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ddtrace/tracer: implement fmt.Formatter interface to support log inje…
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…ction (DataDog#657)

This change implements `fmt.Formatter` to allow printing a span in various formats for logging.
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@knusbaum @mingrammer
knusbaum authored and mingrammer committed Dec 22, 2020
1 parent 37ef903 commit b927c5c
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Showing 2 changed files with 129 additions and 0 deletions.
33 changes: 33 additions & 0 deletions ddtrace/tracer/span.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ package tracer

import (
"fmt"
"os"
"reflect"
"runtime"
"runtime/debug"
Expand All @@ -19,6 +20,8 @@ import (

"gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
"gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
"gopkg.in/DataDog/dd-trace-go.v1/internal/globalconfig"

"github.com/tinylib/msgp/msgp"
"golang.org/x/xerrors"
Expand Down Expand Up @@ -337,6 +340,36 @@ func (s *span) String() string {
return strings.Join(lines, "\n")
}

// Format implements fmt.Formatter.
func (s *span) Format(f fmt.State, c rune) {
switch c {
case 's':
fmt.Fprint(f, s.String())
case 'v':
if svc := globalconfig.ServiceName(); svc != "" {
fmt.Fprintf(f, "dd.service=%s ", svc)
}
if tr, ok := internal.GetGlobalTracer().(*tracer); ok {
if env, ok := tr.config.globalTags[ext.Environment]; ok {
fmt.Fprintf(f, "dd.env=%s ", env)
}
if tr.config.version != "" {
fmt.Fprintf(f, "dd.version=%s ", tr.config.version)
}
} else {
if env := os.Getenv("DD_ENV"); env != "" {
fmt.Fprintf(f, "dd.env=%s ", env)
}
if v := os.Getenv("DD_VERSION"); v != "" {
fmt.Fprintf(f, "dd.version=%s ", v)
}
}
fmt.Fprintf(f, "dd.trace_id=%d dd.span_id=%d", s.TraceID, s.SpanID)
default:
fmt.Fprintf(f, "%%!%c(ddtrace.Span=%v)", c, s)
}
}

const (
keySamplingPriority = "_sampling_priority_v1"
keySamplingPriorityRate = "_sampling_priority_rate_v1"
Expand Down
96 changes: 96 additions & 0 deletions ddtrace/tracer/span_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ package tracer
import (
"errors"
"fmt"
"os"
"strings"
"testing"
"time"
Expand Down Expand Up @@ -404,6 +405,101 @@ func TestSpanSamplingPriority(t *testing.T) {
}
}

func TestSpanLog(t *testing.T) {
t.Run("default", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"))
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("env", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithEnv("testenv"))
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.env=testenv dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("version", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithServiceVersion("1.2.3"))
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("full", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithServiceVersion("1.2.3"), WithEnv("testenv"))
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.env=testenv dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("subservice", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithServiceVersion("1.2.3"), WithEnv("testenv"))
defer stop()
span := tracer.StartSpan("test.request", ServiceName("subservice name")).(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.env=testenv dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("env", func(t *testing.T) {
os.Setenv("DD_SERVICE", "tracer.test")
defer os.Unsetenv("DD_SERVICE")
os.Setenv("DD_VERSION", "1.2.3")
defer os.Unsetenv("DD_VERSION")
os.Setenv("DD_ENV", "testenv")
defer os.Unsetenv("DD_ENV")
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t)
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("dd.service=tracer.test dd.env=testenv dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("badformat", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithServiceVersion("1.2.3"))
defer stop()
span := tracer.StartSpan("test.request").(*span)
expect := fmt.Sprintf("%%!b(ddtrace.Span=dd.service=tracer.test dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d)", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%b", span))
})

t.Run("notracer/options", func(t *testing.T) {
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t, WithService("tracer.test"), WithServiceVersion("1.2.3"), WithEnv("testenv"))
span := tracer.StartSpan("test.request").(*span)
stop()
expect := fmt.Sprintf("dd.service=tracer.test dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})

t.Run("notracer/env", func(t *testing.T) {
os.Setenv("DD_SERVICE", "tracer.test")
defer os.Unsetenv("DD_SERVICE")
os.Setenv("DD_VERSION", "1.2.3")
defer os.Unsetenv("DD_VERSION")
os.Setenv("DD_ENV", "testenv")
defer os.Unsetenv("DD_ENV")
assert := assert.New(t)
tracer, _, _, stop := startTestTracer(t)
span := tracer.StartSpan("test.request").(*span)
stop()
expect := fmt.Sprintf("dd.service=tracer.test dd.env=testenv dd.version=1.2.3 dd.trace_id=%d dd.span_id=%d", span.TraceID, span.SpanID)
assert.Equal(expect, fmt.Sprintf("%v", span))
})
}

func BenchmarkSetTagMetric(b *testing.B) {
span := newBasicSpan("bench.span")
keys := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
Expand Down

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