Call socket.io API from an external file - node.js

Question

I am trying to call my Socket.io interface from another file that is express routes. Lets say I want to create the following group chat with this and then send a notification to the involved users in the group chat,
routes.js
router.post(
"/save-groupchat",
passport.authenticate("jwt", { session: false }),
(req, res) => {
new GroupChat({
creator: req.user._id,
groupName: req.body.groupName,
groupMembers: userList
})
.save()
.then(newGroup => {
GroupChat.findOne(newGroup)
.populate("groupMembers.user")
.then(groupChat => {
//Notify the user's as well
userList.map((user, key) => {
NotificationCenter.findOneAndUpdate(
{ owner: user.user },
{
$push: {
notifications: {
$each: [
{
type: "group-invite",
title:
"You have been invited to " +
req.body.groupName +
" by " +
req.user.name,
notificationTriggeredBy: req.user._id
}
],
$position: 0
}
}
}
)
.then(() => {
//How do I call the socket here <---------------------------------
console.log("Notified User: " + req.body.userList[key].name);
})
.catch(err => {
console.log(
"Error when inviting: " +
req.body.userList[key].name +
"\n " +
err
);
});
});
res.json(groupChat);
});
});
}
);
./microservice/chat/chat (Socket Interface)
And then my socket interface is like this,
let user_list = {};
io.sockets.on("connection", socket => {
socket.on("send-notification", notification => {
console.log("How do I get here from the other file?");
});
})
...
Here is how I have my server.js file
var http = require("http").Server(app);
var io = require("socket.io")(http);
ChatMicroservice = require("./microservice/chat/chat")(io);
How would I access the socket interface and use the user_list of sockets to send out the notifications?

Answer 1

To call socket.io API from an external file you should either create a singleton class and export it or save socket object to a global variable, and save the connected socket id in the database corresponding to the user. so whenever a socket connection is established to the server, the socket id ie, socket.id is saved in the database corresponding to the user-id.
so your socket interface becomes
global.io = io;
io.sockets.on("connection", socket => {
// add your method to save the socket id (socket.id)
// user-id passed can be accessed socket.handshake.query.userId
socket.on("send-notification", notification => {
console.log("How do I get here from the other file?");
});
})
In your other file call
global.io.to(id).emit(event, value);
If you are planning to scale your application horizontally use socket.io-redis in your Socket Interface
const redis = require('socket.io-redis');
global.io.adapter(redis({ host: redisUrl, port: redisPort }));