Ventilations from an engineer — Stephen Crosby is an Internet engineer and explorer of the worldwide series of tubes
In my previous post, I tore apart a Flume water monitor and traced its communication path from the sensor, through the bridge, and up to Flume’s cloud MQTT server. I identified the encryption library (LibHydrogen), extracted a firmware ELF, and even managed to coerce the bridge into sending plaintext by corrupting the public key in flash. But that approach was destructive; the bridge couldn’t…
About a year ago, I bought a smart home water monitor in order to keep an eye my water use at home. The city where I live provides a big rebate on one particular device from San Luis Obispo company Flume. I was immediately curious about how this device could work and was excited to open the box when it arrived and inspect the contents. There are two hardware components in this system. One…
In 2023, I managed to integrate my garage doors with HomeAssistant using a Shelly Uni device. Controlled remote operation is pretty great, but I wanted to document this project because this solution covers remote door control, door state and even door light control is possible, using a single $12 device with no batteries required. The setup is easy to achieve, and leaves all the garage door opener…
A binary clock is hardly a new idea, but this particular concept is something I haven’t seen anywhere else. And it was idling in the back of my mind for over a decade before finally seeing a working prototype. Concept The passage of time can be measured in any number of ways, but when a clock is designed for humans, I think it should be based on a natural concept. Since I live on Earth, I designed…
Now that TLS is free, there’s very little excuse to be running web services over plain HTTP. The easiest way to add TLS to this blog was through AWS Certificate Manager and its native CloudFront Support. But for a while, there was a problem. In order to use a free, trusted certificate from Amazon, I needed to be using CloudFront. In order to be using CloudFront, I needed to be able to resolve the…
AWS Lambda is unique among PaaS offerings. Lambda takes all the utility grid analogies we use to explain the cloud and embraces them to the extreme. Lambda runs a function you define in a Node.js or Java 8 runtime, although you can execute a subshell to run other kinds of processes. Amazon charges you by memory use and execution time in increments of 128 MiB of memory and 100ms. The upper limit…
A recent client of mine needed an app to help him build bite-sized CSV files from a large PostgreSQL table. The problem was simple enough and it takes little time to write a simple Rails action to query a table, generate CSV from the objects in memory and flush it out to the client. Writing an app to do this one thing using a traditional Rails action is a matter of just a few hours. But our client…
My battle with Errbit performance is over for the time being. This concludes an effort I began in June to improve throughput on error inserts and error searching as the database grows over time. If you’re interested in reading about the effort leading up to this point, here are the related posts: Measuring Errbit Performance Why Errbit Is Slow Inserting Errors with the Quickness The short version…
Last week, I continued my exploration into Errbit slowness. I eliminated a few ideas and added a few more conjectures to the list of optimization targets. While testing some ideas, I began to suspect that my test rig was not working as designed. There was a flaw in the way I was using Typheous that was causing the test process to run slower than it should and even worse, report inaccurate…
Round One One of the first things I did when tracking down performance issues was motivated by a lot of experience with Rails apps. A very common issue I’ve seen with Rails applications comes down to a simple misuse of active_record. Errbit doesn’t use active_record, but it does use Mongoid which presents something rather like an active_record interface for mongo-powered applications. After…