• Week 382

    3 May 2020

    Week 382 was primarily a busy week of writing code on Bradnor.

    With last week’s infrastructure in place, capturing messages from physical devices, we could now spend some time processing that data. That meant abstracting out devices from the locations they represent. After all, a device may go offline, or be replaced by another, but it’d be good to be able to see the history of data from a single location, as well as from a single device.

    So we filled out our data model to encompass concepts such as ‘locations’ and ‘devices’ and the relationship between them (as well as logging when they change) Then, I could build another data-processing task, that would copy a ‘device message’ into a list of messages for a specific location if those two items were linked. (This also made it easy to have a ‘disabled’ flag on devices, making it possible to ignore inaccurate messages from possibly defunct devices). In that copying process, we also do a little decoration and transformation of the data, leading to a nice big table of per-location messages, that’s quick to query.

    I could then backfill our location messages with the data from last week, as well as importing historical data from CSV files straight into the ‘location messages’ table.

    There was also a lot of metadata CRUD to do, to make it easy to update and record information about locations, as well as to leave comments and annotations on many of the objects in our system. Rails made this about as straightforward as it could be to hammer out.

    I made sure I had time to work on some belt-and-braces, too: making sure there was appropriate test coverage (especially of key parts like data processors and the end-to-end request cycle of message JSON arriving at a URL), and setting up Rollbar to catch and collate errors.

    With all that done, we had raw data coming in, meaningful information being derived from that data, and the beginnings of a fleet-management tool.

    Finally, I set up a visualisation pipeline using Grafana. The client had been using Grafana in their previous stack, so it made sense to keep doing so - especially as it was both easy to deploy (thanks to its preference for being deployed as a Docker image) and easy to integrate into Postgres (thanks to the Postgres plugin being supplied as default). With that deployed, we could spelunk away, and a short while hacking away at some SQL got me to a nice dashboard showing data for a set of monitoring locations grouped over time, and navigable with Grafana’s time-series tools (which make it easy to scroll around time and to zoom in and out). As new monitoring locations were added and new historical data dropped in, more lines appeared in the graph. Satisfying to see!

    All this meant I largely wrapped up Bradnor this week. There’s just some spit and polish and handover reamining.

    It’s not the most sophisticated set of tools, but it is built out of well-known building blocks - application frameworks, databases, protocosls - that are maintainable, testable, and knowable. We’ve simplified the platform infrastrcture a little, but still have a good base to build upon, perhaps to add new features to or to extract to smaller services if necessary. Tests help verify that the code is doing what it should be, and by using known, mature tools, it becomes easier to recruit others to work on it should I be unavailable. I was pleased with the shape of this project - what looked like a quick software build project actually turned in an opportunity to lay some good foundations, re-examine infrastructure, invest in more than just lines of code.

    On other fronts, I signed paperwork for Easington, which should kick off in week 383, and take me right through the summer. This is going to be an exciting, challenging R&D project to pour myself into, and I’m looking forward to it.