From 1.5.0+ version onwards, Logstash plugins are separated from the core package and are maintained as separate self-contained packages using RubyGems. It facilitates the release of plugin updates separately from Logstash releases. Also, it reduces the overall size of the Logstash core package.
Logstash plugins are developed in Ruby.
Note
RubyGems is a package manager for the Ruby programming language that provides a standard format to distribute Ruby programs and libraries (in a self-contained format called a "gem"). It is a tool designed to easily manage the installation of gems, and a server to distribute them.
Logstash core plugins and community plugins are published on https://rubygems.org/, and can be easily downloaded from here and installed.
All Logstash plugins are stored in GitHub at the following repository: