pelle.io

One of the many fun aspects when taking over an existing codebase is that you inevitably learn something new - if you want or not ;-).

Today a user reported a bug, that some numbers that are derived from the diff of two dates produced incoherent results. Looking at the code, it turned out that the code in question uses PostgreSQLs AGE function to get the interval between two dates. The shortest reproduce I was able to come up with that shows the questionable behavior looks like this:

SELECT AGE('2021-06-30','2021-05-19') AS age1, AGE('2021-07-01','2021-05-20') AS age2;

and returns the following surprising results

+-------------------------------------+-------------------------------------+
|age1                                 |age2                                 |
+-------------------------------------+-------------------------------------+
|0 years 1 mons 11 days 0 hours 0 mins|0 years 1 mons 12 days 0 hours 0 mins|
+-------------------------------------+-------------------------------------+

The correct answer for both cases should be 0 years 1 mons 11 days but the period for age2 is off by one day. This post will try to shed some light on the AGE function, why it produces the unexpected results and show alternatives that produce a (maybe) better result.

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For projects with roots in the Java ecosystem the combination if Liquibase and Jooq is a popular approach on creating and evolving database schemas, as well as interacting with the created data afterwards.

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An often overlooked alternative to the big players in the cloud market is the Hetzner Cloud, developed by the well known German hosting company Hetzner. Of course, it can’t compete with the 2 gazillion services from AWS but it doesn’t need to, because it already contains the basic building blocks for deploying scalable applications.. Namely, an equivalent for EC2, VPC, ALB, and EBS. What’s missing though is a replacement for RDS which makes it difficult to run any application that stores state in an SQL database. [Read More]

This post will show you how to use vault, signed SSH keys and some bash glue code to secure SSH connections, make them more verifiable and allow flexible access to your SSH servers.

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