A few months ago I wrote an article on how to clear single cache items from NGINX with LUA, with a simple O(1) complexity. While it’s certainly possible to use it for simple and low-impact cache invalidation, there is a need for deleting huge parts of the cache with a wildcard pattern.

For some people who’ve been reading this blog for a while now, you’ll remember a post of me generating the headings for invididual posts to use on Twitter. I have since then leveled-up and am now also generating the cover for my book, 12 Factors Applications with Docker and Go.

I am the author of the netdata docker image. I created the image before netdata became the popular real time performance monitoring software which it is today - over 15 thousand stars on GitHub! Wow! Due to the network isolation however, you would have to run it in --net=host mode to monitor your network devices.

Those of you any how familiar with scaling up a service, will by now be familiar with NGINX as a strong workhorse, when it comes to proxy HTTP requests between multiple backend servers. There’s one thing the open source NGINX version doesn’t do however - you can’t issue a PURGE request against a cached resource and delete it from the cache. That is, until we bring in LUA.

Locking serves as a construct which is used to enable writes from several threads or goroutines to the same data structures, to avoid concurrency issues. Imagine if every thread would read a value, add something to this value and then write the value back to the shared data structures - we expect in the best case to lose what we added in some routine, and we have to use a lock to avoid this.

The 12 Factor App methodology is a set of best practices to follow when building modern software applications. It was created by Heroku as a guide for developers to optimize application development for their platform as a service. At the core, the 12FA methodology is a marketing document, but the concepts behind individual practices outline best practices that can be followed regardless of the platform where you publish your apps.