Hellmar Becker's Blog
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  • Summary of Druid native query options

    Jan 21, 2021 • blog, imply, druid

    Druid’s native query language supports five distinct query types. Each of these query types requires that certain attributes be set in the query JSON object.

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  • Generating IBAN numbers for simulated financial transactions

    May 13, 2020 • blog, perl, testing, financial, realtime, graph

    Financial transactions present a whole lot of interesting technology use cases.

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  • Attaching a webcam to a virtual machine using Vagrant and VirtualBox

    May 3, 2020 • linux, windows, virtualization

    It all started with the virtual chroma screen function of Zoom, which does not work on older laptops that do not have a beefy CPU. So, one day on Hacker News, I found an article by Ben Elder that describes how to set up your own virtual webcam on Linux.

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  • A simple way to generate IoT test data

    Apr 25, 2020 • blog, perl, iot, dataflow, nifi

    A while ago, I was called to do a presentation at a large manufacturer of wind turbines. You might have a couple of those installed in the fields around your town if you live in the German countryside, but the more lucrative way of deploying turbines is in offshore windparks.

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  • Rebuilding my mail server using OpenSMTPD on Debian

    Apr 21, 2020 • mail, linux, blog

    So, I had been running my own mail server for more than 10 years. The configuration had degraded over time and been propagated through several major OS upgrades. Security features were not up to date and I had lost track of some of the changes I made years ago. It was time to tear down the entire server and rebuild it from scratch.

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