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opentelemetry-go/sdk/metric/sdk.go
Joshua MacDonald 4047c0877a
Introduce metric constructor errors, MeterMust wrapper (#529)
* Update api for Must constructors, with SDK helpers

* Update for Must constructors, leaving TODOs about global errors

* Add tests

* Move Must methods into metric.Must

* Apply the feedback

* Remove interfaces

* Remove more interfaces

* Again...

* Remove a sentence about a dead inteface
2020-03-11 11:57:57 -07:00

718 lines
20 KiB
Go

// Copyright 2019, 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 metric
import (
"context"
"fmt"
"os"
"reflect"
"runtime"
"sort"
"sync"
"sync/atomic"
"go.opentelemetry.io/otel/api/core"
"go.opentelemetry.io/otel/api/metric"
api "go.opentelemetry.io/otel/api/metric"
export "go.opentelemetry.io/otel/sdk/export/metric"
"go.opentelemetry.io/otel/sdk/export/metric/aggregator"
)
type (
// SDK implements the OpenTelemetry Meter API. The SDK is
// bound to a single export.Batcher in `New()`.
//
// The SDK supports a Collect() API to gather and export
// current data. Collect() should be arranged according to
// the batcher model. Push-based batchers will setup a
// timer to call Collect() periodically. Pull-based batchers
// will call Collect() when a pull request arrives.
SDK struct {
// current maps `mapkey` to *record.
current sync.Map
// observers is a set of `*observer` instances
observers sync.Map
// empty is the (singleton) result of Labels()
// w/ zero arguments.
empty labels
// currentEpoch is the current epoch number. It is
// incremented in `Collect()`.
currentEpoch int64
// batcher is the configured batcher+configuration.
batcher export.Batcher
// lencoder determines how labels are uniquely encoded.
labelEncoder export.LabelEncoder
// collectLock prevents simultaneous calls to Collect().
collectLock sync.Mutex
// errorHandler supports delivering errors to the user.
errorHandler ErrorHandler
}
instrument struct {
descriptor *export.Descriptor
meter *SDK
}
// orderedLabels is a variable-size array of core.KeyValue
// suitable for use as a map key.
orderedLabels interface{}
// labels implements the OpenTelemetry LabelSet API,
// represents an internalized set of labels that may be used
// repeatedly.
labels struct {
meter *SDK
// slice is a slice of `ordered`.
slice sortedLabels
// ordered is the output of sorting and deduplicating
// the labels, copied into an array of the correct
// size for use as a map key.
ordered orderedLabels
}
// mapkey uniquely describes a metric instrument in terms of
// its InstrumentID and the encoded form of its LabelSet.
mapkey struct {
descriptor *export.Descriptor
ordered orderedLabels
}
// record maintains the state of one metric instrument. Due
// the use of lock-free algorithms, there may be more than one
// `record` in existence at a time, although at most one can
// be referenced from the `SDK.current` map.
record struct {
// refMapped keeps track of refcounts and the mapping state to the
// SDK.current map.
refMapped refcountMapped
// modified is an atomic boolean that tracks if the current record
// was modified since the last Collect().
//
// modified has to be aligned for 64-bit atomic operations.
modified int64
// labels is the LabelSet passed by the user.
labels *labels
// descriptor describes the metric instrument.
descriptor *export.Descriptor
// recorder implements the actual RecordOne() API,
// depending on the type of aggregation. If nil, the
// metric was disabled by the exporter.
recorder export.Aggregator
}
observerResult struct {
observer *observer
}
int64ObserverResult struct {
result observerResult
}
float64ObserverResult struct {
result observerResult
}
observerCallback func(result observerResult)
observer struct {
meter *SDK
descriptor *export.Descriptor
// recorders maps ordered labels to the pair of
// labelset and recorder
recorders map[orderedLabels]labeledRecorder
callback observerCallback
}
labeledRecorder struct {
recorder export.Aggregator
labels *labels
modifiedEpoch int64
}
int64Observer struct {
observer *observer
}
float64Observer struct {
observer *observer
}
ErrorHandler func(error)
)
var (
_ api.Meter = &SDK{}
_ api.LabelSet = &labels{}
_ api.InstrumentImpl = &instrument{}
_ api.BoundInstrumentImpl = &record{}
_ api.Int64Observer = int64Observer{}
_ api.Float64Observer = float64Observer{}
_ api.Int64ObserverResult = int64ObserverResult{}
_ api.Float64ObserverResult = float64ObserverResult{}
kvType = reflect.TypeOf(core.KeyValue{})
)
func (r observerResult) observe(number core.Number, ls api.LabelSet) {
r.observer.recordOne(number, ls)
}
func (o *observer) recordOne(number core.Number, ls api.LabelSet) {
if err := aggregator.RangeTest(number, o.descriptor); err != nil {
o.meter.errorHandler(err)
return
}
recorder := o.getRecorder(ls)
if recorder == nil {
// The instrument is disabled according to the
// AggregationSelector.
return
}
if err := recorder.Update(context.Background(), number, o.descriptor); err != nil {
o.meter.errorHandler(err)
return
}
}
func (o *observer) getRecorder(ls api.LabelSet) export.Aggregator {
labels := o.meter.labsFor(ls)
lrec, ok := o.recorders[labels.ordered]
if ok {
lrec.modifiedEpoch = o.meter.currentEpoch
o.recorders[labels.ordered] = lrec
return lrec.recorder
}
rec := o.meter.batcher.AggregatorFor(o.descriptor)
if o.recorders == nil {
o.recorders = make(map[orderedLabels]labeledRecorder)
}
// This may store nil recorder in the map, thus disabling the
// observer for the labelset for good. This is intentional,
// but will be revisited later.
o.recorders[labels.ordered] = labeledRecorder{
recorder: rec,
labels: labels,
modifiedEpoch: o.meter.currentEpoch,
}
return rec
}
func (o *observer) unregister() {
o.meter.observers.Delete(o)
}
func (r int64ObserverResult) Observe(value int64, labels api.LabelSet) {
r.result.observe(core.NewInt64Number(value), labels)
}
func (r float64ObserverResult) Observe(value float64, labels api.LabelSet) {
r.result.observe(core.NewFloat64Number(value), labels)
}
func (o int64Observer) Unregister() {
o.observer.unregister()
}
func (o float64Observer) Unregister() {
o.observer.unregister()
}
func (i *instrument) Meter() api.Meter {
return i.meter
}
func (m *SDK) SetErrorHandler(f ErrorHandler) {
m.errorHandler = f
}
func (i *instrument) acquireHandle(ls *labels) *record {
// Create lookup key for sync.Map (one allocation)
mk := mapkey{
descriptor: i.descriptor,
ordered: ls.ordered,
}
if actual, ok := i.meter.current.Load(mk); ok {
// Existing record case, only one allocation so far.
rec := actual.(*record)
if rec.refMapped.ref() {
// At this moment it is guaranteed that the entry is in
// the map and will not be removed.
return rec
}
// This entry is no longer mapped, try to add a new entry.
}
// There's a memory allocation here.
rec := &record{
labels: ls,
descriptor: i.descriptor,
refMapped: refcountMapped{value: 2},
modified: 0,
recorder: i.meter.batcher.AggregatorFor(i.descriptor),
}
for {
// Load/Store: there's a memory allocation to place `mk` into
// an interface here.
if actual, loaded := i.meter.current.LoadOrStore(mk, rec); loaded {
// Existing record case. Cannot change rec here because if fail
// will try to add rec again to avoid new allocations.
oldRec := actual.(*record)
if oldRec.refMapped.ref() {
// At this moment it is guaranteed that the entry is in
// the map and will not be removed.
return oldRec
}
// This loaded entry is marked as unmapped (so Collect will remove
// it from the map immediately), try again - this is a busy waiting
// strategy to wait until Collect() removes this entry from the map.
//
// This can be improved by having a list of "Unmapped" entries for
// one time only usages, OR we can make this a blocking path and use
// a Mutex that protects the delete operation (delete only if the old
// record is associated with the key).
// Let collector get work done to remove the entry from the map.
runtime.Gosched()
continue
}
// The new entry was added to the map, good to go.
return rec
}
}
func (i *instrument) Bind(ls api.LabelSet) api.BoundInstrumentImpl {
labs := i.meter.labsFor(ls)
return i.acquireHandle(labs)
}
func (i *instrument) RecordOne(ctx context.Context, number core.Number, ls api.LabelSet) {
ourLs := i.meter.labsFor(ls)
h := i.acquireHandle(ourLs)
defer h.Unbind()
h.RecordOne(ctx, number)
}
// New constructs a new SDK for the given batcher. This SDK supports
// only a single batcher.
//
// The SDK does not start any background process to collect itself
// periodically, this responsbility lies with the batcher, typically,
// depending on the type of export. For example, a pull-based
// batcher will call Collect() when it receives a request to scrape
// current metric values. A push-based batcher should configure its
// own periodic collection.
func New(batcher export.Batcher, labelEncoder export.LabelEncoder) *SDK {
m := &SDK{
batcher: batcher,
labelEncoder: labelEncoder,
errorHandler: DefaultErrorHandler,
}
m.empty.meter = m
return m
}
func DefaultErrorHandler(err error) {
fmt.Fprintln(os.Stderr, "Metrics SDK error:", err)
}
// Labels returns a LabelSet corresponding to the arguments. Passed
// labels are de-duplicated, with last-value-wins semantics.
func (m *SDK) Labels(kvs ...core.KeyValue) api.LabelSet {
// Check for empty set.
if len(kvs) == 0 {
return &m.empty
}
ls := &labels{ // allocation
meter: m,
slice: kvs,
}
// Sort and de-duplicate. Note: this use of `ls.slice` avoids
// an allocation by using the address-able field rather than
// `kvs`. Labels retains a copy of this slice, i.e., the
// initial allocation at the varargs call site.
//
// Note that `ls.slice` continues to refer to this memory,
// even though a new array is allocated for `ls.ordered`. It
// is possible for the `slice` to refer to the same memory,
// although in the reflection code path of `computeOrdered` it
// costs an allocation to yield a slice through
// `(reflect.Value).Interface()`.
//
// TODO: There is a possibility that the caller passes values
// without an allocation (e.g., `meter.Labels(kvs...)`), and
// that the user could later modify the slice, leading to
// incorrect results. This is indeed a risk, one that should
// be quickly addressed via the following TODO.
//
// TODO: It would be better overall if the export.Labels interface
// did not expose a slice via `Ordered()`, if instead it exposed
// getter methods like `Len()` and `Order(i int)`. Then we would
// just implement the interface using the `orderedLabels` array.
sort.Stable(&ls.slice)
oi := 1
for i := 1; i < len(kvs); i++ {
if kvs[i-1].Key == kvs[i].Key {
// Overwrite the value for "last-value wins".
kvs[oi-1].Value = kvs[i].Value
continue
}
kvs[oi] = kvs[i]
oi++
}
kvs = kvs[0:oi]
ls.slice = kvs
ls.computeOrdered(kvs)
return ls
}
func (ls *labels) computeOrdered(kvs []core.KeyValue) {
switch len(kvs) {
case 1:
ptr := new([1]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 2:
ptr := new([2]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 3:
ptr := new([3]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 4:
ptr := new([4]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 5:
ptr := new([5]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 6:
ptr := new([6]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 7:
ptr := new([7]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 8:
ptr := new([8]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 9:
ptr := new([9]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
case 10:
ptr := new([10]core.KeyValue)
copy((*ptr)[:], kvs)
ls.ordered = *ptr
default:
at := reflect.New(reflect.ArrayOf(len(kvs), kvType)).Elem()
for i := 0; i < len(kvs); i++ {
*(at.Index(i).Addr().Interface().(*core.KeyValue)) = kvs[i]
}
ls.ordered = at.Interface()
}
}
// labsFor sanitizes the input LabelSet. The input will be rejected
// if it was created by another Meter instance, for example.
func (m *SDK) labsFor(ls api.LabelSet) *labels {
if del, ok := ls.(api.LabelSetDelegate); ok {
ls = del.Delegate()
}
if l, _ := ls.(*labels); l != nil && l.meter == m {
return l
}
return &m.empty
}
func newDescriptor(name string, metricKind export.Kind, numberKind core.NumberKind, opts *api.Options) *export.Descriptor {
return export.NewDescriptor(
name,
metricKind,
opts.Keys,
opts.Description,
opts.Unit,
numberKind,
opts.Alternate)
}
func (m *SDK) newInstrument(name string, metricKind export.Kind, numberKind core.NumberKind, opts *api.Options) *instrument {
descriptor := newDescriptor(name, metricKind, numberKind, opts)
return &instrument{
descriptor: descriptor,
meter: m,
}
}
func (m *SDK) newCounterInstrument(name string, numberKind core.NumberKind, cos ...api.CounterOptionApplier) *instrument {
opts := api.Options{}
api.ApplyCounterOptions(&opts, cos...)
return m.newInstrument(name, export.CounterKind, numberKind, &opts)
}
func (m *SDK) newMeasureInstrument(name string, numberKind core.NumberKind, mos ...api.MeasureOptionApplier) *instrument {
opts := api.Options{}
api.ApplyMeasureOptions(&opts, mos...)
return m.newInstrument(name, export.MeasureKind, numberKind, &opts)
}
func (m *SDK) NewInt64Counter(name string, cos ...api.CounterOptionApplier) (api.Int64Counter, error) {
return api.WrapInt64CounterInstrument(m.newCounterInstrument(name, core.Int64NumberKind, cos...), nil)
}
func (m *SDK) NewFloat64Counter(name string, cos ...api.CounterOptionApplier) (api.Float64Counter, error) {
return api.WrapFloat64CounterInstrument(m.newCounterInstrument(name, core.Float64NumberKind, cos...), nil)
}
func (m *SDK) NewInt64Measure(name string, mos ...api.MeasureOptionApplier) (api.Int64Measure, error) {
return api.WrapInt64MeasureInstrument(m.newMeasureInstrument(name, core.Int64NumberKind, mos...), nil)
}
func (m *SDK) NewFloat64Measure(name string, mos ...api.MeasureOptionApplier) (api.Float64Measure, error) {
return api.WrapFloat64MeasureInstrument(m.newMeasureInstrument(name, core.Float64NumberKind, mos...), nil)
}
func (m *SDK) RegisterInt64Observer(name string, callback api.Int64ObserverCallback, oos ...api.ObserverOptionApplier) (api.Int64Observer, error) {
if callback == nil {
return api.NoopMeter{}.RegisterInt64Observer("", nil)
}
opts := api.Options{}
api.ApplyObserverOptions(&opts, oos...)
descriptor := newDescriptor(name, export.ObserverKind, core.Int64NumberKind, &opts)
cb := wrapInt64ObserverCallback(callback)
obs := m.newObserver(descriptor, cb)
return int64Observer{
observer: obs,
}, nil
}
func wrapInt64ObserverCallback(callback api.Int64ObserverCallback) observerCallback {
return func(result observerResult) {
typeSafeResult := int64ObserverResult{
result: result,
}
callback(typeSafeResult)
}
}
func (m *SDK) RegisterFloat64Observer(name string, callback api.Float64ObserverCallback, oos ...api.ObserverOptionApplier) (api.Float64Observer, error) {
if callback == nil {
return api.NoopMeter{}.RegisterFloat64Observer("", nil)
}
opts := api.Options{}
api.ApplyObserverOptions(&opts, oos...)
descriptor := newDescriptor(name, export.ObserverKind, core.Float64NumberKind, &opts)
cb := wrapFloat64ObserverCallback(callback)
obs := m.newObserver(descriptor, cb)
return float64Observer{
observer: obs,
}, nil
}
func wrapFloat64ObserverCallback(callback api.Float64ObserverCallback) observerCallback {
return func(result observerResult) {
typeSafeResult := float64ObserverResult{
result: result,
}
callback(typeSafeResult)
}
}
func (m *SDK) newObserver(descriptor *export.Descriptor, callback observerCallback) *observer {
obs := &observer{
meter: m,
descriptor: descriptor,
recorders: nil,
callback: callback,
}
m.observers.Store(obs, nil)
return obs
}
// Collect traverses the list of active records and observers and
// exports data for each active instrument. Collect() may not be
// called concurrently.
//
// During the collection pass, the export.Batcher will receive
// one Export() call per current aggregation.
//
// Returns the number of records that were checkpointed.
func (m *SDK) Collect(ctx context.Context) int {
m.collectLock.Lock()
defer m.collectLock.Unlock()
checkpointed := m.collectRecords(ctx)
checkpointed += m.collectObservers(ctx)
m.currentEpoch++
return checkpointed
}
func (m *SDK) collectRecords(ctx context.Context) int {
checkpointed := 0
m.current.Range(func(key interface{}, value interface{}) bool {
inuse := value.(*record)
unmapped := inuse.refMapped.tryUnmap()
// If able to unmap then remove the record from the current Map.
if unmapped {
m.current.Delete(inuse.mapkey())
}
// Always report the values if a reference to the Record is active,
// this is to keep the previous behavior.
// TODO: Reconsider this logic.
if inuse.refMapped.inUse() || atomic.LoadInt64(&inuse.modified) != 0 {
atomic.StoreInt64(&inuse.modified, 0)
checkpointed += m.checkpointRecord(ctx, inuse)
}
// Always continue to iterate over the entire map.
return true
})
return checkpointed
}
func (m *SDK) collectObservers(ctx context.Context) int {
checkpointed := 0
m.observers.Range(func(key, value interface{}) bool {
obs := key.(*observer)
result := observerResult{
observer: obs,
}
obs.callback(result)
checkpointed += m.checkpointObserver(ctx, obs)
return true
})
return checkpointed
}
func (m *SDK) checkpointRecord(ctx context.Context, r *record) int {
return m.checkpoint(ctx, r.descriptor, r.recorder, r.labels)
}
func (m *SDK) checkpointObserver(ctx context.Context, obs *observer) int {
if len(obs.recorders) == 0 {
return 0
}
checkpointed := 0
for encodedLabels, lrec := range obs.recorders {
epochDiff := m.currentEpoch - lrec.modifiedEpoch
if epochDiff == 0 {
checkpointed += m.checkpoint(ctx, obs.descriptor, lrec.recorder, lrec.labels)
} else if epochDiff > 1 {
// This is second collection cycle with no
// observations for this labelset. Remove the
// recorder.
delete(obs.recorders, encodedLabels)
}
}
if len(obs.recorders) == 0 {
obs.recorders = nil
}
return checkpointed
}
func (m *SDK) checkpoint(ctx context.Context, descriptor *export.Descriptor, recorder export.Aggregator, labels *labels) int {
if recorder == nil {
return 0
}
recorder.Checkpoint(ctx, descriptor)
// TODO Labels are encoded once per collection interval,
// instead of once per bound instrument lifetime. This can be
// addressed similarly to OTEP 78, see
// https://github.com/jmacd/opentelemetry-go/blob/8bed2e14df7f9f4688fbab141924bb786dc9a3a1/api/context/internal/set.go#L89
exportLabels := export.NewLabels(labels.slice, m.labelEncoder.Encode(labels.slice), m.labelEncoder)
exportRecord := export.NewRecord(descriptor, exportLabels, recorder)
err := m.batcher.Process(ctx, exportRecord)
if err != nil {
m.errorHandler(err)
}
return 1
}
// RecordBatch enters a batch of metric events.
func (m *SDK) RecordBatch(ctx context.Context, ls api.LabelSet, measurements ...api.Measurement) {
for _, meas := range measurements {
meas.InstrumentImpl().RecordOne(ctx, meas.Number(), ls)
}
}
// GetDescriptor returns the descriptor of an instrument, which is not
// part of the public metric API.
func (m *SDK) GetDescriptor(inst metric.InstrumentImpl) *export.Descriptor {
if ii, ok := inst.(*instrument); ok {
return ii.descriptor
}
return nil
}
func (r *record) RecordOne(ctx context.Context, number core.Number) {
if r.recorder == nil {
// The instrument is disabled according to the AggregationSelector.
return
}
if err := aggregator.RangeTest(number, r.descriptor); err != nil {
r.labels.meter.errorHandler(err)
return
}
if err := r.recorder.Update(ctx, number, r.descriptor); err != nil {
r.labels.meter.errorHandler(err)
return
}
}
func (r *record) Unbind() {
// Record was modified, inform the Collect() that things need to be collected.
// TODO: Reconsider if we should marked as modified when an Update happens and
// collect only when updates happened even for Bounds.
atomic.StoreInt64(&r.modified, 1)
r.refMapped.unref()
}
func (r *record) mapkey() mapkey {
return mapkey{
descriptor: r.descriptor,
ordered: r.labels.ordered,
}
}