I'm developing a cross-platform application and which incoorperates XMPP (ejabberd). How can I share presence among resources?
Please consider the following scenario:
User A is logged onto three devices: PC, Android and iOS. User A, using Android, sets his presence to 'away'. How can I set (synchronise) the other resources to 'away' (and send out presence stanzas)?
I'm looking to solve this problem using the XMPP protocol / ejabberd server; not by adding logic to the clients.
You do not really need to synchronise presence among your resource. What you need is a display rules from your other clients.
For example, if a user has three different resources you may decide:
To display the most available resource of the three.
To display the most recent one.
To display the one with the highest priority.
So, you do not net to synchronize them as you will lose precision. Simply define your presence display rules, based on the goal of your client application.
Related
I am in the process of analizing how to set up an OPCUA server in the cloud, and one of the challenges is data visibility. As data visibility, I mean that a user/customer can see certain data/devices that only belongs to him, and the same will apply to other users.
So the node creation process will depend on who the connected user is.
How can this be implemented in the best way according to OPCUA and specifically eclipse milo? Is it different namespaces for each customer? Any suggestion will be appreciated.
Different namespaces per customer would be an okay approach, but whether you do that or not you ultimately need to be examining the Session during the execution of Browse, Read, Write, and other services to determine which User is connected and what rights they have.
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.
When we connect to googletalk using xmpp, we can set the resource attribute, and can thus identify whether the user is logged in from android, pc etc.
I was wondering if there is any similar way to specify/identify device in facebook chat API.
When I connect with xmpp, facebook do all the internal transation and erase off my resource value.
Is there any other way to achieve this?
This is not what the resource identifier is meant for, even if many users or software put human readable text there. For security reason the resource should be unpredictable.
Use Service Discovery:
http://xmpp.org/extensions/xep-0030.html
Use XEP-0115: Entity Capabilities. Mark up your presence stanzas with caps. Pre-load the caps cache of all of your clients with the disco#info describing each. This will just barely work for your clients on FaceBook, and will interoperate really well on other systems.
Please read the XEP multiple times. Almost everyone misunderstands it at first.
how can i measure stress testing for the iPhone app ?
i need stress testing not performance testing, for example 100 users access the database of the app which is on the server at the same time.
any help?
thanks in advance
First, you need to decide if you need to test the client-side (iPhone) app, the server-side code, or both.
Testing ONLY the server-side, might make this much easier - especially if it is using HTTP to communicate with the server and exchanges data via a text-based format (XML, JSON, etc). There are many web load testing tools available which can handle this scenario. Using our Load Tester product, for example, you would configure the proxy settings on your iPhone to point to our software running on a local machine. Then start a recording and use the application. Load Tester will record the messages exchanged with the server. You can then replay the scenario, en masse, to simulate many users hitting your server simultaneously. The process, at a high level, is the same with most of the web load testing tools.
Of course, the requests to the server can't be replayed exactly as recorded - they'll need to be customized to accurately simulate multiple users. How much customization is needed will depend on the kind of data being exchanged, the complexity of the scenario and the ability of the tool to automatically configure dynamic fields (and this is one area where the abilities of the tools vary greatly).
Hope that helps!
A basic simulation would involve running your unit tests on OS X, using many simultaneous unit test processes (with unique simulated users, and other variables).
If you need more 'stress', add machines - you'll likely end up hitting io or network limits from one machine relatively early on.
I would like to disregard web applications here, because to scale them horizontally, ie to use multiple server instances together, it is "sufficient" to just duplicate the server software over the machines and just use a sort of router that forwards requests to the "less busy" server machine.
But what if my server application allows users to engage together in realtime ?
If the response to the request of a certain client X depends on the context of a client Y whose connection is managed by another machine then "inter machines" communication is needed.
I'd like to know the kind of "design solutions" that people has used in such cases.
For example, the people at Facebook must have already encountered such situation when enabling the chat feature of their social app.
Thank you in advance for any advise.
One solution to achive that is to use distibuted caches like memcache (Facebook also uses that aproach).
Then all the information which is needed on all nodes is stored in that cache (and a database if it needs to be permanent) an so all nodes can access that information (with a very small latency between the nodes).
regards
You should consider some solutions that provide transparent horizontal database scalability and guarantee ACID semantics. There are many solutions that offer this at various levels. People at Facebook which you reference have solved the problem by accepting eventual consistency but your question leads me to believe that you can't accept eventual consistency.