Can't get AWS Lambda function to log (text output) to CloudWatch

Question

I'm trying to set up a Lambda function that will process a file when it's uploaded to an S3 bucket. I need a way to see the output of console.log when I upload a file, but I can't figure out how to link my Lambda function to CloudWatch.

I figured about by looking at the context object that my log group is /aws/lambda/wavToMp3 and the log stream is 2016/05/23/[$LATEST]hex_code_redacted. So I created that group and stream in CloudWatch, yet nothing is being logged to it.

Answer 1

For the Lambda function to be able to create a log group and publish logs to that group, the execution role needs to have the following permissions:

{
"Version": "2012-10-17",
"Statement": [
    {
        "Effect": "Allow",
        "Action": "logs:CreateLogGroup",
        "Resource": "arn:aws:logs:region:accountID:*"
    },

    {
        "Effect": "Allow",
        "Action": [
            "logs:CreateLogStream",
            "logs:PutLogEvents"
        ],
        "Resource": [
            "arn:aws:logs:region:accountID:log-group:/aws/lambda/functionname:*"
        ]
    }
]
}

Reference: https://docs.aws.amazon.com/lambda/latest/operatorguide/access-logs.html