Support a global MeterProvider in go.opentelemetry.io/otel (open-telemetry#3818)

* Move ErrorHandler impl to internal

To avoid the import cycle, the otel/metric package needs to not import
otel. To achieve this, the error handling implementation is moved to the
otel/internal/global package where both can import the needed
functionality.

* Add global metric to go.opentelemetry.io/otel

* Crosslink and update to global metric in otel

* Add changes to changelog

* Set PR number in changelog

* Add global metric unit tests

* Rename MeterProivder() to GetMeterProivder()

* Add TODO to remove nolint comments

Author: MrAlias

CHANGELOG.md

@@ -8,6 +8,13 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- Support global `MeterProvider` in `go.opentelemetry.io/otel`. (#3818)
+  - Use `Meter` for a `metric.Meter` from the global `metric.MeterProvider`.
+  - Use `GetMeterProivder` for a global `metric.MeterProvider`.
+  - Use `SetMeterProivder` to set the global `metric.MeterProvider`.
+
 ### Changed
 
 - Dropped compatibility testing for [Go 1.18].
@@ -17,6 +24,11 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Handle empty environment variable as it they were not set. (#3764)
 
+### Deprecated
+
+- The `go.opentelemetry.io/otel/metric/global` package is deprecated.
+  Use `go.opentelemetry.io/otel` instead. (#3818)
+
 ### Removed
 
 - The deprecated `go.opentelemetry.io/otel/metric/unit` package is removed. (#3814)

bridge/opentracing/go.mod

@@ -18,5 +18,8 @@ require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace go.opentelemetry.io/otel/metric => ../../metric

bridge/opentracing/test/go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/otel/trace v1.14.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
@@ -31,3 +32,5 @@ require (
 	google.golang.org/protobuf v1.28.1 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace go.opentelemetry.io/otel/metric => ../../../metric

example/fib/go.mod

@@ -12,6 +12,7 @@ require (
 require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 )
 
@@ -22,3 +23,5 @@ replace go.opentelemetry.io/otel/exporters/stdout/stdouttrace => ../../exporters
 replace go.opentelemetry.io/otel/sdk => ../../sdk
 
 replace go.opentelemetry.io/otel/trace => ../../trace
+
+replace go.opentelemetry.io/otel/metric => ../../metric

example/jaeger/go.mod

@@ -17,8 +17,11 @@ require (
 require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/otel/trace v1.14.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 )
 
 replace go.opentelemetry.io/otel/trace => ../../trace
+
+replace go.opentelemetry.io/otel/metric => ../../metric

example/namedtracer/go.mod

@@ -17,9 +17,12 @@ require (
 
 require (
 	github.com/go-logr/logr v1.2.3 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 )
 
 replace go.opentelemetry.io/otel/trace => ../../trace
 
 replace go.opentelemetry.io/otel/exporters/stdout/stdouttrace => ../../exporters/stdout/stdouttrace
+
+replace go.opentelemetry.io/otel/metric => ../../metric

example/otel-collector/go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.14.0 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.14.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/proto/otlp v0.19.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
@@ -38,3 +39,5 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace => ../../exporters/otl
 replace go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc => ../../exporters/otlp/otlptrace/otlptracegrpc
 
 replace go.opentelemetry.io/otel/exporters/otlp/internal/retry => ../../exporters/otlp/internal/retry
+
+replace go.opentelemetry.io/otel/metric => ../../metric

example/passthrough/go.mod

@@ -12,6 +12,7 @@ require (
 require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 )
 
@@ -22,3 +23,5 @@ replace (
 )
 
 replace go.opentelemetry.io/otel/exporters/stdout/stdouttrace => ../../exporters/stdout/stdouttrace
+
+replace go.opentelemetry.io/otel/metric => ../../metric

example/zipkin/go.mod

@@ -19,7 +19,10 @@ require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/openzipkin/zipkin-go v0.4.1 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 )
 
 replace go.opentelemetry.io/otel/trace => ../../trace
+
+replace go.opentelemetry.io/otel/metric => ../../metric

exporters/jaeger/go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/stretchr/objx v0.5.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
@@ -25,3 +26,5 @@ replace go.opentelemetry.io/otel/trace => ../../trace
 replace go.opentelemetry.io/otel => ../..
 
 replace go.opentelemetry.io/otel/sdk => ../../sdk
+
+replace go.opentelemetry.io/otel/metric => ../../metric

exporters/otlp/otlpmetric/otlpmetricgrpc/example_test.go

@@ -17,8 +17,8 @@ package otlpmetricgrpc_test
 import (
 	"context"
 
+	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc"
-	"go.opentelemetry.io/otel/metric/global"
 	"go.opentelemetry.io/otel/sdk/metric"
 )
 
@@ -35,7 +35,7 @@ func Example() {
 			panic(err)
 		}
 	}()
-	global.SetMeterProvider(meterProvider)
+	otel.SetMeterProvider(meterProvider)
 
 	// From here, the meterProvider can be used by instrumentation to collect
 	// telemetry.

exporters/otlp/otlpmetric/otlpmetricgrpc/go.mod

@@ -9,7 +9,6 @@ require (
 	go.opentelemetry.io/otel v1.14.0
 	go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.14.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric v0.37.0
-	go.opentelemetry.io/otel/metric v0.37.0
 	go.opentelemetry.io/otel/sdk/metric v0.37.0
 	go.opentelemetry.io/proto/otlp v0.19.0
 	google.golang.org/genproto v0.0.0-20230110181048-76db0878b65f
@@ -26,6 +25,7 @@ require (
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.14.0 // indirect
 	go.opentelemetry.io/otel/trace v1.14.0 // indirect
 	golang.org/x/net v0.7.0 // indirect

exporters/otlp/otlpmetric/otlpmetrichttp/example_test.go

@@ -17,8 +17,8 @@ package otlpmetrichttp_test
 import (
 	"context"
 
+	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp"
-	"go.opentelemetry.io/otel/metric/global"
 	"go.opentelemetry.io/otel/sdk/metric"
 )
 
@@ -35,7 +35,7 @@ func Example() {
 			panic(err)
 		}
 	}()
-	global.SetMeterProvider(meterProvider)
+	otel.SetMeterProvider(meterProvider)
 
 	// From here, the meterProvider can be used by instrumentation to collect
 	// telemetry.

exporters/otlp/otlpmetric/otlpmetrichttp/go.mod

@@ -9,7 +9,6 @@ require (
 	go.opentelemetry.io/otel v1.14.0
 	go.opentelemetry.io/otel/exporters/otlp/internal/retry v1.14.0
 	go.opentelemetry.io/otel/exporters/otlp/otlpmetric v0.37.0
-	go.opentelemetry.io/otel/metric v0.37.0
 	go.opentelemetry.io/otel/sdk/metric v0.37.0
 	go.opentelemetry.io/proto/otlp v0.19.0
 	google.golang.org/protobuf v1.28.1
@@ -24,6 +23,7 @@ require (
 	github.com/google/go-cmp v0.5.9 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.14.0 // indirect
 	go.opentelemetry.io/otel/trace v1.14.0 // indirect
 	golang.org/x/net v0.7.0 // indirect

exporters/otlp/otlptrace/go.mod

@@ -22,6 +22,7 @@ require (
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	golang.org/x/text v0.7.0 // indirect
@@ -36,3 +37,5 @@ replace go.opentelemetry.io/otel/sdk => ../../../sdk
 replace go.opentelemetry.io/otel/trace => ../../../trace
 
 replace go.opentelemetry.io/otel/exporters/otlp/internal/retry => ../internal/retry
+
+replace go.opentelemetry.io/otel/metric => ../../../metric

exporters/otlp/otlptrace/otlptracegrpc/go.mod

@@ -23,6 +23,7 @@ require (
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	go.opentelemetry.io/otel/trace v1.14.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
@@ -39,3 +40,5 @@ replace go.opentelemetry.io/otel/exporters/otlp/otlptrace => ../
 replace go.opentelemetry.io/otel/trace => ../../../../trace
 
 replace go.opentelemetry.io/otel/exporters/otlp/internal/retry => ../../internal/retry
+
+replace go.opentelemetry.io/otel/metric => ../../../../metric

exporters/otlp/otlptrace/otlptracehttp/go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.7.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	golang.org/x/text v0.7.0 // indirect
@@ -38,3 +39,5 @@ replace go.opentelemetry.io/otel/sdk => ../../../../sdk
 replace go.opentelemetry.io/otel/trace => ../../../../trace
 
 replace go.opentelemetry.io/otel/exporters/otlp/internal/retry => ../../internal/retry
+
+replace go.opentelemetry.io/otel/metric => ../../../../metric

exporters/stdout/stdouttrace/go.mod

@@ -19,8 +19,11 @@ require (
 	github.com/go-logr/logr v1.2.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
 
 replace go.opentelemetry.io/otel/trace => ../../../trace
+
+replace go.opentelemetry.io/otel/metric => ../../../metric

exporters/zipkin/go.mod

@@ -16,6 +16,7 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	go.opentelemetry.io/otel/metric v0.37.0 // indirect
 	golang.org/x/sys v0.5.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
@@ -25,3 +26,5 @@ replace go.opentelemetry.io/otel/trace => ../../trace
 replace go.opentelemetry.io/otel => ../..
 
 replace go.opentelemetry.io/otel/sdk => ../../sdk
+
+replace go.opentelemetry.io/otel/metric => ../../metric

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/go-logr/stdr v1.2.2
 	github.com/google/go-cmp v0.5.9
 	github.com/stretchr/testify v1.8.2
+	go.opentelemetry.io/otel/metric v0.37.0
 	go.opentelemetry.io/otel/trace v1.14.0
 )
 
@@ -17,3 +18,5 @@ require (
 )
 
 replace go.opentelemetry.io/otel/trace => ./trace
+
+replace go.opentelemetry.io/otel/metric => ./metric

handler.go

@@ -15,58 +15,16 @@
 package otel // import "go.opentelemetry.io/otel"
 
 import (
-	"log"
-	"os"
-	"sync/atomic"
-	"unsafe"
+	"go.opentelemetry.io/otel/internal/global"
 )
 
 var (
-	// globalErrorHandler provides an ErrorHandler that can be used
-	// throughout an OpenTelemetry instrumented project. When a user
-	// specified ErrorHandler is registered (`SetErrorHandler`) all calls to
-	// `Handle` and will be delegated to the registered ErrorHandler.
-	globalErrorHandler = defaultErrorHandler()
-
-	// Compile-time check that delegator implements ErrorHandler.
-	_ ErrorHandler = (*delegator)(nil)
-	// Compile-time check that errLogger implements ErrorHandler.
-	_ ErrorHandler = (*errLogger)(nil)
+	// Compile-time check global.ErrDelegator implements ErrorHandler.
+	_ ErrorHandler = (*global.ErrDelegator)(nil)
+	// Compile-time check global.ErrLogger implements ErrorHandler.
+	_ ErrorHandler = (*global.ErrLogger)(nil)
 )
 
-type delegator struct {
-	delegate unsafe.Pointer
-}
-
-func (d *delegator) Handle(err error) {
-	d.getDelegate().Handle(err)
-}
-
-func (d *delegator) getDelegate() ErrorHandler {
-	return *(*ErrorHandler)(atomic.LoadPointer(&d.delegate))
-}
-
-// setDelegate sets the ErrorHandler delegate.
-func (d *delegator) setDelegate(eh ErrorHandler) {
-	atomic.StorePointer(&d.delegate, unsafe.Pointer(&eh))
-}
-
-func defaultErrorHandler() *delegator {
-	d := &delegator{}
-	d.setDelegate(&errLogger{l: log.New(os.Stderr, "", log.LstdFlags)})
-	return d
-}
-
-// errLogger logs errors if no delegate is set, otherwise they are delegated.
-type errLogger struct {
-	l *log.Logger
-}
-
-// Handle logs err if no delegate is set, otherwise it is delegated.
-func (h *errLogger) Handle(err error) {
-	h.l.Print(err)
-}
-
 // GetErrorHandler returns the global ErrorHandler instance.
 //
 // The default ErrorHandler instance returned will log all errors to STDERR
@@ -76,21 +34,15 @@ func (h *errLogger) Handle(err error) {
 //
 // Subsequent calls to SetErrorHandler after the first will not forward errors
 // to the new ErrorHandler for prior returned instances.
-func GetErrorHandler() ErrorHandler {
-	return globalErrorHandler
-}
+func GetErrorHandler() ErrorHandler { return global.GetErrorHandler() }
 
 // SetErrorHandler sets the global ErrorHandler to h.
 //
 // The first time this is called all ErrorHandler previously returned from
 // GetErrorHandler will send errors to h instead of the default logging
 // ErrorHandler. Subsequent calls will set the global ErrorHandler, but not
 // delegate errors to h.
-func SetErrorHandler(h ErrorHandler) {
-	globalErrorHandler.setDelegate(h)
-}
+func SetErrorHandler(h ErrorHandler) { global.SetErrorHandler(h) }
 
 // Handle is a convenience function for ErrorHandler().Handle(err).
-func Handle(err error) {
-	GetErrorHandler().Handle(err)
-}
+func Handle(err error) { global.Handle(err) }