Merge pull request #19 from uber/executor-track_task_id-master

Allow tracking task ID to support reporting timeout error details

Author: rudro

Concurrency.xcodeproj/project.pbxproj

@@ -40,7 +40,7 @@
 		41B94842210A4744007E59C8 /* Task.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Task.swift; sourceTree = "<group>"; };
 		41B94848210A4756007E59C8 /* ConcurrentSequenceExecutorTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ConcurrentSequenceExecutorTests.swift; sourceTree = "<group>"; };
 		"Concurrency::Concurrency::Product" /* Concurrency.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; path = Concurrency.framework; sourceTree = BUILT_PRODUCTS_DIR; };
-		"Concurrency::ConcurrencyTests::Product" /* ConcurrencyTests.xctest */ = {isa = PBXFileReference; lastKnownFileType = file; path = ConcurrencyTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
+		"Concurrency::ConcurrencyTests::Product" /* ConcurrencyTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; path = ConcurrencyTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		OBJ_10 /* AtomicInt.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AtomicInt.swift; sourceTree = "<group>"; };
 		OBJ_11 /* AtomicReference.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AtomicReference.swift; sourceTree = "<group>"; };
 		OBJ_12 /* CountDownLatch.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CountDownLatch.swift; sourceTree = "<group>"; };
@@ -193,7 +193,7 @@
 		OBJ_1 /* Project object */ = {
 			isa = PBXProject;
 			attributes = {
-				LastUpgradeCheck = 9999;
+				LastUpgradeCheck = 1000;
 			};
 			buildConfigurationList = OBJ_2 /* Build configuration list for PBXProject "Concurrency" */;
 			compatibilityVersion = "Xcode 3.2";
@@ -302,12 +302,38 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = NO;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
 				ENABLE_NS_ASSERTIONS = YES;
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				ENABLE_TESTABILITY = YES;
+				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_OPTIMIZATION_LEVEL = 0;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				ONLY_ACTIVE_ARCH = YES;
@@ -325,11 +351,36 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				CLANG_ENABLE_OBJC_ARC = YES;
+				CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES;
+				CLANG_WARN_BOOL_CONVERSION = YES;
+				CLANG_WARN_COMMA = YES;
+				CLANG_WARN_CONSTANT_CONVERSION = YES;
+				CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES;
+				CLANG_WARN_EMPTY_BODY = YES;
+				CLANG_WARN_ENUM_CONVERSION = YES;
+				CLANG_WARN_INFINITE_RECURSION = YES;
+				CLANG_WARN_INT_CONVERSION = YES;
+				CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES;
+				CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES;
+				CLANG_WARN_OBJC_LITERAL_CONVERSION = YES;
+				CLANG_WARN_RANGE_LOOP_ANALYSIS = YES;
+				CLANG_WARN_STRICT_PROTOTYPES = YES;
+				CLANG_WARN_SUSPICIOUS_MOVE = YES;
+				CLANG_WARN_UNREACHABLE_CODE = YES;
+				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COMBINE_HIDPI_IMAGES = YES;
 				COPY_PHASE_STRIP = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DYLIB_INSTALL_NAME_BASE = "@rpath";
+				ENABLE_STRICT_OBJC_MSGSEND = YES;
+				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_OPTIMIZATION_LEVEL = s;
+				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
+				GCC_WARN_ABOUT_RETURN_TYPE = YES;
+				GCC_WARN_UNDECLARED_SELECTOR = YES;
+				GCC_WARN_UNINITIALIZED_AUTOS = YES;
+				GCC_WARN_UNUSED_FUNCTION = YES;
+				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				OTHER_SWIFT_FLAGS = "-DXcode";
@@ -345,7 +396,7 @@
 		OBJ_45 /* Debug */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				EMBEDDED_CONTENT_CONTAINS_SWIFT = YES;
+				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PLATFORM_DIR)/Developer/Library/Frameworks",
@@ -364,7 +415,7 @@
 		OBJ_46 /* Release */ = {
 			isa = XCBuildConfiguration;
 			buildSettings = {
-				EMBEDDED_CONTENT_CONTAINS_SWIFT = YES;
+				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				FRAMEWORK_SEARCH_PATHS = (
 					"$(inherited)",
 					"$(PLATFORM_DIR)/Developer/Library/Frameworks",

Concurrency.xcodeproj/xcshareddata/xcschemes/Concurrency-Package.xcscheme renamed to Concurrency.xcodeproj/xcshareddata/xcschemes/Concurrency.xcscheme

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "9999"
+   LastUpgradeVersion = "1000"
    version = "1.3">
    <BuildAction
       parallelizeBuildables = "YES"
@@ -28,16 +28,6 @@
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
       <Testables>
-         <TestableReference
-            skipped = "NO">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "Concurrency::ConcurrencyTests"
-               BuildableName = "ConcurrencyTests.xctest"
-               BlueprintName = "ConcurrencyTests"
-               ReferencedContainer = "container:Concurrency.xcodeproj">
-            </BuildableReference>
-         </TestableReference>
       </Testables>
       <AdditionalOptions>
       </AdditionalOptions>
@@ -70,6 +60,15 @@
       savedToolIdentifier = ""
       useCustomWorkingDirectory = "NO"
       debugDocumentVersioning = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "Concurrency::Concurrency"
+            BuildableName = "Concurrency.framework"
+            BlueprintName = "Concurrency"
+            ReferencedContainer = "container:Concurrency.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
    </ProfileAction>
    <AnalyzeAction
       buildConfiguration = "Debug">

Concurrency.xcodeproj/xcshareddata/xcschemes/ConcurrencyTests.xcscheme

@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Scheme
+   LastUpgradeVersion = "1000"
+   version = "1.3">
+   <BuildAction
+      parallelizeBuildables = "YES"
+      buildImplicitDependencies = "YES">
+   </BuildAction>
+   <TestAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      shouldUseLaunchSchemeArgsEnv = "YES">
+      <Testables>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "Concurrency::ConcurrencyTests"
+               BuildableName = "ConcurrencyTests.xctest"
+               BlueprintName = "ConcurrencyTests"
+               ReferencedContainer = "container:Concurrency.xcodeproj">
+            </BuildableReference>
+         </TestableReference>
+      </Testables>
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </TestAction>
+   <LaunchAction
+      buildConfiguration = "Debug"
+      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
+      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
+      launchStyle = "0"
+      useCustomWorkingDirectory = "NO"
+      ignoresPersistentStateOnLaunch = "NO"
+      debugDocumentVersioning = "YES"
+      debugServiceExtension = "internal"
+      allowLocationSimulation = "YES">
+      <AdditionalOptions>
+      </AdditionalOptions>
+   </LaunchAction>
+   <ProfileAction
+      buildConfiguration = "Release"
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      savedToolIdentifier = ""
+      useCustomWorkingDirectory = "NO"
+      debugDocumentVersioning = "YES">
+   </ProfileAction>
+   <AnalyzeAction
+      buildConfiguration = "Debug">
+   </AnalyzeAction>
+   <ArchiveAction
+      buildConfiguration = "Release"
+      revealArchiveInOrganizer = "YES">
+   </ArchiveAction>
+</Scheme>

Sources/Concurrency/Executor/ConcurrentSequenceExecutor.swift

@@ -27,8 +27,15 @@ public class ConcurrentSequenceExecutor: SequenceExecutor {
     /// - parameter name: The name of the executor.
     /// - parameter qos: The quality of service of this executor. This
     /// defaults to `userInitiated`.
-    public init(name: String, qos: DispatchQoS = .userInitiated) {
+    /// - parameter shouldTackTaskId: `true` if task IDs should be tracked
+    /// as tasks are executed. `false` otherwise. By tracking the task IDs,
+    /// if waiting on the completion of a task sequence times out, the
+    /// reported error contains the ID of the task that was being executed
+    /// when the timeout occurred. The tracking does incur a minor
+    /// performance cost. This value defaults to `false`.
+    public init(name: String, qos: DispatchQoS = .userInitiated, shouldTackTaskId: Bool = false) {
         taskQueue = DispatchQueue(label: "Executor.taskQueue-\(name)", qos: qos, attributes: .concurrent)
+        self.shouldTackTaskId = shouldTackTaskId
     }
 
     /// Execute a sequence of tasks concurrently from the given initial task.
@@ -51,13 +58,18 @@ public class ConcurrentSequenceExecutor: SequenceExecutor {
     // MARK: - Private
 
     private let taskQueue: DispatchQueue
+    private let shouldTackTaskId: Bool
 
     private func execute<SequenceResultType>(_ task: Task, with sequenceHandle: SynchronizedSequenceExecutionHandle<SequenceResultType>, _ execution: @escaping (Task, Any) -> SequenceExecution<SequenceResultType>) {
         taskQueue.async {
             guard !sequenceHandle.isCancelled else {
                 return
             }
 
+            if self.shouldTackTaskId {
+                sequenceHandle.willBeginExecuting(taskId: task.id)
+            }
+
             let result = task.typeErasedExecute()
             let nextExecution = execution(task, result)
             switch nextExecution {
@@ -74,6 +86,7 @@ private class SynchronizedSequenceExecutionHandle<SequenceResultType>: SequenceE
 
     private let latch = CountDownLatch(count: 1)
     private let didCancel = AtomicBool(initialValue: false)
+    private let currentTaskId = AtomicInt(initialValue: nonTrackingDefaultTaskId)
 
     // Use a lock to ensure result is properly accessed, since the read
     // `await` method may be invoked on a different thread than the write
@@ -85,10 +98,14 @@ private class SynchronizedSequenceExecutionHandle<SequenceResultType>: SequenceE
         return didCancel.value
     }
 
+    fileprivate func willBeginExecuting(taskId: Int) {
+        currentTaskId.value = taskId
+    }
+
     fileprivate override func await(withTimeout timeout: TimeInterval?) throws -> SequenceResultType {
         let didComplete = latch.await(timeout: timeout)
         if !didComplete {
-            throw SequenceExecutionError.awaitTimeout
+            throw SequenceExecutionError.awaitTimeout(currentTaskId.value)
         }
 
         resultLock.lock()

Sources/Concurrency/Executor/SequenceExecutor.swift

@@ -18,8 +18,12 @@ import Foundation
 
 /// Errors that can occur during a sequence execution.
 public enum SequenceExecutionError: Error {
-    /// The waiting on sequence completion timed out.
-    case awaitTimeout
+    /// The waiting on sequence completion timed out. The `Int` value
+    /// indicates the ID of the task that was being executed when the
+    /// timeout occurred. If the value is `nonTrackingDefaultTaskId`,
+    /// then the executor was not configured to track task IDs during
+    /// initialization.
+    case awaitTimeout(Int)
 }
 
 /// The handle of the execution of a sequence of tasks, that allows control

Sources/Concurrency/Executor/Task.swift

@@ -16,12 +16,17 @@
 
 import Foundation
 
+public let nonTrackingDefaultTaskId = Int.min
+
 /// An individual unit of work that can be executed in a concurrent
 /// environment by an executor.
 // Task cannot be generic since it needs to be referenced by the executor
 // class which cannot provide type information for specific tasks.
 public protocol Task {
 
+    /// A unique ID number identifying the task.
+    var id: Int { get }
+
     /// Execute this task without any type information.
     ///
     /// - note: This method should only be used by internal executor
@@ -41,8 +46,16 @@ public protocol Task {
 // wildcard generics.
 open class AbstractTask<ResultType>: Task {
 
+    /// A unique ID number identifying the task.
+    public let id: Int
+
     /// Initializer.
-    public init() {}
+    ///
+    /// - parameter id: A unique ID number identifying the task. This value
+    /// defaults to `nonTrackingDefaultTaskId`.
+    public init(id: Int = nonTrackingDefaultTaskId) {
+        self.id = id
+    }
 
     /// Execute this task without any type information.
     ///

Tests/ConcurrencyTests/Executor/ConcurrentSequenceExecutorTests.swift

@@ -122,14 +122,14 @@ class ConcurrentSequenceExecutorTests: XCTestCase {
     }
 
     func test_executeSequence_withNonTerminatingSequence_withTimeout_verifyAwaitTimeout() {
-        let executor = ConcurrentSequenceExecutor(name: "test_executeSequence_withNonTerminatingSequence_withTimeout_verifyAwaitTimeout")
+        let executor = ConcurrentSequenceExecutor(name: "test_executeSequence_withNonTerminatingSequence_withTimeout_verifyAwaitTimeout", shouldTackTaskId: true)
 
-        let sequencedTask = MockSelfRepeatingTask {
+        let sequencedTask = MockSelfRepeatingTask(id: 123) {
             return 0
         }
 
         let handle = executor.executeSequence(from: sequencedTask) { _, _ -> SequenceExecution<Int> in
-            return .continueSequence(MockSelfRepeatingTask {
+            return .continueSequence(MockSelfRepeatingTask(id: 123) {
                 return 0
             })
         }
@@ -138,10 +138,11 @@ class ConcurrentSequenceExecutorTests: XCTestCase {
         let startTime = CACurrentMediaTime()
         do {
             _ = try handle.await(withTimeout: 0.5)
-        } catch SequenceExecutionError.awaitTimeout {
+        } catch SequenceExecutionError.awaitTimeout(let id) {
             didThrowError = true
             let endTime = CACurrentMediaTime()
             XCTAssertTrue((endTime - startTime) >= 0.5)
+            XCTAssertEqual(id, 123)
         } catch {
             XCTFail("Incorrect error thrown: \(error)")
         }
@@ -154,8 +155,9 @@ class MockSelfRepeatingTask: AbstractTask<Int> {
 
     private let execution: () -> Int
 
-    init(execution: @escaping () -> Int) {
+    init(id: Int = nonTrackingDefaultTaskId, execution: @escaping () -> Int) {
         self.execution = execution
+        super.init(id: id)
     }
 
     override func execute() -> Int {