Create CloudWatch Alarms with Python AWS CDK

Create the alarm

Put this into your Python AWS CDK stack to create an alarm on a bucket asigned to a varibale named bucket

bucket = s3.Bucket...

s3_size_alarm = cloudwatch.Alarm(self, 'bucket_overloaded_alarm',
    metric= cloudwatch.Metric(
        namespace = "AWS/S3", 
        metric_name = "BucketSizeBytes",
        dimensions={
            "BucketName": bucket.bucket_name,
            "StorageType": "StandardStorage",
        },
        period = core.Duration.days(1),
        statistic="Maximum",
    ), 
    evaluation_periods=1, 
    threshold=1000000000 #1 GB
)

This will create a CloudWatch alarm which:

• Alarm if the size of the bucket goes over 1GB
• Only monitors objects with the StandardStorage type

Relevant CDK docs:

• https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_cloudwatch/Alarm.html
• https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_cloudwatch/Metric.html

Warning: Don't rely on an alarm watching the BucketSizeBytes metric to make sure your bucket doesn't grow too large. This metric is only collected once a day. Consider opting in to S3 request metrics for more in-depth S3 monitoring

Create alarm action

Alarms aren't very useful if they don't do anything. Setup some actions:

topic = sns.Topic.from_topic_arn(self,'snstopic',"arn:aws:sns:us-east-1:123456789012:alarm-go-ahhhhhhhhhhhh")

s3_size_alarm.add_alarm_action(
    cloudwatch_actions.SnsAction(
        topic = topic
    )
)

Relevant CDK docs:

• https://docs.aws.amazon.com/cdk/api/latest/python/aws_cdk.aws_sns/Topic.html#aws_cdk.aws_sns.Topic.from_topic_arn

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