Facebook Messenger bot not sending messages in ord

Question

I'm playing around with building a simple Facebook Messenger chatbot and I'm having trouble sending messages in sequence.

In the example above, it should have printed "Hello!", "1", "2", "3" in order. I'm currently following the Facebook docs found here to implement this simple text message function. I've included my Express Node.JS server code below:

Defining the sendTextMessage() function:

var request = require("request");
function sendTextMessage(user, text) {
    messageData = {
        text: text
    };
    request({
        url: "https://graph.facebook.com/v2.6/me/messages",
        qs: {access_token: PAGE_ACCESS_TOKEN},
        method: "POST",
        json: {
            recipient: {id: user},
            message: messageData
        }
    }, function(error, response, body) {
        if (error) {
            console.log("Error sending message: ", error);
        } else if (response.body.error) {
            console.log("Error: ", response.body.error);
        } else {
            console.log("Message successfully send.")
        }
    });
}

Using it to send a response:

sendTextMessage(user, "Hello!");
sendTextMessage(user, "1");
sendTextMessage(user, "2");
sendTextMessage(user, "3");

I even tried implementing a simple queue that queues messages and only sends one message at a time after each request's success callback. This is making me suspect that I'm not interacting with the Messenger API correctly.

Has anyone encountered this issue? How can I get messages to send in sequence? Thanks!

EDIT

Because I implemented a simple queue but still experiencing this problem, I'm including the code for my simple queue system here.

var queue = [];
var queueProcessing = false;

function queueRequest(request) {
    queue.push(request);
    if (queueProcessing) {
        return;
    }
    queueProcessing = true;
    processQueue();
}

function processQueue() {
    if (queue.length == 0) {
        queueProcessing = false;
        return;
    }
    var currentRequest = queue.shift();
    request(currentRequest, function(error, response, body) {
        if (error || response.body.error) {
            console.log("Error sending messages!");
        }
        processQueue();
    });
}

queueRequest(/* Message 1 */);
queueRequest(/* Message 2 */);
queueRequest(/* Message 3 */);

UPDATE

This "bug" was reported to Facebook but it sounds like they aren't going to fix it. Please read the ticket thread on Facebook's post here for details on what they say is going on. (Thank you to Louise for getting Facebook's attention on this)

Answer 1

Implement the send request as a Promise and only send consequent messages once the previous one is resolved

const send = (userId, messageData)  => {

      return new Promise((resolve, reject) => {
        request
        (
            {
                url     : BASE_URL + "me/messages",
                qs      : { access_token : PAGE_ACCESS_TOKEN },
                method  : "POST",
                json    : 
                        {
                            recipient: { id : userId },
                            message: messageData,
                        }
            }, (error, response, body) => 
            {
                if (error) { console.log("Error sending message: " + response.error); return reject(response.error); }
                else if (response.body.error) { console.log('Response body Error: ' + response.body.error); return reject(response.body.error); }

                console.log("Message sent successfully to " + userId); 
                return resolve(response);
            }
        );    
    });
};

Answer 2

I had exactly same problem, that solution worked for me:

function sendMessage(recipient, messages, accessToken, i) {


    axios.post(baseURL + 'v2.11/me/messages/?access_token=' + accessToken,
        Object.assign({}, {
            messaging_type: "RESPONSE",
            recipient: {
                id: recipient
            }
        }, messages[i]['payload']) )
        .then(response => {

            if(i < messages.length) sendMessage( recipient, messages, accessToken, i+1 );

            },
            error => {})
        .catch(error => {});

}
sendMessage(recipient, flow['messages'], flow['page']['accessToken'], 0);

That's my question: Sequential Message Sending Using Facebook Send-API

Answer 3

You can try putting them inside a setTimeout function so each one goes after a certain period of time.

So replace this:

sendTextMessage(user, "Hello!");
sendTextMessage(user, "1");
sendTextMessage(user, "2");
sendTextMessage(user, "3");

With this:

sendTextMessage(user, "Hello!");              

// 1 second

setTimeout(function() {
    sendTextMessage(user, "1");
}, 1000)

// 2 seconds

setTimeout(function() {
    sendTextMessage(user, "2");
}, 2000)

// 3 seconds

setTimeout(function() {
    sendTextMessage(user, "3");
}, 3000)    

And they should go one after another. You could also embed the functions inside each other if need be.

Answer 4

I submitted a bug report to Facebook about this because I was having the same problem. They acknowledged that it is indeed a bug and are working to fix it: https://developers.facebook.com/bugs/565416400306038