feat: Adds graceful shutdown to services

Package.swift

@@ -3,7 +3,8 @@
 import PackageDescription
 
 let swiftSettings: [SwiftSetting] = [
-  .enableExperimentalFeature("StrictConcurrency")
+  .enableExperimentalFeature("StrictConcurrency"),
+  .enableUpcomingFeature("InferSendableCaptures")
 ]
 
 let package = Package(
@@ -21,6 +22,7 @@ let package = Package(
   dependencies: [
     .package(url: "https://github.com/swift-server-community/mqtt-nio.git", from: "2.0.0"),
     .package(url: "https://github.com/apple/swift-nio", from: "2.0.0"),
+    .package(url: "https://github.com/apple/swift-log", from: "1.6.0"),
     .package(url: "https://github.com/swift-psychrometrics/swift-psychrometrics", exact: "0.2.3"),
     .package(url: "https://github.com/swift-server/swift-service-lifecycle.git", from: "2.3.0")
   ],
@@ -28,9 +30,12 @@ let package = Package(
     .executableTarget(
       name: "dewPoint-controller",
       dependencies: [
-        "Bootstrap",
+        "Models",
+        "MQTTConnectionService",
+        "SensorsService",
         .product(name: "MQTTNIO", package: "mqtt-nio"),
-        .product(name: "NIO", package: "swift-nio")
+        .product(name: "NIO", package: "swift-nio"),
+        .product(name: "PsychrometricClientLive", package: "swift-psychrometrics")
       ]
     ),
     .testTarget(
@@ -49,6 +54,7 @@ let package = Package(
     .target(
       name: "Models",
       dependencies: [
+        .product(name: "Logging", package: "swift-log"),
         .product(name: "PsychrometricClient", package: "swift-psychrometrics")
       ],
       swiftSettings: swiftSettings
@@ -73,6 +79,7 @@ let package = Package(
       name: "SensorsService",
       dependencies: [
         "Models",
+        "MQTTConnectionService",
         .product(name: "MQTTNIO", package: "mqtt-nio"),
         .product(name: "ServiceLifecycle", package: "swift-service-lifecycle")
       ],

Sources/MQTTConnectionService/MQTTConnectionService.swift

@@ -1,15 +1,22 @@
-import EnvVars
+@preconcurrency import Foundation
 import Logging
+import Models
 import MQTTNIO
 import NIO
 import ServiceLifecycle
 
+// TODO: This may not need to be an actor.
+
 /// Manages the MQTT broker connection.
 public actor MQTTConnectionService: Service {
+
   private let cleanSession: Bool
   public let client: MQTTClient
-  private var shuttingDown = false
+  private let continuation: AsyncStream<Event>.Continuation
+  public nonisolated let events: AsyncStream<Event>
+  private let internalEventStream: ConnectionStream
   nonisolated var logger: Logger { client.logger }
+  // private var shuttingDown = false
 
   public init(
     cleanSession: Bool = true,
@@ -17,6 +24,16 @@ public actor MQTTConnectionService: Service {
   ) {
     self.cleanSession = cleanSession
     self.client = client
+    self.internalEventStream = .init()
+    let (stream, continuation) = AsyncStream.makeStream(of: Event.self)
+    self.events = stream
+    self.continuation = continuation
+  }
+
+  deinit {
+    self.logger.debug("MQTTConnectionService is gone.")
+    self.internalEventStream.stop()
+    continuation.finish()
   }
 
   /// The entry-point of the service.
@@ -25,29 +42,35 @@ public actor MQTTConnectionService: Service {
   /// It will attempt to gracefully shutdown the connection upon receiving
   /// `sigterm` signals.
   public func run() async throws {
-    await withDiscardingTaskGroup { group in
-      await withGracefulShutdownHandler {
+    await withGracefulShutdownHandler {
+      await withDiscardingTaskGroup { group in
         group.addTask { await self.connect() }
-      } onGracefulShutdown: {
-        // try? self.client.syncShutdownGracefully()
-        Task { await self.shutdown() }
+        group.addTask {
+          await self.internalEventStream.start { self.client.isActive() }
+        }
+        for await event in self.internalEventStream.events.cancelOnGracefulShutdown() {
+          if event == .shuttingDown {
+            self.shutdown()
+            break
+          }
+          self.logger.trace("Sending connection event: \(event)")
+          self.continuation.yield(event)
+        }
+        group.cancelAll()
       }
+    } onGracefulShutdown: {
+      self.logger.trace("Received graceful shutdown.")
+      self.shutdown()
     }
   }
 
-  func shutdown() async {
-    shuttingDown = true
-    try? await client.disconnect()
-    try? await client.shutdown()
-  }
-
   func connect() async {
     do {
       try await withThrowingDiscardingTaskGroup { group in
         group.addTask {
           try await self.client.connect(cleanSession: self.cleanSession)
         }
-        client.addCloseListener(named: "SensorsClient") { [self] _ in
+        client.addCloseListener(named: "\(Self.self)") { _ in
           Task {
             self.logger.debug("Connection closed.")
             self.logger.debug("Reconnecting...")
@@ -55,22 +78,75 @@ public actor MQTTConnectionService: Service {
           }
         }
         self.logger.debug("Connection successful.")
+        self.continuation.yield(.connected)
       }
     } catch {
-      logger.trace("Failed to connect.")
+      logger.trace("Failed to connect: \(error)")
+      continuation.yield(.disconnected)
     }
-//     do {
-//       try await client.connect(cleanSession: cleanSession)
-//       client.addCloseListener(named: "SensorsClient") { [self] _ in
-//         Task {
-//           self.logger.debug("Connection closed.")
-//           self.logger.debug("Reconnecting...")
-//           await self.connect()
-//         }
-//       }
-//       logger.debug("Connection successful.")
-//     } catch {
-//       logger.trace("Connection Failed.\(error)")
-//     }
   }
+
+  private nonisolated func shutdown() {
+    logger.debug("Begin shutting down MQTT broker connection.")
+    client.removeCloseListener(named: "\(Self.self)")
+    internalEventStream.stop()
+    // continuation.yield(.shuttingDown)
+    _ = client.disconnect()
+    try? client.syncShutdownGracefully()
+    continuation.finish()
+    logger.info("MQTT broker connection closed.")
+  }
+
+}
+
+extension MQTTConnectionService {
+
+  public enum Event: Sendable {
+    case connected
+    case disconnected
+    case shuttingDown
+  }
+
+  // TODO: This functionality can probably move into the connection service.
+
+  private final class ConnectionStream: Sendable {
+
+    // private var cancellable: AnyCancellable?
+    private let continuation: AsyncStream<MQTTConnectionService.Event>.Continuation
+    let events: AsyncStream<MQTTConnectionService.Event>
+
+    init() {
+      let (stream, continuation) = AsyncStream.makeStream(of: MQTTConnectionService.Event.self)
+      self.events = stream
+      self.continuation = continuation
+    }
+
+    deinit {
+      stop()
+    }
+
+    func start(isActive connectionIsActive: @escaping () -> Bool) async {
+      try? await Task.sleep(for: .seconds(1))
+      let event: MQTTConnectionService.Event = connectionIsActive()
+        ? .connected
+        : .disconnected
+
+      continuation.yield(event)
+//       cancellable = Timer.publish(every: 1.0, on: .main, in: .common)
+//         .autoconnect()
+//         .sink { [weak self] (_: Date) in
+//           let event: MQTTConnectionService.Event = connectionIsActive()
+//             ? .connected
+//             : .disconnected
+//
+//           self?.continuation.yield(event)
+//         }
+    }
+
+    func stop() {
+      continuation.yield(.shuttingDown)
+      continuation.finish()
+    }
+  }
+
 }

Sources/Models/EnvVars.swift

@@ -1,4 +1,5 @@
 import Foundation
+import Logging
 
 /// Holds common settings for connecting to your MQTT broker.  The default values can be used,
 /// they can be loaded from the shell environment, or from a file located in the root directory.

Sources/SensorsService/SensorsService.swift

@@ -1,6 +1,7 @@
 import Foundation
 import Logging
 import Models
+import MQTTConnectionService
 @preconcurrency import MQTTNIO
 import NIO
 import PsychrometricClient
@@ -9,13 +10,17 @@ import ServiceLifecycle
 public actor SensorsService: Service {
   private var sensors: [TemperatureAndHumiditySensor]
   private let client: MQTTClient
-  var logger: Logger { client.logger }
+  private let events: @Sendable () -> AsyncStream<MQTTConnectionService.Event>
+  nonisolated var logger: Logger { client.logger }
+  private var shuttingDown: Bool = false
 
   public init(
     client: MQTTClient,
+    events: @Sendable @escaping () -> AsyncStream<MQTTConnectionService.Event>,
     sensors: [TemperatureAndHumiditySensor]
   ) {
     self.client = client
+    self.events = events
     self.sensors = sensors
   }
 
@@ -25,50 +30,90 @@ public actor SensorsService: Service {
   /// listening for sensor value changes then publishing the dew-point
   /// and enthalpy values of the sensors.
   public func run() async throws {
-    guard client.isActive() else {
-      throw MQTTClientNotConnected()
-    }
-    try await withThrowingDiscardingTaskGroup { group in
-      group.addTask { try await self.subscribeToSensors() }
-      for await result in client.createPublishListener().cancelOnGracefulShutdown() {
-        group.addTask {
-          try await self.handleResult(result)
+    do {
+      try await withGracefulShutdownHandler {
+        try await withThrowingDiscardingTaskGroup { group in
+          client.addPublishListener(named: "\(Self.self)") { result in
+            if self.shuttingDown {
+              self.logger.trace("Shutting down.")
+            } else if !self.client.isActive() {
+              self.logger.trace("Client is not currently active")
+            } else {
+              Task { try await self.handleResult(result) }
+            }
+          }
+          for await event in self.events().cancelOnGracefulShutdown() {
+            logger.trace("Received event: \(event)")
+            if event == .shuttingDown {
+              self.setIsShuttingDown()
+            } else if event == .connected {
+              group.addTask { try await self.subscribeToSensors() }
+            } else {
+              group.addTask { await self.unsubscribeToSensors() }
+              group.addTask { try? await Task.sleep(for: .milliseconds(100)) }
+            }
+          }
         }
+      } onGracefulShutdown: {
+        // do something.
+        self.logger.debug("Received graceful shutdown.")
+        Task { [weak self] in await self?.setIsShuttingDown() }
       }
+    } catch {
+      // WARN: We always get an MQTTNIO `noConnection` error here, which generally is not an issue,
+      // but causes service ServiceLifecycle to fail, so currently just ignoring errors that are thrown.
+      // However we do receive the unsubscribe message back from the MQTT broker, so it is likely safe
+      // to ignore the `noConnection` error.
+      logger.trace("Run error: \(error)")
+      // throw error
     }
   }
 
+  private func setIsShuttingDown() {
+    logger.debug("Received shut down event.")
+    Task { try await publishUpdates() }
+    Task { await self.unsubscribeToSensors() }
+    shuttingDown = true
+    client.removePublishListener(named: "\(Self.self)")
+  }
+
   private func handleResult(
     _ result: Result<MQTTPublishInfo, any Error>
   ) async throws {
-    switch result {
-    case let .failure(error):
-      logger.debug("Failed receiving sensor: \(error)")
-      throw error
-    case let .success(value):
-      // do something.
-      let topic = value.topicName
-      logger.trace("Received new value for topic: \(topic)")
-      if topic.contains("temperature") {
+    logger.trace("Begin handling result")
+    do {
+      switch result {
+      case let .failure(error):
+        logger.debug("Failed receiving sensor: \(error)")
+        throw error
+      case let .success(value):
         // do something.
-        var buffer = value.payload
-        guard let temperature = DryBulb(buffer: &buffer) else {
-          logger.trace("Decoding error for topic: \(topic)")
-          throw DecodingError()
-        }
-        try sensors.update(topic: topic, keyPath: \.temperature, with: temperature)
-        try await publishUpdates()
+        let topic = value.topicName
+        logger.trace("Received new value for topic: \(topic)")
+        if topic.contains("temperature") {
+          // do something.
+          var buffer = value.payload
+          guard let temperature = DryBulb(buffer: &buffer) else {
+            logger.trace("Decoding error for topic: \(topic)")
+            throw DecodingError()
+          }
+          try sensors.update(topic: topic, keyPath: \.temperature, with: temperature)
+          try await publishUpdates()
 
-      } else if topic.contains("humidity") {
-        var buffer = value.payload
-        // Decode and update the temperature value
-        guard let humidity = RelativeHumidity(buffer: &buffer) else {
-          logger.debug("Failed to decode humidity from buffer: \(buffer)")
-          throw DecodingError()
+        } else if topic.contains("humidity") {
+          var buffer = value.payload
+          // Decode and update the temperature value
+          guard let humidity = RelativeHumidity(buffer: &buffer) else {
+            logger.debug("Failed to decode humidity from buffer: \(buffer)")
+            throw DecodingError()
+          }
+          try sensors.update(topic: topic, keyPath: \.humidity, with: humidity)
+          try await publishUpdates()
         }
-        try sensors.update(topic: topic, keyPath: \.humidity, with: humidity)
-        try await publishUpdates()
       }
+    } catch {
+      logger.trace("Handle Result error: \(error)")
+      throw error
     }
   }
 
@@ -82,7 +127,26 @@ public actor SensorsService: Service {
     }
   }
 
+  private func unsubscribeToSensors() async {
+    logger.trace("Begin unsubscribe to sensors.")
+    guard client.isActive() else {
+      logger.debug("Client is not active, skipping.")
+      return
+    }
+    do {
+      let topics = sensors.reduce(into: [String]()) { array, sensor in
+        array.append(sensor.topics.temperature)
+        array.append(sensor.topics.humidity)
+      }
+      try await client.unsubscribe(from: topics)
+      logger.trace("Unsubscribed from sensors.")
+    } catch {
+      logger.trace("Unsubscribe error: \(error)")
+    }
+  }
+
   private func publish(double: Double?, to topic: String) async throws {
+    guard client.isActive() else { return }
     guard let double else { return }
     let rounded = round(double * 100) / 100
     logger.debug("Publishing \(rounded), to: \(topic)")

Sources/dewPoint-controller/Application.swift

@@ -0,0 +1,101 @@
+import Foundation
+import Logging
+import Models
+import MQTTConnectionService
+import MQTTNIO
+import NIO
+import PsychrometricClientLive
+import SensorsService
+import ServiceLifecycle
+
+@main
+struct Application {
+  /// The main entry point of the application.
+  static func main() async throws {
+    let eventloopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 1)
+    var logger = Logger(label: "dewpoint-controller")
+    logger.logLevel = .trace
+
+    logger.info("Starting dewpoint-controller!")
+
+    let environment = loadEnvVars(logger: logger)
+
+    if environment.appEnv == .production {
+      logger.debug("Updating logging level to info.")
+      logger.logLevel = .info
+    }
+
+    let mqtt = MQTTClient(
+      envVars: environment,
+      eventLoopGroup: eventloopGroup,
+      logger: logger
+    )
+
+    let mqttConnection = MQTTConnectionService(client: mqtt)
+    let sensors = SensorsService(
+      client: mqtt,
+      events: { mqttConnection.events },
+      sensors: .live
+    )
+
+    let serviceGroup = ServiceGroup(
+      services: [
+        mqttConnection,
+        sensors
+      ],
+      gracefulShutdownSignals: [.sigterm, .sigint],
+      logger: logger
+    )
+
+    try await serviceGroup.run()
+  }
+}
+
+// MARK: - Helpers
+
+private func loadEnvVars(logger: Logger) -> EnvVars {
+  let defaultEnvVars = EnvVars()
+  let encoder = JSONEncoder()
+  let decoder = JSONDecoder()
+
+  let defaultEnvDict = (try? encoder.encode(defaultEnvVars))
+    .flatMap { try? decoder.decode([String: String].self, from: $0) }
+    ?? [:]
+
+  let envVarsDict = defaultEnvDict
+    .merging(ProcessInfo.processInfo.environment, uniquingKeysWith: { $1 })
+
+  let envVars = (try? JSONSerialization.data(withJSONObject: envVarsDict))
+    .flatMap { try? decoder.decode(EnvVars.self, from: $0) }
+    ?? defaultEnvVars
+
+  logger.debug("Done loading EnvVars...")
+
+  return envVars
+}
+
+private extension MQTTNIO.MQTTClient {
+  convenience init(envVars: EnvVars, eventLoopGroup: EventLoopGroup, logger: Logger?) {
+    self.init(
+      host: envVars.host,
+      port: envVars.port != nil ? Int(envVars.port!) : nil,
+      identifier: envVars.identifier,
+      eventLoopGroupProvider: .shared(eventLoopGroup),
+      logger: logger,
+      configuration: .init(
+        version: .v5_0,
+        disablePing: false,
+        userName: envVars.userName,
+        password: envVars.password
+      )
+    )
+  }
+}
+
+private extension Array where Element == TemperatureAndHumiditySensor {
+  static var live: Self {
+    TemperatureAndHumiditySensor.Location.allCases.map { location in
+      TemperatureAndHumiditySensor(location: location)
+    }
+  }
+}

Tests/MQTTConnectionServiceTests/MQTTConnectionServiceTests.swift

@@ -1,5 +1,6 @@
-import EnvVars
+import Combine
 import Logging
+import Models
 @testable import MQTTConnectionService
 import MQTTNIO
 import NIO
@@ -25,6 +26,8 @@ final class MQTTConnectionServiceTests: XCTestCase {
       try await Task.sleep(for: .seconds(1))
       XCTAssert(client.isActive())
       trigger.triggerGracefulShutdown()
+      // try await Task.sleep(for: .seconds(2))
+      // XCTAssertFalse(client.isActive())
     }
   }
 
@@ -55,4 +58,65 @@ final class MQTTConnectionServiceTests: XCTestCase {
     )
   }
 
+  func testEventStream() async throws {
+    var connection: ConnectionStream? = ConnectionStream()
+
+    let task = Task {
+      guard let events = connection?.events else { return }
+      print("before loop")
+      for await event in events {
+        print("\(event)")
+      }
+      print("after loop")
+    }
+
+    let ending = Task {
+      try await Task.sleep(for: .seconds(2))
+      connection = nil
+    }
+
+    connection?.start()
+    try await ending.value
+    task.cancel()
+  }
+
+}
+
+class ConnectionStream {
+
+  enum Event {
+    case connected
+    case disconnected
+    case shuttingDown
+  }
+
+  let events: AsyncStream<Event>
+  private let continuation: AsyncStream<Event>.Continuation
+  private var cancellable: AnyCancellable?
+
+  init() {
+    let (stream, continuation) = AsyncStream.makeStream(of: Event.self)
+    self.events = stream
+    self.continuation = continuation
+  }
+
+  deinit {
+    print("connection stream is gone.")
+    stop()
+  }
+
+  func start() {
+    cancellable = Timer.publish(every: 1.0, on: .main, in: .common)
+      .autoconnect()
+      .sink { [weak self] _ in
+        print("will send event.")
+        self?.continuation.yield(.connected)
+      }
+  }
+
+  func stop() {
+    continuation.yield(.shuttingDown)
+    cancellable = nil
+    continuation.finish()
+  }
 }

Tests/SensorsServiceTests/SensorsClientTests.swift

@@ -1,6 +1,4 @@
-@testable import ClientLive
 import Dependencies
-import EnvVars
 import Logging
 import Models
 import MQTTNIO

docker-compose.yaml

@@ -5,6 +5,17 @@ services:
     restart: unless-stopped
     env_file: .env
 
+  local:
+    container_name: local-server
+    build:
+      context: .
+      dockerfile: Dockerfile
+    platform: linux/amd64
+    depends_on:
+      - mosquitto
+    environment:
+      - MOSQUITTO_SERVER=mosquitto
+
   test:
     build:
       context: .