I'm using the AWS SDK for JavaScript and it is returning the following error when I try to create a Lambda function:

InvalidParameterValueException: The role defined for the function cannot be assumed by Lambda.

I've double-checked my role and it is perfectly valid. However, I'm still unable to create the Lambda function.

My role trust relationship is:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": [
                    "lambda.amazonaws"
                ]
            },
            "Action": [
                "sts:AssumeRole"
            ]
        }
    ]
}

I'm using the AWS SDK for JavaScript and it is returning the following error when I try to create a Lambda function:

InvalidParameterValueException: The role defined for the function cannot be assumed by Lambda.

I've double-checked my role and it is perfectly valid. However, I'm still unable to create the Lambda function.

My role trust relationship is:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": [
                    "lambda.amazonaws.com"
                ]
            },
            "Action": [
                "sts:AssumeRole"
            ]
        }
    ]
}

• javascript
• node.js
• amazon-web-services
• aws-sdk
• aws-lambda

• I've posted this self-answered question since I've spent a very long time to find the problem. I hope that it may be useful to others. – Zanon Commented May 28, 2016 at 19:34

1 Answer 1

This error happens when the role is invalid (which is not the case) or when you try to create the Lambda function just after the role creation. Amazon needs a few seconds to replicate your new role through all regions. So, the fix here is to wait a few seconds before creating the Lambda function.

Solution - Example 1:

var AWS = require('aws-sdk');
var lambda = new AWS.Lambda();

var params = {}; // define your parameters

lambda.createFunction(params, function(err, data) {
    if (err && err.code === 'InvalidParameterValueException') {

        // try again after a few seconds
        setTimeout(function(){
            lambda.createFunction(params, callback);
        }, 10000);
    } else {
        callback(err, data);
    }
});

Solution - Example 2:

Usually, waiting 5 seconds is enough, but it can also take a little more. For a more robust solution, you can use a retry module like this one.

var AWS = require('aws-sdk');
var retry = require('retry');
var lambda = new AWS.Lambda();

var params = {}; // define your parameters

var operation = retry.operation({
    retries: 3,           // try 1 time and retry 3 times if needed, total = 4
    minTimeout: 1 * 1000, // the number of milliseconds before starting the first retry
    maxTimeout: 15 * 1000 // the maximum number of milliseconds between two retries
});

operation.attempt(function(currentAttempt) {
    lambda.createFunction(params, function(err, data) {
        if (operation.retry(err) && err.code === 'InvalidParameterValueException')
            return;

        callback(err);
    });
});