How can I build a synchronous WCF service that wraps asynchronous MSMQ communications?
Let us have a simple scenario. I have a client which supports only synchronous web service calls. I need to send a synchronous request for "Order", but the back end system exposes this as an asynchronous request and response MSMQs. The WCF does not need to have any logic just wrap the MSMQ asych communication and pass parameters back and forth.
Grateful for your help
Let us have a simple scenario. I have a client which supports only synchronous web service calls
Synchronous call means you are using same link (end point url) or channel for your communication between client and server, so according to your assumption no.
Reason: Every time your client will send a request, it will keep waiting for response from server and will produce error.
Alternatively,You can define two services (different end point url) in your wsdl or webservice, one for request and one for response.
At client side you need to invoke these end point url saperately for sending request and receiving response,so it will appear as synchronous but ultimately it will be asynch. Thats all you can do in this scenario.
As per my understanding.
Related
I have system like this:
Windows service (WCF, data/events) <-> Web app <-> Web client
I need simultaneous response for clients requests. I have some events from service for clients too. So duplex channel is the way to go. But I need high throughput, because clients calls simultaneously.
Request/reply approach
In order not to serialize channel requests I need more channels for parallel calls, right? But how to handle callback channel then? Ho to keep it still open for receiving events, even on channel errors?
OneWay approach
On channel should be enough (no waiting for data preparation), but how to link data sent to callback with original request, to be able to compose response for client?
What is the way to go? Thank you.
In a simple case, when a web client sends a request to the web app, and web app (possibly) sends a request(s) to WCF service, there's no need in duplex binding at all.
As for events, raised by the service to be fired in Web client, I'd suggest to use a message broker which supports WebSockets - for example RabbitMQ. It has a plugin compatible with WebSockets and WCF binding.
Putting things together, one can create a RabbitMQ server, which accepts messages from WCF service and sends it to Web client, which subscribes to the event feed from Javascript.
I have a wcf service and handle a lot of client (server document generation). This service should receive a lot of request and should be handle in queue. It also have a callback. (callback will return successfully generated document). I am still using PIA and will implement OpenXML in the future.
Is it wcf msmq is the way to implement this?
Is there any samples might be related? Previously its running in local machine but now want to change it as a so called "Server generated"
WCF MSMQ doesn't support callback directly - it supports only one-way operations. But for example this article discuss how to add this support. With default configuration you can send message back to original sender but it is not a callback. To support responses every client will have to expose queue and pass address of its queue as part of the request to be able to receive the message from the service. More about responses in MSMQ is in MSDN magazine.
Here is what I would like to do.
1. Service hosted in WCF
2. Client calls asking for a payload of messages
3. Service returns payload of messages and waits for client to respond
3.A. Client returns 200 (OK) status or something confirming messages received.
3.B. Client returns bad error status stating to not delete the messages on server.
4. Depending on 3.A or 3.B Service will take appropriate action.
I would like to do this by doing something like extending IDispatcher and writing extension methods. VS creating another service and having the client call that service to signal which messages it received. Unless that's best practices.
Thanks in advanced.
If acting on HTTP status codes is a requirement then WCF is probably not what you want to use. WCF was created to be able to write transport independent code so the bindings could be changed purely through configuration; no code changes required. The HTTP request handling is buried so deeply into HTTP-based bindings that you're better off using something like the OpenRasta framework to implement your HTTP (REST) style service. It is a very HTTP request aware framework.
Otherwise, look at this wsDualHttpBinding intro to accomplish something similar through the application API level.
Can I listen to a WCF event from a web client? Is this possible? I am not talking about call backs, I want the WCF service to raise and event and the web client to be able to listen. Is there a good example of this in C#?
There are no events in WCF. If you want mimic event you still have to call some operation exposed on all clients = you must call WCF service or callback exposed on client.
What do you mean by web client? Do you mean javascript code running in web browser? In such case no you can't achieve that with WCF. You can only use AJAX calls from borowser and continuously poll the service for possible "event".
If you mean ASP.NET application then the answer is theoretically yes, practiacally it will be pretty hard. The reason is that in ASP.NET you handle only current HTTP request by some handler - for example Page. The lifetime of the handler is only for serving the single request. Due to that using duplex service doesn't make to much sense because for receiving callbacks by duplex service your client proxy must live. If you open the proxy in Page it will die after serving the request. If you open the proxy in separate thread you must somehow corelate incomming callbacks to actual client but the client still have to poll the web server to be notified about callbacks. Similar situation will be with exposing the service on ASP.NET application.
Difference between asynchronnous and duplex calls is big. In asynchronnous pattern single request always have single response. Resonse is not sent without request. In duplex pattern you can make single request and receive thousands callback from server.
I have a WCF service hosted as Windows Service with most of its methods currently defined as:
[OperationContract(IsOneWay = true)]
But, now I need to send response back to the calling Web application for these service methods.
Now, because service methods are bit heavy (FYI, they are reporting methods that needs to do mail merge for a no. of records), I am thinking to either queue them or to process asynchronously, so essentially when the request is sent to the service it should save the request to database/queue, returning Request-Id to calling Web application.
In the mean-time, WCF service can just process incompleted requests from the queue or database.
Then either calling Web application can ping WCF service for status of request because it has Request-Id or
WCF service can ping back to calling app when the process corresponding to a Request-Id is completed.
To achieve above, can anyone please guide what changes I need to make to my WCF service (which currently has all one way operation)?
Also, please guide me whether I need to go for Asynch operation or message queuing?
Thank you!
Of course, going Async is simple:
remove the OneWay on the OperationContract in question and regenerate your Service WITH Async methods. There's a reason why Silverlight forces you to use Async operations. They do force you to rethink your UI.