Database Deadlocks

I have had to explain database deadlocks several times and I had this old code project to produce a database deadlock and I had the following scheme for explanation:



However it was a bit too little or too confusing to get the idea through sometimes, so I retired the project and recreated a new one on the newest Symfony. It runs on Docker and produces a deadlock by running just one command. It’s on Github: https://github.com/varfrog/deadlock-symfony.

The main point is that a deadlock happens when the same records are being locked by different processes in a different sequence. More on this in the README of the project.

Popular posts from this blog

AWS VPN Client on a guest VM

Image
The AWS VPN Client for Linux ( https://docs.aws.amazon.com/vpn/latest/clientvpn-user/client-vpn-connect-linux.html ) at the time of writing (Nov 26, 2023) is only supported on Ubuntu and the latest Ubuntu version supported is 20.04 LTS. This version of Ubuntu is nearly 4 years old and people have been having problems with the client - there have been numerous complaints on the forums by people trying to get it working on newer Ubuntu versions, for example https://repost.aws/questions/QUNJeF_ja_Suykous7EvfX5Q/aws-client-vpn-on-ubuntu-22-04 . While it is possible to get the VPN client working on Ubuntu 22.04, there is a caveat - the client uses an outdated libssl version (libssl1) and Ubuntu 22.04 comes with a libssl3, which makes the client error out.  The workaround is manual installation of libssl1, replacing libssl3. If one uses another distro or simply does not want to downgrade libssl just for the AWS VPN client, one solution is to run the client on guest installation of Ub...
Read more

Cyberghost Vpn on Arch Linux

  CyberGhost has apps or shell scripts for various Linux distros but not for Arch Linux, at least not at the time of writing this. However, it is very easy to configure it for Arch. Here’s what I did. Steps Logged into  https://my.cyberghostvpn.com/,  “My Download Apps” -> “Other Apps” -> “Routers and other devices” -> “Configure New Device”. Make the selections, for my setup I’ve selected “Open VPN” as the protocol. Download the OpenVPN configuration files. Extract the archive, mv the files to  /etc/openvpn/client . chmod 600 /etc/openvpn/client/* chown openvpn:network /etc/openvpn/client/* Create an auth file that stores the login credentials for this VPN connection /etc/openvpn/client/login.conf with the username on the 1st line and the password on the 2nd line. Change  auth-user-pass  in cyberghost.conf to  auth-user-pass login.conf . sudo systemctl start openvpn-client@cyberghost sudo systemctl enable openvpn-client@cyberghost Check the I...
Read more

Go error handling and stack traces voted as the biggest challenge

Image
The results of Go Developer Survey 2022 Q2 came out and showed that error handling and working with stack traces in Go pose the biggest challenge to respondents: "Error handling remains a challenge. Following the release of generics, respondents' top challenge when working with Go shifted to error handling." The answer distribution is as below (click): In this blog post I would like to focus on error handling and try to explain in detail how, in my view, error handling in Go is or should be done. Ready? Let's begin. Error handling in Go explained A function or a method in Go returns a non-nil error if and only if it encounters an error during execution. The caller checks for the returned error value - if it is not nil, it either handles it or returns an error of its own. I hope this blog post makes Go error handling better understood and appreciated.  
Read more