I am builing a win application that has user access control against a sql db, all the data is stored in this db as well.
This project is to be installed in one site on 30-40 machines (I mean to say that it's not web, it's all in one place, maximum call it intranet).
I want that while the program is logged on, the logged-in user should be able to chat to the other logged in users.
Any recommended approaches in C# & VB?
I would appreciate any idea, link or tip.
Please share me with your experience
Thanks!
NOTE: The program is in Wpf if it does matter.
Architecturally, it seems like a publisher-subscriber message bus would be a good pattern for you. You would have a centralized server that each client would register with that will distribute notifications from publishers to subscribers.
Each client will register for notification of the client list upon starting. Each client can register interest in being notified when another client publishes a message. Each client would publish messages to the bus to be delivered to any subscribers for that client.
There is a good example of a pub-sub message bus written in WCF in MSDN: WCF ESSENTIALS What You Need To Know About One-Way Calls, Callbacks, And Events. You could get this up and running fairly quickly.
Related
I have been working on a project that is basically an e-commerce. It's a multi tenant application in which every client has its own domain and the website adjusts itself based on the clients' configuration.
If the client already has a software that manages his inventory like an ERP, I would need a medium on which, when the e-commerce generates an order, external applications like the ERP can be notified that this has happened to take actions in response. It would be like raising events over different applications.
I thought about storing these events in a database and having the client make requests in a short interval to fetch the data, but something about polling and using a REST Api for this seems hackish.
Then I thought about using Websockets, but if the client is offline for some reason when the event is generated, the delivery cannot be assured.
Then I encountered Message Queues, RabbitMQ to be specific. With a message queue, modeling the problem in a simplistic manner, the e-commerce would produce events on one end and push them to a queue that a clients worker would be processing as events arrive.
I don't know what is the best approach, to be honest, and would love some of you experienced developers give me a hand with this.
I do agree with Steve, using a message queue in your situation is ideal. Message queueing allows web servers to respond to requests quickly, instead of being forced to perform resource-heavy procedures on the spot. You can put your events to the queue and let the consumer/worker handle the request when the consumer has time to handle the request.
I recommend CloudAMQP for RabbitMQ, it's easy to try out and you can get started quickly. CloudAMQP is a hosted RabbitMQ service in the cloud. I also recommend this RabbitMQ guide: https://www.cloudamqp.com/blog/2015-05-18-part1-rabbitmq-for-beginners-what-is-rabbitmq.html
Your idea of using a message queue is a good one, better than database or websockets for the reasons you describe. With the message queue (RabbitMQ, or another server/broker based system such as Apache Qpid) approach you should consider putting a broker in a "DMZ" sort of network location so that your internal ecommerce system can push events out to it, and your external clients can reach into without risking direct access to your core business systems. You could also run a separate broker per client.
I'm a PHP developer with a lack of experience on other sever side langages.
I’d like you to give me leads, advice, keywords or whatever that could help me refine my research better.
What I want to do is basically to create a one to one mobile app chat that will scale.
There will be channels of 3 users: User A, User B and the "computer" pushing some messages according to some channels informations like the last time a message has been sent, etc.
User A should know if User B is online, writing, etc.
Every conversation should be stored in a database and would be analyzed by some algorithms. Those algorithms would also analyzed stuffs on user Facebook open graph.
The application should be able to send notification on IOS and Android.
A web administration should allow admin to set some stuff that will define what kind of message would be sent by the "computer".
I'v read lot of posts about websocket, xmpp, node.js, socket.io, etc but I don't have enough knowledge in those areas to decide what architecture should I build to make everything works together. Or maybe there is some cloud base solutions that would fit my needs...
Thanks
As you've stated there are many ways to implement that kind of structure but I am going to write about node.js + socket.io part;
1) It is scalable. You can use cluster, nginx, haproxy. etc. to apply load balancing to your socket.io application (see here) Of course you've to use redis or mongo or some kind of store for socket.io that different servers and processes can communicate each other. (see here)
2) socket.io have rooms. That means clients and any computer bots can join that room to share events with each other. So, in your scenario User A, User B and a computer bot should join to same room and events sent to that room will be broadcasted to every room member. (events can vary as online, typing, new message, anything) (see here)
3) node.js can send push notifications both for iOS and Android.
4) You can write every message to database of your choice on new message event.
5) You can create a REST api with Express framework for your Administration page. And you can use passport for authentication and authorization purposes. You can consume the rest api with Jquery or some other frontend framework like React etc.
Meteor is very well suited for something like this and gives you everything you need. There are also open sourced chat systems built with meteor already to get an idea of where you need to go. The more custom route would be to do what #cdagli said.
I have an Azure hosted web application which works alongside a number of instances of a worker role. Currently the web app passes work to these workers by placing messages in an Azure queue for the workers to pick up. The workers pass status and progress messages back by placing messages into a 'feedback' queue. At the moment, in order to inform my browser clients as to progress, I make ajax based periodic polling calls in the browser to an MVC controller method which in turn reads the Azure 'feedback' queue and returns these messages as json back to the browser.
Obviously, SignalR looks like a very attractive alternative to this clumsy polling / queing approach, but I have found very little guidance on how to go about doing this when we are talking about multiple worker roles (as opposed to the web role) needing to send status to individual or all clients .
The SignalR.WindowsAzureServiceBus by Clemens vasters looks superb but leaves one a bit high and dry at the end i.e. a good example solution is lacking.
Added commentary: From my reading so far it seems that no direct communication from worker role (as opposed to web role) to browser client via the SignalR approach is possible. It seems that workers have to communicate with the web role using queues. This in turn forces a polling approach ie the queues must be polled for messages from the worker roles - this polling has to originate (be driven from) from the browser it appears (how can a polling loop be set up in a web role?)
In summary, SignalR, even with the SignalR.WindowsAzureServiceBus scale out approach of Clemens Vasters, cannot handle direct comunication from worker role to browser.
Any comments from the experts would be appreciated.
You can use your worker roles as SignalR clients, so they will send messages to the web role (which is SignalR server) and the web role in turn will forward messages to clients.
We use Azure Service Bus Queues to send data to our SignalR web roles which then forward on to the clients.
The CAT pages have very good examples of how to set up asynchronous loops and sending.
Keep in mind my knowledge of this two technologies is very basic, I'm just starting. And I might have misunderstood your question, but it seems pretty obvious to me:
Web roles are capable of subscribing to a queue server where the worker role deposits the message?. If so there would be no client "pulling", the queue service would provide the web server side code with a new message, and through SignalR you would push changes to the client without client requests involved. The communication between web and worker would remain the same (which in my opinion, it's the proper way to do it).
If you are using the one of the SignalR scaleout backplanes you can get workers talking to connected clients via your web application.
How to publish messages using the SignalR SqlMessageBus explains how to do this.
It also links to a fully worked example which demonstrates one way of doing this.
Alternative message bus products such as NServiceBus could be worth investigating. NServiceBus has the ability to deliver messages asynchronously across process boundaries without the need for polling.
I'm currently looking into XMPP and I would like to know if there is a way to create dynamic XMPP rosters. I want the contact list of any user be automatically generated by the server / component / plugin.
Can components access and modify rosters?
I know that some servers (like OpenFire) use an external database to store these information but if I modify the database, I don't think the users will be notified in realtime.
Are some people already doing that or do you have an idea how to create it?
Thank you for your time.
In most XMPP servers this is called "shared roster groups".
I can't comment on Openfire in particular because I haven't used it for a long time, but I don't think I know of a server currently in which external roster changes are instantly transmitted to clients. Usually the client will simply pick up the new roster when it next logs in.
It would be possible to push the updates instantly to clients using what XMPP calls "roster pushes". This would require quite some work on the server though to identify what the changes are between what each client knows the roster to be, and what the new roster is, and then transmit just the changes.
If you really need this then a server plugin would probably be the way to go, or pester your server developers for the feature (I know that as a Prosody developer I've already been pestered, and this is something I'm planning to work on).
As for whether components can access users' rosters - this is dependent upon the server implementation and configuration.
Beside the obvious person to person instant message chat, What else have you used a Jabber server's functionality to enable?
Edit: links to working code to really show it off are particularly useful - and will be more likely to be voted up.
There are unlimited uses for XMPP/Jabber.
Take any message/data you want to send somewhere else and you can use jabber. Run a centralised logging service for distributed services? You can jabber the massage.
You want to check if your services/programs are running? XMPP presence will tell you. If you add custom status messages you can see exactly what is going on.
This is why Cisco has got into the game. Picture a server farm where each blade has a built in mini jabber client. On boot up it will register it's presence to the central server as awaiting work. The central server fires off some work in it's direction and it then changes it's status to "Busy". Another blade finished it's work and changes it's status back to "Available"... rinse and repeat.
When you combine the actual jabber messages with it's Out Of Band abilities, these servers can post where the results of the job can be found.
Anything you can think of needing to pass a message can be done with XMPP to some degree. Be this person to person, program to program, or any combination.
You could use a Jabber server to handle/broker messages between a client application and another server application.
It can actually be pretty effective.
Not me but Martin Woodward used jabber to control a "build bunny" that displays the current status of the build server.
http://www.woodwardweb.com/gadgets/000434.html
XMPP is good for sending messages back and forth between computers that don't need to be broken into chunks. They also can't be terribly big. If you use the right library, it can be pretty easy to set up.
Sending messages to a web page. Proof-of-concept: esagila.com
I plan to use it to receive notifications from my system, such as:
Process did not finish
Report was not generated on time
User needs help
I already receive many of these messages as email. But receiving an IM could be much more effective.
You might want to look at Vertebra which is...
a framework for orchestrating complex processes in a Cloud. It is designed with an emphasis on security, fault tolerance, and portability.
From the knowledge base:
Why was XMPP chosen for Vertebra?
XMPP based instant messaging can be a good alternative to search engines for information that is small, complete in itself and required frequently and repeatedly. For example, your daily horoscope - you require it daily and it is not large.
To see an example of this add astro#askme.im to your list of contacts in your jabber client (Gmail Chat/Gtalk/or any other Jabber client) and then initiate chat with this contact by sending the word "help".
Also see www.askme.im for a whole list of chat based solutions.
I've used Jabber in the past to get email notifications. Nowadays I use it for low-priority nagios notifications, it is very useful and way cheaper than SMS:
We use xmpp as both a 'bus' and a real-time API at http://superfeedr.com
Iowa State University Department of Agronomy has created this with Jabber: http://mesonet.agron.iastate.edu/iembot/
If you're a weather freak like I am, this is VERY cool stuff!
Apple implements mobileme's push service using Jabber/XMPP's subscription services to send push notifications. That is the most widespread use of Jabber for non-IM purposes I know of. This article has more details.
My friends have also built a Jabber python bot, which is kinda cute but not all that useful :-)
Edit
The most recent Next Big Thing, Google Wave, uses Jabber under the hood. Further illustrates the power of the protcol.
We have used XMPP and BOSH to enable users to communicate with a webbrowser directly and in realtime from their phone.
For example Code you can view our open source API
The vooices site also has live examples where you can control a map and play a game using your phone via your web browser: http://www.vooices.us/
I've always thought XMPP would be a good way to deliver SNMP data. OIDs are really painful, much of the system is insecure, and the SNMP traps never work quite like you want them to. With an XMPP server in the middle and a smart component to make some choices, you can use it to send out jabber or other notifications, kick off restart jobs, update web pages, or whatever else you need.
The XML data is pretty small in this case, and you can have the one XMPP server both talk to humans in message stanzas, or computers with the same protocol.