Using ServiceStack Architecture to Route Events instead of using Reflection?

ServiceStack Routing
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I am currently working on a ServiceStack plugin for EventStore which can persist and rehydrate aggregates as well as subscribe to named event streams.

At the moment, the plugin handles an event arriving on a watched stream by inspecting the event type and dispatching it to a method that implements IHandle. This works well enough although like all implementations of the Observer Pattern the order in which subscribers are notified is not specified.

Is there a way that, instead of dispatching an event in this way - i.e. using Reflection to dispatch a ProductCreated event to a method that implements IHandle - we could route the event to a service method like Any(OrderCreated @event)? Is the custom ServceRunner designed for this purpose?

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You can call the ServiceController to execute Services by passing in a Request DTO, e.g:

HostContext.ServiceController.Execute(new OrderCreated { ... });

If the EventStore message is a POCO with matching properties you also want to copy to the Request DTO, you can use the built-in Auto Mapping, e.g:

HostContext.ServiceController.Execute(eventStoreMsg.ConvertTo<OrderCreated>());
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Thanks, Demis. That could help us lose a fair bit of boilerplate!

So, we are taking the CLR type name of the event from the event’s own header and then resolving the type from a dictionary created via assembly scanning.

Now, instead of scanning for methods that implement IHandle I guess we could scan for the parameter types of methods in all classes that inherit from Service. Or does ServiceStack already have a list of these types?

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You can get all metadata about your Services from HostContext.Metadata, the /types/metadata route shows some of the metadata available, e.g: http://test.servicestack.net/types/metadata.json

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I’ve used the Execute(DTO) pattern that @mythz mentions in combination with cron schedules (works well), by injecting the DTO to be executed into a Job pattern.

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I got it working.

I’m pleased to say that I was able to jettison about 40 lines of code that was doing assembly scanning and dispatching. Always a Good Thing. :blush:

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A question about HostContext.ServiceController.ExecuteAsync(...)

The signature is public Task<object> ExecuteAsync(object requestDto, IRequest req)

With the synchronous method I have just been passing in my event type/POCO. However, what would I need to pass in (that implements IRequest) as the second parameter to the ExecuteAsync method?

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You can just pass in ‘new BasicRequest()’ which is also what gets passed when you call ‘Execute()’ with only the Request DTO.