Using AWS SNS when ec2 instance is deployed in us-west-1

Question

I have a quick question about usage of AWS SNS.

I have deployed an EC2 (t2.micro, Linux) instance in us-west-1 (N.California). I have written a python script using boto3 to send a simple text message to my phone. Later I discovered, there is no SNS service for instances deployed out of us-east-1 (N.Virginia). Till this point it made sense, because I see this below error when i execute my python script, as the region is defined as "us-west-1" in aws configure (AWS cli) and also in my python script.

botocore.errorfactory.InvalidParameterException: An error occurred (InvalidParameter) when calling the Publish operation: Invalid parameter: PhoneNumber Reason:

But to test, when I changed the "region" in aws conifgure and in my python script to "us-east-1", my script pushed a text message to my phone. Isn't it weird? Can anyone please explain why this is working just by changing region in AWS cli and in my python script, though my instance is still in us-west-1 and I dont see "Publish text message" option on SNS dashboard on N.california region?

Is redefining the aws cli with us-east-1 similar to deploying a new instance altogether in us-east-1? I dont think so. Correct me if I am wrong. Or is it like having an instance in us-west-1, but just using SNS service from us-east-1? Please shed some light.

Here is my python script, if anyone need to look at it (Its a simple snippet).

import boto3

def send_message():
    # Create an SNS client
    client = boto3.client("sns", aws_access_key_id="XXXX", aws_secret_access_key="XXXX", region_name="us-east-1")

    # Send your sms message.
    client.publish(PhoneNumber="XXXX",Message="Hello World!")


if __name__ == '__main__':
    send_message()

Mark B Mark B · Accepted Answer · 2017-08-15T19:10:33

Is redefining the aws cli with us-east-1 similar to deploying a new instance altogether in us-east-1?

No, it isn't like that at all.

Or is it like having an instance in us-west-1, but just using SNS service from us-east-1?

Yes, that's all you are doing. You can connect to any AWS regions' API from anywhere on the Internet. It doesn't matter that it is running on an EC2 instance in a specific region, it only matters what region you tell the SDK/CLI to use.

You could run the same code on your local computer. Obviously your local computer is not running on AWS so you would have to tell the code which AWS region to send the API calls to. What you are doing is the same thing.

Code running on an EC2 server is not limited into using the AWS API in the same region that the EC2 server is in.

Using AWS SNS when ec2 instance is deployed in us-west-1

2 Answers