Remove dependency on DispatchWallTime (fix #384)

Sources/AWSLambdaRuntime/FoundationSupport/Context+Foundation.swift

@@ -20,9 +20,12 @@ import struct Foundation.Date
 #endif
 
 extension LambdaContext {
+    /// Returns the deadline as a Date for the Lambda function execution.
+    /// I'm not sure how usefull it is to have this as a Date, with only seconds precision,
+    /// but I leave it here for compatibility with the FoundationJSONSupport trait.
     var deadlineDate: Date {
-        let secondsSinceEpoch = Double(Int64(bitPattern: self.deadline.rawValue)) / -1_000_000_000
-        return Date(timeIntervalSince1970: secondsSinceEpoch)
+        // Date(timeIntervalSince1970:) expects seconds, so we convert milliseconds to seconds.
+        Date(timeIntervalSince1970: Double(self.deadline.millisecondsSinceEpoch()) / 1000)
     }
 }
 #endif  // trait: FoundationJSONSupport

Sources/AWSLambdaRuntime/Lambda+LocalServer.swift

@@ -650,7 +650,7 @@ internal struct LambdaHTTPServer {
                     "arn:aws:lambda:us-east-1:\(Int16.random(in: Int16.min ... Int16.max)):function:custom-runtime"
                 ),
                 (AmazonHeaders.traceID, "Root=\(AmazonHeaders.generateXRayTraceID());Sampled=1"),
-                (AmazonHeaders.deadline, "\(DispatchWallTime.distantFuture.millisSinceEpoch)"),
+                (AmazonHeaders.deadline, "\(LambdaClock.maxLambdaDeadline)"),
             ])
 
             return LocalServerResponse(

Sources/AWSLambdaRuntime/Lambda.swift

@@ -70,8 +70,8 @@ public enum Lambda {
                             requestID: invocation.metadata.requestID,
                             traceID: invocation.metadata.traceID,
                             invokedFunctionARN: invocation.metadata.invokedFunctionARN,
-                            deadline: DispatchWallTime(
-                                millisSinceEpoch: invocation.metadata.deadlineInMillisSinceEpoch
+                            deadline: LambdaClock.Instant(
+                                millisecondsSinceEpoch: invocation.metadata.deadlineInMillisSinceEpoch
                             ),
                             logger: logger
                         )

Sources/AWSLambdaRuntime/LambdaClock.swift

@@ -0,0 +1,184 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftAWSLambdaRuntime open source project
+//
+// Copyright (c) 2025 Apple Inc. and the SwiftAWSLambdaRuntime project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+#if os(macOS)
+import Darwin.C
+#elseif canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import ucrt
+#else
+#error("Unsupported platform")
+#endif
+
+/// A clock implementation based on Unix epoch time for AWS Lambda runtime operations.
+///
+/// `LambdaClock` provides millisecond-precision timing based on the Unix epoch
+/// (January 1, 1970, 00:00:00 UTC). This clock is designed for Lambda runtime
+/// operations where precise wall-clock time is required.
+///
+/// ## Usage
+///
+/// ```swift
+/// let clock = LambdaClock()
+/// let now = clock.now
+/// let deadline = now.advanced(by: .seconds(30))
+///
+/// // Sleep until deadline
+/// try await clock.sleep(until: deadline)
+/// ```
+///
+/// ## Performance
+///
+/// This clock uses `clock_gettime(CLOCK_REALTIME)` on Unix systems for
+/// high-precision wall-clock time measurement with millisecond resolution.
+///
+/// ## TimeZone Handling
+///
+/// The Lambda execution environment uses UTC as a timezone,
+/// `LambdaClock` operates in UTC and does not account for time zones.
+/// see: TZ in https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
+public struct LambdaClock: Clock {
+    public typealias Duration = Swift.Duration
+
+    /// A moment in time represented as milliseconds since the Unix epoch.
+    ///
+    /// `Instant` represents a specific point in time as the number of milliseconds
+    /// that have elapsed since January 1, 1970, 00:00:00 UTC (Unix epoch).
+    ///
+    /// ## Thread Safety
+    ///
+    /// `Instant` is a value type and is inherently thread-safe.
+    public struct Instant: InstantProtocol {
+        /// The number of milliseconds since the Unix epoch.
+        let instant: Int64
+
+        public typealias Duration = Swift.Duration
+
+        /// Creates a new instant by adding a duration to this instant.
+        ///
+        /// - Parameter duration: The duration to add to this instant.
+        /// - Returns: A new instant advanced by the specified duration.
+        ///
+        /// ## Example
+        ///
+        /// ```swift
+        /// let now = LambdaClock().now
+        /// let future = now.advanced(by: .seconds(30))
+        /// ```
+        public func advanced(by duration: Duration) -> Instant {
+            .init(millisecondsSinceEpoch: Int64(instant + Int64(duration / .milliseconds(1))))
+        }
+
+        /// Calculates the duration between this instant and another instant.
+        ///
+        /// - Parameter other: The target instant to calculate duration to.
+        /// - Returns: The duration from this instant to the other instant.
+        ///           Positive if `other` is in the future, negative if in the past.
+        ///
+        /// ## Example
+        ///
+        /// ```swift
+        /// let start = LambdaClock().now
+        /// // ... some work ...
+        /// let end = LambdaClock().now
+        /// let elapsed = start.duration(to: end)
+        /// ```
+        public func duration(to other: Instant) -> Duration {
+            .milliseconds(other.instant - self.instant)
+        }
+
+        /// Compares two instants for ordering.
+        ///
+        /// - Parameters:
+        ///   - lhs: The left-hand side instant.
+        ///   - rhs: The right-hand side instant.
+        /// - Returns: `true` if `lhs` represents an earlier time than `rhs`.
+        public static func < (lhs: Instant, rhs: Instant) -> Bool {
+            lhs.instant < rhs.instant
+        }
+
+        /// Returns this instant as the number of milliseconds since the Unix epoch.
+        /// - Returns: The number of milliseconds since the Unix epoch.
+        public func millisecondsSinceEpoch() -> Int64 {
+            self.instant
+        }
+
+        /// Creates an instant from milliseconds since the Unix epoch.
+        /// - Parameter milliseconds: The number of milliseconds since the Unix epoch.
+        public init(millisecondsSinceEpoch milliseconds: Int64) {
+            self.instant = milliseconds
+        }
+    }
+
+    /// The current instant according to this clock.
+    ///
+    /// This property returns the current wall-clock time as milliseconds
+    /// since the Unix epoch.
+    /// This method uses `clock_gettime(CLOCK_REALTIME)` to obtain high-precision
+    /// wall-clock time.
+    ///
+    /// - Returns: An `Instant` representing the current time.
+    public var now: Instant {
+        var ts = timespec()
+        clock_gettime(CLOCK_REALTIME, &ts)
+        return .init(millisecondsSinceEpoch: Int64(ts.tv_sec) * 1000 + Int64(ts.tv_nsec) / 1_000_000)
+    }
+
+    /// The minimum resolution of this clock.
+    ///
+    /// `LambdaClock` provides millisecond resolution.
+    public var minimumResolution: Duration {
+        .milliseconds(1)
+    }
+
+    /// Suspends the current task until the specified deadline.
+    ///
+    /// - Parameters:
+    ///   - deadline: The instant until which to sleep.
+    ///   - tolerance: The allowed tolerance for the sleep duration. Currently unused.
+    ///
+    /// - Throws: `CancellationError` if the task is cancelled during sleep.
+    ///
+    /// ## Example
+    ///
+    /// ```swift
+    /// let clock = LambdaClock()
+    /// let deadline = clock.now.advanced(by: .seconds(5))
+    /// try await clock.sleep(until: deadline)
+    /// ```
+    public func sleep(until deadline: Instant, tolerance: Instant.Duration?) async throws {
+        let now = self.now
+        let sleepDuration = now.duration(to: deadline)
+        if sleepDuration > .zero {
+            try await ContinuousClock().sleep(for: sleepDuration)
+        }
+    }
+
+    /// Hardcoded maximum execution time for a Lambda function.
+    public static var maxLambdaExecutionTime: Duration {
+        // 15 minutes in milliseconds
+        // see https://docs.aws.amazon.com/lambda/latest/dg/configuration-timeout.html
+        .milliseconds(15 * 60 * 1000)
+    }
+
+    /// Returns the maximum deadline for a Lambda function execution.
+    /// This is the current time plus the maximum execution time.
+    /// This function is only used by the local server for testing purposes.
+    public static var maxLambdaDeadline: Instant {
+        LambdaClock().now.advanced(by: maxLambdaExecutionTime)
+    }
+}

Sources/AWSLambdaRuntime/LambdaContext.swift

@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Dispatch
 import Logging
 import NIOCore
 
@@ -89,7 +88,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
         let requestID: String
         let traceID: String
         let invokedFunctionARN: String
-        let deadline: DispatchWallTime
+        let deadline: LambdaClock.Instant
         let cognitoIdentity: String?
         let clientContext: ClientContext?
         let logger: Logger
@@ -98,7 +97,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
             requestID: String,
             traceID: String,
             invokedFunctionARN: String,
-            deadline: DispatchWallTime,
+            deadline: LambdaClock.Instant,
             cognitoIdentity: String?,
             clientContext: ClientContext?,
             logger: Logger
@@ -131,7 +130,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
     }
 
     /// The timestamp that the function times out.
-    public var deadline: DispatchWallTime {
+    public var deadline: LambdaClock.Instant {
         self.storage.deadline
     }
 
@@ -156,7 +155,7 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
         requestID: String,
         traceID: String,
         invokedFunctionARN: String,
-        deadline: DispatchWallTime,
+        deadline: LambdaClock.Instant,
         cognitoIdentity: String? = nil,
         clientContext: ClientContext? = nil,
         logger: Logger
@@ -173,30 +172,28 @@ public struct LambdaContext: CustomDebugStringConvertible, Sendable {
     }
 
     public func getRemainingTime() -> Duration {
-        let deadline = self.deadline.millisSinceEpoch
-        let now = DispatchWallTime.now().millisSinceEpoch
-
-        let remaining = deadline - now
-        return .milliseconds(remaining)
+        let deadline = self.deadline
+        return deadline.duration(to: LambdaClock().now)
     }
 
     public var debugDescription: String {
         "\(Self.self)(requestID: \(self.requestID), traceID: \(self.traceID), invokedFunctionARN: \(self.invokedFunctionARN), cognitoIdentity: \(self.cognitoIdentity ?? "nil"), clientContext: \(String(describing: self.clientContext)), deadline: \(self.deadline))"
     }
 
     /// This interface is not part of the public API and must not be used by adopters. This API is not part of semver versioning.
+    /// The timeout is expressed relative to now
     package static func __forTestsOnly(
         requestID: String,
         traceID: String,
         invokedFunctionARN: String,
-        timeout: DispatchTimeInterval,
+        timeout: Duration,
         logger: Logger
     ) -> LambdaContext {
         LambdaContext(
             requestID: requestID,
             traceID: traceID,
             invokedFunctionARN: invokedFunctionARN,
-            deadline: .now() + timeout,
+            deadline: LambdaClock().now.advanced(by: timeout),
             logger: logger
         )
     }

Sources/AWSLambdaRuntime/Utils.swift

@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Dispatch
 import NIOConcurrencyHelpers
 import NIOPosix
 
@@ -39,20 +38,6 @@ enum AmazonHeaders {
     static let invokedFunctionARN = "Lambda-Runtime-Invoked-Function-Arn"
 }
 
-extension DispatchWallTime {
-    @usableFromInline
-    init(millisSinceEpoch: Int64) {
-        let nanoSinceEpoch = UInt64(millisSinceEpoch) * 1_000_000
-        let seconds = UInt64(nanoSinceEpoch / 1_000_000_000)
-        let nanoseconds = nanoSinceEpoch - (seconds * 1_000_000_000)
-        self.init(timespec: timespec(tv_sec: Int(seconds), tv_nsec: Int(nanoseconds)))
-    }
-
-    var millisSinceEpoch: Int64 {
-        Int64(bitPattern: self.rawValue) / -1_000_000
-    }
-}
-
 extension String {
     func encodeAsJSONString(into bytes: inout [UInt8]) {
         bytes.append(UInt8(ascii: "\""))
@@ -103,7 +88,7 @@ extension AmazonHeaders {
         // The version number, that is, 1.
         let version: UInt = 1
         // The time of the original request, in Unix epoch time, in 8 hexadecimal digits.
-        let now = UInt32(DispatchWallTime.now().millisSinceEpoch / 1000)
+        let now = UInt32(LambdaClock().now.millisecondsSinceEpoch() / 1000)
         let dateValue = String(now, radix: 16, uppercase: false)
         let datePadding = String(repeating: "0", count: max(0, 8 - dateValue.count))
         // A 96-bit identifier for the trace, globally unique, in 24 hexadecimal digits.