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// 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 internal
import (
"context"
"sync"
"sync/atomic"
"unsafe"
"go.opentelemetry.io/otel/api/metric"
"go.opentelemetry.io/otel/api/metric/registry"
"go.opentelemetry.io/otel/label"
)
// This file contains the forwarding implementation of MeterProvider used as
// the default global instance. Metric events using instruments provided by
// this implementation are no-ops until the first Meter implementation is set
// as the global provider.
//
// The implementation here uses Mutexes to maintain a list of active Meters in
// the MeterProvider and Instruments in each Meter, under the assumption that
// these interfaces are not performance-critical.
//
// We have the invariant that setDelegate() will be called before a new
// MeterProvider implementation is registered as the global provider. Mutexes
// in the MeterProvider and Meters ensure that each instrument has a delegate
// before the global provider is set.
//
// Bound instrument operations are implemented by delegating to the
// instrument after it is registered, with a sync.Once initializer to
// protect against races with Release().
//
// Metric uniqueness checking is implemented by calling the exported
// methods of the api/metric/registry package.
type meterKey struct {
Name, Version string
}
type meterProvider struct {
delegate metric.MeterProvider
// lock protects `delegate` and `meters`.
lock sync.Mutex
// meters maintains a unique entry for every named Meter
// that has been registered through the global instance.
meters map[meterKey]*meterEntry
}
type meterImpl struct {
delegate unsafe.Pointer // (*metric.MeterImpl)
lock sync.Mutex
syncInsts []*syncImpl
asyncInsts []*asyncImpl
}
type meterEntry struct {
unique metric.MeterImpl
impl meterImpl
}
type instrument struct {
descriptor metric.Descriptor
}
type syncImpl struct {
delegate unsafe.Pointer // (*metric.SyncImpl)
instrument
}
type asyncImpl struct {
delegate unsafe.Pointer // (*metric.AsyncImpl)
instrument
runner metric.AsyncRunner
}
// SyncImpler is implemented by all of the sync metric
// instruments.
type SyncImpler interface {
SyncImpl() metric.SyncImpl
}
// AsyncImpler is implemented by all of the async
// metric instruments.
type AsyncImpler interface {
AsyncImpl() metric.AsyncImpl
}
type syncHandle struct {
delegate unsafe.Pointer // (*metric.HandleImpl)
inst *syncImpl
labels []label.KeyValue
initialize sync.Once
}
var _ metric.MeterProvider = &meterProvider{}
var _ metric.MeterImpl = &meterImpl{}
var _ metric.InstrumentImpl = &syncImpl{}
var _ metric.BoundSyncImpl = &syncHandle{}
var _ metric.AsyncImpl = &asyncImpl{}
func (inst *instrument) Descriptor() metric.Descriptor {
return inst.descriptor
}
// MeterProvider interface and delegation
func newMeterProvider() *meterProvider {
return &meterProvider{
meters: map[meterKey]*meterEntry{},
}
}
func (p *meterProvider) setDelegate(provider metric.MeterProvider) {
p.lock.Lock()
defer p.lock.Unlock()
p.delegate = provider
for key, entry := range p.meters {
entry.impl.setDelegate(key.Name, key.Version, provider)
}
p.meters = nil
}
func (p *meterProvider) Meter(instrumentationName string, opts ...metric.MeterOption) metric.Meter {
p.lock.Lock()
defer p.lock.Unlock()
if p.delegate != nil {
return p.delegate.Meter(instrumentationName, opts...)
}
key := meterKey{
Name: instrumentationName,
Version: metric.NewMeterConfig(opts...).InstrumentationVersion,
}
entry, ok := p.meters[key]
if !ok {
entry = &meterEntry{}
entry.unique = registry.NewUniqueInstrumentMeterImpl(&entry.impl)
p.meters[key] = entry
}
return metric.WrapMeterImpl(entry.unique, key.Name, metric.WithInstrumentationVersion(key.Version))
}
// Meter interface and delegation
func (m *meterImpl) setDelegate(name, version string, provider metric.MeterProvider) {
m.lock.Lock()
defer m.lock.Unlock()
d := new(metric.MeterImpl)
*d = provider.Meter(name, metric.WithInstrumentationVersion(version)).MeterImpl()
m.delegate = unsafe.Pointer(d)
for _, inst := range m.syncInsts {
inst.setDelegate(*d)
}
m.syncInsts = nil
for _, obs := range m.asyncInsts {
obs.setDelegate(*d)
}
m.asyncInsts = nil
}
func (m *meterImpl) NewSyncInstrument(desc metric.Descriptor) (metric.SyncImpl, error) {
m.lock.Lock()
defer m.lock.Unlock()
if meterPtr := (*metric.MeterImpl)(atomic.LoadPointer(&m.delegate)); meterPtr != nil {
return (*meterPtr).NewSyncInstrument(desc)
}
inst := &syncImpl{
instrument: instrument{
descriptor: desc,
},
}
m.syncInsts = append(m.syncInsts, inst)
return inst, nil
}
// Synchronous delegation
func (inst *syncImpl) setDelegate(d metric.MeterImpl) {
implPtr := new(metric.SyncImpl)
var err error
*implPtr, err = d.NewSyncInstrument(inst.descriptor)
if err != nil {
// TODO: There is no standard way to deliver this error to the user.
// See https://github.com/open-telemetry/opentelemetry-go/issues/514
// Note that the default SDK will not generate any errors yet, this is
// only for added safety.
panic(err)
}
atomic.StorePointer(&inst.delegate, unsafe.Pointer(implPtr))
}
func (inst *syncImpl) Implementation() interface{} {
if implPtr := (*metric.SyncImpl)(atomic.LoadPointer(&inst.delegate)); implPtr != nil {
return (*implPtr).Implementation()
}
return inst
}
func (inst *syncImpl) Bind(labels []label.KeyValue) metric.BoundSyncImpl {
if implPtr := (*metric.SyncImpl)(atomic.LoadPointer(&inst.delegate)); implPtr != nil {
return (*implPtr).Bind(labels)
}
return &syncHandle{
inst: inst,
labels: labels,
}
}
func (bound *syncHandle) Unbind() {
bound.initialize.Do(func() {})
implPtr := (*metric.BoundSyncImpl)(atomic.LoadPointer(&bound.delegate))
if implPtr == nil {
return
}
(*implPtr).Unbind()
}
// Async delegation
func (m *meterImpl) NewAsyncInstrument(
desc metric.Descriptor,
runner metric.AsyncRunner,
) (metric.AsyncImpl, error) {
m.lock.Lock()
defer m.lock.Unlock()
if meterPtr := (*metric.MeterImpl)(atomic.LoadPointer(&m.delegate)); meterPtr != nil {
return (*meterPtr).NewAsyncInstrument(desc, runner)
}
inst := &asyncImpl{
instrument: instrument{
descriptor: desc,
},
runner: runner,
}
m.asyncInsts = append(m.asyncInsts, inst)
return inst, nil
}
func (obs *asyncImpl) Implementation() interface{} {
if implPtr := (*metric.AsyncImpl)(atomic.LoadPointer(&obs.delegate)); implPtr != nil {
return (*implPtr).Implementation()
}
return obs
}
func (obs *asyncImpl) setDelegate(d metric.MeterImpl) {
implPtr := new(metric.AsyncImpl)
var err error
*implPtr, err = d.NewAsyncInstrument(obs.descriptor, obs.runner)
if err != nil {
// TODO: There is no standard way to deliver this error to the user.
// See https://github.com/open-telemetry/opentelemetry-go/issues/514
// Note that the default SDK will not generate any errors yet, this is
// only for added safety.
panic(err)
}
atomic.StorePointer(&obs.delegate, unsafe.Pointer(implPtr))
}
// Metric updates
func (m *meterImpl) RecordBatch(ctx context.Context, labels []label.KeyValue, measurements ...metric.Measurement) {
if delegatePtr := (*metric.MeterImpl)(atomic.LoadPointer(&m.delegate)); delegatePtr != nil {
(*delegatePtr).RecordBatch(ctx, labels, measurements...)
}
}
func (inst *syncImpl) RecordOne(ctx context.Context, number metric.Number, labels []label.KeyValue) {
if instPtr := (*metric.SyncImpl)(atomic.LoadPointer(&inst.delegate)); instPtr != nil {
(*instPtr).RecordOne(ctx, number, labels)
}
}
// Bound instrument initialization
func (bound *syncHandle) RecordOne(ctx context.Context, number metric.Number) {
instPtr := (*metric.SyncImpl)(atomic.LoadPointer(&bound.inst.delegate))
if instPtr == nil {
return
}
var implPtr *metric.BoundSyncImpl
bound.initialize.Do(func() {
implPtr = new(metric.BoundSyncImpl)
*implPtr = (*instPtr).Bind(bound.labels)
atomic.StorePointer(&bound.delegate, unsafe.Pointer(implPtr))
})
if implPtr == nil {
implPtr = (*metric.BoundSyncImpl)(atomic.LoadPointer(&bound.delegate))
}
// This may still be nil if instrument was created and bound
// without a delegate, then the instrument was set to have a
// delegate and unbound.
if implPtr == nil {
return
}
(*implPtr).RecordOne(ctx, number)
}
func AtomicFieldOffsets() map[string]uintptr {
return map[string]uintptr{
"meterProvider.delegate": unsafe.Offsetof(meterProvider{}.delegate),
"meterImpl.delegate": unsafe.Offsetof(meterImpl{}.delegate),
"syncImpl.delegate": unsafe.Offsetof(syncImpl{}.delegate),
"asyncImpl.delegate": unsafe.Offsetof(asyncImpl{}.delegate),
"syncHandle.delegate": unsafe.Offsetof(syncHandle{}.delegate),
}
}