Abstract away time source: TracingTime #86
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,72 @@ | ||
| //===----------------------------------------------------------------------===// | ||
| // | ||
| // This source file is part of the Swift Distributed Tracing open source project | ||
| // | ||
| // Copyright (c) 2020-2022 Apple Inc. and the Swift Distributed Tracing project | ||
| // authors | ||
| // Licensed under Apache License v2.0 | ||
| // | ||
| // See LICENSE.txt for license information | ||
| // | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #if swift(>=5.6.0) | ||
| @_implementationOnly @preconcurrency import struct Dispatch.DispatchWallTime | ||
| #else | ||
| @_implementationOnly import struct Dispatch.DispatchWallTime | ||
| #endif | ||
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| /// A wall-clock based time value used to mark the beginning and end of a trace ``Span``. | ||
| /// | ||
| /// ### Rationale for this type | ||
| /// This type is introduced in order to abstract between various time sources, such as | ||
| /// Dispatch's `DispatchWallTime` or any potential future `Clock` type in the Swift | ||
| /// standard library (or elsewhere) that we might want to use as source of time. | ||
| /// | ||
| /// Abstracting away the source of the measurement into this wrapper allows us to | ||
| /// have ``Tracer`` implementations don't care about the user API that is surfaced as `startSpan` | ||
| /// to end-users. As time goes on, this API may evolve, but we will not have to make breaking changes | ||
| /// to tracer implementations themselves. | ||
| public struct TracingTime: Sendable { | ||
| enum Repr { | ||
| case dispatchWallTime(DispatchWallTime) | ||
| } | ||
|
There was a problem hiding this comment. potentially other Clock.Instants or other time sources here... |
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| private var repr: Repr | ||
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| private init(dispatchWallTime: DispatchWallTime) { | ||
|
There was a problem hiding this comment. i attempted to hide away dispatch completely, debatable if we care to do so or not |
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| self.repr = .dispatchWallTime(dispatchWallTime) | ||
| } | ||
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| public static func now() -> TracingTime { | ||
| .init(dispatchWallTime: .now()) | ||
| } | ||
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| public var rawValue: UInt64 { | ||
| switch self.repr { | ||
| case .dispatchWallTime(let wallTime): | ||
| return wallTime.rawValue | ||
| } | ||
| } | ||
| } | ||
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| extension TracingTime: Equatable { | ||
| public static func ==(lhs: TracingTime, rhs: TracingTime) -> Bool { | ||
| switch (lhs.repr, rhs.repr) { | ||
| case (.dispatchWallTime(let l), .dispatchWallTime(let r)): | ||
| return l.rawValue == r.rawValue | ||
| } | ||
| } | ||
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| } | ||
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| extension TracingTime: CustomStringConvertible { | ||
| public var description: String { | ||
| switch self.repr { | ||
| case .dispatchWallTime(let wallTime): | ||
| return "TracingTime(\(wallTime.rawValue))" | ||
| } | ||
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| } | ||
| } | ||
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The important part here is that even if we deprecate Span creation with this type and move to Clock, it would not have to be breaking to Tracer implementations -- they can still work without rushing to a breaking change in time type