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span (experimental): Compress short exit spans (#1134)
Implements the span compression algorithm described in elastic/apm#432. The implementation pretty close to what the spec describes, with a few modifications due to the differences in the Go agent implementation. The span compression is experimental and is disabled by default with the default thresholds for the different compression strategies set: - `ELASTIC_APM_SPAN_COMPRESSION_ENABLED=false` - `ELASTIC_APM_SPAN_COMPRESSION_EXACT_MATCH_MAX_DURATION=50ms` - `ELASTIC_APM_SPAN_COMPRESSION_SAME_KIND_MAX_DURATION=5ms` The implementation uses a new field (cache `*Span`) in `TransactionData` and `SpanData` which is used to cache compressed or compression eligible spans in that field. An additional `composite` field has also been added to the `SpanData` and `TransactionData`. The algorithm states that any exit span that is lower or equal duration than the set `ELASTIC_APM_SPAN_COMPRESSION_EXACT_MATCH_MAX_DURATION` or `ELASTIC_APM_SPAN_COMPRESSION_SAME_KIND_MAX_DURATION` with a destination service set is compressable into a composite span using the appropriate strategy. Compressable spans need to be "exit" and siblings which **have not** propagated their context downstream. Sibling spans are spans that share the same parent span (or transaction). Spans can be compressed with `same_kind` or `exact_match` as a strategy, and their sum is the aggregated duration of of all When a compressed span has been compressed into a composite using the `same_kind` strategy, its name is mutated to `Calls to <span.Type>`. Spans will be compressed into a composite only when the siblings are consecutive and any compression attempt that doesn't meet that, will cause the cache to be evicted. Additionally, two helper functions have been added under the `apmtest`: package: `WriteTraceTable` and `WriteTraceWaterfall`, which help with understanding why a test is failing if they are and debugging those. Signed-off-by: Marc Lopez Rubio <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,161 @@ | ||
| // Licensed to Elasticsearch B.V. under one or more contributor | ||
| // license agreements. See the NOTICE file distributed with | ||
| // this work for additional information regarding copyright | ||
| // ownership. Elasticsearch B.V. licenses this file to you 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 apmtest // import "go.elastic.co/apm/apmtest" | ||
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|
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| import ( | ||
| "bytes" | ||
| "fmt" | ||
| "io" | ||
| "sort" | ||
| "text/tabwriter" | ||
| "time" | ||
| "unicode/utf8" | ||
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|
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| "go.elastic.co/apm/internal/apmmath" | ||
| "go.elastic.co/apm/model" | ||
| ) | ||
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| // WriteTraceTable displays the trace as a table which can be used on tests to aid | ||
| // debugging. | ||
| func WriteTraceTable(writer io.Writer, tx model.Transaction, spans []model.Span) { | ||
| w := tabwriter.NewWriter(writer, 2, 4, 2, ' ', tabwriter.TabIndent) | ||
| fmt.Fprintln(w, "#\tNAME\tTYPE\tCOMP\tN\tDURATION\tOFFSET\tSPAN ID\tPARENT ID\tTRACE ID") | ||
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| fmt.Fprintf(w, "TX\t%s\t%s\t-\t-\t%f\t%d\t%x\t%x\t%x\n", tx.Name, | ||
| tx.Type, tx.Duration, | ||
| 0, | ||
| tx.ID, tx.ParentID, tx.TraceID, | ||
| ) | ||
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| sort.SliceStable(spans, func(i, j int) bool { | ||
| return time.Time(spans[i].Timestamp).Before(time.Time(spans[j].Timestamp)) | ||
| }) | ||
| for i, span := range spans { | ||
| count := 1 | ||
| if span.Composite != nil { | ||
| count = span.Composite.Count | ||
| } | ||
|
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| fmt.Fprintf(w, "%d\t%s\t%s\t%v\t%d\t%f\t+%d\t%x\t%x\t%x\n", i, span.Name, | ||
| span.Type, span.Composite != nil, count, span.Duration, | ||
| time.Time(span.Timestamp).Sub(time.Time(tx.Timestamp))/1e3, | ||
| span.ID, span.ParentID, span.TraceID, | ||
| ) | ||
| } | ||
| w.Flush() | ||
| } | ||
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| // WriteTraceWaterfall the trace waterfall "console output" to the specified | ||
| // writer sorted by timestamp. | ||
| func WriteTraceWaterfall(w io.Writer, tx model.Transaction, spans []model.Span) { | ||
| maxDuration := time.Duration(tx.Duration * float64(time.Millisecond)) | ||
| if maxDuration == 0 { | ||
| for _, span := range spans { | ||
| maxDuration += time.Duration(span.Duration * float64(time.Millisecond)) | ||
| } | ||
| } | ||
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| maxWidth := int64(72) | ||
| buf := new(bytes.Buffer) | ||
| if tx.Duration > 0.0 { | ||
| writeSpan(buf, int(maxWidth), 0, fmt.Sprintf("transaction (%x) - %s", tx.ID, maxDuration.String())) | ||
| } | ||
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| sort.SliceStable(spans, func(i, j int) bool { | ||
| return time.Time(spans[i].Timestamp).Before(time.Time(spans[j].Timestamp)) | ||
| }) | ||
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| for _, span := range spans { | ||
| pos := int(apmmath.Round( | ||
| float64(time.Time(span.Timestamp).Sub(time.Time(tx.Timestamp))) / | ||
| float64(maxDuration) * float64(maxWidth), | ||
| )) | ||
| tDur := time.Duration(span.Duration * float64(time.Millisecond)) | ||
| dur := float64(tDur) / float64(maxDuration) | ||
| width := int(apmmath.Round(dur * float64(maxWidth))) | ||
| if width == int(maxWidth) { | ||
| width = int(maxWidth) - 1 | ||
| } | ||
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| spancontent := fmt.Sprintf("%s %s - %s", | ||
| span.Type, span.Name, | ||
| time.Duration(span.Duration*float64(time.Millisecond)).String(), | ||
| ) | ||
| if span.Composite != nil { | ||
| spancontent = fmt.Sprintf("%d %s - %s", | ||
| span.Composite.Count, span.Name, | ||
| time.Duration(span.Duration*float64(time.Millisecond)).String(), | ||
| ) | ||
| } | ||
| writeSpan(buf, width, pos, spancontent) | ||
| } | ||
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| io.Copy(w, buf) | ||
| } | ||
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| func writeSpan(buf *bytes.Buffer, width, pos int, content string) { | ||
| spaceRune := ' ' | ||
| fillRune := '_' | ||
| startRune := '|' | ||
| endRune := '|' | ||
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| // Prevent the spans from going out of bounds. | ||
| if pos == width { | ||
| pos = pos - 2 | ||
| } else if pos >= width { | ||
| pos = pos - 1 | ||
| } | ||
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| for i := 0; i < int(pos); i++ { | ||
| buf.WriteRune(spaceRune) | ||
| } | ||
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| if width <= 1 { | ||
| width = 1 | ||
| // Write the first letter of the span type when the width is too small. | ||
| startRune, _ = utf8.DecodeRuneInString(content) | ||
| } | ||
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| var written int | ||
| written, _ = buf.WriteRune(startRune) | ||
| if len(content) >= int(width)-1 { | ||
| content = content[:int(width)-1] | ||
| } | ||
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| spacing := (width - len(content) - 2) / 2 | ||
| for i := 0; i < spacing; i++ { | ||
| n, _ := buf.WriteRune(fillRune) | ||
| written += n | ||
| } | ||
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| n, _ := buf.WriteString(content) | ||
| written += n | ||
| for i := 0; i < spacing; i++ { | ||
| n, _ := buf.WriteRune(fillRune) | ||
| written += n | ||
| } | ||
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| if written < width { | ||
| buf.WriteRune(fillRune) | ||
| } | ||
| if width > 1 { | ||
| buf.WriteRune(endRune) | ||
| } | ||
|
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| buf.WriteString("\n") | ||
| } |
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