Solution for using services in a fluent lifecycle event

[monagle (David Monagle)]

Hi all,

I'm interested to know if there is an official or accepted way to achieve the following:

I have a model that is persisted to a postrgresql database. I also have an indexing service based on elasticsearch. For example, I would like to use the didUpdate lifecycle event on the PostgreSQL model to pass the model through to the indexing service. didCreate looks like this:

public func didUpdate(on conn: PostgreSQLConnection) throws -> EventLoopFuture<Account>

Now the problem here is that I don't have access to a container, only a connection - and by extension - an EventLoop.

I think the naive way of solving this would be to make the application a global object, allowing me to request a service from it. What I am curious about is whether Vapor has some mechanism that I haven't come across that allows an elegant way of achieving this?

[tanner0101 (Tanner)]

@monagle

Now the problem here is that I don't have access to a container, only a connection - and by extension - an EventLoop.

That part is by design. We want to keep Fluent decoupled from Vapor's dependency injection pattern.

@monagle

I think the naive way of solving this would be to make the application a global object, allowing me to request a service from it.

I'd recommend against this as it will likely cause threading issues and make testing your code more difficult.

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I think something like "Fluent-event middleware" could be used to solve this problem. They would need to be configurable during boot / initialization time so that any dependencies, such as indexing services, could be injected without prior knowledge of a given DI library. Each middleware could be registered against the events of a single model type, or receive the model type as a generic parameter.

Such a feature would definitely require a pitch / proposal process to iron out, but it's something that has been asked for before and would make Fluent a lot more extensible.