@keiser/metrics-sdk

Keiser Metrics SDK

Project

This SDK facilitates communication between a client system (ie: phone app, website, server) and Keiser Metrics. The SDK is written in TypeScript and supports both browser and NodeJS platforms.

For a more information about this SDK visit the Keiser Developer Zone.

To play around with the SDK try out the Keiser Metrics SDK REPL.

To see the full SDK API view the Keiser Metrics SDK Documentation.

Installation

Install with npm: npm install @keiser/metrics-sdk

Initialization

Import the SDK package root class and instantiate a Metrics connection instance. Each instance maintains a connection to the Keiser Metrics servers so only one instance should be created per an application.

This instance handles multiplexing requests, throttling, and request retries automatically. The default implementation for browsers uses a WebSocket connection, but it will fall back to a normal HTTP request strategy if WebSockets are not supported. The NodeJS implementation will always use HTTP requests.

import Metrics from '@keiser/metrics-sdk'

const metrics = new Metrics()

Authentication

The base Metrics instance is a connection handler with access to only limited information. To access user specific information a UserSession must be created by authenticating through one of the available mechanisms:

• authenticateWithCredentials - Use email and password
• authenticateWithFacebook - Use Facebook OAuth flow
• authenticateWithGoogle - Use Google OAuth flow
• authenticateWithToken - Use a stored refresh token string

const userSession = await metrics.authenticateWithCredentials({email: '[e-mail]', password: 'password'})

The result of an authentication request is a UserSession which contains methods for interacting with the user's data as well as mechanisms for controlling the session.

To log-out a user, call teh logout() method on the UserSession.

await userSession.logout()

To restore an authenticated session, store the refresh token string and use the authenticateWithToken authentication mechanism to restore the session. The refresh token needs to be stored in a secure place that will persist between sessions (ie: Local Storage) and is valid for 90 days from it's creation.

const refreshTokenKey = 'refreshToken'
const userSession = await metrics.authenticateWithCredentials({email: '[e-mail]', password: 'password'})

localStorage.setItem(refreshTokenKey, userSession.refreshToken)

userSession.onRefreshTokenChangeEvent.subscribe(({refreshToken}) => {
  // Will update token in local storage each time it is updated
  localStorage.setItem(refreshTokenKey, refreshToken)
})

// On next application start
const refreshToken = localStorage.getItem(refreshTokenKey)
const userSession = await metrics.authenticateWithToken({token: refreshToken})

Accessing User Data

The UserSession instance contains a user property accessor for the authenticated user's User class.

const userSession = await metrics.authenticateWithCredentials({email: '[e-mail]', password: 'password'})

console.log(userSession.user.profile.name)

All properties exposed by the User class and it's children are instances that are generated on access, so subsequent calls to the same property are not returning the exact same instance. It is recommended to keep accessed instances in scope using local references. This prevents memory leaks and improves performance when dealing with large data sets.

This means that separate instances will also be out of sync as changes to one instance will not be reflected in other instances. The reload() method available on most classes will bring the instance in sync with the current server state.

let userProfile1 = userSession.user.profile
let userProfile2 = userSession.user.profile

console.log(userProfile1 === userProfile2)           // Output: false
console.log(userProfile1.name === userProfile2.name) // Output: true

await userProfile1.update({name: 'Pickle Rick'})
console.log(userProfile1 === userProfile2)           // Output: false
console.log(userProfile1.name === userProfile2.name) // Output: false

await userProfile2.reload()
console.log(userProfile1 === userProfile2)           // Output: false
console.log(userProfile1.name === userProfile2.name) // Output: true

// Recommended usage example
function generateUsername(user: User) {
  const name = user.profile.name

  return name ? name.replace(/\s/, '_').toLowerCase() : 'unknown_username'
}

Error Handling

All errors are handled by throwing inside the method call with the expectation of a try/catch to catch the error.

All errors will be thrown as a typed error instance corresponding to the reason for the error, with the global Error as the base instance, and an intermediate category type inheritance (for easier bucketing).

let userSession
try {
  userSession = await metrics.authenticateWithCredentials({email: '[e-mail]', password: 'wrongPassword'})
} catch (error) {
  if (error instanceof RequestError) {
    if (error instanceof InvalidCredentialsError) {
      this.userCredentialsIncorrect()
    } else if (error instanceof ValidationError) {
      this.userCredentialsValidationError()
    }
  } else if (error instanceof ServerError) {
    this.serverDown()
  }
}

Error Categories

Name	Reason
Request	Issue with the parameters provided for the request
Session	Issue with the session instance (session is no longer valid)
Server	Issue with the server (potentially overloaded or offline)
Connection	Issue with connection to server

Common Errors

Name	Category	Reason
Missing Params	Request	Parameters are missing from action (potentially null or undefined)
Invalid Credentials	Request	Invalid login credentials (don't match any active user)
Validation	Request	Parameters are present but do not pass validation
Unknown Entity	Request	Request target does not exist (deleted or never existed)
Duplicate Entity	Request	Cannot create a new instance because identical one exists
Unauthorized Resource	Request	Insufficient permissions to access the target
Action Prevented	Request	Request cannot be performed for reason other than those above (edge cases)
Facility Access Control	Request	Request is prevented due to facility access control limitations

Closing Connection

The base Metrics instance maintains an active connection until it is disposed, so it is recommended to dispose the connection by calling dispose() once the connection is no longer needed.

metrics.dispose()

Copyright and License

Copyright © 2020 Keiser Corporation.

The Keiser Metrics SDK source code and distributed package are made available through the MIT license.

Using any of the APIs made available through the Keiser Metrics SDK to communicate with Keiser Metrics make you subject to the following agreements. Please read all documents in their entirety as they govern your use of the APIs and Keiser Metrics servers.

• API Agreement
• Brand Guidelines for Developers