Why i am getting this {"message": "Internal server error" } from Postman - amazon-web-services

Question

I am new to AWS, I am getting {"message": "Internal server error"} while running the Lambda function with API Gateway in Postman.
I have checked the CloudWatchLogs, there is no error showing in the logs. But Postman returning {"message": "Internal server error"} this error.

Answer 1

It happens when you don't return the correct API Gateway format.
Try to return this in your Lambda:
def lambda_handler(event, context):
return {
"statusCode": 200,
"body": "{'Test': 'Test'}",
"headers": {
'Content-Type': 'text/html',
}
}

Answer 2

According to the log message you provide, it looks like the log from your Lambda function. I recommend you to enable logging feature on API Gateway side or you can use the test invoke feature on API Gateway console. They both are able to help you to debug your API.
Here is the common issues which might be able to help you diagnose the issue.
1. It doesn't have a right permission to allow API Gateway invoke your Lambda function.
2. It is set as AWS Service Proxy to your Lambda function, the response from your Lambda function doesn't return the response in the proper format.
Ref: https://forums.aws.amazon.com/thread.jspa?messageID=916452

Answer 3

The error can be caused by incorrect quotation marks.
A. Examples that produce the same error in Postman tests:
1. def lambda_handler(event, context):
return {
'statusCode': 200,
"body": {"one": 1000}
}
2. def lambda_handler(event, context):
return {
'statusCode': 200,
"body": "{"one": 1000}"
}
B. Examples that do not produce the error:
3. def lambda_handler(event, context):
return {
'statusCode': 200,
"body": "{'one': 1000}"
}
4. def lambda_handler(event, context):
return {
'statusCode': 200,
"body": '{"one": 1000}'
}
So, the type of quotation marks used after "body": is the reason for the error in this case. Note that while the Amazon lambda console does not produce an error for example 1., Postman says { "message": "Internal server error" }

Answer 4

Resolved it by adding isBase64EncodedFlag to my lambda response
results = {
"statusCode": 200,
"headers": {"Content-Type": "application/json"},
"body": json.dumps(res),
"isBase64Encoded": False
}