Facebook Messenger Bot wait to respond after many request and resume - node.js

Question

When I write the alphabet on my facebook bot, my bot wait to respond.
I write for example : I write "a"... bot respond "a", I write "b"... bot respond "b", etc...
But, for example on the letter "l", the bot waits to respond, and resume after about some minutes :
after about some minutes, the bot responds :
I use the official code, from https://developers.facebook.com/docs/messenger-platform/guides/quick-start/
app.js
app.get('/webhook', function(req, res) {
if (req.query['hub.mode'] === 'subscribe' &&
req.query['hub.verify_token'] === CONFIGURATION.webhook_token) {
console.log("Validating webhook");
res.status(200).send(req.query['hub.challenge']);
} else {
console.error("Failed validation. Make sure the validation tokens match.");
res.sendStatus(403);
}
});
app.post('/webhook', function (req, res) {
let data = req.body;
// Make sure this is a page subscription
if (data.object === 'page') {
// Iterate over each entry - there may be multiple if batched
data.entry.forEach(function(entry) {
let pageID = entry.id;
let timeOfEvent = entry.time;
// Iterate over each messaging event
entry.messaging.forEach(function(event) {
if (event.message) {
receivedMessage(event);
} else {
console.log("Webhook received unknown event: ", event);
}
});
});
// Assume all went well.
//
// You must send back a 200, within 20 seconds, to let us know
// you've successfully received the callback. Otherwise, the request
// will time out and we will keep trying to resend.
res.sendStatus(200);
}
});
function receivedMessage(event) {
let senderID = event.sender.id;
let recipientID = event.recipient.id;
let timeOfMessage = event.timestamp;
let message = event.message;
console.log("Received message for user %d and page %d at %d with message:",
senderID, recipientID, timeOfMessage);
console.log(JSON.stringify(message));
let messageId = message.mid;
let messageText = message.text;
let messageAttachments = message.attachments;
if (messageText) {
// If we receive a text message, check to see if it matches a keyword
// and send back the example. Otherwise, just echo the text we received.
switch (messageText) {
case 'generic':
sendGenericMessage(senderID);
break;
default:
sendTextMessage(senderID, messageText);
}
} else if (messageAttachments) {
sendTextMessage(senderID, "Message with attachment received");
}
}
function sendGenericMessage(recipientId) {
let messageData = {
recipient: {
id: recipientId
},
message: {
attachment: {
type: "template",
payload: {
template_type: "generic",
elements: [{
title: "rift",
subtitle: "Next-generation virtual reality",
item_url: "https://www.oculus.com/en-us/rift/",
image_url: "http://messengerdemo.parseapp.com/img/rift.png",
buttons: [{
type: "web_url",
url: "https://www.oculus.com/en-us/rift/",
title: "Open Web URL"
}, {
type: "postback",
title: "Call Postback",
payload: "Payload for first bubble",
}],
}, {
title: "touch",
subtitle: "Your Hands, Now in VR",
item_url: "https://www.oculus.com/en-us/touch/",
image_url: "http://messengerdemo.parseapp.com/img/touch.png",
buttons: [{
type: "web_url",
url: "https://www.oculus.com/en-us/touch/",
title: "Open Web URL"
}, {
type: "postback",
title: "Call Postback",
payload: "Payload for second bubble",
}]
}]
}
}
}
};
callSendAPI(messageData);
}
function sendTextMessage(recipientId, messageText) {
let messageData = {
recipient: {
id: recipientId
},
message: {
text: messageText
}
};
callSendAPI(messageData);
}
function callSendAPI(messageData) {
request({
uri: 'https://graph.facebook.com/v2.6/me/messages',
qs: { access_token: CONFIGURATION.access_token },
method: 'POST',
json: messageData
}, function (error, response, body) {
if (!error && response.statusCode == 200) {
let recipientId = body.recipient_id;
let messageId = body.message_id;
console.log("Successfully sent generic message with id %s to recipient %s",
messageId, recipientId);
} else {
console.error("Unable to send message.");
console.error(response);
console.error(error);
}
});
}
let server = app.listen(port, function () {
InterfaceLogin.process();
console.log('App listening on port 8080!');
});
server.timeout = 1000;
In my console, During the last respond I see :
Received message for user xxx and page xxx at xxx with message:
{"mid":"mid.$xxx","seq":xxxx,"text":"k"}
Successfully sent generic message with id mid.$xxx to recipient xxxxx
the bot don't respond, and after some minutes I see :
Received message for user xxx and page xxx at xxx with message:
{"mid":"mid.$xxx","seq":xxxx,"text":"l"}
Successfully sent generic message with id mid.$xxx to recipient xxxx
Webhook received unknown event: { sender: { id: 'xxx' },
recipient: { id: 'xxx' },
timestamp: xxx,
delivery:
{ mids: [ 'mid.$xxx' ],
watermark: xxx,
seq: 0 } }
the bots responds
My last respond is :
Received message for user xxx and page xxx at xxx with message:
{"mid":"mid.$xxx","seq":xx,"text":"k"}
Successfully sent generic message with id mid.$xxx to recipient xxx
Received message for user xxx and page xxx at xxx with message:
{"mid":"mid.$xxx","seq":xx,"text":"l"}
Successfully sent generic message with id mid.$xxx to recipient xxxx
Webhook received unknown event: { sender: { id: 'xxx' },
recipient: { id: 'xxx' },
timestamp: xxx,
delivery:
{ mids: [ 'mid.$xxx' ],
watermark: xxx,
seq: 0 } }

Answer 1

The messenger bot platform has rate limit, if you exceed it the requests will queue up and execute later.
https://developers.facebook.com/docs/messenger-platform/reference/send-api/