How to get cloudwatch metrics of a lambda using boto3 and lambda python?

Question

I have a Lambda in which I'm trying to get the metrics (especifically the number of invokes) from Cloudwatch of another Lambda. I was following the docs from https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/cloudwatch.html#CloudWatch.Client.get_metric_data and some other examples I found around the internet, but I'm unable to make it work. When I run the code, the response appears with null values, so I might be missed something.

For example, in the code below, I'm trying to get the metrics from November when I was doing some testing with the Lambda (called "lambda-function-to-analyze") I wish to analyze.

def get_metric_data():
    
    cloudwatch = boto3.client('cloudwatch')
    date = datetime.now()
    first = date.replace(day=1)
    last = date.replace(day = calendar.monthrange(date.year, date.month)[1])
    print('first: ', first)
    print('last: ', last)
    
    targetGroupARN='arn:aws:lambda:us-east-1:1234567890:function:lambda-function-to-analyze'
    tgarray=targetGroupARN.split(':')
    target=tgarray[-1]
    print(target)
    
    response = cloudwatch.get_metric_data(
        MetricDataQueries=[
            {
                'Id': 'myrequest',
                'MetricStat': {
                    'Metric': {
                        'Namespace': 'Invocations',
                        'MetricName': 'Number of invokes',
                        'Dimensions': [
                            {
                                'Name': 'lambda',
                                'Value': target
                            },
                        ]
                    },
                    'Period': 300,
                    'Stat': 'Sum',
                    # 'Unit': 'Count'
                }
            },
        ],
        # StartTime=datetime(first.year, first.month, first.day),
        StartTime=datetime(2021, 11, 1),
        # EndTime=datetime(last.year, last.month, last.day),
        EndTime=datetime(2021, 11, 30),
    )
    
    print(response)
    return response

Answer 1

I think the main problem is your MetricName field. Perhaps try changing your Namespace and MetricName like so:

{
"Namespace": "AWS/Lambda",
"MetricName": "Invocations",
...
}