We currently have an .NET 4 application that consists of Windows Service running in the background and local or remote clients (only 1-3 normally).
The clients have a WPF GUI and need some data from the windows service. Therefore, we use WCF with NamedPipe binding for a local client and NetTcp binding for remote clients. This works, but we often have problems with endpoints that are not reachable (channel faulted or not found etc.). We already try to rebuild faulted connections but it seems to be pretty fragile...
Now enter Web Api: It looks like a HTTP based stack might be more robust (no channels, no endpoints, can be self-hosted in windows service as well). There seems to be no problems with broken channels because each request is handled individually. So if something fails, you just repeat the request. (And we have experience with ASP.NET MVC from other apps, so this not new to us).
Now we are thinking what might be our best bet. Is it better to "harden" our existing WCF service (one service interface with about 15 operations) or to move the interface to Web Api and run it as HTTP requests (with JSON data)? Performance is not our main issue here...
Any ideas?
Hartmut
I recommend you stick with WCF (SOAP) services for your WPF application rather than moving to the Web API. There are a number of reasons for this. First I think we need to consider what the new Web API is trying to address - namely to provide a framework for supporting RESTful/HTTP/hypermedia services. This is likely to be a good fit for building applications that make heavy use of HTTP such as web, mobile and JavaScript applications, where you want to maximise the "reach" or interopability of your services (irrespective of platform). This is not to say that you can't use it for WPF clients but in your case, where all traffic is local to your domain, it makes more sense to stick with your current implementation.
The binding choices you have made for your services / clients sound ok to me. I would focus on why your channels are faulting and address these issues. You may also want to consider hosting your services via IIS and use WAS to expose your non-HTTP endpoints. I have had much success with this in the past and for the most part has been pretty stable. It also takes away a few of the headaches with managing your own host. If you are concerned about the TCP binding faults, then just create a new HTTP or wsHTTP endpoint and use that instead. This will provide you exactly the same transport the web api uses without having to change your programming model.
Related
I am working on an ASP.NET MVC 5 application (based on nopCommerce). I want to use MassTransit to communicate with another application that is used for inventory management, billing, etc. It would be easier if I could add receive endpoints directly into the web application and not have to create a Windows service for that. But the MassTransit documentation says it is not recommended and there is no explanation as to why that is.
MassTransit in a web application
Configuring a bus in a web site is typically done to publish events,
send commands, as well as engage in request/response conversations.
Hosting receive endpoints and persistent consumers is not recommended
(use a service as shown above).
Does anyone know the reasoning behind it? Is it not safe to add receive endpoints in a web application? Will they not work properly?
Hosting endpoints in a web application is not recommended because web applications often restart for various reasons. These reasons are typically outside the control of the application itself.
While using a standalone Windows service is highly recommended, as long as the bus is properly started and stopped using the Application_Start and Application_End methods, it can be okay if you have no other options available.
I have a standard nteir setup :-
Web server -> App server -> DB server
I have an MVC 5 web application sitting on the web server with controllers calling a WCF services project sitting on the App server. WCF services project uses EF6 to marshal data on the DB server.
I am wondering if WCF is overkill? Is there is an easier way to achieve this same architecture? I am thinking I should have gone with Web API on the app server and then just call the web API from the controllers with the HTTPClient?
Or, I could even just use a plain MVC project on the App server returning JSONResults to the MVC controller on the web server?
It depends...
You have to understand what are the benefits of each set up. This is not exhaustive, just a quick brain dump. This should give you some hints to look further as in the wild world there might be many more reasons for choosing one or another solution.
Why WCF. Are you going to have different clients to your backend ? You need some entreprisy security between clients and you backend ? With WCF you could configure Http, TCP endpoints, set message or transport security and a lot more. It could be needed for example if your doing an intranet application and you would like not only to have your UI (MVC application) but other systems going to it. If this is not needed WCF seems overkill here.
Web Api is also agreat choice if you would like to built more REST oriented api, enabling content-negotiation for different clients (different media-types). Building REST is not about issuing JSON, it's much more and this would be too long to explain it here. If your client is not only your MVC app, but you could have a need for a api for other mobile devices, OAuth authentication and the so, this could be a good way to do.
Plain MVC app would also fit if you don't have any special needs, go for it. No overhead needed. Keep It Simple And Stupid.
I hope this helps
I would not change this.
WCF is a good choice for communication between Web Tier and App Tier. I would never put my App Tier exposed to outside world, so if there is any communication to my app from outside world, it would be through Web tier only and if there is a need to support multiple clients, I would create a WebAPI on web tier and expose that.
I would keep App tier only available to Organization internal and with WCF I would have flexibility to write service code and contracts which can then be exposed over various bindings (transport, security, etc.).If you are building a service in your organization and plan to support multiple protocols, or simply use protocols other than HTTP (tcp, name pipes, udp, etc.) then WCF is indeed a good choice.
In the last few years, I have seen the rise of many Web APIs - services exposed over plain HTTP rather than through a more formal service contract (like SOAP or WS*). Microsoft has just launched a new framework called "ASP.NET Web API" hat makes it easy to build HTTP services that reach a broad range of clients. Event if I am a .net fan, it is another communication framework (after asmx, wcf, ria, ...). Now, working as an happy architect, I have to take decision over technologies.
Is Asp.net Web Api really a good choice for a new architecture? Remember Linq2Sql, I do not want to invest in a "disposable" api.
Is there still a use for WebBindings in WCF?
The problem with this question, in terms of it being a stack overflow question, is that it's basically subjective. As a result, I'm pretty sure it'll be closed - but I'm going to stick my 2 pence (it's more like £2 actually) anyway and if it gets closed so be it.
First Linq2Sql isn't 'disposable' - it's still there and not going to go away. It's not being developed - that's another matter entirely.
Anyway - The Asp.Net Web API is a formalization of REST web service support by many people from the same team that work(ed) on Asp.Net MVC and uses a very similar approach to extensibility, pipelining, cross-cutting concerns (e.g. authentication, logging, validation) and such. Whether you use it or not is entirely down to whether you are intending to develop RESTful web services. If you are, and you're on .Net 4+, then, in my opinion, you'd be mad not to.
The overall architecture in the Web API is very good and you can extend most of it without too much effort at all. In particular, the way that they have handled content negotiation is very very nice, making it trivial to, for example, support JSON requests but returning XML responses just because a client sends Content-Type:application/json and Accepts:application/xml.
As a server technology it's also very very fast; partly because it's entirely asynchronous (increasing scalability) but also because the stack between a request coming in, to your code being called, is very shallow.
Not only that but you can host it in both IIS and in any .Net application also - which increases your hosting options but also makes it a candidate for intra-network communications within a common network (i.e. non-internet) environment.
If, however, you want to write a SOAP or WS-HTTP service then, no, the Web API is not for you - you'd stick with WCF.
In short - you need to think of the Asp.Net Web API purely as a server and client technology running on .Net as opposed to a protocol or web architecture. It enables you to build RESTful web services - you can also do that in MVC, WebForms (if you really wanted to), .ashx handlers, or by writing your own HttpListener.
Which of those you choose is entirely up to you to decide.
We can call ASP.NET Web API a replacer of WCF Web API.
It will support more platform oriented service.
I have a database on a database server. No web service in place to be consumed by a web application.
If I want my iOS app to communicate with a database server (send & receive data), I know I can create a web service and then call that service from my iOS app. But what web service is recommended for this? Should I just write a .asmx web service in .NET or should I go for MVC WEB API or may be go for WCF ?? I have spend hours doing research on this. Please help.
A lot will depend on where you expect the service to be hosted, and what technology stack(s) are supported by the host. If you are self-hosting, then do whatever works in the technologies you know and understand. If you want to use a host that targets its services to small-to-midsize independent development teams, many providers like Heroku support things like Rails services. PHP is always an option as well. Microsoft-based solutions and Java-based solutions tend to be more widely used in larger enterprises and data centers, and if that's where you'll host your service then these would also be good options. And of course I'm speaking in broad generalities here: For any general trends I might list here there are lots of exceptions where other approaches make sense.
If you'd rather let the decision be driven by what makes things easiest for your iOS code, I would recommend you start with server-side technologies that support REST-ful interfaces using JSON to represent your service's resources. REST-ful services are very easy to consume from iOS, and JSON-based representations of resources are very easy to parse and produce in Objective-C.
I am personally used this approach to set a direction for my app. For the service side, I am going with a Rails implementation of REST-ful web services. I'm a Java developer by profession, but for a small independent project the options for hosting Java services were more limiting than with Rails so I've picked up rails on the side to make my project work. So far it's suited my project quite well.
I have some delphi code which, given a list of items, calculates the total price taking into account any special deals that might apply.
This code is non-trivial to rewrite in another language.
How should I set it up to communicate with a website running on the same server? The website will need to ask it for a price every time the user updates their shopping cart. It's possible that there will be multiple concurrent requests.
The delphi code needs to maintain an in-memory list of special deals, periodically refreshed from a database. So it cannot simply be executed every time or anything as simple as that.
I don't know what the website is written in, or even which http server it runs under, so I'm just looking for ideas or standard methods.
It sounds like the win32 app is already running as a Windows Service on the box. So, if you can't modify that service, you are going to have to deal with whatever way it wants to accept and respond to requests. This could be through sockets or some higher level communication protocol like web services.
You could do a couple of things. Write an assembly that knows how to communicate with the service and have your web site use that assembly. Or you could build a shim service that knows how to communicate with the legacy service, but exposes communication over higher level protocols such as web services. Either way will have the benefit of hiding the concurrency, threading and communications issue behind an easy to call interface, but the latter will make communicating with the service easier for everyone going forward.
If you can modify the delphi app to take an XML request and respond with an XML answer over a TCP socket (ideally using the HTTP protocol), you will be able to make it interoperate with most web server frameworks relatively easily. But the exact details of how to make that integration happen will depend on the language/framework it was written in.
If the web server is on windows you can compile your delphi app as a DLL that can return XML or HTML, taking parameters as part of the URL or a POST operation. Some details on making a Delphi DLL for web servers are here.
It doesn't matter what web server or OS the existing system is running under. What matters is what you want YOUR code to run under. If it is windows then the easiest solution would be to use WebBroker and write a custom ISAPI application, or use SOAP to expose web services. The first method could be used if you wanted to write a rest like API for instance, the second if your web application has the ability to consume web services.
Another option, if you are running both on the same box under IIS, is to create a COM/Automation object which you then invoke via server side scripting (ASP). If the application is an ASP.NET application, then I would use PRISM to port your code into an assembly.
I have done this with a quite complicated workers compensation calculator. I created a windows service using RemObjects Sdk. The calculations are exposed as a soap method so it can be accessed by nearly anything.
It's not necessary to use RemObjects in the service but it makes it much easier to do as it handles a lot of the underlying plumbing. The clients don't need RemObjects, they just need to be able to call soap methods. Nearly any programming langugae can do that.
You could also create an isapi dll for IIS that exposes a soap interface. This would be useful if other websites on different servers needed access to the methods. However I have handled this in my case by opening a port in the firewall to access my windows service.
There is a lot of examples on the web. A couple of places to start reading are About.Com and Dr Bob.
Torn this app into Windows Service. Write Web Service that will communicate with your windows service. You should spend some time designing your Web Service, because this Web Service is going to be your consistent interface, shielding old Delphi app. So in the future whenever you will want to write web app, mobile app, or whatever you will imagine, you will have one consistent interface – XML Web Service.
A popular way to integrate a web application with background services is a message broker.
The message flow would be:
the web application sends a "calculation request" message to a message destination on the message broker, which contains all needed parameters and also a correlation id to match the calculation request with the response from the Delphi service
one (or, in a high availability / load balanced environment more) Delphi services handle the messages: pull the next incoming message, process it by feeding the parameters to the calculation engine, and send a "calculation result message" back to the web server
the web server can either synchronously wait for the response (and discard responses which have no matching correlation ide) and build the result HTML document, or continue with other tasks and asynchronously receive the calculation result in a separate thread, for example in a Ajax based web application
See for an introduction this slideshow about the Dopplr image service:
http://de.slideshare.net/carsonified/dopplr-its-made-of-messages-matt-biddulph-presentation
If you can make it a service (but not a library), you have to do inter-process communication somehow - there are a few ways to do this on Windows:
Sockets directly which is hardest since you have to do marshalling/auth yourself
Shared Memory (yuck!)
RPC which works great but isn't trivial
DCOM which is easier but a pain to configure
WCF - but can you call it from your Windows Service written in Delphi?