Currently I maintain an application that runs as a Windows service, reads messages from a message queue server, processes them and puts the result back into the message queue server. But it also contains a health monitoring component that is accessible through a web API.
It is implemented as a console app that uses Katana to self-host the health monitoring sub-system.
I'm now trying to figure out if we can move this to .NET Core and ASP.NET Core once they RTM. I know the Windows Service part cannot be ported, but I could also run the console app as a detached Docker container to basically achieve the same thing, in terms of main functionality.
But how will the health monitoring work? From what I can see the Katana project has been updated to ASP.NET 5 (which I guess is ASP.NET Core 1 before the big rename), but it does not run on the .NET Core CLR. Katana will require the full CLR. So that means Katana is out.
Does this mean that the way we build our app is impossible with .NET Core? Or does hosting the app through Kestrel not rule out the possibility of running code before the first request? With IIS the app does not live until the first request (unless you use the auto-start, but it's more of a speed-optimisation than have the app behave like an "allways-running-app") and generally the app is request-based and not continually running. Background threads in a IIS hosted app are a really bad idea.
Is this the same with Kestrel? Or will DNX start your app and keep it running until it's shutdown, much like a console app, so we can run all the background threads we want?
It follows the console app model. Katana is actually more the spiritual predecessor to kestrel. It is invoked for normal ASP.NET Core projects from the Main method with a normal method call. There are countless tutorials how to setup a server in RC1 (see Startup.cs Main method) and some for the upcoming RC2 (there is a builder for it). That would allow you to do both, your app code and your web api based monitoring, in a console app. Kestrel and DNX are not at all an application server like IIS. Kestrel is a plain HTTP server library and nothing more. You start it up and it listens from that moment on.
Nevertheless, you have to adjust your WebApi 2 and Katana based application to the new ASP.NET Core interfaces and middleware concept. But that should be easy compared to your message queuing adaption.
Related
We are building a web application in Asp.Net Core that will be used to centralize and communicate with a lot of instances of a custom servers(which is in C# too).
We need versionning, because updating those custom servers is really time consuming and can be a blocker for people to install newer version of the web app.
For the HTTP part, it's "easy", we have to use the Asp.Net Core versionning and a given version of the custom server will know how to communicate with a given version of the web app.
But we have a SignalR service that is used to provide notification to the custom servers from the web app, and request some data, some actions, ... Is there a way to provide several version of the client interface for this? And having the signalR server able to transform the message to each version?
Thank you
For background process listening to a service bus topic, what would be the considerations for choosing between running a hosted service in ASP.NET core VS creating a worker service?
I'm seeing several options from the internet and I'm wondering which scenarios would make one go for each of these options:
Running API & Worker service separately
Running API with hosted service
Running worker service with API inside (not for us)
Our system will have an ASP.NET Core API as well, so I'm wondering whether to add a hosted service to this API or to separate the application as a worker service.
We also want to run this in container and deploy it in Azure container app (if that makes a difference to the considerations)
I saw someone mentioned if health check is needed for the background process then it's better to go with ASP.NET with hosted service implementation. But then I found this lib https://github.com/bruceharrison1984/TinyHealthCheck which seems to add health check functionality to worker service
The API and the worker should be separated. You can then scale the two separately. Especially if you plan to deploy the worker on Azure Container App, you can scale automatically the worker depending on the message number on the bus using KEDA. When no message is in the queue it will automatically scale down to 0 !
Your API in the other hand should be always up.
To create a worker you should consider using the generic host of .Net.
In my opinion, this is related with the relationship with the web api and the worker service.
If this worker service is just used for this asp.net core web api, I suggest you could choose 2 or 3.
If this work service is also used for other web api or else, I suggest you should run API & Worker service separately.
From the comments you have added I can see that the API and the worker service are separate and that you are deploying using docker. For those reasons I would suggest that you deploy these two things separately in their own containers. I would choose this because it makes each application simpler and easier to maintain. A good place to start is here Background tasks with hosted services in ASP.NET Core. There is a simple dotnet cli template to create the project
dotnet new worker -o [your project name]
I've been reading and learing about the new Worker Service features provided in .Net Core 3.0. I have been using this link from Microsoft: Background tasks with hosted services in ASP.NET Core
What I don't understand is this, can these worker service concepts be introduced into an existing ASPNET Web Project, like a Razor Pages site? Or must you create a new project and then deploy that project as a service using whatever mechanism the host OS proivdes for that?
Yes, you can host any number of hosted services (IHostedService) within ASP.NET Core applications. With version 3, ASP.NET Core uses the generic host (Host.CreateDefaultBuilder) which is the framework that is hosting these hosted services when the application starts. In fact, the ASP.NET Core web application is an IHostedService itself.
To add additional hosted services to your ASP.NET Core application, just register additional hosted services with your service collection, e.g. within the Startup’s ConfigureServices:
services.AddHostedService<MyHostedService>();
That service will then launch together with the ASP.NET Core web server when the application runs.
The Worker SDK that is mentioned in the documentation is actually a subset of the Web SDK that you are using with ASP.NET Core application. Microsoft.NET.Sdk.Worker is basically Microsoft.NET.Sdk.Web without the web-specific stuff like Razor compilation and wwwroot folder stuff. It basically sets up automatic file globbing e.g. for the appsettings.json and does some other useful things that the core Microsoft.NET.Sdk does not have.
Ultimately this means, that when you are using the Web SDK, then you already have everything the Worker SDK offers. So you do not need to specify the Worker SDK just to host additional background services.
Is it possible to use IIS's logging with an asp.net core application? We've developed several .net core applications and they are all hosted under IIS so I'm trying to take advantage of IIS's logging.
Unfortunately, enabling logging with a No Managed Code app seems to produce no logs. Managed Code applications do produce logs correctly.
When I publish under Visual Studio 2015 CTP 5 then I don't have to do setting for application pool CLR version.
Now for ASP.net core application and as per documentation (http://docs.asp.net/en/latest/publishing/iis.html) we have to do setting for application pool clr to No managed code.
Why it is like that ?
ASP.NET Core applications no longer run inside IIS but run out-of-process and IIS acts only as a reverse proxy. This functionality is provided by the AspNetCoreModule which is a native IIS module. Since no managed code runs in the IIS process it is recommended to set application pool as "No managed code".
I wrote a detailed blog post describing how ASP.NET Core applications are running with IIS. You can find it here.
This is because ASP.NET Core runs as a plain old command line application outside of the IIS. Therefore, IIS is merely a pass-through to Kestrel, which is the ASP.NET Core web server which runs in it's own separate process. This platform is what provides the cross-platform capabilities of .NET Core.