Creating and Using Services

What are Services?

Services are the core building blocks of a Feathers application. A service is simply an object or class that implements one or more of the standard service methods for CRUD operations.

Service Methods

Feathers services can implement the following standard methods:

find(params) - Retrieve multiple records
get(id, params) - Retrieve a single record by ID
create(data, params) - Create one or more records
update(id, data, params) - Replace a record
patch(id, data, params) - Merge data into a record
remove(id, params) - Remove a record

Creating a Basic Service

The simplest way to create a service is with an object that implements service methods:

const messageService = {
  async find(params) {
    return [
      { id: 1, text: 'Hello' },
      { id: 2, text: 'World' }
    ]
  },
  
  async get(id, params) {
    return {
      id,
      text: `Message ${id}`
    }
  },
  
  async create(data, params) {
    return {
      id: Date.now(),
      ...data
    }
  },
  
  async patch(id, data, params) {
    return {
      id,
      ...data,
      updatedAt: new Date()
    }
  },
  
  async remove(id, params) {
    return { id, deleted: true }
  }
}

app.use('/messages', messageService)

Service methods must be async or return a Promise. Synchronous methods are not supported.

Registering Services

Choose a Path

The first argument is the service path - this will be the endpoint for your service:

app.use('/users', userService)
app.use('/api/messages', messageService)
app.use('/', rootService)  // Root-level service

Provide the Service

The second argument is your service object or class instance:

// Object
app.use('/messages', messageService)

// Class instance
app.use('/users', new UserService())

Add Service Options (Optional)

The third argument allows you to configure service behavior:

app.use('/messages', messageService, {
  methods: ['find', 'get', 'create'],  // Limit available methods
  events: ['customEvent'],              // Add custom events
  serviceEvents: []                     // Override default events
})

Accessing Services

Once registered, access services using app.service():

Accessing Services

// Get service instance
const userService = app.service('users')

// Call service methods
const users = await app.service('users').find()
const user = await app.service('users').get(1)
const newUser = await app.service('users').create({
  email: '[email protected]',
  password: 'secret'
})

// Slashes are stripped automatically
app.service('/users/')    // Same as app.service('users')
app.service('users')      // Same as app.service('/users')

Service Parameters

All service methods receive a params object as their last argument. This object can contain:

query - Query parameters for filtering, sorting, pagination
user - The authenticated user (if using authentication)
provider - The transport used (rest, socketio, etc.)
Custom properties added by hooks or middleware

Using Parameters

const messageService = {
  async find(params) {
    const { query, user, provider } = params
    
    console.log('Query:', query)           // { $limit: 10, status: 'active' }
    console.log('User:', user)             // { id: 1, email: '...' }
    console.log('Provider:', provider)     // 'rest' or 'socketio'
    
    // Use query to filter results
    return messages.filter(msg => {
      if (query.status) {
        return msg.status === query.status
      }
      return true
    })
  },
  
  async create(data, params) {
    // Add the authenticated user's ID
    return {
      ...data,
      userId: params.user?.id,
      createdAt: new Date()
    }
  }
}

Memory Service

Feathers provides a built-in in-memory service adapter for prototyping and testing:

Memory Service

import { memory } from '@feathersjs/memory'

// Create an in-memory service
const messageService = memory({
  id: 'id',          // The property to use as the ID
  startId: 1,        // Starting ID for auto-increment
  store: {},         // Initial data store
  paginate: {        // Enable pagination
    default: 10,
    max: 50
  }
})

app.use('/messages', messageService)

// Use the service
const message = await app.service('messages').create({
  text: 'Hello World'
})

const messages = await app.service('messages').find({
  query: {
    text: { $ne: null },
    $limit: 10,
    $sort: { createdAt: -1 }
  }
})

Database Adapters

Feathers provides adapters for popular databases that implement all service methods:

import { MongoDBService } from '@feathersjs/mongodb'
import { MongoClient } from 'mongodb'

const client = await MongoClient.connect('mongodb://localhost:27017')
const database = client.db('myapp')

app.use('/users', new MongoDBService({
  Model: database.collection('users'),
  paginate: {
    default: 10,
    max: 50
  }
}))

Service Options

When registering a service, you can configure its behavior with options:

Service Options

app.use('/messages', messageService, {
  // Specify which methods are available
  methods: ['find', 'get', 'create', 'patch'],
  
  // Add custom events beyond the defaults
  events: ['typing', 'seen'],
  
  // Override all service events
  serviceEvents: ['created', 'customEvent']
})

Default Service Events

By default, services emit events for data-modifying operations:

created - After create()
updated - After update()
patched - After patch()
removed - After remove()

Listening to Service Events

app.service('messages').on('created', (message) => {
  console.log('New message:', message)
})

app.service('users').on('patched', (user) => {
  console.log('User updated:', user)
})

Custom Service Methods

You can add custom methods to your services beyond the standard CRUD operations:

Custom Methods

class MessageService {
  async find(params) {
    return []
  }
  
  async get(id, params) {
    return { id }
  }
  
  async create(data, params) {
    return data
  }
  
  // Custom method
  async sendNotification(messageId, params) {
    const message = await this.get(messageId, params)
    // Send notification logic
    return { sent: true, messageId }
  }
}

app.use('/messages', new MessageService(), {
  methods: ['find', 'get', 'create', 'sendNotification']
})

// Use custom method
await app.service('messages').sendNotification(123, {})

Custom methods cannot use protected names like setup, teardown, hooks, on, emit, or any EventEmitter method names.

Service Lifecycle

Services can implement setup() and teardown() lifecycle methods:

Service Lifecycle

class UserService {
  connection = null
  
  async setup(app, path) {
    console.log(`Setting up service at ${path}`)
    this.connection = await connectToDatabase()
  }
  
  async teardown(app, path) {
    console.log(`Tearing down service at ${path}`)
    await this.connection?.close()
  }
  
  async find(params) {
    return this.connection.query('SELECT * FROM users')
  }
  
  async get(id, params) {
    return this.connection.query('SELECT * FROM users WHERE id = ?', [id])
  }
}

setup(app, path) - Called when the application starts or when the service is registered after startup
teardown(app, path) - Called when the application shuts down

Removing Services

You can dynamically remove services using app.unuse():

Removing Services

// Register a service
app.use('/temp', tempService)

// Later, remove it
const removedService = await app.unuse('/temp')

// Service teardown is called automatically

Complete Service Example

Here’s a complete example of a custom service with validation and lifecycle methods:

Complete Service Example

class TaskService {
  tasks = new Map()
  nextId = 1
  
  async setup(app, path) {
    console.log(`Task service ready at /${path}`)
    this.app = app
  }
  
  async find(params) {
    const { query = {} } = params
    let tasks = Array.from(this.tasks.values())
    
    // Filter by status
    if (query.status) {
      tasks = tasks.filter(t => t.status === query.status)
    }
    
    // Filter by assignee
    if (query.assignedTo) {
      tasks = tasks.filter(t => t.assignedTo === query.assignedTo)
    }
    
    return tasks
  }
  
  async get(id, params) {
    const task = this.tasks.get(id)
    if (!task) {
      throw new Error(`Task ${id} not found`)
    }
    return task
  }
  
  async create(data, params) {
    const task = {
      id: this.nextId++,
      ...data,
      status: data.status || 'pending',
      createdAt: new Date(),
      createdBy: params.user?.id
    }
    
    this.tasks.set(task.id, task)
    return task
  }
  
  async patch(id, data, params) {
    const task = await this.get(id, params)
    const updated = {
      ...task,
      ...data,
      updatedAt: new Date(),
      updatedBy: params.user?.id
    }
    
    this.tasks.set(id, updated)
    return updated
  }
  
  async remove(id, params) {
    const task = await this.get(id, params)
    this.tasks.delete(id)
    return task
  }
  
  async teardown(app, path) {
    console.log(`Cleaning up ${this.tasks.size} tasks`)
    this.tasks.clear()
  }
}

app.use('/tasks', new TaskService())

Getting Started

Core Concepts

Guides

Creating and Using Services

What are Services?

Service Methods

Creating a Basic Service

Registering Services

Accessing Services

Service Parameters

Memory Service

Database Adapters

Service Options

Default Service Events

Custom Service Methods

Service Lifecycle

Removing Services

Complete Service Example

Build docs developers (and LLMs) love

Getting Started

Core Concepts

Guides

​What are Services?

​Service Methods

​Creating a Basic Service

​Registering Services

​Accessing Services

​Service Parameters

​Memory Service

​Database Adapters

​Service Options

​Default Service Events

​Custom Service Methods

​Service Lifecycle

​Removing Services

​Complete Service Example

Build docs developers (and LLMs) love

What are Services?

Service Methods

Creating a Basic Service

Registering Services

Accessing Services

Service Parameters

Memory Service

Database Adapters

Service Options

Default Service Events

Custom Service Methods

Service Lifecycle

Removing Services

Complete Service Example