Add X-Ray specific MetadataProvider. (#14)

* Add X-Ray specific MetadataProvider.

* Added MetadataProvider unit tests.

Sources/OpenTelemetryXRay/MetadataProvider+OTelXRay.swift

@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift OpenTelemetry open source project
+//
+// Copyright (c) 2021 Moritz Lang and the Swift OpenTelemetry project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import Logging
+import ServiceContextModule
+
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
+extension Logger.MetadataProvider {
+    /// A metadata provider exposing the current trace and span ID using X-Ray specific formatting.
+    ///
+    /// - Parameters:
+    ///   - traceIDKey: The metadata key of the trace ID. Defaults to "trace-id".
+    ///   - spanIDKey: The metadata key of the span ID. Defaults to "span-id".
+    /// - Returns: A metadata provider ready to use with Logging.
+    public static func otelXRay(traceIDKey: String = "trace-id", spanIDKey: String = "span-id") -> Logger.MetadataProvider {
+        .init {
+            guard let spanContext = ServiceContext.current?.spanContext else { return [:] }
+
+            let traceIDBytes = spanContext.traceID.hexBytes
+            let timestampBytes = traceIDBytes[0 ..< 8]
+            let randomBytes = traceIDBytes[8...]
+
+            return [
+                traceIDKey: "1-\(String(decoding: timestampBytes, as: UTF8.self))-\(String(decoding: randomBytes, as: UTF8.self))",
+                spanIDKey: "\(spanContext.spanID)",
+            ]
+        }
+    }
+
+    /// A metadata provider exposing the current trace and span ID using X-Ray specific formatting.
+    public static let otelXRay = Logger.MetadataProvider.otelXRay()
+}

Tests/OpenTelemetryXRayTests/MetadataProviderTests.swift

@@ -0,0 +1,130 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift OpenTelemetry open source project
+//
+// Copyright (c) 2021 Moritz Lang and the Swift OpenTelemetry project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@testable import Logging
+@testable import OpenTelemetryXRay
+@testable import OpenTelemetry
+import ServiceContextModule
+import XCTest
+
+final class MetadataProviderTests: XCTestCase {
+    func test_providesMetadataFromSpanContext_withDefaultLabels() throws {
+        guard #available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) else {
+            throw XCTSkip("Task locals are not supported on this platform.")
+        }
+
+        let stream = InterceptingStream()
+        var logger = Logger(label: "test")
+        logger.handler = StreamLogHandler(label: "test", stream: stream, metadataProvider: .otelXRay)
+
+        var generator = XRayIDGenerator()
+
+        let spanContext = OTel.SpanContext(
+            traceID: generator.generateTraceID(),
+            spanID: generator.generateSpanID(),
+            traceFlags: .sampled,
+            isRemote: true
+        )
+
+        var context = ServiceContext.topLevel
+        context.spanContext = spanContext
+        ServiceContext.$current.withValue(context) {
+            logger.info("This is a test message", metadata: ["explicit": "42"])
+        }
+
+        XCTAssertEqual(stream.strings.count, 1)
+        let message = try XCTUnwrap(stream.strings.first)
+
+        let traceIDBytes = spanContext.traceID.hexBytes
+        let timestampBytes = traceIDBytes[0 ..< 8]
+        let randomBytes = traceIDBytes[8...]
+        let expectedTraceId = "1-\(String(decoding: timestampBytes, as: UTF8.self))-\(String(decoding: randomBytes, as: UTF8.self))"
+
+        XCTAssertTrue(message.contains("span-id=\(spanContext.spanID)"))
+        XCTAssertTrue(message.contains("trace-id=\(expectedTraceId)"))
+        XCTAssertTrue(message.contains("explicit=42"))
+        XCTAssertTrue(message.contains("This is a test message"))
+    }
+
+    func test_providesMetadataFromSpanContext_withCustomLabels() throws {
+        guard #available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) else {
+            throw XCTSkip("Task locals are not supported on this platform.")
+        }
+
+        let stream = InterceptingStream()
+        var logger = Logger(label: "test")
+        let metadataProvider = Logger.MetadataProvider.otelXRay(traceIDKey: "custom_trace_id", spanIDKey: "custom_span_id")
+        logger.handler = StreamLogHandler(label: "test", stream: stream, metadataProvider: metadataProvider)
+
+        var generator = XRayIDGenerator()
+
+        let spanContext = OTel.SpanContext(
+            traceID: generator.generateTraceID(),
+            spanID: generator.generateSpanID(),
+            traceFlags: .sampled,
+            isRemote: true
+        )
+
+        var context = ServiceContext.topLevel
+        context.spanContext = spanContext
+        ServiceContext.$current.withValue(context) {
+            logger.info("This is a test message", metadata: ["explicit": "42"])
+        }
+
+        XCTAssertEqual(stream.strings.count, 1)
+        let message = try XCTUnwrap(stream.strings.first)
+
+        let traceIDBytes = spanContext.traceID.hexBytes
+        let timestampBytes = traceIDBytes[0 ..< 8]
+        let randomBytes = traceIDBytes[8...]
+        let expectedTraceId = "1-\(String(decoding: timestampBytes, as: UTF8.self))-\(String(decoding: randomBytes, as: UTF8.self))"
+
+        XCTAssertTrue(message.contains("custom_span_id=\(spanContext.spanID)"))
+        XCTAssertTrue(message.contains("custom_trace_id=\(expectedTraceId)"))
+        XCTAssertTrue(message.contains("explicit=42"))
+        XCTAssertTrue(message.contains("This is a test message"))
+    }
+
+    func test_doesNotProvideMetadataWithoutSpanContext() throws {
+        guard #available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) else {
+            throw XCTSkip("Task locals are not supported on this platform.")
+        }
+
+        let stream = InterceptingStream()
+        var logger = Logger(label: "test")
+        let metadataProvider = Logger.MetadataProvider.otelXRay
+        logger.handler = StreamLogHandler(label: "test", stream: stream, metadataProvider: metadataProvider)
+
+        logger.info("This is a test message", metadata: ["explicit": "42"])
+
+        XCTAssertEqual(stream.strings.count, 1)
+        let message = try XCTUnwrap(stream.strings.first)
+
+        XCTAssertFalse(message.contains("trace-id"))
+        XCTAssertFalse(message.contains("span-id"))
+        XCTAssertTrue(message.contains("explicit=42"))
+        XCTAssertTrue(message.contains("This is a test message"))
+    }
+}
+
+final class InterceptingStream: TextOutputStream {
+    var interceptedText: String?
+    var strings = [String]()
+
+    func write(_ string: String) {
+        strings.append(string)
+        interceptedText = (interceptedText ?? "") + string
+    }
+}
+
+extension InterceptingStream: @unchecked Sendable {}