Matrix is a Distributed Real-time Database Video

Curious to know a bit more about Matrix? This video goes into the details of what kinds of requests you need to send to write a Matrix client, and why it’s interesting to write a Matrix server.

Slides: Matrix is a Distributed Real-time Database Slides

Really excited that since I started my job working on Matrix, I have become more enthusiastic about it, rather than less.

Improving my vimrc live on stream

I was becoming increasingly uncomfortable with how crufty my neovim config was getting, and especially how I didn’t understand parts of it, so I decided to wipe it clean and rebuild it from scratch.

I did it live on stream, to make it feel like a worthwhile activity:

Headline features of the new vimrc:

  • A new theme, using the base16 theme framework
  • A file browser (NERDTree)
  • A minimalist status line with vim-airline
  • Search with ripgrep
  • Rust language support with Coc

Note: after the stream I managed to resolve the remaining issues with highlight colours not showing by triggering re-applying them after the theme has been applied:

augroup tabs_in_make
    autocmd!
    autocmd ColorScheme * highlight MatchParen cterm=none ctermbg=none ctermfg=green
augroup END

You can find my current neovim config at gitlab.com/andybalaam/configs/-/tree/main/.config/nvim.

Republishing Bartosz Milewski’s Category Theory lectures

Category Theory is an incredibly exciting and challenging area of Maths, that (among other things) can really help us understand what programming is on a fundamental level, and make us better programmers.

By far the best explanation of Category Theory that I have ever seen is a series of videos by Bartosz Milewski.

The videos on YouTube have quite a bit of background noise, and they were not available on PeerTube, so I asked for permission to edit and repost them, and Bartosz generously agreed! The conversation was in the comments section of Category Theory 1.1: Motivation and Philosophy and I reproduce it below.

So, I present these awesome videos, with background noise removed using Audacity, for your enjoyment:

Category Theory by Bartosz Milewski

Permission details:

Andy Balaam: Utterly brilliant lecture series.  Is it available under a free license?  I'd like to try and clean up audio and repost it to PeerTube, if that is permitted. Bartosz Milewski: You have my permission. I consider my lectures public domain.

Andy Balaam: Utterly brilliant lecture series. Is it available under a free license? I’d like to try and clean up audio and repost it to PeerTube, if that is permitted.
Bartosz Milewski: You have my permission. I consider my lectures public domain.

Streaming video with Owncast on a free Oracle Cloud computer

I just streamed about 40 minutes of me playing Trials Fusion using Owncast. Owncast is a self-hosted alternative to streaming services like Twitch and YouTube live.

Normally, you would need to pay for a computer to self-host it on. Owncast suggest this will cost about $5/month.

But, Oracle Cloud has a “Always Free” tier that includes a “Compute Instance” (a virtual machine running Linux) that is capable of running Owncast.

Here’s how I did it:

Register for Oracle Cloud

This was probably the worst bit.

I went to oraclecloud.com and clicked “Sign up for free cloud tier”. It didn’t work in Firefox(!) so I had to use Chromium.

I had to enter my name, address, email address, phone number and credit card details. The email was verified, the phone number was verified (with a text message), and the credit card was verified (with a real transaction), so there was no getting around any of it.

They promise that they won’t charge my card. I’ll let you know if I discover differently.

Create a Compute Instance

Once I was logged in to the Oracle “console” (web site), I clicked the burger menu in the top left, chose “Compute” and then “Instances” to create a new instance. I followed all the default settings (including using the default “image”, which meant my instance was running Oracle Linux, which I think is similar to Red Hat), and when I got to the ssh keys part, I supplied the public key of my existing SSH key pair. Read the docs there if you don’t have one of these.

As soon as that was done, and I waited for the instance to be created and started, I was able to SSH in to my instance using a username of opc and the Public IP Address listed:

ssh opc@PUBLIC_IP

(Note: here and below, if I say “PUBLIC_IP”, I mean the IP address listed in the information about your compute instance. It should be a list of four numbers separated by dots.)

Allow connecting to the instance on different ports

Owncast listens for HTTP connections on port 8080, and RTMP streams on 1935, so I needed to do two things to make that work.

Modify the Security List to add Ingress Rules

  • On the information about my instance, I clicked on the name of the Subnet (under Primary VNIC).
  • In the subnet, I clicked the name of the Security List (“Default Security List for …”) in the Security Lists list.
  • In the Security List I clicked Add Ingress Rules and entered:
    Stateless: unchecked
    Source Type: CIDR
    Source CIDR: 0.0.0.0/0
    IP Protocol: TCP
    Source Port Range: (blank)
    Destination Port Range: 8080
    Description: (blank)

    and then clicked Add Ingress Rules to create the rule.

  • I then added another Ingress Rule that was identical, except Destination Port Range was 1935.

Allow ports 8080 and 1935 on the instance’s own firewall

It took me a long time to figure out, but it turns out the Oracle Linux running on the Compute Instance has its own firewall. Eventually, thanks to a blog post by meinside: When Oracle Cloud’s Ubuntu instance doesn’t accept connections to ports other than 22, and some Oracle docs on ways to secure resources, I found that I needed to SSH in to the machine (like I showed above) and run these commands:

sudo firewall-cmd --zone=public --permanent --add-port=8080/tcp
sudo firewall-cmd --zone=public --permanent --add-port=1935/tcp
sudo firewall-cmd --reload

Now I was able to connect to the services I ran on the machine on those ports.

Install Owncast

The Owncast install was incredibly easy. I just followed the instructions at Owncast Quickstart. I SSHd in to the instance as before, and ran:

curl -s https://owncast.online/install.sh | bash

and then edited the file owncast/config.yaml to have a custom stream key in it. You can do that by typing:

nano owncast/config.yaml

There is information about this file at: owncast.online/docs/configuration.

Run Owncast

I ran the service like this:

cd owncast
./owncast

In future, if I want to leave it running, I may run it inside screen, or even use systemd or similar.

Open the web site

I could now see the web site by typing this into my browser’s address bar:

http://PUBLIC_IP:8080

(Where PUBLIC_IP is the Public IP copied from the Instance info as before.)

Stream some video

Finally, in OBS‘s Settings I chose the Stream section and entered:

Service: Custom...
Server: rtmp://PUBLIC_IP/live
Stream key: STREAM_KEY

Where “STREAM_KEY” means the stream key I added to config.yaml earlier.

Now, when I clicked “Start Streaming” in OBS, my stream appeared on the web site!

Costs and limits

Oracle stated during sign-up that I would not be charged unless I explicitly chose to use a different tier.

The Compute Instance is part of the “Always Free” tier, so in theory it should stay up and working.

However, if you use lots of resources (which streaming for a long time probably does), I would expect services would be throttled and/or stopped completely. I have no idea whether they will allow enough resources for regular streaming, or whether this is all waste of time. We shall see.