#180

The War in Ukraine

Well, this week has certainly been something. The fog of war makes much uncertain, but I’ve been watching the BBC coverage to keep as up-to-date as I can. I found this article by Bret Devereaux a good explanation of the background and potential outcomes.

Ukraine is doing better than I expected. Better than Russia expected too, it seems. But Russia is huge: unless internal pressure makes Putin back down, I don’t have much faith that the Ukrainians could defeat the entire Russian army.

We’ll have to wait and see what the future brings.

Books

This week I read:

• Microservices Patterns by Chris Richardson

  I decided to get this book because the engineering manager for the team I’ll be joining at GoCardless casually threw around terms I wasn’t familiar with, like “two-phase commit” and “saga pattern”, when we talked. I googled for those and found the website for this book, which looked promising.

  But now having read it I think I should have just stuck with the website.

  It has some overlap with Designing Data-Intensive Applications, but covers that material much less well. There’s a consistent example throughout (a Just Eat or Deliveroo-like service), which is nice to have, but the Java examples throughout the book were not so useful: they use the author’s custom Java microservice framework (which has a silly name: Eventuate Tram), and they were also pretty abbreviated.

  The book, like Java, is also quite verbose. The author religiously follows the “say what you’re going to say, say it, and then say what you said” mantra. That’s fine for chapters. But every section was like that, and every subsection ended with a phrase like “Now that we’ve seen how to use [topic of this subsection], let’s look at [topic of next subsection].” For example:

  

  Putting aside those issues, I also think it’s aimed at someone with less experience than me. The latter chapters of the book are dedicated to topics like testing, deployment, and monitoring. All very potentially interesting things! But the testing chapter starts out by assuming the reader is unfamiliar with automated testing, since apparently most companies still do mainly manual testing. There was a surprisingly good section about kubernetes and service meshes, though.

• Volumes 2 and 3 of That Time I Got Reincarnated as a Slime by Fuse

  In contrast to my poor impression of volume 1, these were alright. I’m still not convinced, so I’ll read another few volumes before deciding to buy the whole series, but I’m no longer going to immediately drop it. In particular, the amount of space dedicated to character development improved—including some scenes the anime skipped—and the prose just felt better. In fact, the prose felt so much better that I checked whether the translator had been changed, but no, same guy as volume 1.

  It’s still not brilliant though. For example, in volume 2 the chief of the lizardmen is thrown in jail as a result of his son’s coup. While he’s in his cell, he imagines how terrible it must be for the women and children sheltering from the invading orc army. The book then cuts away to other characters for several pages. When it returns to the chief, he is no longer in his cell, he is now armed and defending the women and children from orcs. I thought maybe I missed something, so I re-read those sections a few times, but I don’t think I did. Did the author just… forget that the chief is supposed to be locked in a cell, his hands in chains, in a different room entirely? Seems so. In the anime, the chief is locked up until he gets rescued: a scene notably absent from the book.

Programming

I’ve been working on implementing a little DNS resolver over the past couple of days. I’m writing this in asynchronous Rust, using the tokio runtime. Currently I’m following the two main DNS RFCs:

• RFC 1034: DOMAIN NAMES - CONCEPTS AND FACILITIES
• RFC 1035: DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION

The goal is to have a recursive resolver with custom records and blocklists: something that could serve as a Pi-hole replacement. I’ve now got a basic non-recursive resolver, which can give answers based on static records configured in a config file, and the outline of a recursive resolver.

The DNS wire format is a bit cryptic, but I got there in the end, and it’s cool to see my resolver working with dig.

My immediate goals are:

1. Finish the recursive resolver
2. Implement caching
3. Add tests

Getting there would be pretty cool, as I’d then have a proof-of-concept (if somewhat clunky to operate) recursive resolver. To make it pleasant to use I’d then need to add:

1. A parser for zone files, to read:
   • the root hints file
   • static records
2. A way to read a DNS blocklist from a file
3. A way to trigger an asynchronous reload of the root hints and blocklist

I think if I get all this done, I could feasibly replace my Pi-hole. Running a hand-written DNS resolver for my local network would be very neat. And then, if I still needed things to do, a couple of stretch goals could be:

• A Prometheus metrics endpoint
• Fuzz testing of the network packet handling logic
• Working through more modern DNS RFCs (eg, adding support for AAAA records, DNSSEC, or DoH)

Link Roundup

• The Ultra-Introverts Who Live Nocturnally
• Why is the ISS being retired and what will happen to it?
• NASA’s Lunar Gateway: The plans for a permanent space station that will orbit the Moon