I need to build a server to an application who's client side is written in Lua using Corona SDK (application for mobile smartphones and tablets), and server side in .NET.
I have thousands of clients who I need to push data to in a form of XML file or JSON array, every few hours or daily. (Not notifications. Data that needs to reach the application directly and trigger certain actions).
Is there a way to push the data without WCF?
The only other way I found was SignalR, but my client isn't a web browser so I ruled it out.
In my searches I found in stackoverflow a question with a recommendation to push data using 0MQ (http://zeromq.org/), I just found it hard to understand if it fits my needs, can I queue so many clients in one server and delay the answer a few hours or days?
Other recommendations would be greatly appreciated, thank you.
Related
I'm designing a database monitoring application. Basically, the database will be hosted in the cloud and record-level access to it will be provided via custom written clients for Windows, iOS, Android etc. The basic scenario can be implemented via web services (ASP.NET WebAPI). For example, the client will make a GET request to the web service to fetch an entry. However, one of the requirements is that the client should automatically refresh UI, in case another user (using a different instance of the client) updates the same record AND the auto-refresh needs to happen under a second of record being updated - so that info is always up-to-date.
Polling could be an option but the active clients could number in hundreds of thousands, so I'm looking for a more robust and lightweight (on server) solution. I'm versed in .NET and C++/Windows and I could roll-out a complete solution in C++/Windows using IO Completion Ports but feel like that would be an overkill and require too much development time. Looked into ASP.NET WebAPI but not being able to send out notifications is its limitation. Are there any frameworks/technologies in Windows ecosystem that can address this scenario and scale easily as well? Any good options outside windows ecosystem e.g. node.js?
You did not specify a database that can be used so if you are able to use MSSQL Server, you may want to lookup SQL Dependency feature. IF configured and used correctly, you will be notified if there are any changes in the database.
Pair this with SignalR or any real-time front-end framework of your choice and you'll have real-time updates as you described.
One catch though is that SQL Dependency only tells you that something changed. Whatever it was, you are responsible to track which record it is. That adds an extra layer of difficulty but is much better than polling.
You may want to search through the sqldependency tag here at SO to go from here to where you want your app to be.
My first thought was to have webservice call that "stays alive" or the html5 protocol called WebSockets. You can maintain lots of connections but hundreds of thousands seems too large. Therefore the webservice needs to have a way to contact the clients with stateless connections. So build a webservice in the client that the webservices server can communicate with. This may be an issue due to firewall issues.
If firewalls are not an issue then you may not need a webservice in the client. You can instead implement a server socket on the client.
For mobile clients, if implementing a server socket is not a possibility then use push notifications. Perhaps look at https://stackoverflow.com/a/6676586/4350148 for a similar issue.
Finally you may want to consider a content delivery network.
One last point is that hopefully you don't need to contact all 100000 users within 1 second. I am assuming that with so many users you have quite a few servers.
Take a look at Maximum concurrent Socket.IO connections regarding the max number of open websocket connections;
Also consider whether your estimate of on the order of 100000 of simultaneous users is accurate.
I'm evaluating Urban Airship as a push solution and I was wondering if it's possible to export my device tokens should I decide to stop using their service?
I've noticed they have an API endpoint to download device data (http://docs.urbanairship.com/reference/api/v3/device_information.html#device-token-list-api) but I was wondering if anyone actually went through the process of switching their push solution from UA to an internal solution (i.e. run my own push server and ping old users).
Thank you!
I'm not sure if there is an API call for it, but you could go to Audience->device tokens, and make a script to fetch all of them.
In the company I work, we decided on a different approach.
All communication with Urban Airships goes through our own backend, where we at the same time store the devicetokens sent from the device. That way we can shift to another way of sending push notifications without modifying our apps. It is of course a bit more time consuming to do the initial development. On the other hand, if you go for the solution you are currently considering, the switch to you own implementation (or another push provider) will properly require several migrations, or at least maintaining two different ways of sending push notification for a considerable time.
BTW:we have been using UA for almost 3 years, and have been very happy with their service.
I have been given access to a real time data feed which provides location information, and I would like to build a website around this, but I am a little unsure on what architecture to use to achieve my needs.
Unfortunately the feed I have access to will only allow a single connection per IP address, therefore building a website that talks directly to the feed is out - as each user would generate a new request, which would be rejected. It would also be desirable to perform some pre-processing on the data, so I guess I will need some kind of back end which retrieves the data, processes it, then makes it available to a website.
From a front end connection perspective, web services sounds like it may work, but would this also create multiple connections to the feed for each user? I would also like the back end connection to be persistent, so that data is retrieved and processed even when the site is not being visited, I believe IIS will recycle web services and websites when they are idle?
I would like to keep the design fairly flexible - in future I will be adding some mobile clients, so the API needs to support remote connections.
The simple solution would have been to log all the processed data to a database, which could then be picked up by the website, but this loses the real-time aspect of the data. Ideally I would be looking to push the data to the website every time the data changes or now data is received.
What is the best way of achieving this, and what technologies are there out there that may assist here? Comet architecture sounds close to what I need, but that would require building a back end that can handle multiple web based queries at once, which seems like quite a task.
Ideally I would be looking for a C# / ASP.NET based solution with Javascript client side, although I guess this question is more based on architecture and concepts than technological implementations of these.
Thanks in advance for all advice!
Realtime Data Consumer
The simplest solution would seem to be having one component that is dedicated to reading the realtime feed. It could then publish the received data on to a queue (or multiple queues) for consumption by other components within your architecture.
This component (A) would be a standalone process, maybe a service.
Queue consumers
The queue(s) can be read by:
a component (B) dedicated to persisting data for future retrieval or querying. If the amount of data is large you could add more components that read from the persistence queue.
a component (C) that publishes the data directly to any connected subscribers. It could also do some processing, but if you are looking at doing large amounts of processing you may need multiple components that perform this task.
Realtime web technology components (D)
If you are using a .NET stack then it seems like SignalR is getting the most traction. You could also look at XSockets (there are more options in my realtime web tech guide. Just search for '.NET'.
You'll want to use signalR to manage subscriptions and then to publish messages to registered client (PubSub - this SO post seems relevant, maybe you can ask for a bit more info).
You could also look at offloading the PubSub component to a hosted service such as Pusher, who I work for. This will handle managing subscriptions and component C would just need to publish data to an appropriate channel. There are other options all listed in the realtime web tech guide.
All these components come with a JavaScript library.
Summary
Components:
A - .NET service - that publishes info to queue(s)
Queues - MSMQ, NServiceBus etc.
B - Could also be a simple .NET service that reads a queue.
C - this really depends on D since some realtime web technologies will be able to directly integrate. But it could also just be a simple .NET service that reads a queue.
D - Realtime web technology that offers a simple way of routing information to subscribers (PubSub).
If you provide any more info I'll update my answer.
A good solution to this would be something like http://rubyeventmachine.com/ or http://nodejs.org/ . It's not asp.net, but it can easily solve the issue of distributing real time data to other users. Since user connections, subscriptions and broadcasting to channels are built in to each, that will make coding the rest super simple. Your clients would just connect over standard tcp.
If you needed clients to poll for updates then you would need a que system to store info for the next request. That could be a simple array, or a more complicated que system depending on your requirements and number of users.
There may be solutions for .net that I am not aware of that do the same thing, but those are the 2 I know of.
I am working on an AIR app which should work in both online and offline model. The user can do various actions, while offline and the results would get saved in a local DB. The same needs to get synced up with the global DB once the user goes online. I googled a bit on it, and it seems that Adobe LCDS (lifecycle data services) is the only available option to do it. However, it is an enterprise solution, and way too costly.
Is there any other implementation for this? Has anyone used CouchDB for online/offline synchronization?
Thanks and Regards,
Kapil Kaushik
For doing a DB sync with your server when the Air app is only, you do not have any requirements as for which backend technology you use. LCDS makes it simpler, but it's not your only option. Heck, you could use just a normal PHP script to do the sync for you if you'd like.
The hard part of it all is that you need to figure out your syncing algorithm so that you don't lose any information. Normally what I do is that when the app is connected online again, it sends all the information that was modified/create (with timestamps on when it was modified) while offline to the server, then the server has an algorithm that checks if the offline information is newer than what was done previous (or does some other business rule depending on your situation). When the server decides which data is good, it then sends the updated data to the client and effectively syncs everything.
This can be done through a normal HTTP request, polling or pushing.
I'm developing chat application. I use flash as front end and asp.net back-end. My question is: can my asp.net web app send data to flash app in browser without post back ?actually it mean asp.net push data to flash client. I don't know much about flash or siverlight, dose flash support to do that ? or other way help me connect direct from server to browser without using post back or Jabber ? Please give me your advise, thanks so much !
Here is the 100% solution, called Diffusion sever:
http://demo.pushtechnology.com/docs/manual/apis/flash/index.html
This is another option for you written by people at Microsoft:
http://laharsub.codeplex.com/
We use it and so far so good. Very fast.
No, the server cannot push data to the client without postback. It's the client application that needs to fetch it from the server. In fact there's the WebSocket API draft in HTML5 that allows the server to push data to the client but it still has limited browser support and you will need a server that is capable of handling this protocol.
So currently the only reliable way of doing this is by having the client poll the server for data.
Flash has support for socket communication, that can be used to push data to the client without polling.
You mention asp.net, I'm no expert in that area, but maybe the "Active Server Pages" aspect doesn't fit so well with socket communication, but I'm pretty sure you can build the server side of a chat, pushing data via sockets, in .Net.