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src/models/ApiDataSource is a base class for REST API data sources that is being used by Falcon Server application.


This method will be triggered by ApiContainer (initialize method will be called by GraphQL itself with the proper context argument). It can optionally return a config object received from the back-end system.


This method must be defined if ApiDataSource supports Dynamic Routing. It should provide a simple logic to determine custom priority or return a default priority (this.fetchUrlPriority equals ApiUrlPriority.NORMAL by default).

ApiDataSource internal methods

ApiDataSource class provides a set of extra methods and hooks.

context - is an object, that could be passed to init argument (3rd argument) of the following REST methods - get, post, patch, put and delete:

async getInfo() {
return this.get('info', {}, {
context: {
isAuthRequired: true,
foo: 'bar'

This context object will be passed to willSendRequest method so you could perform a context-specific changes to your request before it gets send:

protected async willSendRequest(request) {
const { context } = request;
if (context && context.isAuthRequired && this.authorizeRequest) {
await this.authorizeRequest(request);
if ( {
// do something else...

Base ApiDataSource class provides a small isAuthRequired hook by default. If your class defines authorizeRequest method and you pass isAuthRequired context flag to any of the REST methods - ApiDataSource will call authorizeRequest method before sending the actual request further.

If you pass async context.didReceiveResult callback - it will be triggered right between parsing REST response and saving this response to the internal cache, so this way - you have full control what to store in the cache. All further calls for this endpoint - ApiDataSource will get from the cache, so this context.didReceiveResult won't be triggered again.

api.processPagination() is an internal method that helps you to process and generate a proper "pagination" object, which is used by GraphQL type.


src/models/Extension is a base class for any extension that is being used by Falcon Server Application. It adds a few helpful methods to provide a seamless integration with Falcon Server applications.


await extension.initialize() will be called by ExtensionContainer automatically. Optionally, it can optionally return a back-end configuration object, received from the assigned ApiDataSource instance (by calling await api.preInitialize() method).


This method will be called by ExtensionContainer to get Extension's GraphQL configuration, which will be merged with the rest of the extensions' configs (see example below).


By default, this method will trigger api.getFetchUrlPriority(url: string) method (if it was defined in the assigned ApiDataSource instance) and pass the current URL to determine API's priority (for sort order) when Falcon Client fetches URL info from available extensions; if such method was not defined - it will return null, meaning that this ApiDataSource does not support "Dynamic Routing" and should be skipped.


This method is optional and should be defined if ApiDataSource supports Dynamic Routing. Its signature mimics GraphQL Resolver function signature (root, params, context, info).

Using ApiDataSource together with Extension

Sample config:

"apis": [
"name": "api-wordpress",
"package": "@deity/falcon-wordpress-api",
"config": {
"host": "",
"protocol": "https",
"apiPrefix": "/blog-api",
"apiSuffix": "/wp/v2"
"extensions": [
"package": "@deity/falcon-blog-extension",
"config": {
"api": "api-wordpress"

Sample ApiDataSource class:

const { ApiDataSource } = require('@deity/falcon-server-env');

class WordpressApi extends ApiDataSource {
async getPost(id) {
// Calling '<id>' endpoint
return this.get(`/post/${id}`);

Sample Extension class:

const { Extension } = require('@deity/falcon-server-env');

class BlogExtension extends Extension {
async getGraphQLConfig() {
return {
schemas: [
`type Post {
name: String
`extend Query {
getPost(id: String!): Post
dataSources: {
[]: this.api
resolvers: {
Query: {
getPost: (root, { id }, { dataSources }) => {
/* @type {WordpressApi} */
const dataSource = dataSources[];

return dataSource.getPost(id);

ApiContainer and ExtensionContainer will do the rest of the job:

  • Creating instances of both classes
  • Assigning specified extension.config.api Instance to Extension
  • Generating, stitching and merging GraphQL Schema for FalconServer