I'm reading into WCF and Service Bus topics, but I don't get the use of Service Bus in some topics. Check this image of the use of Service Bus:
http://ecn.channel9.msdn.com/o9/learn/Azure/Labs/IntroServiceBus/Lab.html/html/images/4a0aa8f8-f4d1-49b6-b950-cf954402c599.png
In above image Your Service is behind a firewall, and then you apparently need a Service Bus. But if you want to expose Your Service, isn't the solution to simply remove the firewall? And then every client can connect to Your Service.
I understand that you don't want to remove the firewall for your total network, but you can create a publicly visible webserver with IIS and run Your Service on that. Or am I missing something?
A service Bus helps you enhance your services architecture.
Many organizations have what is refereed to as point to point or spaghetti integration.
This is not good.
A service bus would help you have a single point of integration. e.g. in the image you linked (The Azure Service BUS architecture), by adding the service to the ESB you can unify service authentication using Access Control even if they sit behind a firewall instead of each service being responsible for authenticating itself. Further , even if the address of the service changed you would only have to change it in one place (the ESB) instead of all the applications that reference it.
A service bus can do many other things including validating services messages, enhancing them in case they don't meet your requirements, transforming them e.g from plain old XML to SOAP , routing messages, enhancing messages etc.
WCF is a way of setting up and managing communication interfaces. It cares not for the content of your messages.
A service bus, however, is different in that it's responsible for message routing.
You can build a service bus using WCF and other bits, but WCF in and of itself isn't a service bus.
Service Bus is a relay service so all clients will point in the cloud. Hackers will attack relay service in the cloud rather than your WCF service. All security aspects taken care by relay service.
To precisely answer your question, not all WCF services are hosted on service bus and your solution may be just sufficient. It depends on your need and existing infrastructure.
I highly recommend Juval Lowy's this article.
Excerpt from the article:
The relay service is a service residing in the cloud, whose job is to assist in the connectivity, relaying the client calls to the service. Such a relay solution does require both the client and the service intranets to allow connections to the cloud, but since the cloud constitutes neutral territory for both the client and the service, most environments allow calls out to the Internet. First, both the service and the client must establish connections and authenticate against the relay service. At this point, the relay also records where the service is and how to best call back to it. When the client calls the relay service, the relay service forwards the call (the client message) to the service. While the sequence seems straightforward, in practice it involves a considerable amount of intricate network programming, messaging and standards know-how, security expertise, and more. Such a solution is simply out of reach for the vast majority of applications. This is exactly the gap the Microsoft .NET Service Bus is designed to fill. It is a ready-made relay service, hosted and managed at a Microsoft data center. The .NET Service Bus acts as a perimeter network in the cloud, providing a single place to manage credentials of the client and services. The .NET Service Bus is the front end of the service; it encapsulates and isolates the service from malicious callers lurking on the Internet and is responsible for repelling various attacks from denial-of-service to replay attacks, while obscuring the identity and true location of the actual service.
The main difference between connecting to a regular Windows Communication Foundation (WCF) service and using the relay service revolves around hosting. In the relayed case, the service must connect to the .NET Service Bus, authenticate itself, and listen to calls from the relay service before the client sends its requests. This means that you either must launch the host explicitly or use an NT Service as a host, and that you cannot benefit from hosting in Windows Activation Service (WAS) (or IIS) since WAS will launch the host only after the first request comes in, and that will never happen because the host has not connected to the .NET Service Bus in the first place.
The .NET Service Bus supports a WCF-friendly programming model by offering a set of dedicated bindings and behaviors. By and large, except for a few slight twists to the programming model, working with the relay service is no different than working with any other WCF service. The .NET Service Bus supports the core WCF features of reliable messaging, message security, and transport security.
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.
I am working on a web application which acts like a Devicemanager. Clients can register with the devicemanager and connect to the devices that the manager provides.
I was thinking of using a duplex WCF service for the device connection/disconnection.
Is WCF the correct technology to use?
I will need the clients to be constantly registered to be able to connect/disconnect.
Duplex WCF service implements callback function in web services world.
With callback client sends request to server with some kind of reference to its own method that should be called by server when time came. This allows server to communicate with client when server think it is necessary.
You situation contains no need for callback implementation because process is always controlled by client:
Clients can register with the devicemanager
Clients can connect to the devices that the manager provides
So answer for Duplex is NO (if my understanding of your question is correct)
Should you use WCF – YES.
WCF is right technology if you want to set up communication channel between two applications and TCP/IP is too low level for your needs.
I am designing a WCF service that will serve clients that request things like 'GetProduct' and 'UpdateProduct'. In addition, there will be another service that the clients will subscribe to that will send them PUSH notifications.
The 'PULL' and 'PUSH' WCF services will run under a Windows service.
I would like to encapsulate some sort of monitoring solution that allows me to open a WPF application that will connect to the services and show me how many clients are connected right now to both services (supposed to be identical) and will allow me to disconnect clients from the service and maybe view logs that the service has logged.
How do I design this on the services side ?
Do I need to create a 3rd service for the 'monitoring' app that when requested - will check how many clients are connected to the 'PULL' and 'PUSH' services ?
Or do I just add a function 'GetNumOfClients' and 'DisconnectClient' to the 'PUSH' and 'PULL' services ? this seems wrong, because it introduces logic to these services that does not belong there, and also allows clients to disconnect each other...
For logging use log4net or health monitoring. Log4net is versatile and configurable. You can turn on WCF diagnostics logging which has extensive information about what is going on with your service on You can read here how to turn on and use WMI providers to instrument your service and what performance counters are available.
Why is there a requirement for disconnecting a client? You can "disconnect" the client when you throw an exception in your method which fault's the client channel but beyond that you should not be concerned with managing service connections.
I have a WCF service running inside Windows Service and it is located on my local network. What I want is to be able to discover WCF from my Silverlight app on my WP7 (on the same network).
I know there a Discovery feature in WCF, however it requires to UDP, which is not supported on WP7. So are there any other ways to discover local WCF?
I also do not know prior to launching WCF the IP address of the WCF service.
The solution I came up with, is to use Sockets as on WP7 they support multicast.
So set up would like this:
Desktop service - Windows Service hosting WCF and small Socket app
which listens on specific port.
WP7 client - before connecting to WCF
a broadcast would be sent using Sockets to find out an IP address of
the machine which runs WCF, when got a response connect to WCF.
For a WCF Service to be referenced in a WP7 project the WCF Service MUST be a BasicEndpoint
You could provide a basic endpoint that exposes a kind of catalog service. It doesn't have to implement UDDI but it could be a custom protocol to suit your needs and return addresses of web services.
This way you only need to know a single address. Of course you can cache returned addresses and query the catalog service only when you are not able to connect.
I am learing the theory of WCF. In one of the book about WCF it reads that IIS and WAS supports dynamic activation, therefore it is possibile to create service host factory. What is dynamic activation?
It sounds like you are trying to understand what the Windows Process Activation Services (abbrreviated as 'WAS' in Microsoft's infinite wisdom) is and what it provides. WAS works with IIS to serve up an instance of a WCF service on demand. The demand is a request sent over some transport (HTTP, TCP, MSMQ) containing the soap or REST-based message for the WCF service to process. This is the dynamic activation of a service instance to process the message.
The alternative to "dynamic activation" is to write something like a Windows NT Service application to host the a WCF service. Dynamic activation is preferred because it provides the ability of the service to scale to handle a heavy load and later release those resources for other processes to use. With an NT service based host, the WCF service instance is always running and you need to decide how to handle scalability requirements. If you what to understand all the details, look at this article that explains how a WCF service can be hosted.