message: "Internal server error" when try to access aws gateway api

You need to pass the statusCode after executing the Lambda function. If you don't pass it the API Gateway will trigger an error 502 Bad Gateway by default.

message = {
  'message': 'Execution started successfully!'
}
return {
  'statusCode': 200,
  'headers': {'Content-Type': 'application/json'},
  'body': json.dumps(message)
}

EDIT: This sample is for Python. For node.js you just need to handle callback, the message is basically the same.

callback(null, {
  statusCode: 200,
  body: JSON.stringify(message),
  headers: {'Content-Type': 'application/json'}
});

Don't forget to click Deploy API under AWS API Gateway. Without it, change doesn't work.

For accessing dynamodb through lambda function from api gateway it needs:

1. Create a role in AWS console that have access to dynamodb operations.

2. Create a lambda function and assign the above created role to your lambda function.

3. Create a api from API gateway in AWS management console and allow it to access to your lambda function.

4. In order for your api to show a proper response the return type of lambda function should be a specific format i.e :

return {
  "statusCode": 200,
  "body": json.dumps(your response)
}

It's already explained above, but my problem was this worked for me with just calling the lambda:

exports.handler = async (event) => {
    return "gugus"
};

So all the tests in lambda were fine. The logs looked fine too. Just the API response was not ok.

To call it with the API gateway it needs something like this:

exports.handler = async (event) => {
...
    var res ={
        "statusCode": 200,
        "headers": {
            "Content-Type": "*/*"
        }
    };
    res.body = "gugus";
    return res;
};

Be sure to pass the body across as a string in the response. If it's an object it will fail and give you the error you see. See here for more - http://www.awslessons.com/2017/lambda-api-gateway-internal-server-error/

I had this problem using API Gateway + Lambda. In my case the problem was simply a permission issue. I was using stages in my API.

I had to execute

aws lambda add-permission --function-name X --source-arn "X" --principal apigateway.amazonaws.com --statement-id X --action lambda:InvokeFunction

Hope this helps.

When returning JSON body, added isBase64Encoded = False which solved it, this is actually happening when using Proxy Integration on API Gateway,

so this should work:

import json
return {
   “statusCode”: 200,
   “headers”:{‘Content-Type’: ‘application/json’},
   “body”: json.dumps(json_body),
   “isBase64Encoded”: False
}

callback(null, {
    statusCode: 200,
    body: JSON.stringify(message),
    headers: {'Content-Type': 'application/json'}
});

This worked for me perfectly

In my case the problem was that I created API Gateway from Lambda. In this case no method was created on the API Gateway side of REST API.

Fixed by going to API Gateway, create method manually (GET), attach Lambda function, and (!) Deploy changes.

After this link started to work.

I had this problem, but in my case I was using API Gateway and java lambda function. When looking in cloudwatch there was no error, every things look fine. The problem happen when API Gateway is attempting to render the response. In my case, I had in my response object, the statusCode which was not an int while API gateway need it to be a int.

This

    private final ResponseCode statusCode;
    private final String body;
    private final Map<String, String> headers;
    private final boolean isBase64Encoded;

After I change statusCode to int

    private final int statusCode;

This works

Sometimes CloudWatch logs nothing for this error. To see the error details go to the Lambdas page, click on the Test tab, and execute your function with a test event. You should see what CloudWatch isn't showing.

This error indicates that there was a problem with the configuration of the API. If you enable CloudWatch Logs you can see more information: https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-cloudwatch-logs/

In my case spelling of headers is wrong, it was 'header' in place of 'headers' so make sure you have the right JSON response body.

Try increasing the function timeout. Configuration (Tab) -> General Configuration -> Edit -> Timeout

In my case deleting the CloudFormation Stack fixed this error.

Just to add another potential answer for someone,

For me it ended up being that I had called my function lambdaHandler() instead of lambda_handler(), which it was looking for.

CloudWatch logs showed me that. (I was in Python, not Node)