When working on many feature branches, they tend to accumulate in the local Git clone. Even if they get deleted in upstream shared repos, they need to be cleared locally, too, otherwise they will stick around forever.

Here’s a quick one-liner to clean up every branch that is fully merged to main. It does make sure not to delete main and develop, though.

git branch -d $(git branch --merged main | grep -vE '(^\*|master|main|develop)')
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When migrating a database from MySQL to PostgreSQL, I bumped into a slight issue with timestamp formatting. PostgreSQL supports many date/time formats, but no native support to output ISO-8601 UTC time & date format (e.g., 2023-08-05T13:54:22Z), favouring consistency with RFC3339 instead.

ISO 8601 specifies the use of uppercase letter T to separate the date and time. PostgreSQL accepts that format on input, but on output it uses a space rather than T, as shown above. This is for readability and for consistency with RFC 3339 as well as some other database systems. https://tools.ietf.org/html/rfc3339

Fortunately, StackOverflow had a solution, including some notes about how to handle timestamps with timezones.

SELECT to_char(now() AT TIME ZONE 'Etc/Zulu', 'yyyy-mm-dd"T"hh24:mi:ss"Z"');
A diagram of a CloudFormation template creating a TLS-secured CloudFront distribution serving content from an S3 bucket.

As I mentioned in a previous post, I am migrating a number of static websites from Apache on bare metal to an object store and a CDN in the cloud. Namely, this is AWS S3 and CloudFront. To avoid too much manual grooming of pet yaks, I also went directly for Infrastructure-as-Code with CloudFormation, with the objective of creating a relatively simple reusable web+CDN template.

This is not a new topic, and a number of resources already exist around the web. I, for example, started with this one, which does a fairly decent job. There are, however, a number of fine details which I have found were tricky to get right, could lead into incompatibilities, and for which accurate documentation was hard to find (even ChatGPT failed to provide a correct answer, though this is not entirely surprising).

ChatGPT confidently states things that aren’t true.

The goal of this post is to call those out, and provide the CloudFormation template mentioned above for those looking for a base. The template will:

  1. create an S3 bucket for use as a website endpoint
  2. create a CloudFront distribution using that bucket as an Origin
  3. create a few DNS entries
  4. create a TLS certificate for the service

tl;dr:

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I talk about restoring backups often recently. This is because the disk on my trusty bare-metal server died. This gave me the opportunity to reassess my hosting choices, and do the ground work to move from where it was to where I want it to be.

One of those changes is moving static website hosting away from a Apache HTTPd, running on an OS I administrate (read: “frequently broke”), to a more focused and hands-off system in the cloud, AWS S3 with a CloudFront CDN (more on this in a later post).

Unfortunately, decades of running Apache have left me with a number of static sites using some on-the-fly templating by relying on Server-side Includes (SSI). Headers, footers, geeky IPv6 and last-modified tags, … none of those work with a truly static host. I needed a solution to render those snippets into full pages.

At first, I thought I’d just write a simple parser in Python. I quickly gave up on the idea, however, when I realised I used included templates with parameters. Pretty nifty stuff, but also not trivial to write a parser for.

Then I realised I already had the perfect parser: Apache. All I needed was to let it render all the pages one last time, and publish those instead! This was packed quickly with a relatively simple Docker container, and the trusty wget. The busy person can find a Gist of the Dockerfile here.

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Backups. What a better time to test ’em than when you need ’em. Don’t lie. I know you’ve been there too. In an unfortunate turn of events, I had to restore a number of bare git repos from recent off-site copies (made with the handy rdiff-backup), but they needed a bit more work to be functional.

Once restored, I couldn’t pull or push from my existing working copies. I was greeted with cryptic error messages instead: fatal: git upload-pack: not our ref 0000000000000000000000000000000000000000 and ! [remote rejected] master -> master (missing necessary objects), respectively.

No amount of searching led to an adequate solution. So I simply leveraged git’s distributedness, and used one of the clone to recreate my bare repo. I was nonetheless a bit worried about having lost a few commits on the tip.

Playing in the bare repo later on led me to a more satisfying solution. Apparently, the refs/heads/master file was corrupted (empty), and editing it to contain the full sha-1 of the tip was enough to fix the issue. I found the sha-1 of the desired commit in the packed-refs file at the root of the bare repo. Once done, everything worked as before, and pre-existing working copies were able to pull and push without issue.

I learned two things:

  • A bit more about git
  • That I didn’t actually have any more commits there

Backups! Yay!

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Due to an unplanned outage of my main ISP, I had to get a mobile data SIM in a hurry, to use as an LTE backup uplink for my Mikrotik hAP ac3 (the whole setup of which I’ll describe one day). Given the price discrepancy of those, I wanted to make every transferred byte count: No unnecessary update fetching or immediate download of high-res sepia-toned photos of bulldogs in tutus.

Android can advertise itself as a metered network to its (Android) clients, so how do I do the same with Router OS 7?

(router agnostic) tl;dr:

  1. Make DHCP Option 43 (Vendor-Specific Option) contain the string ANDROID_METERED;
  2. The option should be sent even if not requested by the client (not standard compliant, but doesn’t hurt).
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I recently had to restore databases from a rough mysqldump backup in a piecemeal fashion. One necessity is to SET the environment correctly, lest some weird encoding issues happen when restoring the data, leading to failures.

A sed one-liner can help for this.

DBNAME=mydb
sed -n "/^-- Server version/,/^-- Current Database/p;/^-- Current Database.*${DBNAME}\`/,/^-- Current Database/{p}" mysqldump.sql > ${DBNAME}.sql

This extracts SQL from the initial header, to the first database, which contains all the sessions SETs. It then captures statements any time the target database is the current one. Note that this doesn’t restore the GRANTs.

Befor blindly piping the output SQL into mysql, one would be well advised to review the contents of the file, to ensure only the desired modifications are included.

We’ve been having some fun with Click and Python decorators at work.

We had a situation where we wanted to

  1. transform any Exception to a click.ClickException, so they would be rendered nicely, and
  2. catch one particular exception, and retry the function that raised it with a different parameter value as a fallback.

We got the first behaviour quickly into a decorator. We then realised that the second could also be done nicely with a decorator, too.

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