REST API: Request failed with status code 431

Describe the bug I have an aws-serverless-express lambda function, created by Amplify, that is invoked by an Amplify created API. The API was configured to not require authorization. However, when using the Auth module, it appears that the x-amz-security-token is put in both multiValueHeaders and headers, in the lambda event object. Example structure (notice “headers” and “multValueHeaders”):

{
    "resource": <OMITTED>,
    "path": <OMITTED>,
    "httpMethod": "GET",
    "headers": {
        "Accept": "application/json, text/plain, */*",
        "Accept-Encoding": "br, gzip, deflate",
        "Accept-Language": "en-us",
        "CloudFront-Forwarded-Proto": "https",
        "CloudFront-Is-Desktop-Viewer": "true",
        "CloudFront-Is-Mobile-Viewer": "false",
        "CloudFront-Is-SmartTV-Viewer": "false",
        "CloudFront-Is-Tablet-Viewer": "false",
        "CloudFront-Viewer-Country": "US",
        "Host": <OMITTED>,
        "User-Agent": "aws-amplify/1.0.25 react-native",
        "Via": <OMITTED>,
        "X-Amz-Cf-Id": <OMITTED>,
        "x-amz-date": "20190501T155047Z",
        "x-amz-security-token": <SECURITY_TOKEN>,
        "X-Amzn-Trace-Id": "Root=1-5cc9c057-73b3fb6ac5775296d659372c",
        "X-Forwarded-For": "24.243.147.62, 70.132.9.87",
        "X-Forwarded-Port": "443",
        "X-Forwarded-Proto": "https"
    },
    "multiValueHeaders": {
        "Accept": [
            "application/json, text/plain, */*"
        ],
        "Accept-Encoding": [
            "br, gzip, deflate"
        ],
        "Accept-Language": [
            "en-us"
        ],
        "CloudFront-Forwarded-Proto": [
            "https"
        ],
        "CloudFront-Is-Desktop-Viewer": [
            "true"
        ],
        "CloudFront-Is-Mobile-Viewer": [
            "false"
        ],
        "CloudFront-Is-SmartTV-Viewer": [
            "false"
        ],
        "CloudFront-Is-Tablet-Viewer": [
            "false"
        ],
        "CloudFront-Viewer-Country": [
            "US"
        ],
        "Host": [
            <OMITTED>
        ],
        "User-Agent": [
            "aws-amplify/1.0.25 react-native"
        ],
        "Via": [
            <OMITTED>
        ],
        "X-Amz-Cf-Id": [
            <OMITTED>
        ],
        "x-amz-date": [
            "20190501T155047Z"
        ],
        "x-amz-security-token": [
             <SECURITY_TOKEN>
        ],
        "X-Amzn-Trace-Id": [
            "Root=1-5cc9c057-73b3fb6ac5775296d659372c"
        ],
        "X-Forwarded-For": [
            "24.243.147.62, 70.132.9.87"
        ],
        "X-Forwarded-Port": [
            "443"
        ],
        "X-Forwarded-Proto": [
            "https"
        ]
    },
    "queryStringParameters": null,
    "multiValueQueryStringParameters": null,
    "pathParameters": null,
    "stageVariables": null,
    "requestContext": {
        "resourceId": <OMITTED>,
        "resourcePath": <OMITTED>,
        "httpMethod": "GET",
        "extendedRequestId": <OMITTED>,
        "requestTime": "01/May/2019:15:50:47 +0000",
        "path": <OMITTED>,
        "accountId": "<OMITTED>,
        "protocol": "HTTP/1.1",
        "stage": "dev",
        "domainPrefix": "4xnuilt9x4",
        "requestTimeEpoch": 1556725847460,
        "requestId": <OMITTED>,
        "identity": {
            "cognitoIdentityPoolId": null,
            "accountId": null,
            "cognitoIdentityId": null,
            "caller": null,
            "sourceIp": <OMITTED>,
            "accessKey": null,
            "cognitoAuthenticationType": null,
            "cognitoAuthenticationProvider": null,
            "userArn": null,
            "userAgent": "aws-amplify/1.0.25 react-native",
            "user": null
        },
        "domainName": <OMITTED>,
        "apiId": <OMITTED>
    },
    "body": null,
    "isBase64Encoded": false
}

To Reproduce Steps to reproduce the behavior:

1. amplify add auth (fine-grained multi-access IAM)
2. amplify add api (create a serverless lambda function with no authentication required)
3. configure the lambda function in the AWS console, to use a custom runtime (node 12).
4. set a layer to ARN to arn:aws:lambda:<region>:553035198032:layer:nodejs12:1
5. call the api using API.get(<API>, "/path") and you might get an error like the one below:

Error: Request failed with status code 431
    at createError (createError.js:16)
    at settle (settle.js:18)
    at XMLHttpRequest.handleLoad (xhr.js:77)
    at XMLHttpRequest.dispatchEvent (event-target.js:172)
    at XMLHttpRequest.setReadyState (XMLHttpRequest.js:572)
    at XMLHttpRequest.__didCompleteResponse (XMLHttpRequest.js:394)
    at XMLHttpRequest.js:507
    at RCTDeviceEventEmitter.emit (EventEmitter.js:181)
    at MessageQueue.__callFunction (MessageQueue.js:366)
    at MessageQueue.js:106

Expected behavior Just a few days ago, I was able to make these sort of API calls, and after removing and replacing the API with a slightly different config (no dynamodb dependency in the lambda function), I get 431 on all my calls.

Desktop (please complete the following information):

• OS: mac osx
• Browser: chrome

Smartphone (please complete the following information):

• Device: iOS Simulator iPhone X
• OS: iOS 12.0 (i think)

Sample Code index.js (had to be slightly altered form default, to run with node 11+)

const app = require("./app");

const server = awsServerlessExpress.createServer(app);

exports.handler = (event, context) => {
  console.log(EVENT: ${JSON.stringify(event)}`);
  console.log(Buffer.byteLength(JSON.stringify(event)));
  awsServerlessExpress.proxy(server, event, context);
};```

[potatopotaro]

Aha!! I was trying to set NODE_OPTIONS="--max-http-header-size=16000" under process.env without any luck, however setting the variable in the aws console for lambda works. You da man! Thanks!

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