I've finished at the Co-op after four years. I was feeling emotional and wrote some "wise words". I thought I'd record them here. In the future, when I'm reminiscing, they can transport me back to this feeling.

Here is something I had to write down at work. Something I've tried to say (with varying success) more than once. That I'm publishing here so I can refer back to it in future and in case it is useful for someone else

When I am thinking about this, I am thinking about three things

Two of the agile principles

• Continuous attention to technical excellence and good design enhances agility.

• Simplicity–the art of maximising the amount of work not done–is essential.

And the XP Rule

• Refactor Mercilessly

Since October 2017 I've been keeping week notes. I've found them a fantastic tool to track my focus and to remember to reflect on success (or lack of it). I didn't write them for most of 2020. When pandemic hit it seemed too self-centered. I wish I'd kept them up now.

I wrote year notes last year. Surprisingly that was the only blog post I wrote last year 😱

Here are mine for 2020… It feels egotistical… but it's intended to remind me to reflect. Hopefully it's useful to me in the future even if it isn't to anyone else.

Since October 2017 I've been keeping week notes. I've found them a fantastic tool to track my focus and to remember to reflect on success (or lack of it).

Some colleagues and some tooters have written year notes as 2019 ends. And here are mine… It feels egotistical… but hopefully it's useful to me in the future even if it isn't to anyone else.

At the 2019 Manchester Java Unconference I attended a discussion on "Cloud Native Functions". It turned out nobody in the group had used "cloud native" but I've been working with teams using serviceful systems.

I have a bad habit of talking more than I should but, despite my best efforts, the group expressed interest in hearing what teams at Co-op Digital had learned in the last ten months or so of working with serviceful systems in AWS.

We defined some terms, covered some pitfalls and gotchas, some successes, and most of all our key learning: that once you can deploy one serviceful system into production you can move faster than you ever have before.

Let's spend a little while defining our terms…

Part One - describing event-driven and serverless systems

Part Two - Infrastructure as code walking skeleton

Part Three - SAM Local and the first event producer

Part Four - Making streams of events

Part Five - Making a read model

In part 5 the code was written to make sure that whenever a destination changes the recent destinations read model will update. Now that read model can be used to realise a view that a human can use. We'll add code to create a HTML view behind AWS cloudfront. This will demonstrate how event driven systems can be created by adding new code instead of changing existing code.

Part One - describing event-driven and serverless systems

Part Two - Infrastructure as code walking skeleton

Part Three - SAM Local and the first event producer

Part Four - Making streams of events

OK, four months since part four. I got a puppy and have written the code for this part of the series in 2 minute blocks after sleepless nights. Not a productive way to do things!

Getting ready to make some HTML

Now that the API lets clients propose destinations to the visit plannr the home page for the service can be built. It's going to show the most recently updated destinations.

In a CRUD SQL system the application would have been maintaining the most up-to-date state of each destination in SQL and you'd read them when the HTML is requested. But this application isn't storing the state of the destinations but the facts that it has been told about the destinations.

As an aside a lot of people don't realise that CRUD SQL stands for C an we R eally not U se SQL D atabases they may S eem familiar but all the ORM stuff is well over our Q uota for comp L icated dependencies.

In an event driven system applications subscribe to be notified when new events occur. They can create read models as the events arrive. Those read models are what the application uses to, erm, read data. So they're used in places many applications make SQL queries. Now this visit plannr application needs a read model for recently updated destinations.

DRY or WET?

DRY, in software development, stands for Don't Repeat Yourself. This is often taken to mean remove any duplication of lines of code. See the anti-example in the wiki page comparing to WET code - which stands for Write Everything Twice. This reinforces the idea that this is about the amount you type.

Below we're going to look at what the impact of removing duplication of lines of code does to some software, hopefully demonstrate that it isn't desirable as an absolute rule, and show what the better way might be.

Part One - describing event-driven and serverless systems

Part Two - Infrastructure as code walking skeleton

Part Three - SAM Local and the first event producer

In this post we start to see how we can build a stream of events that lets us create state. We'll do this by adding an event subscrber that waits until a user proposes a destination to visit and validates the location they've provided.

Part One - describing event-driven and serverless systems

Part Two - Infrastructure as code walking skeleton

In this post we will look at how SAM local let's you develop locally and write the first lambda function. To take a ProposeDestination command and write a DestinationProposed event to the eventstream.

"SAM Local can be used to test functions locally, start a local API Gateway from a SAM template, validate a SAM template, and generate sample payloads for various event sources."