Use ComponentLifecycle in HBApplication

[slashmo]

In my server applications I usually have two servers running, one for the public API of a service and one for the admin API (e.g. to expose a /metrics route), but I still want them to run in the same process/container. I'd like to be able to use ServiceLifecycle to pull them all together but that's currently not possible since HBApplication creates its own top-level lifecycle. If we were to use ComponentLifecycle instead, an HBApplication and all its lifecycle tasks could be registered as a subcomponent of a larger lifecycle, which could look like this:

let lifecycle = ServiceLifecycle()

let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
lifecycle.registerShutdown(label: "event-loop-group", .async(eventLoopGroup.shutdownGracefully))

let publicApp = HBApplication(
    configuration: .init(
        address: .hostname(options.host, port: Int(options.publicPort)),
        serverName: "Example API",
        logLevel: options.logLevel
    ),
    eventLoopGroupProvider: .shared(eventLoopGroup)
)
lifecycle.register(publicApp.lifecycle)

let adminApp = HBApplication(
    configuration: .init(
        address: .hostname(options.host, port: Int(options.adminPort)),
        serverName: "Example API [Admin]",
        logLevel: options.logLevel
    ),
    eventLoopGroupProvider: .shared(eventLoopGroup)
)
lifecycle.register(adminApp.lifecycle)

try lifecycle.startAndWait()

[codecov]

Codecov Report

Base: 78.15% // Head: 78.15% // No change to project coverage 👍

Coverage data is based on head (092cd48) compared to base (8a117a1).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 092cd48 differs from pull request most recent head e93340d. Consider uploading reports for the commit e93340d to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #142   +/-   ##
=======================================
  Coverage   78.15%   78.15%           
=======================================
  Files          72       72           
  Lines        3094     3094           
=======================================
  Hits         2418     2418           
  Misses        676      676           

Impacted Files	Coverage Δ
Sources/Hummingbird/Application.swift	98.30% <100.00%> (ø)

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[adam-fowler]

LGTM
It is API breaking but I've not committed to a v1.0 yet so not too fussed about that

[adam-fowler]

One issue, which is an issue with service lifecycle to some degree. ComponentLifecycle on its own does not catch interrupts like Ctrl+C.

[slashmo]

ComponentLifecycle on its own does not catch interrupts like Ctrl+C.
@adam-fowler

Oh, I hadn't realized that. Maybe we could fix it by adding something like a ServiceLifecycleProvider (inspired by NIOEventLoopGroupProvider) which defaults to .createNew, keeping the same behavior as before of creating a full ServiceLifecycle, but has another case .embedded(lifecycle: ServiceLifecycle) which would create a component life cycle and add itself to the given ServiceLifecycle. This could potentially also solve the API breakage if we choose to expose the full lifecycle either way. What do you think?

[adam-fowler]

Oh, I hadn't realized that. Maybe we could fix it by adding something like a ServiceLifecycleProvider

Yeah that would work. Might as well keep the same terminology as EventLoopGroupProvider which is createNew and shared.

[slashmo]

Agreed, I'll update the PR later today.

[adam-fowler]

Looks good.
A couple of minor nits