[Prototype] propagation: add EnvCarrier

propagation/env.go

@@ -0,0 +1,58 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package propagation // import "go.opentelemetry.io/otel/propagation"
+
+import (
+	"os"
+	"strings"
+)
+
+// EnvCarrier is a TextMapCarrier that uses the environment variables as a
+// storage medium for propagated key-value pairs. The keys are uppercased
+// before being used to access the environment variables.
+// This is useful for propagating values that are set in the environment
+// and need to be accessed by different processes or services.
+// The keys are uppercased to avoid case sensitivity issues across different
+// operating systems and environments.
+type EnvCarrier struct {
+	// SetEnvFunc is a function that sets the environment variable.
+	// Usually, you want to set the environment variable for processes
+	// that are spawned by the current process.
+	// By default implementation, it does nothing.
+	SetEnvFunc func(key, value string) error
+}
+
+var _ TextMapCarrier = EnvCarrier{}
+
+// Get returns the value associated with the passed key.
+// The key is uppercased before being used to access the environment variable.
+func (EnvCarrier) Get(key string) string {
+	k := strings.ToUpper(key)
+	return os.Getenv(k)
+}
+
+// Set stores the key-value pair in the environment variable.
+// The key is uppercased before being used to set the environment variable.
+// If SetEnvFunc is not set, this method does nothing.
+func (e EnvCarrier) Set(key, value string) {
+	if e.SetEnvFunc == nil {
+		return
+	}
+	k := strings.ToUpper(key)
+	_ = e.SetEnvFunc(k, value)
+}
+
+// Keys lists the keys stored in this carrier.
+// This returns all the keys in the environment variables.
+func (EnvCarrier) Keys() []string {
+	keys := make([]string, 0, len(os.Environ()))
+	for _, kv := range os.Environ() {
+		kvPair := strings.SplitN(kv, "=", 2)
+		if len(kvPair) < 1 {
+			continue
+		}
+		keys = append(keys, kvPair[0])
+	}
+	return keys
+}

propagation/env_test.go

@@ -0,0 +1,124 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package propagation_test
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
+)
+
+func TestExtractValidTraceContextEnvCarrier(t *testing.T) {
+	stateStr := "key1=value1,key2=value2"
+	state, err := trace.ParseTraceState(stateStr)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name string
+		envs map[string]string
+		want trace.SpanContext
+	}{
+		{
+			name: "sampled",
+			envs: map[string]string{
+				"TRACEPARENT": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
+			},
+			want: trace.NewSpanContext(trace.SpanContextConfig{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
+			}),
+		},
+		{
+			name: "valid tracestate",
+			envs: map[string]string{
+				"TRACEPARENT": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00",
+				"TRACESTATE":  stateStr,
+			},
+			want: trace.NewSpanContext(trace.SpanContextConfig{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceState: state,
+				Remote:     true,
+			}),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+			for k, v := range tc.envs {
+				t.Setenv(k, v)
+			}
+			ctx = prop.Extract(ctx, propagation.EnvCarrier{})
+			assert.Equal(t, tc.want, trace.SpanContextFromContext(ctx))
+		})
+	}
+}
+
+func TestInjectTraceContextEnvCarrier(t *testing.T) {
+	stateStr := "key1=value1,key2=value2"
+	state, err := trace.ParseTraceState(stateStr)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name string
+		want map[string]string
+		sc   trace.SpanContext
+	}{
+		{
+			name: "sampled",
+			want: map[string]string{
+				"TRACEPARENT": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-01",
+			},
+			sc: trace.NewSpanContext(trace.SpanContextConfig{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceFlags: trace.FlagsSampled,
+				Remote:     true,
+			}),
+		},
+		{
+			name: "with tracestate",
+			want: map[string]string{
+				"TRACEPARENT": "00-4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-00",
+				"TRACESTATE":  stateStr,
+			},
+			sc: trace.NewSpanContext(trace.SpanContextConfig{
+				TraceID:    traceID,
+				SpanID:     spanID,
+				TraceState: state,
+				Remote:     true,
+			}),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+			ctx = trace.ContextWithRemoteSpanContext(ctx, tc.sc)
+			c := propagation.EnvCarrier{
+				SetEnvFunc: func(key, value string) error {
+					t.Setenv(key, value)
+					return nil
+				},
+			}
+
+			prop.Inject(ctx, c)
+
+			for k, v := range tc.want {
+				if got := os.Getenv(k); got != v {
+					t.Errorf("got %s=%s, want %s=%s", k, got, k, v)
+				}
+			}
+		})
+	}
+}