Is there any standard way of implementing some sort of a write-through buffer for a WCF call? I need a mechanism to be able to write to a bufffer or cache which gets persisted and then writes it to the service. If the service is down the call will be transfered when the service is up and running again. I know you can use WCF over MSMQ which does exactly what I need, but I wounder if there is another way of doing this, so I don't need to deploy MSMQ to the client.
Best regards,
Michael
The problem is that MSMQ is designed to do this - if you want to do this without MSMQ then you must implement your own queuing mechanism that functions like MSMQ and deploy that to the client.
Related
I have a wcf application to upload files from clients to my server. I am using NetTcpbinding and WSHttpBinding but I need to control the bandwidth, how can I accomplish this??
AFAIK, there is no built-in throughput throttling at the WCF level. You might be able to leverage the QoS features built into Windows for that, but honestly, I've never tried it. I guess you could always write your own transport channel that supports it, though.
I am writing an application that has one Windows Service that needs to communicate with another Windows Service. The "target" service will accept a request from the "source" service and will perform a task. The "source" service will not wait for a response, so the request should return as soon as possible.
The plan was to have the "target" service host a WCF service which the "source" will communicate with. Once the request is received I need to communicate with the host Windows Service to tell it to do the work. I was thinking that the "target" WCF service would put a message on a MSMQ which the "target" Windows service will monitor. Once this is done the WCF service can return back to the caller.
Does this sound like a sensible approach for allowing a WCF service to tell a hosting Windows Service to perform a task?
Kind Regards
Michael
Allow me to disagree. Based simply on what you've described, using MSMQ to communicate between the "target" WCF service and the hosting Windows service seems extremely heavyweight to me. MSMQ allows different processes to communicate in a failsafe manner. In your case, the WCF service is hosted in the same process as the Windows service. Thus, while MSMQ as a commmunication mechanism between the two would work, it's not necessary.
Additionally, using the MSMQ binding between the "target" WCF service and the "source" WCF service makes sense if the two WCF services are not always running at the same time. For example, if the "target" WCF service is not always running, the MSMQ binding would allow the "source" WCF service to still send tasks. These tasks would be stored in the MSMQ to be retrieved when the "target" WCF service begins running. However, it sounds like both services will be running, so I can't see the need for the MSMQ binding.
For selecting WCF bindings, refer to this SO post.
C# - WCF - inter-process communication
Let me address one other thing. When your "target" WCF service receives a task request from the "source," simply communicating the task back to the Windows service is not going to do anything in and of itself. The Windows service is running, yes, but it does not have a thread of execution that you can leverage. The point is that in order to make task processing asynchronous, you'll need to start a thread to manage the task(s). I would suggest leveraging the ThreadPool to do this.
Hope this helps.
Yeah, that is a good approach. MSMQ is perfect for this task - the source service can send a request to the target by putting a message on the queue via WCF. MSMQ is good anytime you want to send a request to a service for asynchronous processing, especially if you don't need to get a response back. If you do need a response, you can setup the source as a WCF service as well, and the target can send a message back if needed. There are several different ways to accomplish this with the MSMQ binding.
#Matt
Thanks for your help.
After thinking about it a bit more and see how your approach would make things easier to setup and use. I need to have the "target" service send the outcome of the work back to the "source", so I will probably use nettcp and use a callback. The plan then is to setup a new thread, do the work and once its finished send a response back to the "source".
#Andy
Thanks for you help.
I took a look at msmq, but seeing as I would probably have to setup a new thread once I receive the message I might as well let the web service do the work.
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 have develop a silverlight chat application. my question is (a) can netmsmqbinding support unlimited connections of wcf service. because first im use pollingduplex binding but it support only 10 connection on iis6 also on server edition.im allready set service throttling options but not effect on server iis. so that now i want to go for netmsmqbinding. please explain me msmqbinding limitations.can its better for chat application or not?
help me for take decision.
Thanks
As far as I know (but I don't know Silverlight all that well), it supports only the basicHttpBinding.
And even if Silverlight did support MSMQ - this is definitely not a good protocol to use when you're creating a chat application. The queue can buffer messages and deliver them later. That works well in many scenarios, but when I chat with someone, I want my message to show up right away - not "some time later".....
So if you really need to use MSMQ in some way, I think you'd have to have a BasicHttp-based front-end service that goes from your Silverlight client to the server, and then on the server actually route your message forward to a MSMQ queue.
Marc
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.