Messenger Multi-Page Support

This doc outlines how to build a single Bottender app to serve multiple Facebook Pages. For example, you can create a single Bottender app of dental appointments for multiple clinics with individual clinic info.

In our case, we use Bottender to build our online chatbot builder, Creator. Every user can use Creator to build his/her bots. Technically speaking, each user's outcome of Creator is bot configs followed by a predefined structure. Finally, we use a single Bottender app with different bot configs to provider various Messenger Bots for each Facebook Page.

The core concept that makes one Bottender app serves multiple Facebook Pages is context. It covers not only the user's message, Page Id, but also the Page token for bot response. For more info, you may check out Bottender's doc, Handling Messenger Events.

In the following sections, you can see three essential steps:

• Enable mapPageToAccessToken feature of Bottender
• Prepare Facebook Page Access Token for each Facebook Page
• Manage Facebook Page Subscriptions Fields your bot needs

Note: If you can't wait to begin with an example code, please visit Messenger Multi-pages Example.

Enable mapPageToAccessToken feature of Bottender

You have to tell Bottender you are developing a Bottender app to serve for multiple Facebook Pages by fill channels.messenger.mapPageToAccessToken in bottender.config.js.

// bottender.config.js
module.exports = {
  channels: {
    messenger: {
      enabled: true,
      path: '/webhooks/messenger',
      pageId: process.env.MESSENGER_PAGE_ID,
      accessToken: process.env.MESSENGER_ACCESS_TOKEN,
      appId: process.env.MESSENGER_APP_ID,
      appSecret: process.env.MESSENGER_APP_SECRET,
      verifyToken: process.env.MESSENGER_VERIFY_TOKEN,
      mapPageToAccessToken: (pageId) => {
        // resolve corresponding access token
      },
    },
  },
};

Prepare Facebook Page Access Token for Each Facebook Page

To make your bot to reply to users, you need Facebook Page Access Token for each Facebook Page. So, you have to implement your mapPageToAccessToken function to tell Bottender how to get the corresponding access token of each Facebook Page.

Note: All operations require a Facebook Page Access Token with manage_pages permission.

Fetching Token Statically

If you only need your bot to apply to a fixed set of Facebook Pages, you may check the sample code below.

function mapPageToAccessToken(pageId) {
  switch (pageId) {
    case PAGE_1_PAGE_ID:
      return PAGE_1_ACCESS_TOKEN;
    case PAGE_2_PAGE_ID:
      return PAGE_2_ACCESS_TOKEN;
  }
}

For more information, you can check the Bottender example, Messenger Multi-pages Example.

Fetching Token Dynamically

We assume that an advanced developer like you might need to support more Facebook Pages dynamically. Plus, you don't want to modify the mapPageToAccessToken function every time you add your bot to a new Page.

In this case, you may dynamically load tokens from SQL Database, MongoDB, Redis, REST API, or whatever you want:

async function mapPageToAccessToken(pageId) {
  return fetchTokenFromSomewhere(pageId);
}

Manage Facebook Page Subscriptions Fields Your Bot Needs

Facebook has dedicated permission controls; please remember to subscribe Facebook Page Subscriptions Fields you need.

We recommend you at least enable the following fields:

• messages
• messaging_postbacks
• messaging_optins
• messaging_referrals
• messaging_policy_enforcement

Subscribe Facebook Page Subscriptions Fields

We assume that you might need to add your bot to a Facebook Pages dynamically. In the following code, you can see how to subscribe Facebook Page Subscriptions Fields your bot needs.

const { MessengerClient } = require('messaging-api-messenger');

const config = require('./bottender.config.js');

const messenger = new MessengerClient(config.channels.messenger);

// subscribe app for page
await messenger.axios.post(
  `/${pageId}/subscribed_apps?access_token=${accessToken}`,
  {
    subscribedFields: [
      'messages',
      'messaging_postbacks',
      'messaging_optins',
      'messaging_referrals',
      'messaging_policy_enforcement',
    ].join(','),
  }
);

Unsubscribe Facebook Page Subscriptions Fields

We assume that you might need to remove your bot from Facebook Pages dynamically. In the following code, you can see how to unsubscribe Facebook Page Subscriptions Fields your bot have subscribed.

// unsubscribe app for page
await messenger.axios.delete(
  `/${pageId}/subscribed_apps?access_token=${accessToken}`
);