I am building a multiplayer video game with blazor.
This game is very basic and will be playable through a web browser.
The hard work is for making possible real time communication between players. I used to work with socketservers like red5 in the past.
Today, i want to build this video game with Microsoft tools: Blazor and signalr.
My problem is i need some threads on server side. This threads will manage game logic. I have tried to create a BackgroundService Task. It works fine. I can communicate with players through signalr hub. But i am scared about something on BackgroundService's: They are attached to http server process. Sometimes IIS kills and create new processes. So how can i be sure my BackgroundService will always be alive ? (even if no player is connected, at night for example). How can i be sure my BackgroundService won't be killed and re-created by IIS ?
I have tried to work with kestrel web server and put it behing an nginx proxy. My BackgroundService is never killed. But i am wondering if kestrel is designed to handle a lot of web clients at the same time...
Are there alternatives to BackgroundService object ? I have think to create a separate program but i prefer a monolithic approach...
Thanks a lot
I don't think your web app will automatically be restarted if that is what you are asking. The only time when it restarts is if you deploy or if you manually restart or stop/start. So I think it's safe to use background services for light workloads.
But if you plan to have any kind of scaling, I suggest you look into Hangfire.
Related
I'm writing a Qt/C++ application and i plan to add a network part with socket connection to a server implemented in Qt also.
If i host locally the server there is no real problem.
But if i want to share my application (client part) with some people and then be sure my server is always running, the best way would be to have a distant server.
Could you give me some clue to do it ? It's not still clear for me for steps to follow in this case.
Is it a better way for that ?
Can i find free hosting ?
Thanks a lot! :-)
There are generally 3 options:
1. Local hosting
This is server running at Your physical location. You can set it clearly as You want and the server will do whatever You want. But must be turned on the whole time, when there is no other work it will just consume power. Also You must get all the hardware (server components), software for running (Operation system), network device and connection (some router, which needs to have special set-up [NAT, port-forward, ...], speed and reachability of the internet connection) and most likely also some security device/SW (firewalls or so).
This is best idea for basic developement and testing. But once the service should work for public audience, it is not really worth to run server Yourself.
2. Remote hosting (virtualized or dedicated server)
This option was the top in last 20-30 years, where all the Web developers and App developers were putting their software on some prepared server. Dedicated is physical server running at some providers' location, who are lending You the hardware (and maybe some license for OS/other SW). Virtualized machine is just 1 hardware piece (server) with multiple virtual servers on it (more clients running on same hardware).
This got generally benefits as the networking/security/hardware issues are being carried out by the hosting owner. You are just borrowing some diskspace and computer time/performance. Normally the company will provide whole server, on which You can set up several services, run multiple protocols, etc..
Ideal solution for webs and single/few (not much) instances of server application(s).
3. Cloud hosting
This is the newest technology at the moment (alive around 10-15 years [eg. AWS running since 2006, Azure since 2010]). Datacenter owners (from 2. point) get better and created some applications on the servers, which will do all the work for You (mostly automatically). In few clicks the servers are running and application can be deployed, used database engines, web pages, IOT hubs, ... quite lot of stuff. Benefits are clearly that You just have to spent minimum of time to set up things and they will run. With high uptime (eg.: 99.9995%).
Difference between dedicated & cloud: On dedicated server there can be put almost any OS which fits the needs, run just services You want, have full control. In cloud solution, You don't have so much of "physical" control and the data moreless live somewhere in Datacenters all over the world. But generally it is more scalable solution and once Your app will be used by lot of users from public sector, this is best way to go.
Common ideology:
The most common solution is that when You develop, You create local server on which You deploy, test, improve. Once stable, order a server either on cloud or as dedicated/virtual machine and deploy it there. Some developers knows that their App will run on cloud services from the very beggining so they order it and start developing against it, but in most cases there is no need for that.
I have a web app that will run forever (at least for a few days) on my local machine using the technique (hack?) described in Jeff Atwood's post: https://blog.stackoverflow.com/2008/07/easy-background-tasks-in-aspnet/
However when I run it on App Harbor my app doesn't run for more than an hour or so (I'm not sure when it dies) as long as I hit the site it stays up so I'm assuming it is being killed after an idle period, but I'm not sure why.
My app doesn't save any state or persist anything. It makes web service calls and survives errors in any calls.
I turned on a ping service to keep my app alive but I'm curious why this works on my local machine but not on App Harbor?
The guys behind App Harbor pays for EC2 instances for all running apps, so they naturally want to limit the cpu usage as much as possible. One way to achieve this is to shut down unused applications very fast and only restart them when someone actually try to access them. Paid hosting should not be limited in this way.
(As far as I have been informed they are able to host around 100k sites on less than twenty medium instances which is certainly quite impressive and calls for a very economic use of resources.)
To overcome the limitation you would need a cron job to ping your app harbour site. But this of course a quite recursive problem since you need app harbour to act as a cron job ;)
AppHarbor recycles the Application Pool frequently to keep sleeping websites from using idle CPU time. This is simply the price you pay of using a shared website hosting plan.
If you really want to run a background job then you should be using AppHarbor's background workers, since this is exactly the type of task they were built to run.
http://support.appharbor.com/kb/getting-started/background-workers
Simply build a new console application that runs your logic and include it in your solution. When you push the code the workers will be started automatically. If you happen to already have other exe's in your solution make sure to edit the app.config and set the 'deploy background worker' value to false.
We have a core windows service hosting around 9 WCF service and acting as a client to another 3 WCF services. We have a front-end website that communicates with this windows service through WCF.
At somepoint, the windows services is executing some heavy operations which results in 100% CPU utilization, usually split 60-40 between the windows service and SQL server.
This is where the WCF connection/requests between the website times out, and this results in a very non responsive UI.
I am looking for a way to make sure any UI-related WCF calls gets executed anyway and takes the highest priority.
Our main problem is that we need to stick with this deployment scenario, where the windows service, the website and SQL server are all running on one machine. We are required to maintain a responsive UI even with a 100% CPU utilization. I am not sure where to start looking for a fix for that ...
It sounds like you should split your service endpoint onto two separate hosts, one for high volume, or process-intensive operations and one for low latency operations. The high-volume endpoint would process from a queue offline, and the low-latency endpoint would handle requests synchronously from the UI.
The kind of problems you are having are typical of when you try to balance the conflicting resource needs of high volume and low latency together in the same process.
If you cannot scale out in this way then I can't really suggest much you can do about it and must apologize for not answering your question directly.
Another thing you could look at is moving everything asynchronous and using a pattern such as CQRS to provide separation between your read and write requirements.
A looooong time ago, we're talking 8 years now, I prototyped a proof of concept of using a web site as an alternative to a Windows service or SQL Server Agent by retaining an application pool's uptime state and as such retaining an object that can maintain state and, for example, retain a service timer for Agent-like tasks. I implemented this by having the web application invoke itself over HTTP and store its state in the application cache.
I am not trying to push this so much as to ask for advice. I am still pondering this as a reasonable alternative to SQL Agent for doing things like reminder e-mails, etc., for web applications. I know I can also do things like cron jobs (Scheduled Tasks service tasks, etc) or actual Windows Services, but at issue here is the fact that the web applications in question are in a closed environment that developers don't have access to and as such there's too much overhead in supporting non-web deployments of SQL Agent jobs and Windows services.
So again, are there other solutions to this problem than what I have been considering here?
I like quartz.net to handle the cron-like scheduling and state management. A less sophisticated solution is just wire up a simple System.Timer in Application_Start. The key is to make sure the app pool doesn't restart by ensuring traffic to the site (scheduling a task to ping the site) or if you are using IIS 7.5 you can use the auto-start feature.
I am building an ASP.NET website which will collect data from a user and submit it to a 3rd party webservice. The webservice is somewhat unreliable and for this reason there is a backup service.
If a call to the primary service fails (timeout or some other error) then I need to flip a bit in a static class which will trip the system to use the secondary service.
At this point, I need to start polling the primary service (with dummy data) to see if it is back up (at which point I will receive an OK code in return). At this point I need to flip the bit back so that the website starts using the primary service again.
I've had a read of this Should I use a Windows Service or an ASP.NET Background Thread? and I think that separating out the code into a Windows Service would be the cleanest method of performing the polling, but then how would I communicate with the web appication.
One thought I've had is to expose a webservice that the Windows Service could use to communicate into the webapp but this seems both messy and over-kill.
I'd appreciate your thoughts and experiences performing similar tasks.
Thanks
I think the Windows service is the way to go, definitely.
As for the communication between the service and your web site, the best answer depends on the size and scale of your solution. If you are building something that needs to be reliable, I'd suggest you implement some sort of queue between your ASP.NET site and your Windows service. You have a lot of options here too, depending on budget and ability: BizTalk, MSMQ, and SQL Server queues (SSIS). Alternatively if you are looking for something smaller scale, I'd recommend you just stick it into a database table somewhere.
I would avoid using files on the file system because you will encounter issues with file locks and multithreading. I would also avoid directly communicating with the service because you risk losing the in-memory queue if the service fails for any reason.
Edited to add:
If reliability isn't a concern here, you could use a WPF named-pipes hosted service for communication between your website and your Windows service. This avoids much of the overheads normally involved in classic Web Services and is surprisingly quick. The only down-side is that self-hosting a WPF service is tricky and can be difficult to keep the service up.