Collection of cool things I learnt today.
Today I learned how to reload Prometheus configuration without restarting it. There are two ways: Send a SIGHUP signal to the prometheus process kill -HUP 1234 Send a post request to the /-/reload HTTP endpoint. curl -X POST http://localhost:9090/-/reloadcurl -X POST http://localhost:9090/-/reload More
Today I learned about label_values(metric, label) in Grafana. It is used to extract label values from a specific metric. More here
Today I learned that https support has been moved to the apt package starting from apt 1.5 and the apt-transport-https is no longer required. source
Today I learned about paravirtualization. In PV, the hypervisor expose an API to virtual machine that is similar but not identical to that of the underlaying hardware. One example, that helped me understand the concept is Spice with Qemu. In full virtualized setups, the VNC server reads frames from video memory and send them to the VNC client through a network connection. However, in the spice context, the spice-server expose an X driver to the guest....
Today I learned that I can ignore commits introducing white space only using in git blame and git git diff using -w option.
Today I learned about git bisect. It performs a binary search between two git refs and execute a command on each version until it finds the commit where the result changes. (0 good, 1 bad, 125 skip). git bisect start # to enter bisect mode git bisect old(good) <ref> # specify old version git bisect new(bad) <ref> # specify new version git bisect run <command> # perform bisect using the command
Today I learned about the colon built-in : in bash. It has no effect beyond expanding its arguments. also it always returns 0 exit status. It can be useful as a replacement for echos for dynamic comments.