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I have a running system that process short and long running operations with a Request-Response interface based on Agatha-RRSL.

Now we want to change a little in order to be able to send requests via website in Json format so i'm trying many REST server implementation that support Json. REST server will be one module or "shelve" handled by Topshelf, another module will be the processing module and the last the NoSQL database runner module.

To talk between REST and processing module i'm thinking about a servicebus but we have two types of request: short requests that perform work in 1-2 seconds and long requests that do work in 1 minute..

Is servicebus the right choice for this work? I'm thinking about returning a "response" for long running op with a token that can be used to request operation status and results with a new request. The problem is that big part of the requests must be used like sync request in order to complete http response.

I think I have also problems with response size (on MSMQ message transport) when I have to return huge list of objects

Any hint?

Mauro Destro
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NServiceBus is not really suitable for request-response messaging patterns. It's more suited to asynchronous publish-subscribe.

Edit: In order to implement a kind of request response, you would need to message in both directions, but consisting of three logical steps:

  1. So your client sends a message requesting the data.
  2. The server would receive the message, process it, construct a return message with the data, and send it to the client.
  3. The client can then process the data.

Because each of these steps takes place in isolation and in an asynchronous manner there can be no meaningful SLA or timeout enforced between when a client sends a request and receives a response. But this works nicely for large processing job which may take several minutes to complete.

Additionally a common value which can be used to tie the request to the response will need to be present in both messages. Otherwise a client could send more than one request, and receive multiple responses and not know which response was for which request.

So you can do this with NServiceBus but it takes a little more thought.

Also NServiceBus uses MSMQ as the underlying transport, not http.

tom redfern
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  • so what's your hint? How can I talk to the processing module that return huge amount of data (1-2MB probably) after long time? The two modules can also not be in the same server. – Mauro Destro Sep 09 '11 at 07:35
  • Have expanded my answer above. – tom redfern Sep 09 '11 at 07:36
  • MSMQ has max message size of 4MB. That's 2MB Unicode characters. – John Breakwell Sep 09 '11 at 15:43
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    NServiceBus has built-in correlation for request/response semantics and you can see in the AsyncPages sample how that can integrate very easily into the ASP.NET pipeline. Also, NServiceBus allows you to expose an endpoint as a regular web/wcf service so it can accept messages from any and all clients. – Udi Dahan Sep 09 '11 at 17:21