# Handling Lambda errors with an API Gateway API

API Gateway treats all invocation and function errors as internal errors. If the Lambda API rejects the invocation request, API Gateway returns a 500 error code. If the function runs but returns an error, or returns a response in the wrong format, API Gateway returns a 502. In both cases, the body of the response from API Gateway is `{"message": "Internal server error"}`.
**Note** 
API Gateway does not retry any Lambda invocations. If Lambda returns an error, API Gateway returns an error response to the client.
The following example shows an X-Ray trace map for a request that resulted in a function error and a 502 from API Gateway. The client receives the generic error message.
![Trace map for a function error with API Gateway.](http://docs.aws.amazon.com/lambda/latest/dg/images/tracemap-apig-502.png)
To customize the error response, you must catch errors in your code and format a response in the required format.
**Example [index.mjs](https://github.com/awsdocs/aws-lambda-developer-guide/tree/main/sample-apps/nodejs-apig/function/index.mjs) – Error formatting** 
```
var formatError = function(error){
 var response = {
 "statusCode": error.statusCode,
 "headers": {
 "Content-Type": "text/plain",
 "x-amzn-ErrorType": error.code
 },
 "isBase64Encoded": false,
 "body": error.code + ": " + error.message
 }
 return response
}
```
API Gateway converts this response into an HTTP error with a custom status code and body. In the trace map, the function node is green because it handled the error.
![Trace map for a formatted error with API Gateway.](http://docs.aws.amazon.com/lambda/latest/dg/images/tracemap-apig-404.png)
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