AWS: Publish SNS message for Lambda function via boto3 (Python2)

Question

I am trying to publish to an SNS topic which will then notify a Lambda function, as well as an SQS queue. My Lambda function does get called, but the CloudWatch logs state that my "event" object is None. The boto3 docs states to use the kwarg MessageStructure='json' but that throws a ClientError.

Hopefully I've supplied enough information.

Example Code:

import json
import boto3

message = {"foo": "bar"}
client = boto3.client('sns')
response = client.publish(
    TargetArn=arn,
    Message=json.dumps(message)
)

You only need the MessageStructure param if you are trying to send different messages to different types of subscribers (e.g. email vs. SMS). Could you include the code for your Lambda function? I'm assuming that the code shown above works without any errors, right? — garnaat
– garnaat, Commented Dec 2, 2015 at 14:00
If you're running this using the Python SDK on say an EC2-Instance don't forget to add a region inside the client e.g., client = boto3.client('sns', region_name='us-east-1') bradmontgomery.net/blog/… — Kyle Bridenstine
– Kyle Bridenstine, Commented May 18, 2018 at 16:35

ryantuck · Accepted Answer · 2016-05-03 16:24:44Z

111

you need to add a default key to your message payload, and specify MessageStructure:

import json
import boto3

message = {"foo": "bar"}
client = boto3.client('sns')
response = client.publish(
    TargetArn=arn,
    Message=json.dumps({'default': json.dumps(message)}),
    MessageStructure='json'
)

answered May 3, 2016 at 16:24

ryantuck

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7 Comments

Chris Johnson Over a year ago

Your example doesn't include a default

ryantuck Over a year ago

sure it does - it's in the dict passed to the Message arg.

Kyle Bridenstine Over a year ago

I don't understand what your message object is in terms of the foo bar stuff. What's a real example? message = {"body": "Hello World!"}?

Kyle Bridenstine Over a year ago

If you're running this using the Python SDK on say an EC2-Instance don't forget to add a region inside the client e.g., client = boto3.client('sns', region_name='us-east-1') bradmontgomery.net/blog/…

abc Over a year ago

@ryantuck Is the 2nd json.dumps() necessary at all?

|

Amir · Accepted Answer · 2017-11-22 23:10:48Z

41

Just in case you want to have different messages for sms and email subscribers:

import json
import boto3

message = {"foo": "bar"}
client = boto3.client('sns')
response = client.publish(
    TargetArn=arn,
    Message=json.dumps({'default': json.dumps(message),
                        'sms': 'here a short version of the message',
                        'email': 'here a longer version of the message'}),
    Subject='a short subject for your message',
    MessageStructure='json'
)

answered Nov 22, 2017 at 23:10

Amir

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2 Comments

Kyle Bridenstine Over a year ago

If you're running this using the Python SDK on say an EC2-Instance don't forget to add a region inside the client e.g., client = boto3.client('sns', region_name='us-east-1') bradmontgomery.net/blog/…

Narendra Maru Over a year ago

help full in my case

Kerem · Accepted Answer · 2021-02-01 17:16:12Z

5

In case you are publishing your message with a filter policy, you should also use MessageAttributes parameter to add your SNS filter.

To invoke your Lambda with this SNS subscription filter policy {"endpoint": ["distance"]}:

import json
import boto3

message = {"foo": "bar"}
client = boto3.client('sns')
response = client.publish(
    TargetArn=arn,
    Message=json.dumps({'default': json.dumps(message)}),
    MessageStructure='json',
    MessageAttributes={
                        'foo': {
                            'DataType': 'String',
                            'StringValue': 'bar'
                        }
                    },
)

answered Feb 1, 2021 at 17:16

Kerem

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