I'm trying to parse data with Lambda when an alarm is triggered in Cloudwatch. I am currently using SNS to trigger the lambda; however, I want to know what data is being sent to that Lambda so that I can parse it correctly.
How can I read the JSON alarm data that's passed into Lambda by SNS?
After you subscribe an HTTP/HTTPS endpoint, Amazon SNS sends a subscription confirmation message to the HTTP/HTTPS endpoint. This message contains a SubscribeURL value that you must visit to confirm the subscription (alternatively, you can use the Token value with the ConfirmSubscription).
Amazon CloudWatch uses Amazon SNS to send email. First, create and subscribe to an SNS topic. When you create a CloudWatch alarm, you can add this SNS topic to send an email notification when the alarm changes state.
The simplest and the most accurate way is to print(event)
and actually see what's inside the payload, the official AWS doco provides the following structure for SNS event Amazon SNS Sample Event, reference
{
"Records": [
{
"EventVersion": "1.0",
"EventSubscriptionArn": eventsubscriptionarn,
"EventSource": "aws:sns",
"Sns": {
"SignatureVersion": "1",
"Timestamp": "1970-01-01T00:00:00.000Z",
"Signature": "EXAMPLE",
"SigningCertUrl": "EXAMPLE",
"MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
"Message": "Hello from SNS!",
"MessageAttributes": {
"Test": {
"Type": "String",
"Value": "TestString"
},
"TestBinary": {
"Type": "Binary",
"Value": "TestBinary"
}
},
"Type": "Notification",
"UnsubscribeUrl": "EXAMPLE",
"TopicArn": topicarn,
"Subject": "TestInvoke"
}
}
]
}
also, this CloudWatch specific example could be useful
{
"Records": [
{
"EventSource": "aws:sns",
"EventVersion": "1.0",
"EventSubscriptionArn": "arn:aws:sns:eu-west-1:000000000000:cloudwatch-alarms:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
"Sns": {
"Type": "Notification",
"MessageId": "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
"TopicArn": "arn:aws:sns:eu-west-1:000000000000:cloudwatch-alarms",
"Subject": "ALARM: \"Example alarm name\" in EU - Ireland",
"Message": "{\"AlarmName\":\"Example alarm name\",\"AlarmDescription\":\"Example alarm description.\",\"AWSAccountId\":\"000000000000\",\"NewStateValue\":\"ALARM\",\"NewStateReason\":\"Threshold Crossed: 1 datapoint (10.0) was greater than or equal to the threshold (1.0).\",\"StateChangeTime\":\"2017-01-12T16:30:42.236+0000\",\"Region\":\"EU - Ireland\",\"OldStateValue\":\"OK\",\"Trigger\":{\"MetricName\":\"DeliveryErrors\",\"Namespace\":\"ExampleNamespace\",\"Statistic\":\"SUM\",\"Unit\":null,\"Dimensions\":[],\"Period\":300,\"EvaluationPeriods\":1,\"ComparisonOperator\":\"GreaterThanOrEqualToThreshold\",\"Threshold\":1.0}}",
"Timestamp": "2017-01-12T16:30:42.318Z",
"SignatureVersion": "1",
"Signature": "Cg==",
"SigningCertUrl": "https://sns.eu-west-1.amazonaws.com/SimpleNotificationService-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.pem",
"UnsubscribeUrl": "https://sns.eu-west-1.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-west-1:000000000000:cloudwatch-alarms:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
"MessageAttributes": {}
}
}
]
}
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With