# Extending Krawler

In the future we might consider others options to extend krawler like a plugin architecture but for now you can use the following ways to do so.

# Extend services

In order to keep krawler generic all services are not tied to specific implementations. As a consequence, each time a create operation is run on a service it expects as input a type and options parameters used to delegate the actual instantiation to a user-registered construction function. The base service (opens new window) class is used to implement this behavior on all our services, to register a new constructor:

.registerGenerator(typeName, (options) => {
  return a service entity based on provided options

The type of the created entity depends on the service being extended:

If you do not use the services in your app but the CLI mode, you should extend the default services used by the CLI like this:

import { StoresService, TasksService, JobsService } from '@kalisio/krawler'

.registerGenerator('custom-store', (options) => {
  return a store entity based on provided options

# Extend hooks

It is possible to add user-registered hook constructor functions like this:

import { hooks } from '@kalisio/krawler'
// A krawler hook constructor function
let hook = (options = {}) => {
  // Standard FeathersJS hook function
  return (hook) => {
    ...do something that depends on options
    return hook
hooks.registerHook('custom', hook)

After that you can use your custom hook like the built-in ones with the CLI.


For this to work you need to add krawler as a dependency in the package.json of your job module or link to it in development mode. Please refer to our installation section

# Complete example

A complete example of extension is available in the samples (opens new window).