When using syspatch on OpenBSD, the upgrade sometimes fails with
Relinking to create unique kernel... failed! !!! "/usr/libexec/reorder_kernel" must be run manually to install the new kernel
This generally happens after a system upgrade, or an otherwise manual change of kernel. This fix is to update the kernel hash, before re-running reorder_kernel.
# sha256 /bsd > /var/db/kernel.SHA256 # /usr/libexec/reorder_kernel
I wrote this article for the Learnosity blog, where it originally appeared. I repost it here, with permission, for archival. With thanks to Micheál Heffernan for countless editing passes.
The dramatic increase in Learnosity users during the back-to-school period each year challenges our engineering teams to find new approaches to ensuring rock-solid reliability at all times.
Stability is a core part of Learnosity’s offering. Prior to back-to-school (known as “BTS” internally) we load-test our system to handle a 5x to 10x increase on current usage. That might sound excessive, but it accounts for the surge of first-time users that new customers bring to the fold as well as the additional users that existing customers bring.
Since the BTS traffic spike occurs from mid-August to mid-October, we start preparing in March. We test our infrastructure and apps to find and remove any bottlenecks.
Last year, a larger client ramped up their testing. This created a 3x usage increase of our Events API. In the process, several of our monitoring thresholds were breached and the message delivery latency increased to an unacceptable level.
As a result, we poured resources into testing and ensuring our system was stable even under exceptional stress. To detail the process, I’ve broken the post into two parts:
Here’s a snapshot of what I cover in this post:
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.
Surprisingly it also showed as a substantially reduced load on low-power machines. But beware of the --fork parameter to munin-asyncd.
Sometimes, one just needs an OAuth access token (for the client credential authentication flow).
export ACCESS_TOKEN=$(curl -X POST \
--user "${CLIENT_ID}:${CLIENT_SECRET}" \
--data-urlencode "grant_type=client_credentials" \
--data-urlencode "scope=${SCOPE}" \
${TOKEN_URL} \
| jp -u access_token)
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).
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.
lpr -P <PRINTER> /usr/share/cups/data/testprint
Devoid of any meaning.
Read, Start at the top;
Thread of discussion:
We’ve been here before, but Oracle keeps being a pain in everyone’s rear end. This time, we want to keep testing against version 7 of the JDK with Travis CI.
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.
develop before code review (original developer)develop before functional review (functional reviewer)