kibana/src/core/PRINCIPLES.md

Common dictionary

Plugin - a piece of software expressing specific subject of the business unit within the code.

Platform - functionality required to run all the Kibana plugins.

New platform principles

Explicit business domains separation

The plugins code should be structured on the top level to reflect business units.

// GOOD
src/plugins
 - apm
  - server
  - public
 - search
 ..
// BAD
src/plugins
 - server
  - apm
  - search

Explicit dependencies

Each plugin should declare dependencies on the other plugins explicitly. Plugins cannot have circular dependencies. Plugins shouldn't access runtime objects, HTTP endpoints, DOM nodes, etc. created by a third party plugin without declaring a dependency on this plugin.

"requiredPlugins": ["search"],
"optionalPlugins": ["apm"],

Explicit API declaration

Each plugin has to define an explicit API. Any other API's that has not been declared explicitly as public should be considered private. HTTP endpoints belonging to other plugins are considered private. Plugins should expose a JavaScript client on top of these HTTP endpoints for other plugins to consume.

// GOOD
deps.plugin.getData();
// BAD.
`GET /api/plugin/data`

Encapsulated state

Each plugin encapsulates its internal state. It doesn't rely on any kind of global state. Plugins provide an internal state via explicit API, reflecting the dynamic nature of the state (an event bus, observables, getter/setter functions). A plugin can change other plugin state by calling its public API method.

// GOOD
deps.plugin.getData();
deps.plugin.data$.subscribe();
deps.plugin.setAddress('...');
// BAD.
deps.plugin._data;
deps.plugin.data = '...';