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ddtrace/tracer: encode span IDs in execution traces efficiently (#2268)
We were previously encoding span IDs into execution traces as base-10 strings. This is wasteful, in terms of CPU time to encode the ID and more importantly in terms of how much of the limited execution trace data the profiler collects will be taken up by span IDs. They can be encoded directly as 8-byte unsigned integers.
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Original file line number | Diff line number | Diff line change |
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// Unless explicitly stated otherwise all files in this repository are licensed | ||
// under the Apache License Version 2.0. | ||
// This product includes software developed at Datadog (https://www.datadoghq.com/). | ||
// Copyright 2016 Datadog, Inc. | ||
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// Tests in this file rely on parsing execution tracer data, which can change | ||
// formats across Go releases. This guard should be updated as the Go trace | ||
// parser library is upgraded to support new versions. | ||
//go:build !go1.21 | ||
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package tracer | ||
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import ( | ||
"bytes" | ||
"context" | ||
"encoding/binary" | ||
rt "runtime/trace" | ||
"testing" | ||
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"github.com/stretchr/testify/assert" | ||
gotraceui "honnef.co/go/gotraceui/trace" | ||
) | ||
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func TestExecutionTraceSpans(t *testing.T) { | ||
if rt.IsEnabled() { | ||
t.Skip("runtime execution tracing is already enabled") | ||
} | ||
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buf := new(bytes.Buffer) | ||
if err := rt.Start(buf); err != nil { | ||
t.Fatal(err) | ||
} | ||
// Ensure we unconditionally stop tracing. It's safe to call this | ||
// multiple times. | ||
defer rt.Stop() | ||
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_, _, _, stop := startTestTracer(t) | ||
defer stop() | ||
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root, ctx := StartSpanFromContext(context.Background(), "root") | ||
child, _ := StartSpanFromContext(ctx, "child") | ||
root.Finish() | ||
child.Finish() | ||
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rt.Stop() | ||
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execTrace, err := gotraceui.Parse(buf, nil) | ||
if err != nil { | ||
t.Fatalf("parsing trace: %s", err) | ||
} | ||
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type traceSpan struct { | ||
name string | ||
parent string | ||
spanID uint64 | ||
} | ||
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spans := make(map[int]*traceSpan) | ||
for _, ev := range execTrace.Events { | ||
switch ev.Type { | ||
case gotraceui.EvUserTaskCreate: | ||
id := int(ev.Args[0]) | ||
name := execTrace.Strings[ev.Args[2]] | ||
var parent string | ||
if p, ok := spans[int(ev.Args[1])]; ok { | ||
parent = p.name | ||
} | ||
spans[id] = &traceSpan{ | ||
name: name, | ||
parent: parent, | ||
} | ||
case gotraceui.EvUserLog: | ||
id := int(ev.Args[0]) | ||
span, ok := spans[id] | ||
if !ok { | ||
continue | ||
} | ||
key := execTrace.Strings[ev.Args[1]] | ||
if key == "datadog.uint64_span_id" { | ||
span.spanID = binary.LittleEndian.Uint64([]byte(execTrace.Strings[ev.Args[3]])) | ||
} | ||
} | ||
} | ||
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want := []traceSpan{ | ||
{name: "root", spanID: root.Context().SpanID()}, | ||
{name: "child", parent: "root", spanID: child.Context().SpanID()}, | ||
} | ||
var got []traceSpan | ||
for _, v := range spans { | ||
got = append(got, *v) | ||
} | ||
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assert.ElementsMatch(t, want, got) | ||
} |
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