i have an Autocomplete ajax control that calls a WCF service method automatically.
this method gets a string as an input parameter and return a list of strings.
i don't make that call from the client , the control does it, but i write the content of this method.
Can i store some data somewhere in the WCF service when that method is called and extract it later when i use the WCF from the client ?
i mean , i want the control to call the method, in the method i'll store some data and later when i use the WCF client object i'll extract it.
is there such "WCF cache" mechanism?
No, there's no such thing as a 'WCF cache' mechanism. But WCF is .NET, and in a .NET application you can use the Caching Application Block.
Caching has very little if anything to do with WCF. You cache inside your application, but the caching mechanism for a WCF service is fundamentally the same as a Windows Forms application or a managed Windows Service (or an ASMX webservice, or a ASP.NET application, or any .NET application). The only difference is how you use and rely on the cache & how the applicaton's lifecycle is managed.
If your WCF service is hosted in IIS (as is very popular), then when the application pool is recycled (or the website is restarted) you will lose everything in the cache. Will this be a problem?
The typical use case for a cache is when you have a set of data stored (in, say, a database) that will need to retrieved over and over again. Rather than get from the database everytime, you get from the cache. If it's not in the cache, you get from the database and put it in the cache so it's there for next time. It sounds like you want to store some data from the client application in the cache. You can do this, but what will happen if it's not there when you go to retrieve it.
Related
Now I need to reference a WCF service in a UWP program. However, the address of the WCF service may change frequently in the future.
I don't want to rebuild/republish the project every time when the address change.
So I want to use a LocalSettings to Save/Load the address of WCF service. Every the program begins, it will reload the address from the LocalSettings. And if the address changes, I just only let the customer change the LocalSettings from UI but not need to rebuild/republish the project.
How can I do it? Or there is any other better to do it?
If it's a RESTful service, you could use HttpClient relevant APIs to consume a REST service in UWP.
Please note that REST is a resource that implements a uniform interface using standard HTTP GET, POST, PUT methods that can be located by URI. So, you could use HttpClient to call it in code-behind. You will get response after you send http request, then you could analysis the response result.
The similar thread for your reference: Calling web service asynchronously in page constructor.
Using LocalSettings for such thing is a good solution.
LocalSettings are just a dictionary where you can assign values you want to store and later take out.
ApplicationData.Current.LocalSettings["ServiceAddress"] = "something";
Debug.WriteLine(ApplicationData.Current.LocalSettings["ServiceAddress"]);
Such setting will survive app restart and is stored in applicaton's private storage.
You will probably want to seed this setting with a default value at first startup.
I currently have 2 static dictionaries in a wcf restful service. These both hold look up data that's not worth putting in a database. Will these stay in memory until the application restarts or should I put them in HttpContext.Current.Application?
The static data will remain until the process recycles or stops, the same as HttpContext.Current.Application.
If you are looking for a more sophisticated caching option, check out the System.Runtime.Caching namespace introduced in 4.0. It is easy to use, works in any .NET application, and offers features like setting expiration times and creating callback functions to execute on expire.
So bear with me, i am new at MVC and WCF. I already have a set of services (WCF) that exposes my BLL and I am trying to consume those from my MVC.net web application but i am unsure on how to perform security operations here.
These are my app requirements:
Be able to consume WCF services using different credentials for every user on the web application
My BLL (WCF) needs to know what consumer is calling it (right now I only have the MVC app but i am planning to add iOS and Andriod calls to it, so later on i will add REST services to the WCF endpoints) Is there any design pattern for this out there? (or should i just use the soap header to include the caller ID? should i use some sort of caller secret or something?)
I need a security mechanism like Tokens or something so I dont have to pass the username and password on every call of the service method (WCF)
What i have so far:
WCF uses a certificate and and with a custom username validator.
I have manually coded proxies using the contract interfaces instead of generated proxies: But I hate the fact that i have to validate username and password every time a call is made to a WCF service. How in heaven can i use Tokens here? like to know if a given token sent on the soap header is valid or not yet expired? i have searched a lot and no tutorial/code/example is clear enough for me to actually start coding that ;(
I am trying to cache the ChannelFactory but should I? i mean, i will need to cache a channer factory per logged in user per contract ;( is that ok? what can i do here?
Thanks in advance!
Should you cache the ChannelFactory per user per contract?
It depends. There are a couple of considerations. Instantiating a channel factory could take up to 70ms. If you are doing this repeatedly, you will see a noticeable performance hit if you are not caching the ChannelFactory and instantiating one (or more) each time a user makes a http request to your MVC app that results in controller actions calling web services. This would indicate that caching the channelFactory would be beneficial for speed.
On the other hand, depending on the number of users you have, if you are caching a lot of channel factories (in a static dictionary for example), you are going to start to use a non-trivial amount of memory - this may become an issue for you.
You have to decide if the cost of instantiating channel factories on the fly (and correctly closing / aborting them and their contained channels) is too high a price vs increasing memory utilisation in the application pool hosting your MVC app.
Either way, I strongly advise to profile your app before you deploy to production.
I am migrating a web service to WCF so I can use binary encoding. I am now realizing that the session calls and application state calls are not recognized. WCF is supposed to be better then a web service so I am assuming that there is a better way to do things.
1) How do I maintain session and call a web service that uses session?
2) How do I replace the application object?
For those of you who are migrating a large project and cannot afford to be so ideological, I found a real answer here:
http://megakemp.wordpress.com/2008/11/27/migrating-aspnet-web-services-to-wcf/
In WCF, the best practice is not to have any state whenever possible, since your clients should be calling you with a "per-call" approach - each call from a client gets a new instance of your WCF service class, which is totally independent of anything else, ideally.
If you need to have persistent state, store it in a persistent store - typically a database.
WCF is also by default totally independent of ASP.NET and IIS, and thus cannot leverage the HttpContext, HttpSessionState and so forth objects - since it might be self-hosted in a console app which has no knowledge of IIS, HTTP context etc.
The question is: what exactly do you really use from those HttpSessionState and HttpApplicationState objects? Somehow, you need to abstract that away or solve it some other way, e.g. have the client send you that information (as a parameter on your web service method call, or as a header in the message), or have the client send you a "token" of sorts which allows you to retrieve the relevant info from e.g. a database table.
Chapter 4 in Juval Lowy's excellent Programming WCF Services (link) is all about Instance Management. There are sections on Per-Session services and Durable services, each of which might be what you're looking for.
However, Marc's point is very valid. There are a lot of cons to using session with WCF services, but it is possible. Lowy discusses a lot of this in some detail.
I have been working on splitting up the app tier and web tier of a web application. In the app tier, I managed to separate the business logic into a bunch of services exposed using WCF proxies. The problem is that these services talk to another legacy application that uses a large CLR object as its primary means of communication. To keep things quick, I had been keeping a copy of this object in the session after I created it the first time. Now I know that WCF can do sessions, but the session storage is per service whereas my business logic is now split into multiple services (as it should be).
Now the questions:
Is there a way to share session storage between WCF services hosted on the same host?
Is this even something I should be doing?
If not, then what are the best practices here?
This is probably not the first time somebody’s had a large business object on the server. Unfortunately for me, I really do need to cache this object per user (hence the session).
It’s possible the answer is obvious and I'm just not seeing it. Help please!
I think instance context sharing can help
http://msdn.microsoft.com/en-us/library/aa354514.aspx
As far as I understand WCF, it is designed to be as stateless as it could be. In a session you can remember some values in your service, but objects are not meant to live outside the scope of a session.
Therefore, I'd think you are in trouble.
Of course, there might be some way to store and exchange objects between sessions that I don't know (I use WCF, but I don't know very much about it, apart from what I need for myself).
(if there is a way to share objects between services, it probably would only work on services you host yourself. IIS hosting might recycle your service sometimes)
Perhaps you can wrap this object in a singleton service. This is a service with only one instance, which will not be destroyed between calls. Because you need an object for each user, this service has to manage a list of them and the calling services has to provide the needed authentication data (or sessionid). Don't forget a timeout to get rid of unneeded objects...
Create a facade service which hosts the large CLR object on behalf of the other app tier services. It can work as an adapter, allowing more specific session identifiers to the more advanced app tier services you have created. The facade can provide a session identifier, like a GUID, which your app tier services can use to get re-connected with the large CLR object.
This provides a few advantages:
Some of your app tier might not need to know about the CLR object at all. They only communicate with the remote facade.
the 'large CLR object' host retains the session object on behalf of the other services who can now share it.
The app tiers now have a facade through which they talk to the legacy service. As you work to refactor this legacy service, the app tier doesn't have to change.
Depending on your setup, you may be able to host the facade via in proc hosting which will give retain performance boost you are seeking.
Breaking things up into subservices seems like a good idea if you want to be able to spread the app out over a farm. However, it's important to keep in mind that whenever an object crosses the appdomain boundary at the vary least it will have to be copied in memory.
It all depends on how big the object is and what kind of data it holds.
If you don't want to pass the object because it's too large you may want to make a query API for the service which receives it. In this way you could manipulate that object without having to do expensive serialization or remoting.
Keep it simple. Since you already have access to Session in your WCF, you can use the SessionID from there. Now:
Create a static dictionary somewhere, where the Key is your sessionId and the value is the business object you want to store.
Instead of accessing the business object in session, just access the sessionid and get the business object from the Value of your dictionary.
(You can also use some type of caching if you wish, for example System.Web.Caching, that way you don't have to cleanup the dictionary manually)