The summary Vapor service manufacturing facility design sample

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I’ve written a number of articles about manufacturing facility design patterns on my weblog and this time I would like to speak a few particular one, which you’ll be able to encounter if you happen to work with Vapor. This is a little bit recap about my manufacturing facility design sample weblog posts, all written in Swift:

Now let’s dive in to the “Fluent sample”. With a view to perceive this structure, first we should always study the associated Swift packages first. There’s the FluentKit library and a number of other Fluent database driver implementations (SQLite, PostgreSQL, MySQL, and many others.), all primarily based on the FluentKit product. Additionally there’s one bundle that connects Fluent with Vapor, this one is solely known as: Fluent. 📀

  • FluentKit – incorporates the summary interface (with out Vapor, utilizing SwiftNIO)
  • Fluent[xy]Driver – incorporates the implementation outlined in FluentKit
  • Fluent – connects FluentKit with Vapor, by extending Vapor

That is the bottom construction, the FluentKit library supplies the next summary interfaces, which it’s important to implement if you wish to create your personal driver implementation. Sadly you will not be capable of discover correct documentation for these interfaces, so I am going to clarify them a bit:

  • Database – Question execution and transaction associated features
  • DatabaseContext – Holds the config, logger, occasion loop, historical past and web page dimension restrict

  • DatabaseDriver – A manufacturing facility interface to create and shutdown Database cases
  • DatabaseID – A novel ID to retailer database configs, drivers and cases
  • DatabaseError – A generic database associated error protocol
  • DatabaseConfiguration – A protocol to create DatabaseDriver objects
  • DatabaseConfigurationFactory – A box-like object to cover driver associated stuff
  • Databases – Shared config, driver and working occasion storage

As you may see there are lots of protocols concerned on this structure, however I am going to attempt to stroll you thru the complete driver creation stream and hopefully you can perceive how the items are associated, and the way can construct your personal drivers and even Vapor parts primarily based on this.

Fluent is written as a service for Vapor utilizing the underlying shared storage object, that is what shops a reference to the Databases occasion. This object has two hash maps, for storing configurations and working driver cases utilizing the DatabaseID as a key for each. 🔑

Once you ask for a driver, the Databases object will verify if that driver exists, if sure, it will merely return it and story over. The attention-grabbing half occurs when the motive force doesn’t exists but within the Databases storage. First the system will verify for a pre-registered driver implementation.

app.databases.use(.sqlite(.file("db.sqlite")), as: .sqlite)

This line above registers a brand new driver configuration for the shared Databases. The .sqlite() technique is a static operate on the DatabaseConfigurationFactory which creates a brand new SQLite particular configuration and hides it utilizing the init(make:) name. The SQLite associated configuration implements the DatabaseConfiguration protocol, so it may be used as a sound config when the system creates the precise database context.

The config object can be liable for creating the precise driver object utilizing the Databases object if wanted. At this level we have got a configuration and a driver occasion registered within the databases storage. What occurs if somebody asks for a database occasion?

Relying on the context, you may ask for a Database implementation via the app.db or req.db properties. That is outlined within the FluentProvider code and behind the scenes every part might be traced again to the Databases class. Because you solely need to have a single shared storage for all of the drivers, however you additionally need to keep away from the singleton sample, it is best to hook this service as much as the Software class. That is how the Vapor of us did it anyway. 🤓

let db: Database = req.db
let db: Database = req.db(.sqlite)

let db: Database = app.db
let db: Database = app.db(.sqlite)

Once you ask for a database, or a database with an express identifier, you’re primarily calling a make technique contained in the Databases class, which goes search for a registered configuration and a driver implementation utilizing the hashes and it will name the motive force’s make technique and move across the logger, the occasion loop and the present database configuration as a database context object.

We will say that after you ask for an summary Database driver, a brand new DatabaseDriver occasion reference (related to a given DatabaseID) shall be saved contained in the Databases class and it will at all times make you a brand new Database reference with the present DatabaseContext. If the motive force already exists, then it will be reused, however you continue to get new Database references (with the related context) each time. So, it is very important notice that there’s just one DatabaseDriver occasion per configuration / database identifier, however it could actually create a number of Database objects. 🤔

Okay, I do know, it is fairly sophisticated, however here is an oversimplified model in Swift:

last class Databases {
    var configs: [DatabaseID: DatabaseConfiguration] = [:]
    var drivers: [DatabaseID: DatabaseDriver] = [:]

    func make(
        _ id: DatabaseID,
        logger: Logger,
        on eventLoop: EventLoop
    ) -> Database {
        let config = configs[id]!

        if drivers[id] == nil {
            drivers[id] = config.make(self)
        let context = DatabaseContext(config, logger, eventLoop)
        return drivers[id]!.make(context)

    func use(_ config: DatabaseConfiguration, for id: DatabaseID) {
        configs[id] = config

And the Vapor service extension may very well be interpreted considerably like this:

extension Software {

    var databases: Databases {
        get {
            if storage[DatabasesKey.self] == nil {
                storage[DatabasesKey.self] = .init()
            return storage[DatabasesKey.self]
        set {
  [MyConfigurationKey.self] = newValue

    var db: Database {
            logger: logger, 
            eventLoop: eventLoopGroup.subsequent()

You possibly can apply the identical ideas and create an extension over the Request object to entry a Database occasion. After all there’s much more taking place below the hood, however the objective of this text is to get a primary overview of this sample, so I am not going into these particulars now. 🙃

Actually I actually like this method, as a result of it is elegant and it could actually fully cover driver particular particulars via these abstractions. I adopted the very same ideas once I created the Liquid file storage driver for Vapor and realized so much in the course of the course of. Though, it is best to notice that not every part is an efficient candidate for being applied an “summary Vapor service manufacturing facility” design sample (or no matter we name this method). Anyway, I actually hope that this fast tutorial will enable you to create your personal Vapor parts, if wanted. 🤷‍♂️

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