fix(otelzap): write core.ctx only when init

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix data race when writing log entries with `context.Context` fields in `go.opentelemetry.io/contrib/bridges/otelzap`. (#7368)
+
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->
 

bridges/otelzap/core.go

@@ -223,10 +223,11 @@ func (o *Core) Write(ent zapcore.Entry, fields []zapcore.Field) error {
 	if ent.Stack != "" {
 		r.AddAttributes(log.String(string(semconv.CodeStacktraceKey), ent.Stack))
 	}
+	emitCtx := o.ctx
 	if len(fields) > 0 {
 		ctx, attrbuf := convertField(fields)
 		if ctx != nil {
-			o.ctx = ctx
+			emitCtx = ctx
 		}
 		r.AddAttributes(attrbuf...)
 	}
@@ -235,7 +236,7 @@ func (o *Core) Write(ent zapcore.Entry, fields []zapcore.Field) error {
 	if ent.LoggerName != "" {
 		logger = o.provider.Logger(ent.LoggerName, o.opts...)
 	}
-	logger.Emit(o.ctx, r)
+	logger.Emit(emitCtx, r)
 	return nil
 }
 

bridges/otelzap/core_test.go

@@ -5,6 +5,7 @@ package otelzap
 
 import (
 	"context"
+	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -144,6 +145,38 @@ func TestCore(t *testing.T) {
 	})
 }
 
+func TestCoreConcurrentSafe(t *testing.T) {
+	rec := logtest.NewRecorder()
+	zc := NewCore(loggerName, WithLoggerProvider(rec))
+	logger := zap.New(zc)
+
+	t.Run("Write", func(t *testing.T) {
+		var wg sync.WaitGroup
+		const n = 2
+		wg.Add(n)
+		ctx := context.Background()
+		for i := 0; i < n; i++ {
+			go func() {
+				defer wg.Done()
+				logger.Info(testMessage, zap.String(testKey, testValue), zap.Any("ctx", ctx))
+			}()
+		}
+		wg.Wait()
+
+		result := rec.Result()
+		require.Len(t, result, 1)
+		require.Len(t, result[logtest.Scope{Name: "name"}], 2)
+		got := result[logtest.Scope{Name: "name"}][0]
+
+		assert.Equal(t, testMessage, got.Body.AsString())
+		assert.Equal(t, log.SeverityInfo, got.Severity)
+		assert.Equal(t, zap.InfoLevel.String(), got.SeverityText)
+		assert.Equal(t, []log.KeyValue{
+			log.String(testKey, testValue),
+		}, got.Attributes)
+	})
+}
+
 func TestCoreEnabled(t *testing.T) {
 	enabledFunc := func(c context.Context, param log.EnabledParameters) bool {
 		return param.Severity >= log.SeverityInfo