A filter plugin is used to perform transformations on data. It allows us to combine one or more plugins, and the order of the plugins defines the order in which the data is transformed. A sample filter section in a Logstash pipeline would look as follows:

The generated event from the input plugin goes through each of the plugins defined in the filter section, during which it transforms the event based on the plugins defined. Finally, it is sent to the output plugin to send the event to the appropriate destination.

In the following sections, we will explore some common filter plugins that are used for transformation.