NATS Data Series

This repository contains the sample code for the NATS Data Series blog posts. Each post has its own directory which includes a Taskfile that can be used to run the code.

Prerequisites

We rely on a few things to be installed on your system to run the code. The following is a list of tools we expect to be available:

• Task for running the code and making your life easier
• NATS cli for running the server and interacting with it
• Go for building the code

Make sure you have these installed before running the code.

Running the server

To run the server, you can use the following command:

task server

This will start a server on your system that will be used as part of the examples. It will also create a nats-cli context you can use to interact with the server.

run nats context select rethink to select it

Get In Touch

Hop into the Data Series Slack Channel and share your thoughts. I would love

Posts

Introduction

The first post in the series sets the stage for the rest of the series. It is a brief recap of how we got to where we are today and why we need to rethink the way we build systems.

Rethinking the system of record

This post explores how to use NATS to build a system of record that can be used to store and retrieve data from a distributed system.

Running the code

1. Start the server if it hasn't been started yet
2. Run task rethink:setup to build the code and create the JetStream stream and KV store
3. Run task rethink:listen:low_stock to start listening for low stock events
4. Run the next few commands in their own terminal windows
   1. Run task rethink:run:low_stock_detector to start detecting low stock items
   2. Run task rethink:run:stock_updater to start updating the stock levels on stock.sold and stock.replenished events
   3. Run task rethink:run:stock_event_generator to start generating stock events

What you should see

The stock_event_generator will send change events and print out the updates it made:

Replenished 53 Pears (54 left)
Replenished 14 Grapes (15 left)
Sold 27 Pears (27 left)
Sold 60 Oranges (8 left)
...

The stock_updater will update the stock based on the stock.sold and stock.replenished events:

Received stock sold event: {"product_name":"Grapes","quantity":1}
Received stock replenished event: {"product_name":"Grapes","quantity":63}
Received stock replenished event: {"product_name":"Oranges","quantity":34}
Received stock sold event: {"product_name":"Apples","quantity":4}
Received stock sold event: {"product_name":"Pears","quantity":4}
...

The low_stock_detector will look at the stock levels and send an event when the stock is low. It will not output anything but send a message stock.low message

The listener will listen for the stock.low events and print out the message it received:

[#182] Received on "product.Pears"
myorg_type: stock.low
myorg_format: application/json
myorg_msg_id: mBZvheMnM10QcgS9ZPCguH

{"product_name":"Pears"}


[#183] Received on "product.Pears"
myorg_format: application/json
myorg_msg_id: A3WBvfAGUqwQCnZPeHBU8x
myorg_type: stock.low

{"product_name":"Pears"}

Cleaning up

1. Each of the tasks can be stopped by pressing ctrl+c. Just keep the server running for the time being
2. Run task rethink:teardown to remove the JetStream stream and KV store
3. Stop the server by pressing ctrl+c
4. Run task clean to remove any lingering server files