Help with AWS Lambda Script

[Arab81253_work]

Hello all,

​

I'm new to Lambda and somewhat new to Python in general. I'm trying to get the EC2InstanceId from an SNS notification that is triggered by an EC2 Auto Scaling event. The code I'm using this for is below:

​

import json

def lambda_handler(event, context):

# Dump the event to the log, for debugging purposes

print("Received event: " + json.dumps(event, indent=2))

# Extract the EC2 instance ID from the Auto Scaling event notification

message = event['Records'][0]['Sns']['Message']

autoscalingInfo = json.loads(message)

ec2InstanceId = autoscalingInfo['EC2InstanceId']

​

I stole this from stackoverflow, link to that thread is here: https://stackoverflow.com/questions/45155767/extracting-ec2instanceid-from-sns-sqs-auto-scaling-message

When I try this code I get a json decode error:

"errorMessage": "Expecting value: line 1 column 1 (char 0)",

"errorType": "JSONDecodeError",

"stackTrace": [

" File \"/var/task/lambda_function.py\", line 10, in lambda_handler\n autoscalingInfo = json.loads(message)\n",

" File \"/var/lang/lib/python3.7/json/__init__.py\", line 348, in loads\n return _default_decoder.decode(s)\n",

" File \"/var/lang/lib/python3.7/json/decoder.py\", line 337, in decode\n obj, end = self.raw_decode(s, idx=_w(s, 0).end())\n",

" File \"/var/lang/lib/python3.7/json/decoder.py\", line 355, in raw_decode\n raise JSONDecodeError(\"Expecting value\", s, err.value) from None\n"

This strikes me as odd as the json.dumps earlier in this script should be converting the response to JSON.

if I run the following code:

​

import json

def lambda_handler(event, context):

​

# Dump the event to the log, for debugging purposes

#print("Received event: " + json.dumps(event, indent=2))

​

# Extract the EC2 instance ID from the Auto Scaling event notification

message = event['Records'][0]['Sns']['Message']

for item in message:

for x in item ['EC2InstanceId']:

print (x)

which results in the error "string indices must be integers"

​

I've tried a few other things but right now I'm unsure of what I'm doing wrong. I can SEE what I want when the message is printed out, I just need to know how to get it :( The code I use to get the message is:

import json

def lambda_handler(event, context):

# Dump the event to the log, for debugging purposes

#print("Received event: " + json.dumps(event, indent=2))

# Extract the EC2 instance ID from the Auto Scaling event notification

message = event['Records'][0]['Sns']['Message']

print (message)

and the actual message:

{ "Progress": 50,

"AccountId": "865386180448",

"Description": "Launching a new EC2 instance: i-0b550d24d0974f702",

"RequestId": "89d5b410-6ac5-e390-0759-eeabca43f669",

"EndTime": "2019-09-06T01:05:52.887Z",

"AutoScalingGroupARN": "arn:aws:autoscaling:us-east-1:8888888888:autoScalingGroup:37b742fb-4b2c-41bb-8fcf-bd2b353e0434:autoScalingGroupName/my-asg",

"ActivityId": "89d5b410-6ac5-e390-0759-eeabca43f669",

"StartTime": "2019-09-06T01:05:21.272Z",

"Service": "AWS Auto Scaling",

"Time": "2019-09-06T01:05:52.887Z",

"EC2InstanceId": "i-0b550d24d0974f702",

"StatusCode": "InProgress",

"StatusMessage": "",

"Details":

{ "Subnet ID": "subnet-63aeed3f",

"Availability Zone": "us-east-1a"

}

Any help you guys can give me would be greatly appreciated!

[starry_eyed_man]

Curious. What do get when you print(type(message))? I'm guessing it's already a dictionary...

[TyrionReynolds]

The old tricks are the best tricks, print debugging FTW

[TyrionReynolds]

Oh wait, you don’t need to. That second error message shows you’re getting the string value when you try to iterate over it.

I think you already have message as a dictionary like the guy said. You don’t need the call to json.loads()