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Wednesday, 19 August 2020

Priority pinning in apt-preferences with different versions and architectures

I'm posting this because I've lost too many hours figuring it out myself, the documentation is missing several important notes and I haven't found any forum posts that really relate to this:

Question: How do I prioritize specific package versions for multiple architectures? In particular, I have a number of different packages which I would like to download for multiple architectures, and I would like to prioritize the versions so that if they're not explicitly provided, apt will try to get a version matching my arbitrary requirements (in my case, the current git branch name) and fall back to our develop branch versions.

eg. I would like to download package my-package for both i386 and amd64 architectures and I would like to pull the latest version that includes my-git-branch-name before falling back to the latest that includes develop.

Answer:

The official documentation is here.

1. In order to support multiple architectures, all packages being pinned must have their architecture specified, and there must be an entry for each architecture. A pinning for the package name without the architecture specified will only influence the default (platform) architecture:

Package: my-package

Pin: version /your regex here/

Pin-Priority: 1001

2. The entries are whitespace-sensitive, although no errors will be reported if you have whitespace. The following pinning will be silently disregarded:

Package: my-package:amd64

    Pin: version /your regex here/

    Pin-Priority: 1001

3. apt update must be called after updating the preferences file in order for them to be respected and after adding additional architectures using (for example) dpkg --add-architecture i386

The following excerpt from /etc/apt/preferences solves the stated problem:


Package: my-package:amd64

Pin: version /-my-git-branch-name-/

Pin-Priority: 1001


Package: my-package:i386

Pin: version /-my-git-branch-name-/

Pin-Priority: 1001


Package: my-package:amd64

Pin: version /-develop-/

Pin-Priority: 900


Package: my-package:i386

Pin: version /-develop-/

Pin-Priority: 900 

Sunday, 16 August 2020

Enabling Programmable Bank Cards To Do All The Things

A little while back, Offerzen and Investec opened up their Programmable Bank Card Beta for South Africans, taking over from Root, and I was excited to be able to sign up!

My long-term goal with programmable banking is to integrate crypto transactions directly with my regular banking - which might be possible quite soon as Investec is starting to roll out its open API offering in addition to the card programme - and as far as I can tell that could be a real game-changer in terms of making crypto trading practical for non-investment purposes.
When I joined, though, what I found was a disparate group of really interesting projects and only a two-second time window to influence whether your card transaction will be approved or not.

I decided to bide my time by building a bridge for everyone else's solutions, one which would provide a central location to determine transaction approval and enable card holders (including myself, of course) to forward their transactions securely to as many services as they like without costing them running time on their card logic.

It was obvious to me that this needed to be a cloud solution, and as someone with zero serverless experience1 I spent some time evaluating AWS, Google and Microsoft's offerings. My priorities were simple:
  • right tool for the job
  • low cost
  • high performance
  • good user experience
In the end AWS was the clear winner with the first two priorities, so much so that I didn't even bother worrying about any potential performance tradeoffs (there probably aren't any) and I was prepared to put up with their generally mixed bag of user experience. I also had the added incentive that my current employer uses AWS in their stack so I would be benefiting my employer at the same time.

Overall, I'm very glad that I chose AWS in spite of the trials and tribulations, which you can follow in my earlier post about building a template for CDK for beginners (like myself). In addition to learning how to use CDK, this project has given me solid experience in adapting to cloud architecture and patterns that are substantially different from anything I've worked with before, and I've already been able to effectively apply my learnings to my contract work.

One of the obligations of the Programmable Bank Card beta programme is sharing your work and presenting it; I was happy to do so, but for months I've been locked down and working in the same space as my wife and four year-old (we don't have room for an office or much privacy in our apartment); with all the distractions of home schooling and having to work while my wife and kid play my favourite video games I've barely been able to keep up my hours with my paid gig, so making time for extra stuff? That hasn't been so easy.

A couple of weeks ago my presentation was due, and I spent a lot of the preceding two weekends in a mad scramble to get my project as production-ready as I could - secure, reliable, usable. Half an hour before "go time" I finally deployed my offering, and I was a little bit nervous doing a live demo... I mean, sure, I'd tested all the end points after each deployment - but as we all know: Things Happen. Usually During Live Demos.

Fortunately, the presentation went very well! I spent the following weekend adding any missing "critical" functionality (such as scheduling lambda warmups and implementing external card usage updates), and I'm hoping that some of my fellow community members get some good use out of it (whether on their own stacks or mine).

The code can be found here on GitLab, and a few days ago OfferZen published the recording of my presentation on their blog along with its transcript2 and my slide deck.

Thank you for joining me on my journey!



1 Although I was employed by one of the major cloud providers for a while, I've only worked "on" their cloud rather than "in", and while I do have extensive experience with Azure none of it included serverless functions.

2 The transcript has a few minor transcription errors, but they're more amusing than confusing.

Priority pinning in apt-preferences with different versions and architectures

I'm posting this because I've lost too many hours figuring it out myself, the documentation is missing several important notes and I...