# SNS
<a name="sam-property-function-sns"></a>

The object describing an `SNS` event source type.

SAM generates [https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html) resource when this event type is set

## Syntax
<a name="sam-property-function-sns-syntax"></a>

To declare this entity in your Amazon Serverless Application Model (Amazon SAM) template, use the following syntax.

### YAML
<a name="sam-property-function-sns-syntax.yaml"></a>

```
  [FilterPolicy](#sam-function-sns-filterpolicy): {{[SnsFilterPolicy](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-filterpolicy)}}
  FilterPolicyScope: {{String}}
  RedrivePolicy: {{Json}}
  [Region](#sam-function-sns-region): {{String}}
  [SqsSubscription](#sam-function-sns-sqssubscription): {{Boolean | SqsSubscriptionObject}}
  [Topic](#sam-function-sns-topic): {{String}}
```

## Properties
<a name="sam-property-function-sns-properties"></a>

 `FilterPolicy`   <a name="sam-function-sns-filterpolicy"></a>
The filter policy JSON assigned to the subscription. For more information, see [GetSubscriptionAttributes](https://docs.amazonaws.cn/sns/latest/api/API_GetSubscriptionAttributes.html) in the Amazon Simple Notification Service API Reference.  
*Type*: [SnsFilterPolicy](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-filterpolicy)  
*Required*: No  
*Amazon CloudFormation compatibility*: This property is passed directly to the `[FilterPolicy](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-filterpolicy)` property of an `AWS::SNS::Subscription` resource.

 `FilterPolicyScope`   <a name="sam-function-sns-filterpolicyscope"></a>
This attribute lets you choose the filtering scope by using one of the following string value types:  
+ `MessageAttributes` – The filter is applied on the message attributes.
+ `MessageBody` – The filter is applied on the message body.
*Type*: String  
*Required*: No  
*Default*: `MessageAttributes`  
*Amazon CloudFormation compatibility*: This property is passed directly to the ` [ FilterPolicyScope](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-filterpolicyscope)` property of an `AWS::SNS::Subscription` resource.

 `RedrivePolicy`   <a name="sam-function-sns-redrivepolicy"></a>
When specified, sends undeliverable messages to the specified Amazon SQS dead-letter queue. Messages that can't be delivered due to client errors (for example, when the subscribed endpoint is unreachable) or server errors (for example, when the service that powers the subscribed endpoint becomes unavailable) are held in the dead-letter queue for further analysis or reprocessing.  
For more information about the redrive policy and dead-letter queues, see [ Amazon SQS dead-letter queues](https://docs.amazonaws.cn/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-dead-letter-queues.html) in the *Amazon Simple Queue Service Developer Guide*.  
*Type*: Json  
*Required*: No  
*Amazon CloudFormation compatibility*: This property is passed directly to the `[ RedrivePolicy](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-redrivepolicy)` property of an `AWS::SNS::Subscription` resource.

 `Region`   <a name="sam-function-sns-region"></a>
For cross-region subscriptions, the region in which the topic resides.  
If no region is specified, CloudFormation uses the region of the caller as the default.  
*Type*: String  
*Required*: No  
*Amazon CloudFormation compatibility*: This property is passed directly to the `[Region](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#cfn-sns-subscription-region)` property of an `AWS::SNS::Subscription` resource.

 `SqsSubscription`   <a name="sam-function-sns-sqssubscription"></a>
Set this property to true, or specify `SqsSubscriptionObject` to enable batching SNS topic notifications in an SQS queue. Setting this property to `true` creates a new SQS queue, whereas specifying a `SqsSubscriptionObject` uses an existing SQS queue.  
*Type*: Boolean \| [SqsSubscriptionObject](sam-property-function-sqssubscriptionobject.md)  
*Required*: No  
*Amazon CloudFormation compatibility*: This property is unique to Amazon SAM and doesn't have an Amazon CloudFormation equivalent.

 `Topic`   <a name="sam-function-sns-topic"></a>
The ARN of the topic to subscribe to.  
*Type*: String  
*Required*: Yes  
*Amazon CloudFormation compatibility*: This property is passed directly to the `[TopicArn](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-sns-subscription.html#topicarn)` property of an `AWS::SNS::Subscription` resource.

## Examples
<a name="sam-property-function-sns--examples"></a>

### SNS Event Source Example
<a name="sam-property-function-sns--examples--sns-event-source-example"></a>

SNS Event Source Example

#### YAML
<a name="sam-property-function-sns--examples--sns-event-source-example--yaml"></a>

```
Events:
  SNSEvent:
    Type: SNS
    Properties:
      Topic: arn:aws:sns:us-east-1:123456789012:my_topic
      SqsSubscription: true
      FilterPolicy:
        store:
          - example_corp
        price_usd:
          - numeric:
              - ">="
              - 100
```