feat: initial tracing support (#1623)

vendor/go.opentelemetry.io/otel/internal/global/internal_logging.go

@@ -0,0 +1,63 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package global // import "go.opentelemetry.io/otel/internal/global"
+
+import (
+	"log"
+	"os"
+	"sync/atomic"
+	"unsafe"
+
+	"github.com/go-logr/logr"
+	"github.com/go-logr/stdr"
+)
+
+// globalLogger is the logging interface used within the otel api and sdk provide deatails of the internals.
+//
+// The default logger uses stdr which is backed by the standard `log.Logger`
+// interface. This logger will only show messages at the Error Level.
+var globalLogger unsafe.Pointer
+
+func init() {
+	SetLogger(stdr.New(log.New(os.Stderr, "", log.LstdFlags|log.Lshortfile)))
+}
+
+// SetLogger overrides the globalLogger with l.
+//
+// To see Info messages use a logger with `l.V(1).Enabled() == true`
+// To see Debug messages use a logger with `l.V(5).Enabled() == true`.
+func SetLogger(l logr.Logger) {
+	atomic.StorePointer(&globalLogger, unsafe.Pointer(&l))
+}
+
+func getLogger() logr.Logger {
+	return *(*logr.Logger)(atomic.LoadPointer(&globalLogger))
+}
+
+// Info prints messages about the general state of the API or SDK.
+// This should usually be less then 5 messages a minute.
+func Info(msg string, keysAndValues ...interface{}) {
+	getLogger().V(1).Info(msg, keysAndValues...)
+}
+
+// Error prints messages about exceptional states of the API or SDK.
+func Error(err error, msg string, keysAndValues ...interface{}) {
+	getLogger().Error(err, msg, keysAndValues...)
+}
+
+// Debug prints messages about all internal changes in the API or SDK.
+func Debug(msg string, keysAndValues ...interface{}) {
+	getLogger().V(5).Info(msg, keysAndValues...)
+}