Go LocalStack Example

This is a simple project that demonstrates how to use LocalStack with Golang It shows a fan-out messaging pattern using S3, SNS, and SQS.

• When LocalStack starts (make start-deps), the script ./aws-init/init.sh is executed. It does the following:

  • Creates an S3 bucket called awesome-bucket
  • Creates an SNS topic called awesome-sns-topic
  • Configures the SNS topic to allow S3 to publish messages to it
  • Adds a notification configuration so that any file uploaded to the S3 bucket with the prefix new-files/ and suffix .txt triggers a message to the SNS topic
  • Creates three SQS queues, with VisibilityTimeout set to 30 and ReceiveMessageWaitTimeSeconds set to 20 (for long polling)
  • Subscribes the three queues to the SNS topic (the famous fan-out pattern)

• Once the infrastructure is set up, you can run the server, This is a simple app with two endpoints to send files to S3:

  • Run the app:

    make start-server

  • Send one file:

    make create-file

    Can send custom text too:

    make create-file text="Hello World"
    

  • Send multiple files: (It creates 10 files by default)

    make create-files

    Or can specify a number of files:

    make create-files n=20

• Start the poller:

  make start-poller

• The poller executes ReceiveMessage on every queue configured and prints the file key. (Each queue has a different configuration so you can see how they behave. Nothing fancy)

To sum up:

Each uploaded file triggers an S3 event → SNS → SQS → Poller prints the S3 file key.

Note: The commands make start-server and make start-poller run the services directly on your machine. To run everything inside Docker, use:

 make start

Prerequisites

• Docker
• Go - If running the app directly on your machine (outside Docker)

Some docs

• sqs
• sns

To-Do

• A couple of tests wouldn’t hurt, lol.