CODEWITHSUNDEEP
c#wcfconfigurationservicebus
Midnight_Blaze
Midnight_Blaze

Reputation: 501

Q: How to build the most basic service aggregation pattern?

I have a set of services I want to be able to access via one end point altogether.

Now I want to build something in wcf rather than use an existing framework/software so that is out of the question.

Suppose I have 10 contracts each representing a contract of an indepedent service that I want to "route" to, what direction should I go? 

 public partial class ServiceBus : ICardsService
    {
        //Proxy
        CMSClient cards = new CMSClient();

        public int methodExample()
        {
            return cards.methodExample(); 
        }

So far I've tried using a partial class "ServiceBus" that implements each contract but then I have more than a few (60+) recurrences of identical function signatures so I think I should think in a different angle.

Anyone got an idea of what I should do? or what direction to research? currently I'm trying to use a normal wcf service that's going to be configured with a lot of client end points directing to each of the services it routes TO - and one endpoint for the 'application' to consume.

I'm rather new at wcf so anything that may seem too trivial to mention please do mention it anyway.

Thanks in advance.

Upvotes: 1

Views: 502

Answers (1)

tom redfern
tom redfern

Reputation: 31770

I have a set of services I want to be able to access via one end point altogether. ... So far I've tried using a partial class "ServiceBus" that implements each contract

It's questionable whether this kind of "service aggregation" pattern should be achieved by condensing multiple endpoints into an uber facade endpoint. Even when implemented well, this will still result in a brittle single failure point in your solution.

Suppose I have 10 contracts each representing a contract of an indepedent service that I want to "route" to, what direction should I go?

Stated broadly, your aim seems to be to decouple the caller and service so that the caller makes a call and based on the call context the call is routed the relevant services.

One approach would be to do this call mediation on the client side. This is an unusual approach but would involve creating a "service bus" assembly containing the capability to dynamically call a service at run-time, based on some kind of configurable metadata.

The client code would consume the assembly in-process, and at run-time call into the assembly, which would then make a call to the metadata store, retrieving the contract, binding, and address information for the relevant service, construct a WCF channel, and return it to the client. The client can then happily make calls against the channel and dispose it when finished.

An alternative is to do the call mediation remotely and luckily WCF does provide a routing service for this kind of thing. This allows you to achieve the service aggregation pattern you are proposing, but in a way which is fully configurable so your overall solution will be less brittle. You will still have a single failure point however, unless you load balance the router service.

I'm not sure about making it client side as I can't access some of the applications (external apis) that are connecting to our service

Well, any solution you choose will likely involve some consumer rewrite - this is almost unavoidable.

I need to make it simple for the programmers using our api

This does not rule out a client side library approach. In fact in some ways this will make it really easy for the developers, all they will need to do is grab a nuget package, wire it up and start calling it. However I agree it's an unusual approach and would also generate a lot of work for you.

I want to implement the aggregation service with one endpoint for a few contracts

Then you need to find a way to avoid having to implment multiple duplicate (or redundant) service operations in a single service implementation.

The simplest way would probably be to define a completely new service contract which exposes only those operations distinct to each of the services, and additionally a single instance of each of the redundant operations. Then you would need to have some internal routing logic to call the backing service operations depending on what the caller wanted to do. On second thoughts not so simple I think.

Do you have any examples of a distinct service operation and a redundant one?

Upvotes: 1

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