Overview

pluginkit lets you build an application out of plugins, where a plugin is an ordinary Go package compiled into your binary. Each one can own its own HTTP routes and its own database tables.

These are compile-time plugins, not downloadable ones. Nothing is loaded at runtime, so the compiler checks every plugin and there is no dynamic loading to go wrong. Adding or removing a plugin means rebuilding.

pluginkit ships three things: the host that starts and stops your plugins, the generator that wires them in, and the guard that protects their routes.

One required interface, four optional capabilities

Every plugin implements Plugin, which is three methods: ID, Start and Stop.

Everything beyond that is optional. A plugin implements the extra interface only if it needs it, and the host finds out at runtime by checking whether the plugin satisfies it:

• Migrator for plugins that own database schema, migrated before anything starts.
• Seeder for plugins that can fill their own schema with development data, asked outside the start path.
• RouteProvider for plugins that serve HTTP under their own namespace.
• PublicPathProvider for endpoints that must answer without a login, such as a signed webhook.

A plugin that serves a GraphQL API has a fifth option, described under GraphQL plugins. It is a separate module, so applications without a graph never pull it in.

The exact signatures are on pkg.go.dev.

Your application owns the seam

pluginkit depends only on the standard library, and it knows nothing about your domain. So plugins do not import pluginkit directly. Instead your application writes a small SDK package that re-exports pluginkit’s interfaces as type aliases, and defines what a plugin receives when it starts:

package sdk

import "github.com/gopherium/pluginkit"

type Plugin   = pluginkit.Plugin
type Migrator = pluginkit.Migrator

type Deps struct {
  DatabaseURL string
  Getenv      func(string) string
}

A Go type alias is the same type under a second name, not a copy. So a plugin written against your SDK satisfies the host without ever importing pluginkit. Deps is entirely yours: put your database URL, your services, whatever plugins need.

Where it sits

pluginkit is a sibling of authentication, extracted from a working product the same way, and it has no third-party dependencies.

Read on with the host lifecycle, then the wiring generator.