What is rmnotify?

Redis is a popular data store, and it can automatically tell you when things happen, like when a specific piece of data changes or gets deleted. These alerts are called "keyspace" and "event space" notifications. However, if you're building a custom add-on (called a "module") for Redis, the official toolkit doesn't yet let your add-on listen for these alerts. rmnotify fills that gap. It's a helper library that lets custom Redis modules subscribe to these notifications in the meantime. At a high level, the library works by letting a developer register a specific piece of code to "listen" for certain events. For example, if you want to know whenever a specific piece of data (say, a key named "foo") is touched, you tell the library to watch "foo" and run your custom code whenever that happens. You can also do the reverse: listen for a specific action (like "delete") across any piece of data, and trigger your code whenever that action occurs anywhere in the system. This tool is built for developers who are writing custom Redis modules in the C programming language. A practical use case would be a developer building a module that needs to react instantly when data changes, perhaps syncing a cached value to another database, or logging whenever certain records are removed. Until Redis officially builds this listening capability into its core module system, this library serves as a temporary bridge. The project is written in C and relies on a supporting library called "hiredis" to function. The README doesn't go into detail on exactly how it intercepts notifications under the hood, but it provides the basic setup instructions and example files to help developers get started quickly.