Metrics stdout export pipeline #265
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| // 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. | ||
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| package stdout // import "go.opentelemetry.io/otel/exporter/metric/stdout" | ||
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| import ( | ||
| "context" | ||
| "encoding/json" | ||
| "fmt" | ||
| "os" | ||
| "strings" | ||
| "time" | ||
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| export "go.opentelemetry.io/otel/sdk/export/metric" | ||
| "go.opentelemetry.io/otel/sdk/metric/aggregator" | ||
| ) | ||
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| type Exporter struct { | ||
| options Options | ||
| } | ||
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| // Options are the options to be used when initializing a stdout export. | ||
| type Options struct { | ||
| // File is the destination. If not set, os.Stdout is used. | ||
| File *os.File | ||
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| // PrettyPrint will pretty the json representation of the span, | ||
| // making it print "pretty". Default is false. | ||
| PrettyPrint bool | ||
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| // DoNotPrintTime suppresses timestamp printing. This is | ||
| // useful to create testable examples or if the are being | ||
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| DoNotPrintTime bool | ||
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| // Quantiles are the desired aggregation quantiles for measure | ||
| // metric data, used when the configured aggregator supports | ||
| // quantiles. | ||
| // | ||
| // Note: this exporter is meant as a demonstration; a real | ||
| // exporter may wish to configure quantiles on a per-metric | ||
| // basis. | ||
| Quantiles []float64 | ||
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| } | ||
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| type expoBatch struct { | ||
| Timestamp *time.Time `json:"time,omitempty"` | ||
| Updates []expoLine `json:"updates,omitempty"` | ||
| } | ||
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| type expoLine struct { | ||
| Name string `json:"name"` | ||
| Max interface{} `json:"max,omitempty"` | ||
| Sum interface{} `json:"sum,omitempty"` | ||
| Count interface{} `json:"count,omitempty"` | ||
| LastValue interface{} `json:"last,omitempty"` | ||
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| // Note: this is a pointer because omitempty doesn't work when time.IsZero() | ||
| Timestamp *time.Time `json:"time,omitempty"` | ||
| } | ||
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| var _ export.Exporter = &Exporter{} | ||
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| func New(options Options) *Exporter { | ||
| if options.File == nil { | ||
| options.File = os.Stdout | ||
| } | ||
| return &Exporter{ | ||
| options: options, | ||
| } | ||
| } | ||
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| func (e *Exporter) Export(_ context.Context, producer export.Producer) error { | ||
| var batch expoBatch | ||
| if !e.options.DoNotPrintTime { | ||
| ts := time.Now() | ||
| batch.Timestamp = &ts | ||
| } | ||
| producer.Foreach(func(record export.Record) { | ||
| desc := record.Descriptor() | ||
| labels := record.Labels() | ||
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| agg := record.Aggregator() | ||
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| var expose expoLine | ||
| if sum, ok := agg.(aggregator.Sum); ok { | ||
| expose.Sum = sum.Sum().Emit(desc.NumberKind()) | ||
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| } else if lv, ok := agg.(aggregator.LastValue); ok { | ||
| ts := lv.Timestamp() | ||
| expose.LastValue = lv.LastValue().Emit(desc.NumberKind()) | ||
| expose.Timestamp = &ts | ||
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| } else if msc, ok := agg.(aggregator.MaxSumCount); ok { | ||
| expose.Max = msc.Max().Emit(desc.NumberKind()) | ||
| expose.Sum = msc.Sum().Emit(desc.NumberKind()) | ||
| expose.Count = msc.Count().Emit(desc.NumberKind()) | ||
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| } else if dist, ok := agg.(aggregator.Distribution); ok { | ||
| expose.Max = dist.Max().Emit(desc.NumberKind()) | ||
| expose.Sum = dist.Sum().Emit(desc.NumberKind()) | ||
| expose.Count = dist.Count().Emit(desc.NumberKind()) | ||
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| // TODO print one configured quantile per line | ||
| } | ||
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| var sb strings.Builder | ||
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| sb.WriteString(desc.Name()) | ||
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| if labels.Len() > 0 { | ||
| sb.WriteRune('{') | ||
| sb.WriteString(labels.Encoded()) | ||
| sb.WriteRune('}') | ||
| } | ||
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| expose.Name = sb.String() | ||
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| batch.Updates = append(batch.Updates, expose) | ||
| }) | ||
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There was a problem hiding this comment. nit: Shouldn't you return err here first if Otherwise you might export output when there's an error that happened as you processed the batch? There was a problem hiding this comment. For this exporter specifically--if it is only an aggregator error not a marshal error--I figured it would be best to continue formatting the output and fill in "NaN". I figure NaN will parse as an error, but this at least yields a human-readable output. A single error is still returned, which the controller will print. I can be convinced to be less tolerant of errors though. |
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| var data []byte | ||
| var err error | ||
| if e.options.PrettyPrint { | ||
| data, err = json.MarshalIndent(batch, "", "\t") | ||
| } else { | ||
| data, err = json.Marshal(batch) | ||
| } | ||
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| if err != nil { | ||
| return err | ||
| } | ||
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| fmt.Fprintln(e.options.File, string(data)) | ||
| return nil | ||
| } | ||
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Use of these extra labels was not obvious until I understood how everything works. Essentially they are ignored because it is using defaultkey batcher which only uses labels defined as part of metric descriptor.
Also, labels set via distributedcontext are not automatically used. It is by design but it is not obvious.
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I sort of feel like throwing away this example. It's full of random, incoherent calls.