Configuring SNS Topic for Application Push Notifications

Question

Pulumi · Accepted Answer

Amazon Simple Notification Service (Amazon SNS) is a managed service that provides message delivery from publishers to subscribers (also known as producers and consumers). It allows you to send messages to a large number of subscribers, including distributed systems, services, and mobile devices.

Here is how to create an SNS Topic configured for application push notifications using Pulumi in TypeScript:

### Prerequisites
1. AWS Account setup with the necessary permissions to create an SNS Topic.
2. Pulumi CLI installed and configured for AWS.

### Explanation of Resources Used
- `aws.sns.Topic`: Represents an SNS Topic where messages can be published.
- `aws.sns.PlatformApplication`: Represents a platform application that is used for sending push notifications to mobile devices.
- `aws.sns.TopicSubscription`: Represents the subscription of an endpoint or a protocol to the SNS topic.

### Program Overview
1. First, we create an SNS Topic which is a logical access point and communication channel for sending messages and notifications to subscribers.
2. Then, we create a Platform Application resource. This resource is part of Amazon SNS that lets you send push notifications directly to mobile devices.
3. After that, you can create a Topic Subscription, which connects an endpoint to the topic. For instance, you can create a subscription to send push notifications to mobile devices.

Here is the Pulumi program to set up these resources:

```typescript
import * as aws from "@pulumi/aws";

// Create an SNS Topic to which messages will be sent.
const appNotificationsTopic = new aws.sns.Topic("appNotificationsTopic", {
    // Optionally, you can add tags or other properties here
});

// Create a Platform Application for sending push notifications
const platformApp = new aws.sns.PlatformApplication("platformApp", {
    platform: "APNS", // For Apple devices use APNS, for Android use GCM/FCM
    
    // These would be credentials obtained from Apple or Google for sending notifications
    platformPrincipal: "base64EncodedPrincipal",
    platformCredential: "base64EncodedCredential",
    
    // Optionally, you can add other configurations like Event delivery failure topic etc.
});

// Create a Subscription for the Platform Application Endpoint
const endpointSubscription = new aws.sns.TopicSubscription("endpointSubscription", {
    // To subscribe an endpoint to the topic, specify the Topic ARN and your endpoint.
    // The protocol in our case would be the application
    topic: appNotificationsTopic.arn,
    protocol: "application",
    endpoint: platformApp.arn, // The Endpoint ARN from the Platform Application
});

// Exports the ARNs of the created resources
export const topicArn = appNotificationsTopic.arn;
export const platformAppArn = platformApp.arn;
export const subscriptionArn = endpointSubscription.arn;
```

In this program, the `PlatformApplication` is given a `platform` which is either `"APNS"` or `"GCM"` for Apple or Android devices, respectively. You need to fill in the `platformPrincipal` and `platformCredential` with the appropriate values that you get from Apple's Push Notification service or Firebase Cloud Messaging service. These are usually in a base64 encoded format.

Finally, the ARN (Amazon Resource Name) of the SNS Topic, Platform Application, and the Topic Subscription are exported. These ARNs can be used to identify the resources in your AWS environment.

To run this Pulumi code, you'll need to save it into a file with a `.ts` extension and then execute it within a Pulumi project. If you don't have a Pulumi project set up yet, you can create one with `pulumi new aws-typescript` and follow the instructions. After that, you can run `pulumi up` to deploy your cloud resources.