AWS Lambda key error

Question

I have lambda function to create new AMI and attach to current auto scale group. This function complete works when I create a test custom test case and pass the payload. Issue occurs when I trigger this from SNS:

import json
import boto3
import time
import sys

asObj = boto3.client('autoscaling')
ec2Obj = boto3.client('ec2')

def lambda_handler(event, context):
    targetASG = event[‘Records’][0][‘Sns’][‘Message’]
    ASG = asObj.describe_auto_scaling_groups(AutoScalingGroupNames=[event['targetASG']])
    sourceInstanceId = ASG.get('AutoScalingGroups')[0]['Instances'][0]['InstanceId']
    Date=time.strftime("%d%m%y")
    Time=time.strftime("%H%M%S")
    amiName = "Automated_%s_%s" % (Date, Time)
    configName = "Automated_%s_%s" % (Date, Time)

    CreateNewImage = ec2Obj.create_image(
        InstanceId = sourceInstanceId,
        Name = amiName,
        Description = 'Automatically Created Image from Lambda Service',
        NoReboot = True)
    Image = []
    Image.append(CreateNewImage)
    def getCreatedID(Image):
        for i in Image:
            ID = i['ImageId']
            return ID
    AMINewID = getCreatedID(Image)
    CreateNewConfig = asObj.create_launch_configuration(
        LaunchConfigurationName = configName,
        ImageId = AMINewID,
        InstanceId = sourceInstanceId)

    updateASG = asObj.update_auto_scaling_group(
        AutoScalingGroupName = event['targetASG'],
        LaunchConfigurationName = configName)
    return 'A new AMI has been Created `%s` Updated ASG `%s` with new launch configuration `%s` which includes AMI `%s`.' % (amiName,event['targetASG'], configName, AMINewID)

To trigger my lambda function I use AWS SNS topic and I publish a msg following message, message type: raw

{   "targetASG": "pre-production-xxx" }

But I get this error:

'targetASG': KeyError Traceback (most recent call last): File "/var/task/lambda_function.py", line 13, in lambda_handler ASG = asObj.describe_auto_scaling_groups(AutoScalingGroupNames=[event['targetASG']]) KeyError: 'targetASG'

How can I resolve this?

H6_ · Accepted Answer · 2018-06-01 11:14:40Z

1

ASG = asObj.describe_auto_scaling_groups(AutoScalingGroupNames=[event['targetASG']])

I think targetASG is not part of the SNS event.. SNS Events look like this:

{ "Records": [ { "EventVersion": "1.0", "EventSubscriptionArn": "arn:aws:sns:EXAMPLE", "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": "arn:aws:sns:EXAMPLE", "Subject": "TestInvoke" } } ] }

You should grab the message and parse the targetASG value from there like e.g.

import json

[...]
targetASG = event[‘Records’][0][‘Sns’][‘Message’]
myMessage = json.loads(targetASG)
name = myMessage['targetASG']
ASG = asObj.describe_auto_scaling_groups(AutoScalingGroupNames=[name])
[...]

edited Jun 1, 2018 at 11:14

answered Jun 1, 2018 at 11:07

H6_

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1 Comment

Frodo Over a year ago

yes superb, so when i trigger lambda from SNS, when deployment is success. i wont able to get the current ASG Name from that payload right? so i went on approach like this. so i trigger lambda when deployment success so i hard coded the ASG name on the function. any better approach ?

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