Author Archives: Olivier Mehani

About Olivier Mehani

Just another random geek.

Using munin-async to reduce gaps in monitoring… and system load

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I use Munin to monitor a few machines, and bubble up alerts when issues show up. It’s pretty good, easy to set up, and has a large number of contributed plugins to monitor pretty much everything. If still out of luck, it’s easy enough to write your own.

To ease the task of viewing the data, each machine runs munin-node, but only a couple of masters do the data collection with munin-update. This works reasonably well, except that machines monitored by more than one server need to work extra time to provide the same data to both.

Fortunately, Munin 2.0 introduced a proxy mode, allowing to decouple running the plugins to collect fresh data (with munin-asyncd) from giving that data to collection servers (via munin-async).

Setting this up is relatively easy, and the benefits show quickly, in the form of a reduced collection time, and fewer gaps in the data.

Reduced update time for the master, and no more gaps in the data.

Surprisingly it also showed as a substantially reduced load on low-power machines. But beware of the --fork parameter to munin-asyncd.

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Shell history and modifiers

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I finally mastered the shell (beit bash or zsh, but really, this is readline)’s history with command replacement. It took me 19 years and my entire family fortune to gather enough wits to read that part of the manual with enough attention and will as to learn to use it.

Essentially, you can recall previous commands from the history with !number. You can then change some content of the previous command programmatically before running it by adding :s/PATTERN/REPLACEMENT/ or :gs/PATTERN/REPLACEMENT/ (the first one will replace the first occurrence, the second one will replace them all).

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Clearing persistent duplicates in the Kodi music library

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I’ve been using Kodi (then XBMC) for more than a decade now (yup, “XB” did stand for X Box alright, but now LibreELEC on a WeTek Core). I’ve also had the library in MySQL for more than half of it. Across migrations, it had developed some quirky content, such as duplicate albums, and some rarities, such as this version of 21, by Adèle, where the description reminds us that her previous album, Ixnay on the Hombre, was only moderately successful on launch; go figure…

As suggested, pretty much everywhere, as the solution for duplicate content in Kodi, I first tried cleaning the library, repeatedly, to no avail. The duplicate albums were still there. One of their noticeable characteristics, though, was that there was always some copy of the album (and in Adèle’s case, the one following Ixnay), that did not have any associated tracks. This felt like it could be a good angle to help me clear those up. Enter some SQL.

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Workflows Don’t Stop at Git Branches

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A Git workflow showing feature branches merged into master and tagged as releases

I wrote this article for the Learnosity blog, where it originally appeared. I repost it here, with permission, for archival.

A few weeks ago, a debate started on our channel for Git-related discussions. Following someone posting a link to Nicola Paolucci’s article on Core [Git] Concept, Workflows And Tips, a question was raised:

Do we really need merge commits?

What sounded like a fairly straightforward question quickly snowballed into one of those long chat threads that left us none the wiser. A follow-up face-to-face discussion helped us get down to the root of the problem: code and functional reviews on feature branches may leave us exposed to integration issues after non-fast-forward merges, and can only be caught too late for comfort.

We had to consider our Git workflow alongside the lifecycle of our tickets to come up with an improvement. Merge commits remain, but we rebase (and fix conflicts) on the latest main branch before any review in order to make sure we look at the final code.

The rest of this article describes our Git workflow, our ticket lifecycle, their interactions, and how we made them better.

tl;dr

  1. Rebase onto develop before code review (original developer)
  2. Rebase onto develop before functional review (functional reviewer)
  3. Deploy to staging as soon as possible (i.e., all codebases merged for the feature; original developer)

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Mitel 5212 phone as SIP client for a FRITZ!Box 7390

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Until last year, work had Mitel 5212 softphones as the main devices on desks. This was the case since 2008, and was apparently high time to replace them. As they had nowhere to go but the bin, I grabbed a few in the hope to use them at home. While Mitel has a proprietary protocol (MiNET), they also support standard SIP through another vendor firmware, which allowed me to add a few more physical phones behind my FRITZ!Box.

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Using Let’s Encrypt certificates with a FRITZ!Box

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Today, when trying to log in remotely to my home router (a FRITZ!Box), I was greeted with an TLS certificate error. I was pretty sure it’s my router, but am I really keen to type in a password into a field that I have no idea whether it is actual my machine, or a nice-looking replica? A clear indication that it is time to use a better cert than a self-signed one that I cannot verify remotely.

I use Let’s Encrypt for all my other certificates, so why not use it on my router? However, I found precious little information about how to use it with the FRITZ!Box. Fortunately, it’s pretty straightforward.

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