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Overview

The SNSTopic construct creates an Amazon SNS topic for pub/sub messaging. Use it to fan out events to multiple subscribers (Lambda, SQS, HTTP endpoints) from a single publish call.

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Import

import { SNSTopic } from "@fjall/components-infrastructure/lib/resources/aws/messaging/sns";

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Basic Usage

const topic = new SNSTopic(scope, "Alerts", {});

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Using the Messaging Factory

The recommended way to add SNS to a Fjall application is through the MessagingFactory: 
import { MessagingFactory } from "@fjall/components-infrastructure/lib/patterns/aws/messaging";

const alerts = app.addMessaging(
  MessagingFactory.build("Alerts", {
    type: "topic",
  }),
);

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Properties

PropertyTypeDefaultDescription
topicNamestringAuto-generatedTopic name
displayNamestringNoneHuman-readable name for SMS subscriptions
fifobooleanfalseCreate a FIFO topic (strict ordering)
contentBasedDeduplicationbooleantrue (FIFO)Content-based deduplication. Defaults to true on FIFO topics, ignored on standard topics
removalPolicy"DESTROY" | "RETAIN""RETAIN"What happens on stack deletion

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Methods

MethodReturnsDescription
getTopicArn()stringTopic ARN
getTopicName()stringTopic name
getTopic()ITopicCDK Topic construct
grantPublish(grantee)GrantGrant permission to publish messages
grantSubscribe(grantee)GrantGrant permission to subscribe to the topic

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Examples

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Standard Topic

const notifications = app.addMessaging(
  MessagingFactory.build("Notifications", {
    type: "topic",
    displayName: "Order Notifications",
  }),
);

notifications.grantPublish(apiService);

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FIFO Topic

FIFO topics deliver messages in order and support deduplication: 
const events = app.addMessaging(
  MessagingFactory.build("Events", {
    type: "topic",
    fifo: true,
    contentBasedDeduplication: true,
  }),
);

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Fan-Out to Multiple Queues

Combine SNS with SQS for fan-out patterns: 
import { SqsSubscription } from "aws-cdk-lib/aws-sns-subscriptions";

const orderTopic = app.addMessaging(
  MessagingFactory.build("OrderEvents", {
    type: "topic",
  }),
);

const billingQueue = app.addMessaging(
  MessagingFactory.build("Billing", {
    type: "queue",
  }),
);

const shippingQueue = app.addMessaging(
  MessagingFactory.build("Shipping", {
    type: "queue",
  }),
);

// Subscribe queues to the topic
orderTopic
  .getTopic()
  .addSubscription(new SqsSubscription(billingQueue.getQueue()));
orderTopic
  .getTopic()
  .addSubscription(new SqsSubscription(shippingQueue.getQueue()));

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CloudFormation Outputs

OutputDescription
{id}TopicArnTopic ARN
{id}TopicNameTopic name

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Next Steps

Messaging Factory

Create messaging resources via the factory pattern

SQS Queue

Combine with SQS for fan-out patterns