It is my understanding that a WCF service configured for net.msmq will not run as an HttpApplication when hosted in IIS/WAS, which means you don't get the events in Global (Application_Start being the important one). Am I correct in this regard?
Does using Windows Server AppFabric to auto-start the service hit the service over HTTP, causing the Application_Start event to fire? If so, is this reliable?
I guess my real question is, where is the "proper" place for initialization code for a non-HTTP WCF service?
Particularly (since the right place may be different for different stuff):
IoC registrations
log4net initialization
Verifying the MSMQ queue exists locally (as Juval Lowy suggests in his WCF book)
Follow-on question: Do the events in a custom IServiceBehavior fire on every request or only once at startup? What about ServiceHost.OnOpening() - every request or only once at startup? (My testing shows it's only once, but does anyone know where the WCF "lifecycle" is documented, because I can't seem to find it anywhere.)
I can't verify that WCF services hosted in IIS/WAS can't be configured to support Application_Start but it is not required to do what you want. I'd recommend you create a custom ServiceHost in conjunction with a custom ServiceHostFactory (for WAS). This approach is documented in an MSDN article and this blog post. Using this approach, you can host your service in IIS/WAS, a Windows Service or a console app because the initialization process will be the same.
Related
What are the pros and cons of hosting a WCF service in IIS versus using a Windows service?
FYI - I have googled but it's surprisingly hard to find relevant answers.
We've just implemented a big WCF service, and did it as a self-hosted windows service. The reason we did it that way was our architects wanted the extra control you get from hosting your own and taking IIS out of the equation. Basically, when you go the self-hosted route,
you process each request
you configure your own endpoints
you configure your certs
you control the exception handling
etc.
Our WCF service is industrial scale with rev proxies, load balancing and about 50 methods attached to the endpoints. And we use multiple encryption protocols depending on the types of devices connecting.
However, if I was doing a smaller WCF web service with just a single server, a single endpoint and a few method calls, I'd probably use IIS to manage the endpoint and implement the SSL letting the UI do the configuration work that would otherwise have to be done in code. It's just easier from what I've seen.
Long story short, if you host it, you control everything in code. If you're interested in a quicker delivery, I'd start with IIS.
We have a windows service that is self-hosting a WCF Data Service, using the DataServiceHost class. Everything is working just fine, but we would like to hook up some HTTPModules to the service, if possible. One of the HTTP Modules would be for custom basic authentication, the other for auditing (including responses, which is why an HTTP Module works so well for this).
Keep in mind that we are running as a regular windows service, so we have no web.config, the service is not hosted by IIS, and it is not an ASP.Net application.
So, my questions are:
Is it possible to have an HTTP Module listen on a self-hosted WCF data service?
If this is not possible, what options would I have that are similiar to the power of an HTTP Module?
WCF doesn't operate on the same request pipeline as standard ASP.NET applications, although you can take advantage of a number of ASP.NET features (like session) if you configure your service for ASP.NET compatibility.
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
However, it looks like you just need something that will let you jump into the pipeline the way that HTTPModules do for an ASP.NET Application. That being the case, there are plenty of options. You can check out this page for a lot of samples.
You mentioned authentication, and there are plenty of options built into WCF that can save you from rolling your own solution. Check it out here.
I'm new to WCF and need some assistance with architecture for the following solution:
I want to create a WCF Service that hosts a FileSystemWatcher. This service must watch a series of folders on the machine and when a file is placed in a folder or is renamed I need this WCF service to 'Publish' an event.
Another WCF service must then 'Subscribe' to this event and do some processing.
The basic idea is that there is one service to monitor a predetermined set of directories, whilst an appropriate service gets notified that there are files available for processing.
So my questions are :-
1. Regarding the FileSystemWatcher WCF Service, I want to host it in AppFabric but am not sure exactly how this is going to work. I.E. When this service is deployed to the server I want the appropriate FileSystemWatcher object to be called and stay 'on' and monitor folders indefinately. Can WCF do this in this manner or is this a better candidate for a Windows Service
2. Can one WCF service publish events and another WCF service subscribe to these events and how? All WCF services hosted inside AppFabric?
WCF is a communication framework that can be used to expose or consume SOAP/REST services. A Windows Service is one way of hosting such applications. WAS/IIS and self-hosting are other methods. A Windows Service provides greater control of service startup/shutdown, which seems relevant to your scenario.Windows Server AppFabric improves some of the control over applications lifecycle hosted in WAS/IIS, but it is still a fundamentally different hosting choice to a Windows Service.
As far as I know WCF has no inbuilt event publishing capability (I assume you're referring to the publish/subscribe pattern). However, you can implement such a pattern using WCF duplex channels. There is no restriction on an application concurrently acting as 'server' and 'client'.
how would you best go about the task of deactivating further use of a IIS6 or 7 hosted WCF service based on framework 3.5, when a custom condition is detected.
I thought perhaps that you could create a static constructor in the service implementation (i.e. .svc code behind file) that validates my app settings, should one of the settings be invalid, I could throw an exception. Thinking that the WCF infrastructure would fail to start and so IIS would provide a 401 error (or alike) when browsing the svc file.
I feel this is to easy, im thinking perhaps this is not the right thing to do, perhaps i need to be implementing another WCF interface to plug into some sort of WCF activation logic and signal a no-start. Or something like that?
Any ideas.
Many thanks
Chris
I have found that the best place to do this is by creating a custom service factory implementation. Perform the validation before service creation, if it fails then throw an exception there, not in the constructor of the service implementation.
Reading up on WCF we have self hosting option available , one limitation here is we have to manage the host process lifecycle ourselves. What I am exploring here is to run the service without IIS and do a self hosting.
Few things come to mind
- How will request management work here. In case of IIS it manages the request and give control to dotnet on a particular thread. In absence of IIS do we need to write code ourselves to manage incoming requests ( say on a tcp port ) or WCF provides some classes to manage request and spawn threads to process each thread.
I am aware that in case of self hosting this needs to be a windows service. In case of self hosting how can me tap on the number of simultaneous requests on the sever , it can be managed by limiting the thread pool ? or we can configure this via wcf ?
Thanks
dc
Self-hosting does not require a Windows service. You can self-host inside a console application if you so desire. It's just that Windows services are a good solution for self-hosting if you require 24/7 access but do not want to, for whatever reason, use IIS.
Managing the lifecycle of the host process is not a big deal. I use a Windows service to host a WCF service. I simply start my WCF service in the OnStart() callback of my Windows service, like so:
private ServiceHost _host;
protected override void OnStart(string[] args)
{
_host = new ServiceHost(typeof(CalculatorService));
_host.Open();
}
Likewise, I close the WCF service in the OnStop() callback of my Windows service:
protected override void OnStop()
{
if (_host != null) _host.Close();
}
This effectively ties the lifecycle of the WCF service to the lifetime of the Windows service. You could do something similar in any kind of application - console, Windows Forms app, etc. For example, in the OnLoad() callback of your Windows Forms app, start the ServiceHost for your WCF service and close it when exiting the app. Simple enough.
WCF gives you a lot of flexibility on how to handle incoming requests. For example, you could make your WCF service a singleton, which means that you'll have one and only one instance of your WCF service. In this case, all incoming requests are handled by this one instance. But you can also have your WCF service handle each incoming request with a new instance of your WCF service. This allows your service to scale better, but will likely require you to synchronize any access to your backend data storage, e.g., database. You can control this behavior using the InstanceContextMode property of the ServiceBehaviorAttribute on your WCF service.
As I read your question again, it sounds like you're just learning WCF, so I hope none of this has overwhelmed you. Check out my answer to this SO question for some links that you may find helpful.
To answer your specific question, the WCF hosting infrastructure will spin up a HTTP listener that works with HTTP.SYS (the same thing IIS uses) which will listen for traffic on the specific port/address you configure.
For any other questions, I'm sure this section in MSDN will answer them.