Add stdout metrics exporter

Sources/Exporters/Stdout/StdoutMetricExporter.swift

@@ -0,0 +1,83 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import Foundation
+import OpenTelemetrySdk
+
+public class StdoutMetricExporter: StableMetricExporter {
+    let isDebug: Bool
+    var aggregationTemporalitySelector: AggregationTemporalitySelector
+
+    public init(isDebug: Bool, aggregationTemporalitySelector: AggregationTemporalitySelector = AggregationTemporality.alwaysCumulative()) {
+        self.isDebug = isDebug
+        self.aggregationTemporalitySelector = aggregationTemporalitySelector
+    }
+
+    public func export(metrics: [OpenTelemetrySdk.StableMetricData]) -> OpenTelemetrySdk.ExportResult {
+        if isDebug {
+            for metric in metrics {
+                print(String(repeating: "-", count: 40))
+                print("Name: \(metric.name)")
+                print("Description: \(metric.description)")
+                print("Unit: \(metric.unit)")
+                print("IsMonotonic: \(metric.isMonotonic)")
+                print("Resource: \(metric.resource)")
+                print("InstrumentationScopeInfo: \(metric.instrumentationScopeInfo)")
+                print("Type: \(metric.type)")
+                print("AggregationTemporality: \(metric.data.aggregationTemporality)")
+                if !metric.data.points.isEmpty {
+                    print("DataPoints:")
+                    for point in metric.data.points {
+                        print("  - StartEpochNanos: \(point.startEpochNanos)")
+                        print("    EndEpochNanos: \(point.endEpochNanos)")
+                        print("    Attributes: \(point.attributes)")
+                        print("    Exemplars:")
+                        for exemplar in point.exemplars {
+                            print("      - EpochNanos: \(exemplar.epochNanos)")
+                            if let ctx = exemplar.spanContext {
+                                print("        SpanContext: \(ctx)")
+                            }
+                            print("        FilteredAttributes: \(exemplar.filteredAttributes)")
+                            if let e = exemplar as? DoubleExemplarData {
+                                print("        Value: \(e.value)")
+                            }
+                            if let e = exemplar as? LongExemplarData {
+                                print("        Value: \(e.value)")
+                            }
+                        }
+                    }
+                }
+                print(String(repeating: "-", count: 40) + "\n")
+            }
+        }  else {
+            let jsonEncoder = JSONEncoder()
+            for metric in metrics {
+                do {
+                    let jsonData = try jsonEncoder.encode(metric)
+                    if let jsonString = String(data: jsonData, encoding: .utf8) {
+                        print(jsonString)
+                    }
+                } catch {
+                    print("Failed to serialize Metric as JSON: \(error)")
+                    return .failure
+                }
+            }
+        }
+
+        return .success
+    }
+
+    public func flush() -> OpenTelemetrySdk.ExportResult {
+        return .success
+    }
+
+    public func shutdown() -> OpenTelemetrySdk.ExportResult {
+        return .success
+    }
+
+    public func getAggregationTemporality(for instrument: OpenTelemetrySdk.InstrumentType) -> OpenTelemetrySdk.AggregationTemporality {
+        return aggregationTemporalitySelector.getAggregationTemporality(for: instrument)
+    }
+}

Sources/OpenTelemetrySdk/Metrics/Stable/Aggregation/AggregationTemporality.swift

@@ -21,7 +21,7 @@ public class AggregationTemporalitySelector : AggregationTemporalitySelectorProt
     public var aggregationTemporalitySelector: (InstrumentType) -> AggregationTemporality
 }
 
-public enum AggregationTemporality {
+public enum AggregationTemporality: Codable {
     case delta
     case cumulative
 

Sources/OpenTelemetrySdk/Metrics/Stable/Data/ExemplarData.swift

@@ -6,7 +6,7 @@
 import Foundation
 import OpenTelemetryApi
 
-public class ExemplarData: Equatable {
+public class ExemplarData: Equatable, Encodable {
     internal init(epochNanos: UInt64, filteredAttributes: [String: AttributeValue], spanContext: SpanContext? = nil) {
         self.filteredAttributes = filteredAttributes
         self.epochNanos = epochNanos

Sources/OpenTelemetrySdk/Metrics/Stable/Data/PointData.swift

@@ -6,7 +6,7 @@
 import Foundation
 import OpenTelemetryApi
 
-public class PointData: Equatable {
+public class PointData: Equatable, Encodable {
     internal init(startEpochNanos: UInt64, endEpochNanos: UInt64, attributes: [String: AttributeValue], exemplars: [ExemplarData]) {
         self.startEpochNanos = startEpochNanos
         self.endEpochNanos = endEpochNanos

Sources/OpenTelemetrySdk/Metrics/Stable/Data/StableMetricData.swift

@@ -6,7 +6,7 @@
 import Foundation
 import OpenTelemetryApi
 
-public enum MetricDataType {
+public enum MetricDataType: Codable {
     case LongGauge
     case DoubleGauge
     case LongSum
@@ -16,7 +16,7 @@ public enum MetricDataType {
     case ExponentialHistogram
 }
 
-public struct StableMetricData: Equatable {
+public struct StableMetricData: Equatable, Encodable {
     public private(set) var resource: Resource
     public private(set) var instrumentationScopeInfo: InstrumentationScopeInfo
     public private(set) var name: String
@@ -28,7 +28,7 @@ public struct StableMetricData: Equatable {
 
     public static let empty = StableMetricData(resource: Resource.empty, instrumentationScopeInfo: InstrumentationScopeInfo(), name: "", description: "", unit: "", type: .Summary, isMonotonic: false, data: StableMetricData.Data(aggregationTemporality: .cumulative, points: [PointData]()))
 
-    public class Data: Equatable {
+    public class Data: Equatable, Encodable {
         public private(set) var points: [PointData]
         public private(set) var aggregationTemporality: AggregationTemporality