Building a Llama 3 Enabled Messenger Chatbot

This step-by-step tutorial shows the complete process of building a Llama-enabled Messenger chatbot. A demo video of using the iOS Messenger app to send a question to a Facebook business page and receive the Llama 3 generated answer is here.

If you're interested in a Llama 3 enabled WhatsApp chatbot, see here for a tutorial.

Overview

Messenger from Meta is a messaging service that allows a Facebook business page to respond to people who are interested in their business using Messenger Platform. The benefits of an intelligent and knowledgable Llama 3 powered chatbot are obvious, including cost saving and better customer experience such as 24x7 availability. In this tutorial, we'll cover the details of integrating Llama 3 with the Messenger Platform to build a basic Llama 3 enabled chatbot - for more Llama 3 application development and deployment demos such as how to integrate your own data with Llama 3, see the recipes.

The diagram below shows the components and overall data flow of the Llama 3 enabled Messenger chatbot demo we built, using an Amazon EC2 instance as an example for running the web server.

Getting Started with Messenger Platform

A Facebook Page is required to send and receive messages using the Messenger Platform - see here for details about Facebook Pages and how to create a new page.
If you have followed the Llama WhatsApp chatbot tutorial, or if you already have a Meta developer account and a business app, then you can skip this step. Otherwise, you need to first create a Meta developer account and then create a business app.
Add the Messenger product to your business app by going to your business app's Dashboard, click "Add Product" and then select "Messenger".
Configure a webhook to receive real time HTTP notifications: follow the Sample Callback URL for Webhooks Testing Guide to create a free account on glitch.com to get your webhook's callback URL, but you can skip the WHATSAPP_TOKEN part in the guide - the rest of setting up webhook is the same for WhatsApp and Messenger.
Open Messenger's API Settings, as shown in the screenshot below, then in "1. Configure webhooks", set the Callback URL and Verify Token set up in the previous step, and subscribe all message related fields for "Webhook Fields". Finally, in "2. Generate access tokens", connect your Facebook page (see step 1) and copy your page access token for later use.

Writing Llama 3 Enabled Web App

The Python-based web app we developed uses LangChain, an open source LLM development framework, and Replicate, a service provider hosting LLM models in the cloud, to receive the user query sent by the webhook, which will be covered in the next section, pass the query to Llama 3, and send the Llama 3 answer back to the webhook. For more information on how to use LangChain or LlamaIndex, another LLM app building framework, and other Llama 3 cloud providers or on-premise deployment options to develop Llama 3 apps, see the recipes.

First, let's create a new conda (or you can use venv if you like) environment and install all the required packages:

conda create -n messenger-llama python=3.8
conda activate messenger-llama
pip install langchain replicate flask requests uvicorn gunicorn

Then, create a Python file named llama_messenger.py that creates a Llama 3 instance and defines an HTTP method msgrcvd_page to:

receive the user message forwarded by the webhook;
ask Llama 3 for the answer;
send the answer back to the sender using the Facebook graph API.

import langchain
from langchain.llms import Replicate

from flask import Flask
from flask import request
import os
import requests
import json

os.environ["REPLICATE_API_TOKEN"] = "<your replicate api token"    
llama3_8b_chat = "meta/meta-llama-3-8b-instruct"

llm = Replicate(
    model=llama3_8b_chat,
    model_kwargs={"temperature": 0.0, "top_p": 1, "max_new_tokens":500}
)

app = Flask(__name__)

@app.route('/msgrcvd_page', methods=['POST', 'GET'])
def msgrcvd_page():    
    message = request.args.get('message')
    sender = request.args.get('sender')
    recipient = request.args.get('recipient')

    answer = llm(message)

    url = f"https://graph.facebook.com/v18.0/{recipient}/messages"
    params = {
        'recipient': '{"id": ' + sender + '}',
        'message': json.dumps({'text': answer}),
        'messaging_type': 'RESPONSE',
        'access_token': '<page_access_token>'
    }
    headers = {
        'Content-Type': 'application/json'
    }
    response = requests.post(url, params=params, headers=headers)

    return message + "<p/>" + answer

Replace with the access token copied in step 5 "Open Messenger's API Settings" of the previous section. Now it's time to modify the webhook to complete the whole app.

Modifying the Webhook

Open your glitch.com webhook URL created earlier, and change your app.js to simply forward the user message and the user and page ids sent by the Messenger Platform to the Llama 3 enabled web app llama_messenger.py described in the previous section:

"use strict";

// Imports dependencies and set up http server
const request = require("request"),
  express = require("express"),
  body_parser = require("body-parser"),
  axios = require("axios").default,
  app = express().use(body_parser.json()); // creates express http server

// Sets server port and logs message on success
app.listen(process.env.PORT || 1337, () => console.log("webhook is listening"));

// Accepts POST requests at /webhook endpoint
app.post("/webhook", (req, res) => {
  // Parse the request body from the POST
  let body = req.body;
  
  let sender = req.body["entry"][0]["messaging"][0]['sender']['id']
  let recipient = req.body["entry"][0]["messaging"][0]['recipient']['id']
  let message = req.body["entry"][0]["messaging"][0]['message']['text']

  // Check if this is an event from a page subscription
  if (body.object === "page") {
    // Returns a '200 OK' response to all requests
    res.status(200).send("EVENT_RECEIVED");
    
    let url = "http://<web server public IP>:5000/msgrcvd_page?sender=" + sender + "&recipient=" + recipient + "&message=" + encodeURIComponent(message)
    console.log(url)
  
    axios.get(url)
      .then(response => {
        // Handle the response data
        console.log(response.data);
      })
      .catch(error => {
        // Handle errors
        console.error('Axios error:', error);
      });    
    } else {
      // Return a '404 Not Found' if event is not from a page subscription
      res.sendStatus(404);
    }
  });

// Accepts GET requests at the /webhook endpoint. You need this URL to setup webhook initially.
// info on verification request payload: https://developers.facebook.com/docs/graph-api/webhooks/getting-started#verification-requests 
app.get("/webhook", (req, res) => {
  /**
   * UPDATE YOUR VERIFY TOKEN
   *This will be the Verify Token value when you set up webhook
  **/
  const verify_token = process.env.VERIFY_TOKEN;

  // Parse params from the webhook verification request
  let mode = req.query["hub.mode"];
  let token = req.query["hub.verify_token"];
  let challenge = req.query["hub.challenge"];

  // Check if a token and mode were sent
  if (mode && token) {
    // Check the mode and token sent are correct
    if (mode === "subscribe" && token === verify_token) {
      // Respond with 200 OK and challenge token from the request
      console.log("WEBHOOK_VERIFIED: " + token);
      res.status(200).send(challenge);
    } else {
      // Responds with '403 Forbidden' if verify tokens do not match
      res.sendStatus(403);
    }
  }
});

Remember to change , which needs to be publicly visible, to the IP of the server where your Llama 3 enabled web app in the previous section runs.

Note: It's possible and even recommended to implement a webhook in Python and call the Llama directly inside the webhook, instead of making an HTTP request, as the JavaScript code above does, to a Python app which calls Llama and sends the answer to Messenger.

Running the Chatbot

On your web server, run the following command on a Terminal (see here for more info on Gunicorn):

gunicorn -b 0.0.0.0:5000 llama_messenger:app

If you use Amazon EC2 as your web server, make sure you have port 5000 added to your EC2 instance's security group's inbound rules.

Now you can open your Messenger app, select the Facebook page you connected in Messenger's API Settings, enter a message and receive the Llama 3's answer shortly, as shown in the demo video in the beginning of this post.

To debug any possible issues, go to your glitch.com app log and copy the URL generated there when a Messenger message is sent, which looks like this:

http://<web server public IP>:5000/msgrcvd_page?sender=<user id>&recipient=<page id>&message=<msg>

Then open the URL in a browser to verify your web server can receive the message and the two ids, and generate a Llama answer before sending the answer back to Messenger.

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