AmazonSQS CloudEvents Sample

Prerequisites

Security and access configuration

Add the AWS Access Key ID and AWS Secret Access Key to the following environment variables:

• Access Key ID in AWS_ACCESS_KEY_ID
• Secret Access Key in AWS_SECRET_ACCESS_KEY
• Default Region in AWS_REGION

See also AWS Account Identifiers, Managing Access Keys for an AWS Account, and IAM Security Credentials.

See also AWS Regions for a list of available regions.

S3 configuration

The S3 bucket should be configured to generate notifications that are ultimately delivered to the SQS queue matching the endpoint. The following is a sample configuration that can be used to generate S3 notifications:

• Configure an S3 bucket to send notifications to SQS
• Create an Amazon EventBridge Pipe that picks up the messages from the SQS queue
• Configure the Amazon EventBridge Pipe to transform messages to the CloudEvents schema as specified in the CloudEvents specification
• Configure the Amazon EventBridge Pipe to call AWS Lambda that would enrich messages with the proper content-type property and send them to the SQS queue matching the endpoint

Code walk-through

This sample shows an endpoint receiving a CloudEvents message from the Amazon Simple Queue Service (Amazon SQS)

• The Endpoint defines the schema for the CloudEvents message.
• The Endpoint enables CloudEvents support and configures the type mapping.
• The Endpoint configures the serializer to support fields and properties with different casing.
• The Endpoint receives the message and calls the proper handler.

CloudEvents message schema

The message schema is defined as follows:

public class AwsBlobNotification :
    IMessage
{
    public string Key { get; set; }
    public int Size { get; set; }
    public string ETag { get; set; }
    public string Sequencer { get; set; }
}

This schema must match the schema of the notification generated by S3.

CloudEvents support configuration

CloudEvents support must be explicitly enabled:

var cloudEventsConfiguration = endpointConfiguration.EnableCloudEvents();

The configuration includes the type mapping to match the message's content-type with the .NET types representing the incoming messages:

cloudEventsConfiguration.TypeMappings["ObjectCreated:Put"] = [typeof(AwsBlobNotification)];

To handle the JSON structured messages that do not have the Content-Type header set properly, enable the Permissive mode:

cloudEventsConfiguration.EnvelopeUnwrappers.Find<CloudEventJsonStructuredEnvelopeUnwrapper>()?.EnvelopeHandlingMode = JsonStructureEnvelopeHandlingMode.Permissive;

To support the differences between uppercase letters and lowercase letters in the schema definition and content, the serializer is configured to use case insensitive mapping:

endpointConfiguration.UseSerialization<SystemJsonSerializer>().Options(new JsonSerializerOptions
{
    PropertyNameCaseInsensitive = true,
    IncludeFields = true
});

Running the sample

1. Run the sample.
2. Generate the ObjectCreated:Put event by creating a new file in the S3 bucket.
3. Observe that the sample prints out the URL of the newly created file.