nested lifecycles

motivation: add ability to create a hirearchy of lifecycles to help manage more complex systems

changes:
* define top-level lifcycle where signal handling and backtraces are handled
* conform Lifecycle to LifecycleItem so that lifecycles can be nested
* change shutdown to return an error to better conform with LifecycleItem api

Author: tomerd

Sources/ServiceLauncher/Lifecycle.swift

@@ -21,13 +21,15 @@ extension Lifecycle.Handler {
     /// - parameters:
     ///    - future: the underlying `EventLoopFuture`
     public static func eventLoopFuture(_ future: @escaping () -> EventLoopFuture<Void>) -> Lifecycle.Handler {
-        return Lifecycle.Handler { callback in
+        return Lifecycle.Handler { queue, callback in
             future().whenComplete { result in
-                switch result {
-                case .success:
-                    callback(nil)
-                case .failure(let error):
-                    callback(error)
+                queue.async {
+                    switch result {
+                    case .success:
+                        callback(nil)
+                    case .failure(let error):
+                        callback(error)
+                    }
                 }
             }
         }

Sources/ServiceLauncherNIOCompat/Bridge.swift

@@ -26,6 +26,7 @@ import XCTest
 @testable import ServiceLauncherTests
 
 XCTMain([
-    testCase(Tests.allTests),
+    testCase(LifeycleTests.allTests),
+    testCase(TopLevelTests.allTests),
 ])
 #endif

Tests/LinuxMain.swift

@@ -0,0 +1,99 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftServiceLauncher open source project
+//
+// Copyright (c) 2019-2020 Apple Inc. and the SwiftServiceLauncher project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftServiceLauncher project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import NIO
+import NIOConcurrencyHelpers
+import ServiceLauncher
+
+class GoodItem: LifecycleItem {
+    let id: String
+    let startDelay: Double
+    let shutdownDelay: Double
+
+    var state = State.idle
+    let stateLock = Lock()
+
+    init(id: String = UUID().uuidString,
+         startDelay: Double = Double.random(in: 0.01 ... 0.1),
+         shutdownDelay: Double = Double.random(in: 0.01 ... 0.1)) {
+        self.id = id
+        self.startDelay = startDelay
+        self.shutdownDelay = shutdownDelay
+    }
+
+    var label: String {
+        return self.id
+    }
+
+    func start(on queue: DispatchQueue, callback: @escaping (Error?) -> Void) {
+        queue.asyncAfter(deadline: .now() + self.startDelay) {
+            self.stateLock.withLock { self.state = .started }
+            callback(nil)
+        }
+    }
+
+    func shutdown(on queue: DispatchQueue, callback: @escaping (Error?) -> Void) {
+        queue.asyncAfter(deadline: .now() + self.shutdownDelay) {
+            self.stateLock.withLock { self.state = .shutdown }
+            callback(nil)
+        }
+    }
+
+    enum State {
+        case idle
+        case started
+        case shutdown
+    }
+}
+
+class NIOItem {
+    let id: String
+    let eventLoopGroup: EventLoopGroup
+    let startDelay: Int64
+    let shutdownDelay: Int64
+
+    var state = State.idle
+    let stateLock = Lock()
+
+    init(eventLoopGroup: EventLoopGroup,
+         id: String = UUID().uuidString,
+         startDelay: Int64 = Int64.random(in: 10 ... 20),
+         shutdownDelay: Int64 = Int64.random(in: 10 ... 20)) {
+        self.id = id
+        self.eventLoopGroup = eventLoopGroup
+        self.startDelay = startDelay
+        self.shutdownDelay = shutdownDelay
+    }
+
+    func start() -> EventLoopFuture<Void> {
+        return self.eventLoopGroup.next().scheduleTask(in: .milliseconds(self.startDelay)) {
+            self.stateLock.withLock { self.state = .started }
+        }.futureResult
+    }
+
+    func shutdown() -> EventLoopFuture<Void> {
+        return self.eventLoopGroup.next().scheduleTask(in: .milliseconds(self.shutdownDelay)) {
+            self.stateLock.withLock { self.state = .shutdown }
+        }.futureResult
+    }
+
+    enum State {
+        case idle
+        case started
+        case shutdown
+    }
+}
+
+struct TestError: Error {}

Tests/ServiceLauncherTests/Helpers.swift

@@ -22,15 +22,13 @@ import XCTest
 /// Do NOT edit this file directly as it will be regenerated automatically when needed.
 ///
 
-extension Tests {
-    static var allTests: [(String, (Tests) -> () throws -> Void)] {
+extension LifeycleTests {
+    static var allTests: [(String, (LifeycleTests) -> () throws -> Void)] {
         return [
             ("testStartThenShutdown", testStartThenShutdown),
             ("testImmediateShutdown", testImmediateShutdown),
             ("testBadStartup", testBadStartup),
             ("testBadShutdown", testBadShutdown),
-            ("testStartAndWait", testStartAndWait),
-            ("testBadStartAndWait", testBadStartAndWait),
             ("testShutdownInOrder", testShutdownInOrder),
             ("testSync", testSync),
             ("testAyncBarrier", testAyncBarrier),