Using Stale Cache Control Directives in TeslaHTTPCache

The article discusses the updates to Elixir HTTP caching libraries, specifically version 0.4.0, which supports the 'stale' cache control directives as defined by RFC5861. These directives enable the serving of stale content under certain conditions, enhancing cache performance. The two key directives, stale-if-error and stale-while-revalidate, allow cached content to be reused when the original resource is unavailable or during the refresh of content. The author provides an example implementation using a minimal Phoenix server and demonstrates how to set up the cache control headers with Tesla. Additionally, the article explains how to effectively utilize these directives to mitigate potential failures when accessing third-party APIs and discusses the role of the new PlugHTTPCache and PlugLoopback libraries in supporting this functionality, including caching behavior enhancements.