AWS Lambda for Client to Client Push Notifications - amazon-web-services

Question

Thanks to this community I've learned that is possible to send AWS SNS Push notifications via Lambda with node.js (as a result of Parse migration). I am still struggling with the following:
Can this be done client to client x likes y's z. Where x is user 1, y is user 2 and z is the object being liked? If so, it seems like Cognito is not required that it can read directly from the database but is that accurate?
Does anyone have an example of how this was implemented?
Again, we don't want to broadcast to all users on a schedule but rather when a client performs an action.
Thanks so much in advance!

Answer 1

Let's say you have Device1 which creates a piece of content. That is distributed to a number of users. Device2 receives this content and "likes" it.
Assumption:
you have registered for push notifications on the device, and created a SNS endpoint on AWS. You have stored that endpoint ARN in your database, and associated it with either the Cognito Id, or the content Id. If your data is normalized, then you'd typically have the SNS endpoint associated with the device.
Your Lambda will need to have access to that data source and look up that SNS endpoint to send push notifications to. This will depend on what sort of data store you are using (RDS, DynamoDB, something else). What sort of access that is, and how you secure it is a whole other topic.
From your Lambda, you fetch the ARN to send the push notification to. If you pass in the content Id from the Like, and have the Cognito Id from the device that Liked it, you can then look up the information you need. You then construct a SNS payload (I'm assuming APNS in this example), then send it off to SNS.
var message = {
"default": "New Like!",
"APNS": {
"aps": {
"alert": "New Like!"
}
}
};
var deviceParams = {
Message: JSON.stringify(message),
Subject: "New Like",
TargetArn: targetArn,
MessageStructure: "json"
};
self.sns.publish(deviceParams, function (err) {
if (err) {
console.error("Error sending SNS: ", err);
}
});
It's not all done for you like it might be with Parse. You need to work a lot harder on AWS, but you have near unlimited power to do what you want.
If this is a bit too much, you may want to consider Google's newly updated Firebase platform. It's very Parse-like: https://firebase.google.com/
Hope that helps you move forward a bit.
Further reading:
http://docs.aws.amazon.com/sns/latest/dg/mobile-push-apns.html
https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/TheNotificationPayload.html
http://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/SNS.html