# Plugins

Heptio Ark has a plugin architecture that allows users to add their own custom functionality to Ark backups & restores 
without having to modify/recompile the core Ark binary. To add custom functionality, users simply create their own binary 
containing an implementation of one of Ark's plugin kinds (described below), plus a small amount of boilerplate code to 
expose the plugin implementation to Ark. This binary is added to a container image that serves as an init container for 
the Ark server pod and copies the binary into a shared emptyDir volume for the Ark server to access. 

A fully-functional [sample plugin repository][1] is provided to serve as a convenient starting point for plugin authors.

## Plugin Kinds

Ark currently supports the following kinds of plugins:

- **Object Store** - persists and retrieves backups, backup logs and restore logs
- **Block Store** - creates volume snapshots (during backup) and restores volumes from snapshots (during restore)
- **Backup Item Action** - executes arbitrary logic for individual items prior to storing them in a backup file
- **Restore Item Action** - executes arbitrary logic for individual items prior to restoring them into a cluster

## Plugin Naming

Ark relies on a naming convention to identify plugins. Each plugin binary should be named `ark-<plugin-kind>-<name>`,
where `plugin-kind` is one of `objectstore`, `blockstore`, `backupitemaction`, or `restoreitemaction`, and `name` is
unique within the plugin kind.

## Plugin Logging

Ark provides a [logger][2] that can be used by plugins to log structured information to the main Ark server log or 
per-backup/restore logs. See the [sample repository][1] for an example of how to instantiate and use the logger 
within your plugin.



[1]: https://github.com/heptio/ark-plugin-example
[2]: https://github.com/heptio/ark/blob/master/pkg/plugin/logger.go