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Page updated Mar 19, 2024

Call a GraphQL API from a Lambda function

You can call an AppSync GraphQL API from a Node.js app or a Lambda function. Take a basic Todo app as an example:

type Todo @model @auth(rules: [{ allow: public }]) {
  name: String
  description: String
}

This API will have operations available for Query, Mutation, and Subscription. Let's take a look at how to perform both a query as well as a mutation from a Lambda function using Node.js.

Utilizing Lambda function template (IAM authorization)

First, create a Lambda function with amplify add function and choose the AppSync - GraphQL API request (with IAM) to get started. Be sure to grant access to your GraphQL API when prompted by the CLI to grant access to other resources in the project. Alternatively, you can create the function from scratch.

amplify add function
? Select which capability you want to add: Lambda function (serverless function)
? Provide an AWS Lambda function name: myfunction
? Choose the runtime that you want to use: NodeJS
? Choose the function template that you want to use: AppSync - GraphQL API request (with IAM)


Available advanced settings:
- Resource access permissions
- Scheduled recurring invocation
- Lambda layers configuration
- Environment variables configuration
- Secret values configuration


? Do you want to configure advanced settings? Yes
? Do you want to access other resources in this project from your Lambda function? Yes
? Select the categories you want this function to have access to. api
? Select the operations you want to permit on <YOUR_API_NAME> Query, Mutation, Subscription


You can access the following resource attributes as environment variables from your Lambda function
	API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT
	API_<YOUR_API_NAME>_GRAPHQLAPIIDOUTPUT
	API_<YOUR_API_NAME>_GRAPHQLAPIKEYOUTPUT
	ENV
	REGION

The function can only be added when the GraphQL API with IAM authorization exists.

Create from scratch

amplify add function
? Select which capability you want to add: Lambda function (serverless function)
? Provide an AWS Lambda function name: myfunction
? Choose the runtime that you want to use: NodeJS
? Choose the function template that you want to use: Hello World


Available advanced settings:
- Resource access permissions
- Scheduled recurring invocation
- Lambda layers configuration
- Environment variables configuration
- Secret values configuration


? Do you want to configure advanced settings? Yes
? Do you want to access other resources in this project from your Lambda function? Yes
? Select the categories you want this function to have access to. api
? Select the operations you want to permit on <YOUR_API_NAME> Query, Mutation, Subscription


You can access the following resource attributes as environment variables from your Lambda function
	API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT
	API_<YOUR_API_NAME>_GRAPHQLAPIIDOUTPUT
	API_<YOUR_API_NAME>_GRAPHQLAPIKEYOUTPUT
	ENV
	REGION

The examples on this page use node-fetch to make a HTTP request to your GraphQL API. When the Node.js v18 runtime is released for Lambda this dependency can be removed in favor of native fetch To get started, add the node-fetch module as a dependency:

CommonJS:

For functions written using CommonJS, you will need to install version 2 of node-fetch

{
  "name": "myfunction",
  "version": "2.0.0",
  "description": "Lambda function generated by Amplify",
  "main": "index.js",
  "license": "Apache-2.0",
+ "dependencies": {
+   "node-fetch": "2"
+ },
  "devDependencies": {
    "@types/aws-lambda": "^8.10.92"
  }
}

ESM:

{
  "name": "myfunction",
+ "type": "module",
  "version": "2.0.0",
  "description": "Lambda function generated by Amplify",
  "main": "index.js",
  "license": "Apache-2.0",
+ "dependencies": {
+   "node-fetch": "^3.2.3"
+ },
  "devDependencies": {
    "@types/aws-lambda": "^8.10.92"
  }
}

Query

Using an API Key for authenticating your requests, you can query the GraphQL API to get a list of all Todos. To paginate over the list queries, you need to pass in a limit and nextToken on the listTodos query. See more at GraphQL pagination .

import { default as fetch, Request } from 'node-fetch';


const GRAPHQL_ENDPOINT = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT;
const GRAPHQL_API_KEY = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIKEYOUTPUT;


const query = /* GraphQL */ `
  query LIST_TODOS {
    listTodos {
      items {
        id
        name
        description
      }
    }
  }
`;


/**
 * @type {import('@types/aws-lambda').APIGatewayProxyHandler}
 */
export const handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);


  /** @type {import('node-fetch').RequestInit} */
  const options = {
    method: 'POST',
    headers: {
      'x-api-key': GRAPHQL_API_KEY,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ query })
  };


  const request = new Request(GRAPHQL_ENDPOINT, options);


  let statusCode = 200;
  let body;
  let response;


  try {
    response = await fetch(request);
    body = await response.json();
    if (body.errors) statusCode = 400;
  } catch (error) {
    statusCode = 400;
    body = {
      errors: [
        {
          status: response.status,
          message: error.message,
          stack: error.stack
        }
      ]
    };
  }


  return {
    statusCode,
    body: JSON.stringify(body)
  };
};

Mutation

In this example you will create a mutation showing how to pass in variables as arguments to create a Todo record.

import { default as fetch, Request } from 'node-fetch';


const GRAPHQL_ENDPOINT = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT;
const GRAPHQL_API_KEY = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIKEYOUTPUT;


const query = /* GraphQL */ `
  mutation CREATE_TODO($input: CreateTodoInput!) {
    createTodo(input: $input) {
      id
      name
      createdAt
    }
  }
`;


/**
 * @type {import('@types/aws-lambda').APIGatewayProxyHandler}
 */
export const handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);


  const variables = {
    input: {
      name: 'Hello, Todo!'
    }
  };


  /** @type {import('node-fetch').RequestInit} */
  const options = {
    method: 'POST',
    headers: {
      'x-api-key': GRAPHQL_API_KEY,
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({ query, variables })
  };


  const request = new Request(GRAPHQL_ENDPOINT, options);


  let statusCode = 200;
  let body;
  let response;


  try {
    response = await fetch(request);
    body = await response.json();
    if (body.errors) statusCode = 400;
  } catch (error) {
    statusCode = 400;
    body = {
      errors: [
        {
          status: response.status,
          message: error.message,
          stack: error.stack
        }
      ]
    };
  }


  return {
    statusCode,
    body: JSON.stringify(body)
  };
};

IAM Authorization

Let's take a look at another example schema that uses iam authorization.

type Todo @model @auth(rules: [{ allow: private, provider: iam }]) {
  name: String
  description: String
}

The CLI will automatically configure the Lambda execution IAM role to call the GraphQL API. Before writing your Lambda function you will first need to install the appropriate AWS SDK v3 dependencies:

{
  "name": "myfunction",
+ "type": "module",
  "version": "2.0.0",
  "description": "Lambda function generated by Amplify",
  "main": "index.js",
  "license": "Apache-2.0",
+ "dependencies": {
+   "@aws-crypto/sha256-js": "^2.0.1",
+   "@aws-sdk/credential-provider-node": "^3.76.0",
+   "@aws-sdk/protocol-http": "^3.58.0",
+   "@aws-sdk/signature-v4": "^3.58.0",
+   "node-fetch": "^3.2.3"
+ },
  "devDependencies": {
    "@types/aws-lambda": "^8.10.92"
  }
}

Then, the following example will sign the request to call the GraphQL API using IAM authorization.

import crypto from '@aws-crypto/sha256-js';
import { defaultProvider } from '@aws-sdk/credential-provider-node';
import { SignatureV4 } from '@aws-sdk/signature-v4';
import { HttpRequest } from '@aws-sdk/protocol-http';
import { default as fetch, Request } from 'node-fetch';


const { Sha256 } = crypto;
const GRAPHQL_ENDPOINT = process.env.API_<YOUR_API_NAME>_GRAPHQLAPIENDPOINTOUTPUT;
const AWS_REGION = process.env.AWS_REGION || 'us-east-1';


const query = /* GraphQL */ `
  query LIST_TODOS {
    listTodos {
      items {
        id
        name
        description
      }
    }
  }
`;


/**
 * @type {import('@types/aws-lambda').APIGatewayProxyHandler}
 */
export const handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);


  const endpoint = new URL(GRAPHQL_ENDPOINT);


  const signer = new SignatureV4({
    credentials: defaultProvider(),
    region: AWS_REGION,
    service: 'appsync',
    sha256: Sha256
  });


  const requestToBeSigned = new HttpRequest({
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      host: endpoint.host
    },
    hostname: endpoint.host,
    body: JSON.stringify({ query }),
    path: endpoint.pathname
  });


  const signed = await signer.sign(requestToBeSigned);
  const request = new Request(GRAPHQL_ENDPOINT, signed);


  let statusCode = 200;
  let body;
  let response;


  try {
    response = await fetch(request);
    body = await response.json();
    if (body.errors) statusCode = 400;
  } catch (error) {
    statusCode = 500;
    body = {
      errors: [
        {
          message: error.message
        }
      ]
    };
  }


  return {
    statusCode,
    body: JSON.stringify(body)
  };
};

CommonJS

When writing functions with CommonJS, you will need to install version 2 of node-fetch:

{
  "name": "myfunction",
  "version": "2.0.0",
  "description": "Lambda function generated by Amplify",
  "main": "index.js",
  "license": "Apache-2.0",
+ "dependencies": {
+   "@aws-crypto/sha256-js": "^2.0.1",
+   "@aws-sdk/credential-provider-node": "^3.76.0",
+   "@aws-sdk/protocol-http": "^3.58.0",
+   "@aws-sdk/signature-v4": "^3.58.0",
+   "node-fetch": "2"
+ },
  "devDependencies": {
    "@types/aws-lambda": "^8.10.92"
  }
}

Similar to the example above you can now write your handler. The difference here is the use of require() rather than import ... from

const { Sha256 } = require('@aws-crypto/sha256-js');
const { defaultProvider } = require('@aws-sdk/credential-provider-node');
const { SignatureV4 } = require('@aws-sdk/signature-v4');
const { HttpRequest } = require('@aws-sdk/protocol-http');
const { default: fetch, Request } = require('node-fetch');


const GRAPHQL_ENDPOINT =
  process.env.API_ < YOUR_API_NAME > _GRAPHQLAPIENDPOINTOUTPUT;
const AWS_REGION = process.env.AWS_REGION || 'us-east-1';


const query = /* GraphQL */ `
  query LIST_TODOS {
    listTodos {
      items {
        id
        name
        description
      }
    }
  }
`;


/**
 * @type {import('@types/aws-lambda').APIGatewayProxyHandler}
 */
exports.handler = async (event) => {
  console.log(`EVENT: ${JSON.stringify(event)}`);


  const endpoint = new URL(GRAPHQL_ENDPOINT);


  const signer = new SignatureV4({
    credentials: defaultProvider(),
    region: AWS_REGION,
    service: 'appsync',
    sha256: Sha256
  });


  const requestToBeSigned = new HttpRequest({
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      host: endpoint.host
    },
    hostname: endpoint.host,
    body: JSON.stringify({ query }),
    path: endpoint.pathname
  });


  const signed = await signer.sign(requestToBeSigned);
  const request = new Request(GRAPHQL_ENDPOINT, signed);


  let statusCode = 200;
  let body;
  let response;


  try {
    response = await fetch(request);
    body = await response.json();
    if (body.errors) statusCode = 400;
  } catch (error) {
    statusCode = 500;
    body = {
      errors: [
        {
          message: error.message
        }
      ]
    };
  }


  return {
    statusCode,
    body: JSON.stringify(body)
  };
};
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