A cache-busting http server script in ruby

"All of this can be yours/just give me what I want/and no one gets hurt"

– Bono, Vertigo

If you’ve done much Javascript development, or simple web development without a webserver backend, you don’t want to set up a complex framework. Just give me the pages: I want to be able to start a simple webserver to give me the current directory structure as a website. You can’t simply load the pages into a browser using file:// because that screws up the relative paths that our sites rely on. What’s the best way of doing this?

Python’s SimpleHTTPServer

One simple way is:

python -m SimpleHTTPServer

This does a great job, but there’s one small problem: caching. Ordinarily during development you’ll want the browser to request the HTML each time, and the python server doesn’t do that out of the box.

Ruby’s WEBrick with adding cache-busting

Here’s a small script I borrowed from pmarti and tweaked. It lives in the bin/http file on my path: I just type http in the relevant folder and I’m set.

#!/usr/bin/env ruby

require 'webrick'
class NonCachingFileHandler < WEBrick::HTTPServlet::FileHandler
  def prevent_caching(res)
    res['ETag']          = nil
    res['Last-Modified'] = Time.now + 100**4
    res['Cache-Control'] = 'no-store, no-cache, must-revalidate, post-check=0, pre-check=0'
    res['Pragma']        = 'no-cache'
    res['Expires']       = Time.now - 100**4
  end

  def do_GET(req, res)
    super
    prevent_caching(res)
  end
end

server = WEBrick::HTTPServer.new :Port => 8989

server.mount '/', NonCachingFileHandler , Dir.pwd
trap('INT') { server.stop }
server.start

Hope it’s helpful. Do you know of a better way of doing it? Feel free to share…

How to Build a Robust LLM Application

Last month at Cherrypick we launched a brand new meal generator that uses LLMs to create personalized meal plans.

It has been a great success and we are pleased with the results. Customers are changing their plans 30% less and using their plans in their baskets 14% more.

However, getting to this point was not straightforward, and we learned many things that can go wrong when building these types of systems.

Here is what we learned about building an LLM-based product that actually works, and ends up in production rather than languishing in an investor deck as a cool tech demo.

Your Code Is A Liability

Every chunk of code you commit is more for someone else to read, digest and understand.

Every complex “clever” expression requires another few minutes of effort for each of your team. They must now interpret what you wrote and why you wrote it.

Every line you add limits your project’s responsiveness to change.

Your code is a liability. Never forget this.

The Sol Trader Christmas Eve update: moddable missions

The relative radio silence from Sol Trader Towers is for a reason: I’ve been working hard on a flexible and moddable mission structure, that allows players to take a variety of interesting quests in-game.

This build is now available on the forums should you have access (there’s still time if you don’t.)

I’ve built a few missions to start with, including delivering parcels for business or personal reasons, taking characters on business trips and making other characters disappear. It’s great fun to have a variety of things to do for characters now and adds yet more colour to the game. Because it’s completely moddable, I’m also excited to see what storylines other people come up with!

Under the hood

The full details of how to create your own missions are available as a lengthy forum post, which will be kept up to date with changes and clarifications. Here’s an overview:

The missions are organised into packs, which exists under the data/missions subfolder. If you have access to the beta builds, you’ll see there’s one pack there already: these are the missions that are built in to the game.

There are several csv files in each mission folder:

• requirements.csv: This file details the cases in which this mission might be triggered. Each character in the game has a chance of picking this mission (and becoming the ‘giver’ of the mission), based on the conditions imposed by this file.
• conversation_player.csv: The extra conversation options available to the player because of this mission.
• conversation_ai_response.csv: The extra options the AI can choose from as conversation responses.
• opinions.csv: The extra opinion triggers, used for reactions to the generation and completion of these missions.
• strings.csv: The new strings needed for the previous CSV files.

The possibilities for you to build your own missions are expanding all the time, as I add new missions triggers and possible goals for the AI.

What’s next?

At the moment it’s possible to take on any mission from any person, which isn’t very realistic. I need to allow players to gain other character’s trust, so that they will only give you sensitive missions in certain cases. Additionally it will soon be possible to start a career with an organisation, which will give you a rank, a certain amount of built in trust, and access to more senior characters.

I’m also going to be working on the in-space AI very soon. At the moment only freelance traders fly around between planets: it’s time we had passenger ships, military guards and pirates thrown into the mix.

Have a fantastic Christmas and I’ll see you all in the new year with some more updates.

New Sol Trader beta: the science of blame and unforgiveness

Previously I wrote about how I’m modelling opinions and prejudice in Sol Trader. It’s time to put some of that information to use.

The opinions a character has of other people, based on the partial events that they know about them, will now directly affect the things that happen in the history generation. This creates new events, which will in turn feed more character opinions.

There’s a new beta available on the forums if you have insider access.

Dudley and Meredith

In the example on the left, we can see that an acrimonious divorce of Meredith’s parents has left an indelible mark on her childhood. She now has a very low opinion of her father, Dudley.

When characters are adults, they can then generate a series of ‘favours’ (or ‘missions’) that they want completed. This is a source of work for the players, although completing certain missions does have real consequences on your relationships with the target of the mission. If they find out you’ve taken a mission against them, then they won’t be happy with you.

To continue our example, Meredith, whom we are now married to, wants us to find out some potentially incriminating information about our own father-in-law, Dudley. It’s up to us whether we take it or not. If he finds out, we’ll make an enemy of him.

Is it worth getting involved in this feud?

As the game goes on, the player will get embroiled in these relationships between the various characters and be able to directly affect their stories. Choosing what to take on and who to ally yourself with forms a major part of Sol Trader’s gameplay.

Sarina’s spiral of doom

Another example: the sad tale of Sarina, our older half sister. I picked Dagny and Warren in history generation to be my character’s parents, knowing that Dagny was cheating on her husband Hayden, mostly to see what happened. Little did I know how much it would affect Sarina, Dagny and Hayden’s eight year old daughter. When she found out about my birth, she got very upset.

She didn’t blame me, thankfully, although she never thought much of me. However, she never really spoke to our mother again, especially since her beloved father Hayden died soon after we were born.

She left home at a young age, and became a political assistant, but she didn’t make too many friends. She was doing ok for a time, only to find out that the love of her life, Richard Ruhr, had been having an affair behind her back all along.

She divorced him, got depressed, quit her job and by the time I grew to adulthood at the start of the game, she was living in a hippie commune somewhere on Mercury, trying desperately to get some gossip on her ex-husband.

New beta out now

This new beta is now available from the forum if you have purchased insider access (if you haven’t there’s still time.) Let me know if you find any other interesting stories such as these!