Articles

It’s that period of the year already ! With December comes the Advent of Code programming challenge, and its daily mental workout. Advent of Code is an Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like. The complexity level of the programming challenges increase every day, and tend to be notoriously hard during the last few days. However, as of writing this article, it’s only day 9, and there were a few problems that didn’t require too much processing cycles, provided you spent enough mathematical effort and didn’t come up with only the brute-force solution. ...

A few months ago, I found myself needing to know about the reliability of some internal DNS provider’s servers, after getting a series of hardly trackable random network issues, aka “It’s always DNS”. More specifically, I needed to know about the following: number of errors/timeouts capability to query over TCP or UDP capability to monitor multiple DNS servers at once return codes received in the answer (i.e. NOERROR, SERVFAIL, NXDOMAIN, you name it) ...

Graceful leader changes When needing to restart some Kubernetes control-plane nodes on which etcd also happens to be running, you will prefer a graceful transfer of the leadership of the etcd cluster, to reduce the transition period that comes with a leader election. This can be achieved with the following script, provided you specify the adequate environment variables in /etc/profile.d/etcd-all file. set -o pipefail && \ source /etc/profile.d/etcd-all && \ AM_LEADER=$(etcdctl endpoint status | grep $(hostname) | cut -d ',' -f 5 | tr -d ' ') && \ if [[ $AM_LEADER = "true" ]] then NEW_LEADER=$(etcdctl endpoint status | grep -v $(hostname) | cut -d ',' -f 2 | tr -d ' ' | tail -n '-1') && \ etcdctl move-leader $NEW_LEADER && sleep 15 fi Info: the following environment variables need to be set, for example through a file such as: /etc/profile.d/etcd-all ...

A few months ago, I had to understand in detail how Container Network Interface (CNI) is implemented to, well, simply get a chaos testing solution working on a bare-metal installation of Kubernetes. At that time, I found a few resources that helped me understand how this was implemented, mainly Kubernetes’ official documentation on the topic, and the official CNI specification. And yes, this specification simply consists of a Markdown document, which I needed to invest a consequent amount of energy to digest and process. ...