PermalinkPlugin Development - Accessing the datastore

PermalinkIntroduction

Kong interacts with the model layer through classes we refer to as “DAOs”. This chapter will detail the available API to interact with the datastore.

Kong supports two primary datastores: Cassandra and PostgreSQL .

Permalinkkong.db and kong.dao

All entities in Kong are represented by:

• A schema that describes which table the entity relates to in the datastore, constraints on its fields such as foreign keys, non-null constraints etc… This schema is a table described in the plugin configuration chapter.
• An instance of the DAO class mapping to the database currently in use (Cassandra or PostgreSQL). This class’ methods consume the schema and expose methods to insert, update, find and delete entities of that type.

The core entities in Kong are: Services, Routes, Consumers and Plugins. Services, Routes, and Consumers are available through the new kong.db singleton. The rest of the entities are available through kong.dao. In the future, all entities will be gradually migrated to kong.db, including custom plugins entities (currently relying on kong.dao).

Both the DAO Factory and the new db interface are singleton instances in Kong and thus, are accessible through the kong global:

-- Core DAOs
local services_dao = kong.db.services
local routes_dao = kong.db.routes
local consumers_dao = kong.db.consumers
local plugins_dao = kong.dao.plugins

The kong global exposes the Plugin Development Kit, and its kong.dao and kong.db properties are instances of the DAO and DB singletons.

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PermalinkThe DAO Lua API

The DAO class is responsible for the operations executed on a given table in the datastore, generally mapping to an entity in Kong. All the underlying supported databases (currently Cassandra and PostgreSQL) comply to the same interface, thus making the DAO compatible with all of them.

For example, inserting a Service (with kong.db) and a Plugin (with kong.dao) is as easy as:

local inserted_service, err = kong.db.services:insert({
  name = "mockbin",
  url = "http://mockbin.org"
})

local inserted_plugin, err = kong.dao.plugins:insert({
  name = "key-auth",
  service_id = inserted_service.id
})

For a real-life example of the DAO being used in a plugin, see the Key-Auth plugin source code.

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Next: Custom Entities ›