I can imagine that the 'server' can be a machine/host but can be also a program like ftp server, smtp server, etc..
The 'service' on the other hand refers mainly to applications/programms..
Why can then for example the Sql Server cannot be called as Sql Service? It has the same semanthics. Or the other way round: MS Azure service: why it isn't called Azure Server? :)
I would say:
A server is expected to give a response
A service is not
Additionally, a service may include more than a server - it may well be an environment, hardware, SLA and more.
The services are features offered by the servers.
A server is a (possibly virtualized) piece of equipment that can be used to provide a service.
A service is something that you can use (usually remotely) that is provided by one or more servers.
The other difference is that these are really concepts at different levels of abstraction. Servers are concrete things. Services are abstract. Yet people mostly use services, and don't really care about what servers are used to implement them. Do you care about what servers are used to provide Google's web search service? No, you don't. Do you care about what servers are used to provide Amazon's cloud service? No, you don't.
A server is a a software program, or the computer on which that program runs, that provides a specific kind of service to client software running on the same computer or other computers on a network.
Per Microsoft - Windows Azure: operating system as an online service.
SQL Server is a Server, Any Stored Procedures or functions you write are Services. (A Query is a dynamic Service that has a life of just the call, it is sent to the Database, compiled, The Server executes the compiled code and returns the results)
I would say that there's no difference. They're used more-or-less interchangeably.
Or, if you prefer: you can come up with a definition, and someone will come up with a counter-example.
Related
I want to know if their any way to invoke a windows service from SQL query ?
note that : the windows service is installed on the same SQL server
Thank you
No, because windows services cannot be invoked. A service is just a process that is started by the SCM and responds to the SCM commands, there is no such concept as 'invoking' a service. What you can interact with is the service API, which implies a communication protocol with the service. Depending on the API and protocol used, that may be possible to do from T-SQL. Eg. COM based APIs can be interacted using sp_OAcreate, managed APIs may be interacted using SQLCLR and so on. But is always a Bad Idea. T-SQL is not the proper layer to introduce dependencies on external services, it may impact the SQL performance dramatically and, most importantly, is almost always incorrect due to not proerly considering rollbacks.
Do any/all service interaction in the application layer, where it belongs.
My management is evaluating non-Azure Microsoft Windows Service Bus (Azure is out of consideration for security reasons). It will be used to setup topic/subscription model with a number of WCF services with netMessagingBinding that we building, so I just have a few basic questions about that.
Are there any specific hardware requirements like dedicated server, dedicated database etc. for WSB to run in production environment?
It's easy to configure WCF service to listen on a specific topic subscription. Is there any way for WCF service to listen to multiple subscriptions?
Appreciate the answers.
You can install the service components and the databases all on one server (that is the default). However, for a number of reasons, we installed the services on a dedicated app server and then created the Service bus databases on an existing database server. The install package allows you to specify a different db server. Check this article for the minimum server requirements
Yes you can get one WCF service to listen to multiple subscriptions. You would need to create two (or more) System.ServiceModel.ServiceHost instances and then run them inside one process. For example we had one windows service running two ServiceHost's. Each host listened at a different queue and therefore implemented a different contract. This meant where queues were logically grouped we didn't need a new windows service per queue. You could do the same with subscriptions.
For question one, you will have to go through the exercise of hardware sizing. the good news is that WCF services can scale vertically, so you can add up servers if there were issues in handling client load.
To do hardware sizing you will have to make an estimate the expected load and then do performance/scalablity testing to figure the load bearing capacity of your serviceBus/services .
you could find a lot of resources for load testing like this one http://seroter.wordpress.com/2011/10/27/testing-out-the-new-appfabric-service-bus-relay-load-balancing/
once you do load testing and come up with the numbers, you can then do sizing using references like this one http://msdn.microsoft.com/en-us/library/bb310550.aspx
I want to communicate xml serialized objects from the server to the client and the other way arround. Now it is (probably) easy to invoke methods from a mobile client (compact framework) using WCF, but is there a way so that the server can invoke methods on the client side or some other way to pull data from the client? I know that callback contracts are not available in the compact framework as you can see here: http://blogs.msdn.com/andrewarnottms/archive/2007/09/13/calling-wcf-services-from-netcf-3-5-using-compact-wcf-and-netcfsvcutil-exe.aspx
Originally I thought of socket programming and of developing this by myself, then someone here mentioned WCF. But it seems like WCF only would work in a non mobile environment as I need callbacks.
Anyone can help me with this? Is it possible to develop a two way communication with a desktop server and multiple mobile clients using WCF, or will I have to do socket programming?
Thanks for any advice or any kind of help!
at ctacke
Thank you for your help. I actually stumbled across your Padran web server before.Havent really checked it out yet. But I definitely will do that later on. Anyway, a socket solution does not seem that bad at the moment. In the meanwhile I figured that it is quite easy to send data from multiple clients to a 'socket server'. If I can manage those connections somehow I can send data back to the clients. And then I would have to come up with some kind if protocol which handles the data or commands I send over the network... I guess the hardest part would be to make up such a protocol as I do not have a clue about that atm...
Even if you go to sockets it might be a bit difficult due to routing, carrier filtering and NAT translations (you've not mentioned what your actual network topology is). This is the reason that most mobile applications have to poll the server, even if it is a "push" paradigm (like Exchange's push mechanism, where the client actually polls).
Generally speaking, unless you're on something like a local wireless network where you have solid, routable, unfiltered network access, the client should periodically call the server and ask if the server has data. If it does, then it pulls the data from the server.
EDIT
Now that we know a little more about your topolgy from your comment, I can steer you a little more. Unfortunately Microsoft has not made it easy for Windwos CE devices to host services (WCF or otherwise). There is, in theory, the required infrstructure to build up your own WCF channel and actually host a service, but it's not a trivial task. I looked into it quite some time ago and figured it was a couple months of work and that would have been with the assistance of someone in Redmond that knew how the existing Exchange channel works.
Personally I'd opt for hosting a REST-based web service using our Padarn web server because it's simple to do and I've done it for quite a number of clients now. I realize that it's a little self-serving to propose Padarn as a solution but the entire reason I implemented custom IHttpHandlers in Padarn was because I couldn't find anything else out there that really provided any easy way for a CE device to host it's own services and it's a problem we often have to provide a solution for.
The other options would be things like a proprietary socket solution, hosting an FTP server on the device, using the (abhorrent, IMO) MS-provided HTTP server with ISAPI, Telnet or something along those lines. All of them seem either a hack, a lot of work or both.
Just a technology update, now that .NET 4.0 is out.
I write an application that communicates to the server through what is basically a message bus (instead of method calls). This is based on the internal architecture of the application (which is multi threaded, passing the messages around).
There are a limited number of messages to go from the client to the server, quite a lot more from the server to the client. Most of those can be handled via a separate specialized mechanism, but at the end we talk of possibly 10-100 small messages per second going from the server to the client.
The client is supposed to operate under "internet conditions". THis means possibly home end users behind standard NAT devices (i.e. typical DSL routers) - a firewalled secure and thus "open" network can not be assumed.
I want to have as little latency and as little overhad for the communication as possible.
What is the technologally best way to handle the message bus callback? I Have no problem regularly calling to the server for message delivery if something needs to be sent...
...but what are my options to handle the messagtes from the server to the client?
WsDualHttp does work how? Especially under a NAT scenario?
Just as a note: polling is most likely out - the main problem here is that I would have a significant overhead OR a significant delay, both aren ot really wanted. Technically I would love some sort of streaming appraoch, where the server can write messags to a stream while he generates them and they get sent to the client as they come. Not esure this is doable with WCF, though (if not, I may acutally decide to handle the whole message part outside of WCF and just do control / login / setup / destruction via WCF).
For bidirectional communications, your best bet is NetTcpBinding, rather than the http bindings, if they're available.
This has the advantage of only requiring that the client can initiate a connection with the server.
I would go with Windows Azure Service Bus. See my answer in the following question:
WCF, 4.0, Bidirectional
Take a look at Windows AppFabric, good place to start is Here. It fundamentally wraps up WCF and WF into an application server, with WCF activation supported through WAS. Its where I would host this type of app. It offerd full duplex connection orientated, p2p or sessions between client and server. Don't confuse the Windows appfabric with Azure appfabric, (formely called Azure Service Bus).
As regards bindings above, both NetTcpBinding and WsDualHttp offer callbacks, but the ws binding you get a lot for your cash, especially if it's a mixed programming environment and you have to flatten the wsdl to make interop work. I also think that WsDual is easier on routers traversal, although I understand talking to friends, that Windows AppFabric mitigates this, with new Relay Services, (which i've not seen, and I think have now been renamed).
Hope that helps.
I am looking at using MSMQ as a solution to do asynchronous execution in my upcoming project. I want to know the differences between using WCF and frameworks like MassTransit or even hand written MSMQ client to place/read task off MSMQ.
Basically the application will be several websites (internal through LAN or external through the Internet) reading/writing data through a service layer (be it WCF or normal web service). Then this service layer will do one of two things: 1. write data to database 2. and/or trigger the background process by placing a message in the queue. 3. obviously it can also retrieve data from database. The little agent (a windows service) on the other side of the queue will monitor the queue and execute based on the task command.
This architecture will be quite easy to scale (add more queues and agents) and easy to implement compared to RPC or distributed execution or whatever. And the agent processing doesn’t need to be real time. And the agent and service layer are separate applications except they share the common domain objects and Repositories etc.
What do you think? Architecture suggestions for the above requirements are welcomed. Thank you!
WCF adds an abstraction over MSMQ. In fact, once you define compatible contracts (operations must be OneWay), you can switch out MSMQ in the config, transparently. (For instance, you could switch to normal HttpWS or a NetTcp binding.)
You should evaluate the other WCF benefits, like security and so on, to see how those fit in with your needs. Again, they should be reasonably transparent of the fact you're using MSMQ underneath. For instance, adding SOAP security and so on should "just work", independent of using MSMQ.
(Although, IIRC, you still need to login to the desktop on each machine that uses MSMQ, with the service account that will use MSMQ, to generate the certificate in the machines local profile. And then, it doesn't work very well from IIS6, since user profiles aren't loaded. A real pain in general, but nothing to do with WCF specifically.)
Apart from that:
Have you looked at SQL Server Service Broker? After using MSMQ + WCF and SSSB, I think that SSSB is vastly easier to configure and manage. SSSB works with T-SQL commands over any SQL client (I use it from Mono, on Linux, with transactions). It'll also give you transactional send/receive, even remotely (I think MSMQ 4 now allows this). It really takes a lot of the pain away from message queuing, and if you're using SQL Server already...
SSSB is often overlooked since the SQL Management Studio doesn't have GUI designers for it all, but it isn't hard and is a great option. The one downside is that if you want local send capability (i.e., queue message when network is down), you'll need to run a local SQL Express instance.
Your architecture seems sound and reasonable. However you should consider using the WCF net MSMQ transport over hand coded MSMQ classes. WCF wraps this common functionality into a nice programming model. Also I believe there is some improvements in the protocol used by wcf compared to basic System.Messaging
Have a look at the value-add over plain MSMQ:
http://readthedocs.org/docs/masstransit/en/latest/overview/valueadd.html
In summary, you get a lot of messaging concepts clearly presented in the API with MassTransit; to an extent you wouldn't have if you hand-coded it or used WCF.