatewayresponse.header.Access-Control-Allow-Origin: "'*'"
gatewayresponse.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
gatewayresponse.header.Access-Control-Allow-Methods: "'*'"
ResponseType: DEFAULT_5XX
RestApiId:
Ref: 'ApiGatewayRestApi'
GatewayResponseDefault4XX:
Type: 'AWS::ApiGateway::GatewayResponse'
Properties:
ResponseParameters:
gatewayresponse.header.Access-Control-Allow-Origin: "'*'"
gatewayresponse.header.Access-Control-Allow-Headers: "'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'"
gatewayresponse.header.Access-Control-Allow-Methods: "'*'"
ResponseType: DEFAULT_4XX
RestApiId:
Ref: 'ApiGatewayRestApi'
For the frontend im using Angular and I have an error interceptor that captures all this events. Currently im forcing a 504 Request time out and Im able to see that, but also the 401 Unauthorized appears.
This is the code for the interceptor:
intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
return next.handle(request).pipe(catchError(err => {
console.log("error captured", err);
return throwError(err.error.message);
}));
}
The idea is to sign out if I receive 401 from backend but currently if any of my lambdas fails, Im immediately logged out.
Any Idea on what could be the problem?
Edit:
This is a capture from web console:

Answer 1

I have a better solution.Why you don't verify if the token it's valid before send the request to api gateway?
you can install this:
npm i jwt-decode
In my case, I always have a fuction that return me the headers and that allows me to validate in that function the token on every call to the API.
Here a function that validate the token (you only need to pass the token of cognito if you are ussing amplify or something like that).
import jwt_decode from "jwt-decode";
....
some code
....
tokenValidator(){
if(localStorage.getItem('access_token') == null){
//call signout cognito and go to login
}
const decoded = jwt_decode(localStorage.getItem('access_token'));
if (decoded.exp === undefined) return null;
const date = new Date(0);
date.setUTCSeconds(decoded.exp);
if(new Date() > date){
//call signout cognito and go to login
}
}
This solution prevents your problem.