KDOC 664: OpenTelemetry の3つのシグナルの出力を見る

この文書のステータス

  • 作成
    • 2026-10-15 貴島
  • レビュー
    • 2026-10-15 貴島

概要

OpenTelemetry の3つのシグナル(trace、metric、log)を、それぞれいちばん小さい例で出力して見る。どれも標準出力の exporter で JSON を書き出し、整形して出力をそのまま見る。 

# 例ごとに一時ディレクトリを作り、終わったら消す
dir=$(mktemp -d)
trap 'rm -rf "$dir"' EXIT
cd "$dir"
go mod init example >/dev/null 2>&1
go get \
  go.opentelemetry.io/otel@v1.47.0 \
  go.opentelemetry.io/otel/sdk@v1.47.0 \
  go.opentelemetry.io/otel/sdk/metric@v1.47.0 \
  go.opentelemetry.io/otel/sdk/log@v1.47.0 \
  go.opentelemetry.io/otel/log@v1.47.0 \
  go.opentelemetry.io/otel/exporters/stdout/stdouttrace@v1.47.0 \
  go.opentelemetry.io/otel/exporters/stdout/stdoutmetric@v1.47.0 \
  go.opentelemetry.io/otel/exporters/stdout/stdoutlog@v0.23.0 2>/dev/null

trace

親の span の中で子の span を作る。 

<<setup>>
mkdir -p trace
cat > trace/main.go <<'GO'
package main

import (
	"context"

	"go.opentelemetry.io/otel/exporters/stdout/stdouttrace"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

func main() {
	ctx := context.Background()
	exp, _ := stdouttrace.New(stdouttrace.WithPrettyPrint())
	tp := sdktrace.NewTracerProvider(sdktrace.WithSyncer(exp))
	defer tp.Shutdown(ctx)

	tracer := tp.Tracer("example")
	ctx, parent := tracer.Start(ctx, "parent")
	_, child := tracer.Start(ctx, "child")
	child.End()
	parent.End()
}
GO
go mod tidy 2>/dev/null
go run ./trace

{
	"Name": "child",
	"SpanContext": {
		"TraceID": "23fc88efba48028dd9d7717ccb8a1b61",
		"SpanID": "af787e4c4d7bf055",
		"TraceFlags": "01",
		"TraceState": "",
		"Remote": false
	},
	"Parent": {
		"TraceID": "23fc88efba48028dd9d7717ccb8a1b61",
		"SpanID": "d3973a5b2f677925",
		"TraceFlags": "01",
		"TraceState": "",
		"Remote": false
	},
	"SpanKind": 1,
	"StartTime": "2026-10-15T09:50:57.99213578+09:00",
	"EndTime": "2026-10-15T09:50:57.99213599+09:00",
	"Attributes": null,
	"Events": null,
	"Links": null,
	"Status": {
		"Code": "Unset",
		"Description": ""
	},
	"DroppedAttributes": 0,
	"DroppedEvents": 0,
	"DroppedLinks": 0,
	"ChildSpanCount": 0,
	"Resource": [
		{
			"Key": "service.name",
			"Value": {
				"Type": "STRING",
				"Value": "unknown_service:trace"
			}
		},
		{
			"Key": "telemetry.sdk.language",
			"Value": {
				"Type": "STRING",
				"Value": "go"
			}
		},
		{
			"Key": "telemetry.sdk.name",
			"Value": {
				"Type": "STRING",
				"Value": "opentelemetry"
			}
		},
		{
			"Key": "telemetry.sdk.version",
			"Value": {
				"Type": "STRING",
				"Value": "1.47.0"
			}
		}
	],
	"InstrumentationScope": {
		"Name": "example",
		"Version": "",
		"SchemaURL": "",
		"Attributes": null
	},
	"InstrumentationLibrary": {
		"Name": "example",
		"Version": "",
		"SchemaURL": "",
		"Attributes": null
	}
}
{
	"Name": "parent",
	"SpanContext": {
		"TraceID": "23fc88efba48028dd9d7717ccb8a1b61",
		"SpanID": "d3973a5b2f677925",
		"TraceFlags": "01",
		"TraceState": "",
		"Remote": false
	},
	"Parent": {
		"TraceID": "00000000000000000000000000000000",
		"SpanID": "0000000000000000",
		"TraceFlags": "00",
		"TraceState": "",
		"Remote": false
	},
	"SpanKind": 1,
	"StartTime": "2026-10-15T09:50:57.992133605+09:00",
	"EndTime": "2026-10-15T09:50:57.992240576+09:00",
	"Attributes": null,
	"Events": null,
	"Links": null,
	"Status": {
		"Code": "Unset",
		"Description": ""
	},
	"DroppedAttributes": 0,
	"DroppedEvents": 0,
	"DroppedLinks": 0,
	"ChildSpanCount": 1,
	"Resource": [
		{
			"Key": "service.name",
			"Value": {
				"Type": "STRING",
				"Value": "unknown_service:trace"
			}
		},
		{
			"Key": "telemetry.sdk.language",
			"Value": {
				"Type": "STRING",
				"Value": "go"
			}
		},
		{
			"Key": "telemetry.sdk.name",
			"Value": {
				"Type": "STRING",
				"Value": "opentelemetry"
			}
		},
		{
			"Key": "telemetry.sdk.version",
			"Value": {
				"Type": "STRING",
				"Value": "1.47.0"
			}
		}
	],
	"InstrumentationScope": {
		"Name": "example",
		"Version": "",
		"SchemaURL": "",
		"Attributes": null
	},
	"InstrumentationLibrary": {
		"Name": "example",
		"Version": "",
		"SchemaURL": "",
		"Attributes": null
	}
}
  • 子の Parent.SpanID が親の SpanID と同じで、TraceID も同じである。これで1つのトレースの中の親子を表現している
  • 親の Parent.SpanID はすべて 0 で、根の span である
  • WithSyncer を使っていて span が終わったときにすぐに書き出すので先に終わった子が先に出力される

metric

カウンタに 1、2、3 を足す。 

<<setup>>
mkdir -p metric
cat > metric/main.go <<'GO'
package main

import (
	"context"

	"go.opentelemetry.io/otel/exporters/stdout/stdoutmetric"
	sdkmetric "go.opentelemetry.io/otel/sdk/metric"
)

func main() {
	ctx := context.Background()
	exp, _ := stdoutmetric.New(stdoutmetric.WithPrettyPrint())
	mp := sdkmetric.NewMeterProvider(sdkmetric.WithReader(sdkmetric.NewPeriodicReader(exp)))
	defer mp.Shutdown(ctx)

	counter, _ := mp.Meter("example").Int64Counter("requests")
	counter.Add(ctx, 1)
	counter.Add(ctx, 2)
	counter.Add(ctx, 3)
}
GO
go mod tidy 2>/dev/null
go run ./metric

{
	"Resource": [
		{
			"Key": "service.name",
			"Value": {
				"Type": "STRING",
				"Value": "unknown_service:metric"
			}
		},
		{
			"Key": "telemetry.sdk.language",
			"Value": {
				"Type": "STRING",
				"Value": "go"
			}
		},
		{
			"Key": "telemetry.sdk.name",
			"Value": {
				"Type": "STRING",
				"Value": "opentelemetry"
			}
		},
		{
			"Key": "telemetry.sdk.version",
			"Value": {
				"Type": "STRING",
				"Value": "1.47.0"
			}
		}
	],
	"ScopeMetrics": [
		{
			"Scope": {
				"Name": "example",
				"Version": "",
				"SchemaURL": "",
				"Attributes": null
			},
			"Metrics": [
				{
					"Name": "requests",
					"Description": "",
					"Unit": "",
					"Data": {
						"DataPoints": [
							{
								"Attributes": [],
								"StartTime": "2026-10-15T09:50:58.694178323+09:00",
								"Time": "2026-10-15T09:50:58.69420339+09:00",
								"Value": 6
							}
						],
						"Temporality": "CumulativeTemporality",
						"IsMonotonic": true
					}
				}
			]
		}
	]
}
  • 3回の Add が、値 6 に集計された

log

ログを1件書く。 

<<setup>>
mkdir -p log
cat > log/main.go <<'GO'
package main

import (
	"context"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
	"go.opentelemetry.io/otel/log"
	sdklog "go.opentelemetry.io/otel/sdk/log"
)

func main() {
	ctx := context.Background()
	exp, _ := stdoutlog.New(stdoutlog.WithPrettyPrint())
	lp := sdklog.NewLoggerProvider(sdklog.WithProcessor(sdklog.NewSimpleProcessor(exp)))
	defer lp.Shutdown(ctx)

	var r log.Record
	r.SetSeverity(log.SeverityInfo)
	r.SetBody(attribute.StringValue("hello"))
	lp.Logger("example").Emit(ctx, r)
}
GO
go mod tidy 2>/dev/null
go run ./log

{
	"Timestamp": "0001-01-01T00:00:00Z",
	"ObservedTimestamp": "2026-10-15T09:50:59.139404628+09:00",
	"Severity": 9,
	"SeverityText": "",
	"Body": {
		"Type": "STRING",
		"Value": "hello"
	},
	"Attributes": [],
	"TraceID": "00000000000000000000000000000000",
	"SpanID": "0000000000000000",
	"TraceFlags": "00",
	"Resource": [
		{
			"Key": "service.name",
			"Value": {
				"Type": "STRING",
				"Value": "unknown_service:log"
			}
		},
		{
			"Key": "telemetry.sdk.language",
			"Value": {
				"Type": "STRING",
				"Value": "go"
			}
		},
		{
			"Key": "telemetry.sdk.name",
			"Value": {
				"Type": "STRING",
				"Value": "opentelemetry"
			}
		},
		{
			"Key": "telemetry.sdk.version",
			"Value": {
				"Type": "STRING",
				"Value": "1.47.0"
			}
		}
	],
	"Scope": {
		"Name": "example",
		"Version": "",
		"SchemaURL": "",
		"Attributes": {}
	},
	"DroppedAttributes": 0
}
  • Scope にロガーに渡した文字列が入っている

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