K8s and limits

On K8s, for every pod you can define how much memory and CPU the pod needs. To make things "simpler", K8s define two set of values: requests and limits, both for CPU and memory. After some trouble on GCP, I was forced to dig a bit in the subject.

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Your software is slow? It could be your fault. Lets dive into one of the most important aspect seldom explained by Senior IT Architects

August throughts

Programming is like writing.

Code must be easy to read, and understand. For this reason I do not like very much technologies like:

1. Aspect oriented programming
2. SQL Triggers
3. Web filters
4. Last minute event listeners (like the one check before an entity save and 'patch' some data on the fly or launch additional events).

These technology are nice,  but works 'outside' the logic of a piece of code you are writing/reading, and are mostly side effects.

Side effects are the evil of programing in my humble opinion because can create unexpected bugs.

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I the last years I decided to put a stop on my RasperryPI2 and have a mini pc always on.

It is a very slow centrino with 2 CPU threads and 8Gb of RAM, a huble micro SATA SSD and works great with Debian Linux. I use it as a benchmark to understand if a project is worth studying: if the CPU Load stay low, the code is very well written.

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A friend of mine asked some insight on how to harden a Gitea server on Internet. Gitea is a web application for manging git repositories.

Gitea is quite compact and is less feature-rich than GitLab, but it is light and can manage issues, wiki and users.

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Bullet points:

1. 1979: Unix V7 Introduced the chroot command to isolate the filesystem a process "access" to.
2. Various technology was introduced up to 2006, like Virtuozzo (which patched Linux in a proprietary ways)
3. 2006: Process Containers Launched by Google in 2006 was designed for limiting, accounting and isolating resource usage (CPU, memory, disk I/O, network) of a collection of processes. It was renamed “Control Groups (cgroups)” a year later and eventually merged to Linux kernel 2.6.24.
4. 2008: LXC LXC (LinuX Containers) was the first, most complete implementation of Linux container manager. It was implemented in 2008 using cgroups and Linux namespaces, and it works on a single Linux kernel without requiring any patches.
5. 2013: Docker Docker used LXC in its initial stages and later replaced that container manager with its own library, libcontainer. Docker offered a way to configure and manage containers, i.e a standard de-facto for this technology. As you see Docker was based on cgroups and LXC, seven-years old technologies
6. On September 2014 Google published the first release of Kubernetes
7. In 2015 Docker, CoreOS and others founded the Open Container Initiative's (OCI). K8s does not need docker anymore to work, but Docker traction is still strong.

 

References:

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NILFS is a log-structured file system supporting versioning of the entire file system and continuous snapshotting, which allows users to even restore files mistakenly overwritten or destroyed just a few seconds ago.

NILFS was developed by NTT Laboratories and published as an open-source software under GPL license, and now available as a part of Linux kernel.

Discussion on Hacker News

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https://github.com/feathericons/feather