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Publishing large messages with Amazon SNS

Amazon SNS supports message payloads up to 1 MiB (1,048,576 bytes) when you configure the MaximumMessageSize topic attribute. By default, topics accept messages up to 256 KiB. Topics with MaximumMessageSize set above 256 KiB support Amazon Data Firehose, Amazon SQS, and AWS Lambda subscriptions, with up to 100 total subscriptions per topic.

How publishing large messages works

You can set the MaximumMessageSize topic attribute to any integer value between 1,024 and 1,048,576 bytes. By default, all existing and newly created topics have a MaximumMessageSize of 262,144 bytes (256 KiB).

When you publish a message, Amazon SNS validates the combined size of the message body and message attributes against the topic's configured MaximumMessageSize. If the combined size exceeds the limit, Amazon SNS returns an InvalidParameter error on publish.

Supported configuration

When you set MaximumMessageSize above 256 KiB, Amazon SNS supports the following configuration.

Subscription limits

The topic supports up to 100 total subscriptions. If you attempt to create additional subscriptions, Amazon SNS returns an InvalidParameter error.

Supported endpoint types

Topics with MaximumMessageSize above 256 KiB support the following endpoint types:

Topics with MaximumMessageSize at 256 KiB or below also support HTTP/HTTPS, SMS, email, email-json, and mobile push (application) endpoints.

Setting MaximumMessageSize on existing topics

You can increase or decrease a topic's MaximumMessageSize at any time. After you change the value, Amazon SNS validates new publish requests against the updated limit.

To set MaximumMessageSize above 256 KiB, the topic must have 100 or fewer total subscriptions, all of which must be supported endpoint types (Amazon Data Firehose, Amazon SQS, or AWS Lambda). If the topic has unsupported endpoint types or more than 100 subscriptions, Amazon SNS returns an InvalidParameter error.

Configuring your topic for large messages

Using the AWS Management Console

Using the AWS CLI

Set MaximumMessageSize when creating a new topic:

aws sns create-topic \
    --name my-large-message-topic \
    --attributes MaximumMessageSize=1048576

Replace my-large-message-topic with your topic name and 1048576 with your desired maximum message size in bytes.

Set MaximumMessageSize on an existing topic:

aws sns set-topic-attributes \
    --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \
    --attribute-name MaximumMessageSize \
    --attribute-value 1048576

Replace arn:aws:sns:us-east-1:123456789012:my-topic with the ARN of your topic and 1048576 with your desired maximum message size in bytes.

Verify your topic's current MaximumMessageSize. If the attribute has not been explicitly set, it does not appear in the response, and the topic uses the default of 262,144 bytes (256 KiB).

aws sns get-topic-attributes \
    --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic

Amazon SNS API reference for large messages

Large message support uses existing Amazon SNS APIs. You don't need new API operations.

Endpoint compatibility

The following list describes how Amazon SNS delivers your large messages to each supported endpoint type.

Best practices

Configure dead-letter queues

We recommend configuring a dead-letter queue (DLQ) on all subscriptions to handle failed message delivery. A DLQ captures messages that Amazon SNS can't successfully deliver to the subscribed endpoint, allowing you to inspect and reprocess them. For more information, see Amazon SNS dead-letter queues.

Monitor with CloudWatch metrics and alarms

Use CloudWatch metrics to monitor message delivery and set alarms on failed deliveries. The NumberOfNotificationsFailed metric tracks messages that Amazon SNS can't deliver to subscribed endpoints. Create a CloudWatch alarm on this metric to receive alerts when delivery failures occur. For more information, see Monitoring Amazon SNS topics using CloudWatch.

Publishing messages larger than 1 MiB with Amazon S3

To publish messages larger than 1 MiB, use the Amazon SNS Extended Client Library for Java or the Amazon SNS Extended Client Library for Python to store payloads in Amazon S3 and publish a reference through Amazon SNS. These libraries support messages up to 2 GB and are compatible with both Standard and FIFO topics. For instructions on increasing MaximumMessageSize before choosing this approach, see Configuring your topic for large messages.