# Custom API Hooks

Custom API Hooks allow running custom logic when a specified event occurs within your project. They can be registered as either "blocking" or immediate.

# 1. Create a Hook File

Custom hooks are dynamically loaded from within your extensions folder. By default this directory is located at /extensions, but it can be configured within your project's env file to be located anywhere.

# Default Standalone Hook Location

/extensions/hooks/<hook-id>/index.js

# 2. Define the Event

Next, you will want to define your event. You can trigger your custom hook with any of the platform's many API events. System events are referenced with the format:

<scope>.<action>(.<before>)
// eg: items.create
// eg: files.create
// eg: collections.*
// eg: users.update.before

# Scope

The scope determines the API endpoint that is triggered. The * wildcard can also be used to include all scopes.

System Scope

Currently all system tables are available as event scopes except for directus_migrations and directus_sessions, which don't have relevant endpoints or services.

# Action

Defines the triggering operation within the specified context (see chart below). The * wildcard can also be used to include all actions available to the scope.

# Before

Many scopes (see chart below) support an optional .before suffix for running a blocking hook prior to the event being fired. This allows you to check and/or modify the event's payload before it is processed.

items.create.before (Blocking)
items.create (Non Blocking, also called 'after' implicitly)

This also allows you to cancel an event based on the logic within the hook. Below is an example of how you can cancel a create event by throwing a standard Directus exception.

module.exports = function registerHook({ exceptions }) {
	const { InvalidPayloadException } = exceptions;

	return {
		'items.create.before': async function (input) {
			if (LOGIC_TO_CANCEL_EVENT) {
				throw new InvalidPayloadException(WHAT_IS_WRONG);
			}

			return input;
		},
	};
};

# Event Format Options

Scope	Actions	Before
`cron()`	See below for configuration	No
`server`	`start` and `stop`	Optional
`init`		Optional
`routes.init`	`before` and `after`	No
`routes.custom.init`	`before` and `after`	No
`middlewares.init`	`before` and `after`	No
`request`	`not_found`	No
`response`		No^[1]
`error`		No
`auth`	`login`, `logout`^[1] and `refresh`^[1]	Optional
`oauth.:provider`^[2]	`login` and `redirect`	Optional
`items`	`read`^[3], `create`, `update` and `delete`	Optional
`activity`	`create`, `update` and `delete`	Optional
`collections`	`create`, `update` and `delete`	Optional
`fields`	`create`, `update` and `delete`	Optional
`files`	`upload`^[3], `create`, `update` and `delete`	Optional
`folders`	`create`, `update` and `delete`	Optional
`permissions`	`create`, `update` and `delete`	Optional
`presets`	`create`, `update` and `delete`	Optional
`relations`	`create`, `update` and `delete`	Optional
`revisions`	`create`, `update` and `delete`	Optional
`roles`	`create`, `update` and `delete`	Optional
`settings`	`create`, `update` and `delete`	Optional
`users`	`create`, `update` and `delete`	Optional
`webhooks`	`create`, `update` and `delete`	Optional

¹ Feature Coming Soon
² oAuth provider name can replaced with wildcard for any oauth providers oauth.*.login
³ Doesn't support .before modifier

# Interval (cron)

Hooks support running on an interval through node-cron (opens new window). To set this up, provide a cron statement in the event scope as follows: cron(<statement>), for example cron(15 14 1 * *) (at 14:15 on day-of-month 1) or cron(5 4 * * sun) (at 04:05 on Sunday). See example below:

const axios = require('axios');

module.exports = function registerHook() {
	return {
		'cron(*/15 * * * *)': async function () {
			await axios.post('http://example.com/webhook', { message: 'Another 15 minutes passed...' });
		},
	};
};

# 3. Register your Hook

Each custom hook is registered to its event scope using a function with the following format:

const axios = require('axios');

module.exports = function registerHook() {
	return {
		'items.create': function () {
			axios.post('http://example.com/webhook');
		},
	};
};

# 4. Develop your Custom Hook

Hooks can impact performance when not carefully implemented. This is especially true for before hooks (as these are blocking) and hooks on read actions, as a single request can result in a large ammount of database reads.

# Register Function

The register function (eg: module.exports = function registerHook()) must return an object where the key is the event, and the value is the handler function itself.

The registerHook function receives a context parameter with the following properties:

services — All API internal services
exceptions — API exception objects that can be used for throwing "proper" errors
database — Knex instance that is connected to the current database
getSchema — Async function that reads the full available schema for use in services
env — Parsed environment variables

# Event Handler Function

The event handler function (eg: 'items.create': function()) receives a context parameter with the following properties:

event — Full event string
accountability — Information about the current user
collection — Collection that is being modified
item — Primary key(s) of the item(s) being modified
action — Action that is performed
payload — Payload of the request
schema - The current API schema in use
database - Current database transaction

# Auth

The auth and oauth hooks have the following context properties:

event — Full event string
accountability — Information about the current user
action — Action that is performed
payload — Payload of the request
schema - The current API schema in use
status - One of pending, success, fail
user ^† - ID of the user that tried logging in/has logged in

^† Not available in oauth

# 5. Restart the API

To deploy your hook, simply restart the API by running:

npx directus start

# Full Example

extensions/hooks/sync-with-external/index.js:

const axios = require('axios');

module.exports = function registerHook({ services, exceptions }) {
	const { MailService } = services;
	const { ServiceUnavailableException, ForbiddenException } = exceptions;

	return {
		// Force everything to be admin-only at all times
		'items.*': async function ({ item, accountability }) {
			if (accountability.admin !== true) throw new ForbiddenException();
		},
		// Sync with external recipes service, cancel creation on failure
		'items.create.before': async function (input, { collection, schema }) {
			if (collection !== 'recipes') return input;

			const mailService = new MailService({ schema });

			try {
				await axios.post('https://example.com/recipes', input);
				await mailService.send({
					to: 'person@example.com',
					template: {
						name: 'item-created',
						data: {
							collection: collection,
						},
					},
				});
			} catch (error) {
				throw new ServiceUnavailableException(error);
			}

			input[0].syncedWithExample = true;

			return input;
		},
	};
};

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