rust on krtffl.dev

one schema crate, two analyzers: bilingual full-text search with embedded tantivy

Mon, 15 Jun 2026 00:00:00 +0000

you can see the word. it’s right there on the page — filósofos, third line of a plutarch translation i typed out by hand. you paste it into the search box, hit enter, and the archive tells you it has never heard of it. no error, no red box, no “did you mean.” a clean, confident, empty result set — byte-for-byte the same empty set you’d get for a word that genuinely isn’t in the corpus.

the index knew the word. i had watched it index the word. the reader just asked for it in a dialect the writer never spoke.

two databases, one binary: duckdb for reads, sqlite for state

Mon, 08 Jun 2026 00:00:00 +0000

the tracking endpoint has exactly one job: say 202 and get out of the way. a beacon fires on someone else’s website, my server catches it, and the visitor is already three paragraphs into an article before my response even lands. nobody is waiting on that request — the whole point of a sendBeacon is that the page has already moved on. so the afternoon i read a flame graph and found the ingest handler parked inside a duckdb INSERT, holding a request open while the disk did its thing, i felt a very specific kind of stupid. i’d taken a fire-and-forget pixel and taught it to block on fsync.

fixing that is most of this post. but the fix only makes sense on top of a decision most tutorials would have talked me out of: i put two different databases in one small rust binary, on purpose.

brute-forcing the pit window: when 'just try them all' is the right call

Mon, 01 Jun 2026 00:00:00 +0000

lights out. and this time the car has to stop.

two posts ago i drew stintlab’s charts in rust on canvas2d and swore a chart was just rectangles and lines. one post ago i fit the tire-degradation model by hand — ordinary least squares, cramer’s rule, and a singular-matrix guard that turned a collinearity bug into an honest None. both of those were setup. this is the payoff: the thing that takes that model and actually makes a decision.

because a degradation model, on its own, just draws a number — how much slower a tire gets, lap after lap. lovely. now what? a real race is decided in one call from the pit wall: when do you box, and onto what rubber? stop too early and you throw away tire life; too late and you bleed seconds to a fresher car behind. that call wins races. i wanted to make it automatically, and the algorithm i reached for is the single dumbest one in the book: try every option and keep the best.

and i’m going to argue that’s exactly right.

a query language in ~1000 lines: lexer, parser, evaluator

Mon, 25 May 2026 00:00:00 +0000

here’s a question that sounds trivial and isn’t: show me every 5xx response that also mentions a timeout.

in grep that’s a fragile little dance — grep -E 'status[=:] ?5[0-9]{2}' piped into another grep timeout, and now you’re matching 500 inside a request id, timeout inside a url, and you’ve quietly stopped trusting the output. what you wanted was this:

text

status >= 500 AND message contains "timeout"

and have the machine read >= as numeric greater-or-equal, AND as boolean conjunction, and "timeout" as a substring on one named field. that’s not grep. that’s a little language, and little languages need a lexer, a parser, and something to run them.

clean and verified are different claims: a two-axis trust state machine in postgres

Mon, 11 May 2026 00:00:00 +0000

ask a language model for a line of tacitus in spanish and it will hand you a sentence. fluent, confident, correctly punctuated. and sometimes the sentence contains a word that no translator ever wrote — a word a scanner invented, when it read the á in a 1919 printing as the digit 4, or turned violento into violen10, and then a spell-checker came along afterward and smoothed the wreckage into something that looks like spanish.

the text is clean. it is not correct. and nothing about the way it reads tells you which.

cookieless analytics: how a rotating daily salt kills the consent banner

Mon, 04 May 2026 00:00:00 +0000

every week i click “reject all” maybe forty times. cookie wall, reject all. cookie wall, manage preferences, uncheck the eight hundred “legitimate interest” partners, confirm. the banner that buries its reject button two clicks deep because the law says both choices must be equally easy and everyone pretends theirs is. it’s the loading screen of the modern web, and almost nobody consents to anything — they just want the thing gone.

here’s the part that took me embarrassingly long to internalise: most of those banners exist to prop up analytics that never needed your personal data in the first place.

hand-rolling ols regression in rust, and the collinearity trap that ate my coefficients

Mon, 27 Apr 2026 00:00:00 +0000

lights out, again.

last time out i argued that a chart is just rectangles and lines, drew stintlab’s entire ui in rust on canvas2d to prove it, and promised — right at the bottom of that post — to come back for the degradation model itself: the math the pictures are pictures of. this is that post.

the pictures draw a number. how much slower a tire gets, lap after lap, as it wears out. pin that number down and you can start to guess when a car should box. so i tried to fit it with a multiple linear regression i wrote by hand — no nalgebra, no ndarray, just the normal equations and a determinant — and the thing handed me back confident, well-formed garbage. it took a comment in one of my own tests to explain why.

rust + wasm canvas2d charts with zero javascript libraries

Mon, 20 Apr 2026 00:00:00 +0000

lights out. one car jumps another off the line, and forty laps later a strategist on the pit wall wins the whole race with a single number: when to box. i don’t have a pit wall. i have a laptop, a free public api ↗ , and an unreasonable urge to see tire strategy as a picture instead of a table of lap times.

so i wanted a chart. the boring way to get one is npm install something with a d3 buried in its dependency tree, feed it an array, and move on with my life. i did not do the boring way. i drew the whole thing in rust, compiled it to webassembly, and painted it onto a <canvas> pixel by pixel with zero javascript charting libraries in the bundle.

welford's algorithm and why i never store the samples

Mon, 13 Apr 2026 00:00:00 +0000

you want to know if the error rate just spiked. that’s a z-score: how many standard deviations is right now away from what normal looked like. simple formula, (x - mean) / stddev, you learned it before you could legally drink.

except a standard deviation needs a mean, and a mean needs all the numbers, and the numbers are a log file the size of a small moon. so where, exactly, are you keeping them?

building three mcp servers in rust with rmcp

Mon, 30 Mar 2026 00:00:00 +0000

i wanted to ask an llm “is my server on fire?” without ssh-ing into the box, running htop, squinting, giving up, and running docker ps instead. i wanted it to just know — pull the cpu number, list the containers, hit prometheus, and tell me in a sentence.

the model context protocol makes that possible. you hand an llm a set of tools, it decides when to call them. fine. so i built one server for my infra. then i wanted one for spanish government open data — the boe, the tax calendar, the property registry. then a third for formula 1 telemetry, because it’s my blog and i do what i want.

three servers. and i could already see the future: three near-identical binaries, three copies of the same http-client boilerplate, three subtly different cache bugs. the copy-paste tax.

implementing the drain algorithm in rust

Mon, 23 Mar 2026 00:00:00 +0000

picture the scene: something is on fire in production, you ssh into the box, tail a log file, and you’re greeted by forty thousand lines that all look almost the same but not quite. your eyes glaze over. you grep error, then grep -v the noise, then pipe the whole thing into sort | uniq -c and pray.

there’s a better way, and it’s older than you’d think.

i didn't leave go for rust. i split my stack.

Mon, 16 Mar 2026 00:00:00 +0000

“so are you a go guy or a rust guy now?”

somebody asked me that recently and i realised i’d been dodging it for the better part of a year. the honest answer is annoying, which is why nobody likes it: i’m both. and it’s not a fence i’m sitting on, it’s a split — i write go and i write rust, on purpose, for different jobs. the moment i stopped treating “which language” as a personality question and started treating it as a tooling question, the whole tired argument just dissolved.