Publish messages to an Amazon SNS topic with Step Functions - Amazon Step Functions
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Publish messages to an Amazon SNS topic with Step Functions

Learn how to use Step Functions to publish messages to an Amazon SNS topic. This page lists the supported Amazon SNS API actions and provides example Task states to publish message to Amazon SNS.

Step Functions can control certain Amazon services directly from Using Amazon States Language to define Step Functions workflows (ASL). To learn more, see Integrating other services and Passing parameters to a service API in Step Functions.

How the Optimized Amazon SNS integration is different than the Amazon SNS Amazon SDK integration

There are no optimizations for the Request Response or Wait for a Callback with the Task Token integration patterns.

Supported Amazon SNS APIs:

Note

There is a quota for the maximum input or result data size for a task in Step Functions. This restricts you to 256 KB of data as a UTF-8 encoded string when you send to, or receive data from, another service. See Quotas related to state machine executions.

Parameters in Step Functions are expressed in PascalCase

Even if the native service API is in camelCase, for example the API action startSyncExecution, you specify parameters in PascalCase, such as: StateMachineArn.

The following includes a Task state that publishes to an Amazon Simple Notification Service (Amazon SNS) topic.

{
 "StartAt": "Publish to SNS",
 "States": {
   "Publish to SNS": {
     "Type": "Task",
     "Resource": "arn:aws-cn:states:::sns:publish",
     "Parameters": {
       "TopicArn": "arn:aws-cn:sns:us-east-1:123456789012:myTopic",
       "Message.$": "$.input.message",
       "MessageAttributes": {
         "my_attribute_no_1": {
           "DataType": "String",
           "StringValue": "value of my_attribute_no_1"
         },
         "my_attribute_no_2": {
           "DataType": "String",
           "StringValue": "value of my_attribute_no_2"
         }
       }
     },
     "End": true
    }
  }
}

Passing dynamic values. You can modify the above example to dynamically pass an attribute from this JSON payload:

{
"input": {
  "message": "Hello world"
},
"SNSDetails": {
  "attribute1": "some value",
  "attribute2": "some other value",
}
}

Append the .$ to the StringValue field:

"MessageAttributes": {
  "my_attribute_no_1": {
      "DataType": "String",
      "StringValue.$": "$.SNSDetails.attribute1"
  },
  "my_attribute_no_2": {
      "DataType": "String",
      "StringValue.$": "$.SNSDetails.attribute2"
  }

The following includes a Task state that publishes to an Amazon SNS topic, and then waits for the task token to be returned. See Wait for a Callback with the Task Token.

{  
   "StartAt":"Send message to SNS",
   "States":{  
      "Send message to SNS":{  
         "Type":"Task",
         "Resource":"arn:aws:states:::sns:publish.waitForTaskToken",
         "Parameters":{  
            "TopicArn":"arn:aws:sns:us-east-1:123456789012:myTopic",
            "Message":{  
               "Input.$":"$",
               "TaskToken.$":"$$.Task.Token"
            }
         },
         "End":true
      }
   }
}

For information about how to configure IAM permissions when using Step Functions with other Amazon services, see How Step Functions generates IAM policies for integrated services.