I have a Windows service that acts as a cache server and is implemented using WCF. This service mainly returns a stream of data dictionaries to it's clients. Recently there was a request for me to make this service more "debuggable". One of the things that was in the TODO list was: be able to query the cache service directly for specific data.
After a lot of thought I decided to expose a REST endpoint to do this job. And belive it or not, it was super easy to do that. And so, I dedicate this blog post about the task.
My existing service was a singleton and implemented an interface such as ICacheService interface. I simply added a new interface called ICacheLookup interface with a method like GetCustomer(int customerId).
1: [ServiceContract(Namespace = "http://MyCompany.CacheServiceLookup")]
2: public interface ICacheLookup
3: {
4: [OperationContract()]
5: [WebGet(UriTemplate="GetCustomer?customerId={customerId}", ResponseFormat=WebMessageFormat.Xml)]
6: Customer GetCustomer(int customerId);
7: }
Next for implementation of this method, I used my singleton CacheService implementation and extracted the customer Id from it.
1: public class CacheLookup : ICacheLookup
2: {
3: public Customer GetCustomer(int customerId)
4: {
5: Customer customer = null;
6: CacheService.Instance.CustomersCache.FullEntities.TryGetValue(customerId, out customer);
7: return customer;
8: }
9: }
After this, all that was left was setting up the configuration endpoint and the rest service startup.
1: <services>
2: <service behaviorConfiguration="ServiceBehavior" name="MyCompany.CacheService">
3: <endpoint address="net.tcp://localhost:2000/CacheService"
4: binding="netTcpBinding" bindingConfiguration="TcpBinding" name="TCP"
5: contract="MyCompany.ICacheService" />
6: </service>
7: <service behaviorConfiguration="ServiceBehavior" name="MyCompany.CacheLookup">
8: <endpoint address="http://localhost:2001/CacheService"
9: binding="webHttpBinding" bindingConfiguration="WebBinding" name="Rest"
10: contract="MyCompany.ICacheLookup" />
11: </service>
12: </services>
Starting the REST service in the ServiceHost:
1: private static ServiceHost service = null;
2: private static System.ServiceModel.Web.WebServiceHost webHost = null;
3:
4: public static void StartService()
5: {
6: Uri baseAddress = new Uri(ConfigurationManager.AppSettings["BaseAddress"]);
7: CacheService serviceInstance = CacheService.Instance;
8: CacheServiceHost.service = new ServiceHost(serviceInstance, baseAddress);
9: CacheServiceHost.service.Open();
10:
11: CacheServiceHost.webHost = new System.ServiceModel.Web.WebServiceHost(typeof(CacheLookup), baseAddress);
12: CacheServiceHost.webHost.Open();
13: }
No changes were needed for deployment, the REST endpoint simply worked and was accessible using the following url:
http://localhost:2001/CacheService/GetCustomer?customerId=2000
That's all, and it was super easy to get xml serialized data out of the service without much ado. Since then I've become a great fan of REST and declarative programming model : )