Mar 19

Am I really shipper’s only deployment case?

I released shipper 1.14 just now. It takes advantage of the conventional asciidoc extension – .adoc – that GitHub and GitLab have established, to do a useful little step if it can detect that your project README and NEWS files are asciidoc.

And I wondered, as I usually do when I cut a shipper release: am I really the only user this code has? My other small projects (things like SRC and irkerd) tend to attract user communities that stick with them, but I’ve never seen any sign of that with shipper – no bug reports or RFEs coming in over the transom.

This time, it occurred to me that if I am shipper’s only user, then maybe the typical work practices of the open-source community are rather different than I thought they were. That’s a question worth raising in public, so I’m posting it here to attract some comment.

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Mar 08

Declarative is greater than imperative

Sometimes I’m a helpless victim of my urges.

A while back -very late in 2016 – I started work on a program called loccount. This project originally had two purposes.

One is that I wanted a better, faster replacement for David Wheeler’s sloccount tool, which I was using to collect statistics on the amount of virtuous code shrinkage in NTPsec. David is good people and sloccount is a good idea, but internally it’s a slow and messy pile of kludges – so much so that it seems to have exceed his capacity to maintain, at time of writing in 2019 it hadn’t been updated since 2004. I’d been thinking about writing a better replacement, in Python, for a while.

Then I realized this problem was about perfectly sized to be my learn-Go project. Small enough to be tractable, large enough to not be entirely trivial. And there was the interesting prospect of using channels/goroutines to parallelize the data collection. I got it working well enough for NTP statistics pretty quickly, though I didn’t issue a first public release until a little over a month later (mainly because I wanted to have a good test corpus in place to demonstrate correctness). And the parallelized code was both satisfyingly fast and really pretty. I was quite pleased.

The only problem was that the implementation, having been a deliberately straight translation of sloccount’s algorithms in order to preserve comparability of the reports, was a bit of a grubby pile internally. Less so than sloccount’s because it was all in one language. but still. It’s difficult for me to leave that kind of thing alone; the urge to clean it up becomes like a maddening itch.

The rest of this post is about what happened when I succumbed. I got two lessons from this experience: one reinforcement of a thing I already knew, and one who-would-have-thought-it-could-go-this-far surprise. I also learned some interesting things about the landscape of programming languages.

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Mar 05

How not to design a wire protocol

A wire protocol is a way to pass data structures or aggregates over a serial channel between different computing environments. At the very lowest level of networking there are bit-level wire protocols to pass around data structures called “bytes”; further up the stack streams of bytes are used to serialize more complex things, starting with numbers and working up to aggregates more conventionally thought of as data structures. The one thing you generally cannot successfully pass over a wire is a memory address, so no pointers.

Designing wire protocols is, like other kinds of engineering, an art that responds to cost gradients. It’s often gotten badly wrong, partly because of clumsy technique but mostly because people have poor intuitions about those cost gradients and optimize for the wrong things. In this post I’m going to write about those cost gradients and how they push towards different regions of the protocol design space.

My authority for writing about this is that I’ve implemented endpoints for nearly two dozen widely varying wire protocols, and designed at least one wire protocol that has to be considered widely deployed and successful by about anybody’s standards. That is the JSON profile used by many location-aware applications to communicate with GPSD and thus deployed on a dizzying number of smartphones and other embedded devices.

I’m writing about this now because I’m contemplating two wire-protocol redesigns. One is of NTPv4, the packet format used to exchange timestamps among cooperating time-service programs. The other is an unnamed new protocol in IETF draft, deployed in prototype in NTPsec and intended to be used for key exchange among NTP daemons authenticating to each other.

Here’s how not to do it…

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