I am to build a web application which will accept different events from external sources and present them quickly to the user for further actions. I want to use Ruby on Rails for the web application. This project is a internal development project. I would prefer simple and easy to use solutions for rapid development over high reliable and complex systems.
What it should do
The user has the web application opened in his browser. Now an phone call comes is. The phone call is registered by a PBX monitoring daemon. In this case via the Asterisk Manager Interface. The daemon sends the available information (remote extension, local extension, call direction, channel status, start time, end time) somehow to the web application. Next the user receives a notified about the phone call event. The user now can work with this. For example by entering a summary or by matching the call to a customer profile.
The duration from the first event on the PBX (e.g. the creation of a new channel) to the popup notification in the browser should be short. Given a fast network I would like to be within two seconds. The single pieces of information about an event are created asynchronously. The local extension may be supplied separate from the remote extension. The user can enter a summary before the call has ended. The end time, new status etc. will show up on the interface as soon as one party has hung up.
The PBX monitor is just one data source. There will be more monitors like email or a request via a web form. The monitoring daemons will not necessarily run on the same host as the database or web server. I do not image the application will serve thousands of logged in users or concurrent requests soon. But from the design 200 users with maybe about the same number of events per minute should not be a scalability issue.
How should I do?
I am interested to know how you would design such an application. What technologies would you suggest? How do the daemons communicate their information? When and by whom is the data about an event stored into the main database? How does the user get notified? Should the browser receive a complete dataset on behalf of a daemon or just a short note that new data is available? Which JS library to use and how to create the necessary code on the server side?
On my research I came across a lot of possibilities: Message brokers, queue services, some rails background task solutions, HTTP Push services, XMPP and so on. Some products I am going to look into: ActiveMQ, Starling and Workling, Juggernaut and Bosh.
Maybe I am aiming too hight? If there is a simpler or easier way, like just using the XML or JSON interface of Rails, I would like to read this even more.
I hope the text is not too long :)
Thanks.
If you want to skip Java and Flash, perhaps it makes sense to use a technology in the Comet family to do the push from the server to the browser?
http://en.wikipedia.org/wiki/Comet_%28programming%29
For the sake of simplicity, for notifications from daemons to the Web browser, I'd leave Rails in the middle, create a RESTful interface to that Rails application, and have all of the daemons report to it. Then in your daemons you can do something as simple as use curl or libcurl to post the notifications. The Rails app would then be responsible for collecting the incoming notifications from the various sources and reporting them to the browser, either via JavaScript using a Comet solution or via some kind of fatter client implemented using Flash or Java.
You could approach this a number of ways but my only comment would be: Push, don't pull. For low latency it's not only quicker it's more efficient, as your server now doesn't have to handle n*clients once a second polling the db/queue. ActiveMQ is OK, but Starling will probably serve you better if you're not looking for insane levels of persistence.
You'll almost certainly end up using Flash on the client side (Juggernaut uses it last time I checked) or Java. This may be an issue for your clients (if they don't have Flash/Java installed) but for most people it's not an issue; still, a fallback mechanism onto a pull notification system might be prudent to implement.
Perhaps http://goldfishserver.com might be of some use to you. It provides a simple API to allow push notifications to your web pages. In short, when your data updates, send it (some payload data) to the Goldfish servers and your client browsers will be notified, with the same data.
Disclaimer: I am a developer working on goldfish.
The problem
There is an event - either external (or perhaps internally within your app).
Users should be notified.
One solution
I am myself facing this problem. I haven't solved it yet, but this is how I intend to do it. It may help you too:
(A) The app must learn about the event (via an exposed end point)
Expose an end point by which you app can be notified about external events.
When the end point is hit (and after authentication then users need to be notified).
(B) Notification
You can notify the user directly by changing the DOM on the current web page they are on.
You can notify users by using the Push API (but you need to make sure your browsers can target that).
All of these notification features should be able to be handled via Action Cable: (i) either by updating the DOM to notify you when a phone call comes in, or (ii) via a push notification that pops up in your browser.
Summary: use Action Cable.
(Also: why use an external service like Pusher, when you have ActionCable at your disposal? Some people say scalability, and infrastructure management. But I do not know enough to comment on these issues. )
Related
I want to understand how can I integrate VoIP for my WEB app which in my case would be a Rails app.
What I wan't to achieve is sending socket events to the front-end for each call state:
call ringing
call started
call ended
The implementation is already done but I'm not convinced if is the right architecture and the informations I found until now over the internet are poor.
I don't think that makes sense to explain how is currently done (but if needed I can provide), but starting from ruby-asterisk gem which can be used to retrieve data about an extension number what would be the correct architecture in order to retrieve continuously events from call states and send them as socket events to the WEB?
How can you determine if the call is ended?
On the overall implementation, do you see any use of redis for saving previous states of a call and then to determine the new states?
Main issue is : asterisk is PBX
Again: it is small office PBX, not all-in-one platform with API.
So correct architecture for high load is centralized hi-perfomance socket server, which support auth, response on your api calls(if any), event notification etc etc. After that you have use AMI+ dialplan to notify you server about actions on PBX.
You web app should connect to thoose server, not directly to asterisk. Only ONE connection to asterisk recommended for peformance considerations.
If you have low load - doesn't matter what you do, it likly will work ok.
Asterisk not support redis, so use of that unlikly. Use CDRs for end event.
I am wondering about what the best way to keep users in sync with each other in a social network is. The concerned stack is an iOS app with a NodeJS backend. Let me give you an example:
Say X and Y are friends on a social network. Y's posts appear in X's feed, and as such, Y is cached somewhere on the X's phone. This morning, Y decided to change profile pictures however. Everything is well, the new picture is uploaded to the server, but how do we go about letting X know about the change of profile picture?
My possible solution: Create a route /<UID>/updates that contains a stack of "cookies" which lets the user know what and who changed since the last time they made a GET request to the route.
This seems elegant enough, but what worries me is what happens on the client side (am I supposed to make a GET request every 2 minutes during my app's uptime?). Are there any other solutions?
One solution is indeed to poll the server, but that's not very elegant. A better way is to make use of websockets:
WebSockets is an advanced technology that makes it possible to open an interactive communication session between the user's browser and a server. With this API, you can send messages to a server and receive event-driven responses without having to poll the server for a reply.
They are a 2-way connection between client and server, allowing the server to notify the client of any changes. This is the underlying technology used in the Meteor framework for example.
Take a look at this blogpost for an example of how to use websockets between an iOS client and a NodeJS backend. They make use of the open source SocketRocket iOS library.
I'm in the process of planning the development of a mail-server to hand the sending of email across our multiple websites. Below is a description of what we are planning to implement and I'd like your opinion/suggestions.
We use ASP.NET MVC and have many web-sites hosted on Azure. We currently send mail internally within each of the web applications using SMTPServer.Send(). Obviously this is not the ideal way to send emails when you have a decently busy set of websites because the send mail call is blocking and cannot guarantee mails are sent. With this I'm worried out getting an influx of mail requests when we launch our next website (we think it'll get a decent amount of traffic and lots of emails will be sent).
My plan of action : to build a centralised mail-server that runs in the background (we use azure and this will be simply another web-application). When each one of our web applications wants to send a mail, instead of doing this internally, it'll call a web method on the mail-server called sendMail() this function will accept certain parameters and insert the mail parameters, content etc. into a database. The mail server will then poll the database at fixed time intervals, select a set of unsent emails and attempt to send them using the same SMTPServer.Send() function. If an email fails for some reason we won't flag it as sent and in the next poll interval the email will be selected again and another send attempt will be made. (we will cap the number of send attempts to say 20).
This will allow each of the websites to run smoothly without having loads of blocking send mail calls internally and the mail server will handle all the sending sequentially and in a controlled environment as a separate standalone web-application.
Thanks in advance!
Looks like a good design, Don't know the entire scenario which let to you building something like an email server. The problem has been solved well by using a service that already exist like Office 365.
Your design is good, My suggestions would be the following,
You can use Azure WebJobs to build the polling agent. You can make the web job run as a scheduled web job that does the polling and sending the mail and it can be written very clean as a simple console app.
You can use Azure API App to build the SendMail() call and you can use the Azure AD Auth on the API to authenticate the caller of the API using the Authentication and Authorization feature to easily secure your email server. You can also enable CORS easily as well to make sure you receive requests from other websites and process it.
Some issues I foresee for you,
Volume and Scaling : You can only process so much email between each polling. If you cannot then you will need to create another polling agent which will making things complicated as they need to know they are picking different sets of emails to send. If you volume is going to be low you should be fine.
Challenge : Why can't the websites send the mail them selves ? And then record it on the database for tracking. All you have to do build module or a component that they use on their web page to create and send the mail. Polymer 1.0 works well for this scenario.
Hope this helps to get you started.
I am working in a Rails application and below is the scenario requiring a solution.
I'm doing some time consuming processes in the background using Sidekiq and saves the related information in the database. Now when each of the process gets completed, we would like to show notifications in a separate area saying that the process has been completed.
So, the notifications area really need to pull things from the back-end (This notification area will be available in every page) and show it dynamically. So, I thought Ajax must be an option. But, I don't know how to trigger it for a particular area only. Or is there any other option by which Client can fetch dynamic content from the server efficiently without creating much traffic.
I know it would be a broad topic to say about. But any relevant info would be greatly appreciated. Thanks :)
You're looking at a perpetual connection (either using SSE's or Websockets), something Rails has started to look at with ActionController::Live
Live
You're looking for "live" connectivity:
"Live" functionality works by keeping a connection open
between your app and the server. Rails is an HTTP request-based
framework, meaning it only sends responses to requests. The way to
send live data is to keep the response open (using a perpetual connection), which allows you to send updated data to your page on its
own timescale
The way to do this is to use a front-end method to keep the connection "live", and a back-end stack to serve the updates. The front-end will need either SSE's or a websocket, which you'll connect with use of JS
The SEE's and websockets basically give you access to the server out of the scope of "normal" requests (they use text/event-stream content / mime type)
Recommendation
We use a service called pusher
This basically creates a third-party websocket service, to which you can push updates. Once the service receives the updates, it will send it to any channels which are connected to it. You can split the channels it broadcasts to using the pub/sub pattern
I'd recommend using this service directly (they have a Rails gem) (I'm not affiliated with them), as well as providing a super simple API
Other than that, you should look at the ActionController::Live functionality of Rails
The answer suggested in the comment by #h0lyalg0rithm is an option to go.
However, primitive options are.
Use setinterval in javascript to perform a task every x seconds. Say polling.
Use jQuery or native ajax to poll for information to a controller/action via route and have the controller push data as JSON.
Use document.getElementById or jQuery to update data on the page.
Summary: is there a daemon that will do postbacks when a user connects/disconnects via TCP, or is it a good idea to write one?
Details:
There are a number of questions based around this already; but I believe that this is a different "twist" on it. We're writing a Ruby on Rails web application, and we would like to be able to tell if a user is "online" or "offline", where the following definitions apply:
"online" - the user's browser is open and maintaining a TCP connection to one of our servers.
"offline" - the user's browser is no longer connected to one of our servers.
What we're thinking is a convenient way of doing this is to run a completely separate "online state" server that each of our users will connect to (exactly once):
when a connection is made to the "online state" server, it will postback to our actual RoR site and let it know "this user just logged on".
when a connection is lost from the "online state" server, it will postback to our actual RoR site and let it know "this user just logged off".
This methodology seems reasonable and keeps things quite modularized (the online state server, for instance, will be quite simple, which is nice). We're able to write this online state server, but have the following questions:
Any specific problems with the above architecture that we haven't taken into account?
Is there a daemon or application out there that does this already? Why reinvent the wheel, if it has already been written?
Is there a push server out there that offers this functionality (i.e. it maintains connections to the users, but will postback or send notifications upstream to the web servers when a user connects or disconnects?)
Is this something you envisage users would install on their systems?
If you are looking for a browser based system, WebSockets are probably your only option using something like Socket.IO http://socket.io/.
The node.js socket server provided as part of this project can be found on github: http://github.com/LearnBoost/Socket.IO-node
Node.js is a great platform designed for exactly this problem domain and there are a number of WebSocket servers for node.
Unless your app is entirely ajax based and uses a single parent page, you would need to create a persistent parent frame containing the socket that wraps your application, as each time the user clicks a link the page unloads and reloads, resulting in disconnection and re-connection from the state server.