Demonstrate zap logger wrapped core concept

bridges/otelzap/core.go

@@ -225,6 +225,90 @@
 	return nil
 }
 
+// WrappedCore is a [zapcore.Core] that wraps a core and sends logging records to OpenTelemetry.
+type WrappedCore struct {
+	delegate zapcore.Core
+	provider log.LoggerProvider
+}
+
+// Compile-time check *Core implements zapcore.Core.
+var _ zapcore.Core = (*WrappedCore)(nil)
+
+// Compile-time check *Core implements zapcore.CheckWriteHook.
+var _ zapcore.CheckWriteHook = (*WrappedCore)(nil)
+
+func NewWrappedCore(delegate zapcore.Core, provider log.LoggerProvider) *WrappedCore {
+	return &WrappedCore{
+		delegate: delegate,
+		provider: provider,
+	}
+}
+
+func (o *WrappedCore) Enabled(level zapcore.Level) bool {
+	return o.delegate.Enabled(level)
+}
+
+func (o *WrappedCore) With(fields []zapcore.Field) zapcore.Core {
+	// TODO: figure out if / how to interact with otel context
+	return o.delegate.With(fields)
+}
+
+func (o *WrappedCore) clone() *WrappedCore {
+	return &WrappedCore{
+		delegate: o.delegate,
+		provider: o.provider,
+	}
+}
+
+func (o *WrappedCore) Sync() error {
+	return o.delegate.Sync()
+}
+
+func (o *WrappedCore) Check(ent zapcore.Entry, ce *zapcore.CheckedEntry) *zapcore.CheckedEntry {
+	return o.delegate.Check(ent, ce).After(ent, o)
+}
+
+func (o *WrappedCore) OnWrite(ent *zapcore.CheckedEntry, fields []zapcore.Field) {
+	ctx := context.Background()
+	r := log.Record{}
+	r.SetTimestamp(ent.Time)
+	r.SetBody(log.StringValue(ent.Message))
+	r.SetSeverity(convertLevel(ent.Level))
+	r.SetSeverityText(ent.Level.String())
+
+	if ent.Caller.Defined {
+		r.AddAttributes(
+			log.String(string(semconv.CodeFilepathKey), ent.Caller.File),
+			log.Int(string(semconv.CodeLineNumberKey), ent.Caller.Line),
+			log.String(string(semconv.CodeFunctionKey), ent.Caller.Function),
+		)
+	}
+	if ent.Stack != "" {
+		r.AddAttributes(log.String(string(semconv.CodeStacktraceKey), ent.Stack))
+	}
+	if len(fields) > 0 {
+		context, attrbuf := convertField(fields)
+		if context != nil {
+			ctx = context
+		}
+		r.AddAttributes(attrbuf...)
+	}
+
+	var logger log.Logger
+	if ent.LoggerName != "" {
+		logger = o.provider.Logger(ent.LoggerName)
+		// TODO: figure out what to do with context
+	} else {
+		logger = o.provider.Logger("unknown")
+	}
+	logger.Emit(ctx, r)
+
+}
+
+func (o *WrappedCore) Write(ent zapcore.Entry, fields []zapcore.Field) error {
+	return o.delegate.Write(ent, fields)
+}
+
 func convertField(fields []zapcore.Field) (context.Context, []log.KeyValue) {
 	var ctx context.Context
 	enc := newObjectEncoder(len(fields))

bridges/otelzap/example_test.go

@@ -5,7 +5,10 @@ package otelzap_test
 
 import (
 	"context"
+	"go.opentelemetry.io/otel/exporters/stdout/stdoutlog"
+	"go.opentelemetry.io/otel/sdk/log"
 	"os"
+	"testing"
 
 	"go.opentelemetry.io/contrib/bridges/otelzap"
 	"go.opentelemetry.io/otel/log/noop"
@@ -14,6 +17,43 @@ import (
 	"go.uber.org/zap/zapcore"
 )
 
+func TestAltAppender(t *testing.T) {
+	// Configure otel log provider, which uses simple processor and stdout exporter for simplicity
+	logExporter, err := stdoutlog.New()
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	provider := log.NewLoggerProvider(
+		log.WithProcessor(log.NewSimpleProcessor(logExporter)),
+	)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// Configure a zap core using whatever configuration you typically use
+	core := zapcore.NewCore(zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig()), zapcore.AddSync(os.Stdout), zapcore.WarnLevel)
+	// Wrap the core in an otel wrapper, which bridges all logs the core decides to write (i.e. all logs for which core.Write is invoked) to the otel log provider
+	wrappedCore := otelzap.NewWrappedCore(core, provider)
+	// Create a logger from the wrapped core, and proceed as usual
+	logger := zap.New(wrappedCore).Named("my.logger")
+
+	logger.Warn("message level warn")
+	logger.Info("message level info")
+
+	// Output:
+	// {"level":"warn","ts":1742414003.3163369,"msg":"message level warn"}
+	// {"Timestamp":"2025-03-19T14:53:23.316337-05:00","ObservedTimestamp":"2025-03-19T14:53:23.316363-05:00","Severity":13,"SeverityText":"warn","Body":{"Type":"String","Value":"message level warn"},"Attributes":[],"TraceID":"00000000000000000000000000000000","SpanID":"0000000000000000","TraceFlags":"00","Resource":[{"Key":"service.name","Value":{"Type":"STRING","Value":"unknown_service:___TestAltAppender_in_go_opentelemetry_io_contrib_bridges_otelzap.test"}},{"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":"1.35.0"}}],"Scope":{"Name":"unknown","Version":"","SchemaURL":"","Attributes":{}},"DroppedAttributes":0}
+
+	// Notes:
+	// - Only the warn level log is written, since the core specifies zapcore.WarnLevel
+	// - The log is written to stdout twice:
+	//    - Once by the core's configured stdout writer w/ JSON encoded
+	//    - Second by the otel log provider's stdout log exporter.
+	// - Typically, the otel log provider would be configured with a batch processor and otlp exporter, which would result in the log being written to stdout once, and OTLP once.
+}
+
 func Example() {
 	// Use a working LoggerProvider implementation instead e.g. use go.opentelemetry.io/otel/sdk/log.
 	provider := noop.NewLoggerProvider()

bridges/otelzap/go.mod

@@ -5,18 +5,23 @@ go 1.23.0
 require (
 	github.com/stretchr/testify v1.10.0
 	go.opentelemetry.io/otel v1.35.0
+	go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.11.0
 	go.opentelemetry.io/otel/log v0.11.0
+	go.opentelemetry.io/otel/sdk/log v0.11.0
 	go.uber.org/zap v1.27.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/go-logr/logr v1.4.2 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/google/uuid v1.6.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.1.0 // indirect
 	go.opentelemetry.io/otel/metric v1.35.0 // indirect
+	go.opentelemetry.io/otel/sdk v1.35.0 // indirect
 	go.opentelemetry.io/otel/trace v1.35.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
+	golang.org/x/sys v0.30.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

bridges/otelzap/go.sum

@@ -7,6 +7,8 @@ github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
+github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
 github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
@@ -21,10 +23,16 @@ go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJyS
 go.opentelemetry.io/auto/sdk v1.1.0/go.mod h1:3wSPjt5PWp2RhlCcmmOial7AvC4DQqZb7a7wCow3W8A=
 go.opentelemetry.io/otel v1.35.0 h1:xKWKPxrxB6OtMCbmMY021CqC45J+3Onta9MqjhnusiQ=
 go.opentelemetry.io/otel v1.35.0/go.mod h1:UEqy8Zp11hpkUrL73gSlELM0DupHoiq72dR+Zqel/+Y=
+go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.11.0 h1:k6KdfZk72tVW/QVZf60xlDziDvYAePj5QHwoQvrB2m8=
+go.opentelemetry.io/otel/exporters/stdout/stdoutlog v0.11.0/go.mod h1:5Y3ZJLqzi/x/kYtrSrPSx7TFI/SGsL7q2kME027tH6I=
 go.opentelemetry.io/otel/log v0.11.0 h1:c24Hrlk5WJ8JWcwbQxdBqxZdOK7PcP/LFtOtwpDTe3Y=
 go.opentelemetry.io/otel/log v0.11.0/go.mod h1:U/sxQ83FPmT29trrifhQg+Zj2lo1/IPN1PF6RTFqdwc=
 go.opentelemetry.io/otel/metric v1.35.0 h1:0znxYu2SNyuMSQT4Y9WDWej0VpcsxkuklLa4/siN90M=
 go.opentelemetry.io/otel/metric v1.35.0/go.mod h1:nKVFgxBZ2fReX6IlyW28MgZojkoAkJGaE8CpgeAU3oE=
+go.opentelemetry.io/otel/sdk v1.35.0 h1:iPctf8iprVySXSKJffSS79eOjl9pvxV9ZqOWT0QejKY=
+go.opentelemetry.io/otel/sdk v1.35.0/go.mod h1:+ga1bZliga3DxJ3CQGg3updiaAJoNECOgJREo9KHGQg=
+go.opentelemetry.io/otel/sdk/log v0.11.0 h1:7bAOpjpGglWhdEzP8z0VXc4jObOiDEwr3IYbhBnjk2c=
+go.opentelemetry.io/otel/sdk/log v0.11.0/go.mod h1:dndLTxZbwBstZoqsJB3kGsRPkpAgaJrWfQg3lhlHFFY=
 go.opentelemetry.io/otel/trace v1.35.0 h1:dPpEfJu1sDIqruz7BHFG3c7528f6ddfSWfFDVt/xgMs=
 go.opentelemetry.io/otel/trace v1.35.0/go.mod h1:WUk7DtFp1Aw2MkvqGdwiXYDZZNvA/1J8o6xRXLrIkyc=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
@@ -33,6 +41,8 @@ go.uber.org/multierr v1.11.0 h1:blXXJkSxSSfBVBlC76pxqeO+LN3aDfLQo+309xJstO0=
 go.uber.org/multierr v1.11.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
 go.uber.org/zap v1.27.0 h1:aJMhYGrd5QSmlpLMr2MftRKl7t8J8PTZPA732ud/XR8=
 go.uber.org/zap v1.27.0/go.mod h1:GB2qFLM7cTU87MWRP2mPIjqfIDnGu+VIO4V/SdhGo2E=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
 gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=