AWS Lambda timeout after GraphQL query on AWS AppSync

Question

I deployed an AWS AppSync GraphQL endpoint with Amplify following this tutorial:

https://aws-amplify.github.io/docs/js/api#amplify-graphql-client

I created a Lambda function with Node.js and TypeScript to query data the data:

import { APIGatewayEvent, Callback, Context, Handler } from 'aws-lambda';
import Amplify, { API, graphqlOperation } from "aws-amplify";
import * as queries from './src/graphql/queries';
import * as mutations from './src/graphql/mutations';
import { CreateBlogInput } from './src/API';
import aws_config from "./src/aws-exports";

Amplify.configure(aws_config);

export const list: Handler = async (event: APIGatewayEvent, context: Context, cb: Callback) => {
  const allBlogs = await API.graphql(graphqlOperation(queries.listBlogs));

  // this seems to be working
  console.log(JSON.stringify(allBlogs));

  const response = {
    statusCode: 200,
    body: JSON.stringify(allBlogs),
  };

  cb(null, response);
}

Now, when I call the Lambda function via HTTP, it retrieves the data and logs it to the console. But it never finishes the request and responds, it always runs into a timeout, even if I increase the timeout to 30 seconds. The same happens for running a mutation and inserting data.

Any ideas what could be wrong?

Answer 1

The problem here is that you're mixing your lambda signatures.

Either you use async and return (or throw in case of an error):

export const list: Handler = async (event: APIGatewayEvent, context: Context, cb: Callback) => {
  // ... rest of function

  return response;
}

Or you do not use async and you use the callback function:

export const list: Handler = (event: APIGatewayEvent, context: Context, cb: Callback) => {
  // ... rest of function

  cb(null, response);
}