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ddtrace/tracer: Remove log.Debug from hot path (-2 allocs; -5% CPU) #1186

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merged 4 commits into from Mar 8, 2022
Merged

ddtrace/tracer: Remove log.Debug from hot path (-2 allocs; -5% CPU) #1186

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94c09c9
ddtrace/tracer: Remove log.Debug from hot path (-2 allocs; -5% CPU)
evanj Feb 28, 2022
f20206e
eliminate duplication by calling DebugEnabled from Debug
evanj Mar 1, 2022
cf6488d
Merge branch 'v1' into evan.jones/log-debugenabled
Julio-Guerra Mar 8, 2022
e4fc6d0
Merge branch 'v1' into evan.jones/log-debugenabled
Julio-Guerra Mar 8, 2022
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6 changes: 5 additions & 1 deletion ddtrace/tracer/tracer.go
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Expand Up @@ -417,7 +417,11 @@ func (t *tracer) StartSpan(operationName string, options ...ddtrace.StartSpanOpt
span.Service = newSvc
}
}
log.Debug("Started Span: %v, Operation: %s, Resource: %s, Tags: %v, %v", span, span.Name, span.Resource, span.Meta, span.Metrics)
if log.DebugEnabled() {
// avoid allocating the ...interface{} argument if debug logging is disabled
log.Debug("Started Span: %v, Operation: %s, Resource: %s, Tags: %v, %v",
span, span.Name, span.Resource, span.Meta, span.Metrics)
}
return span
}

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9 changes: 9 additions & 0 deletions internal/log/log.go
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Expand Up @@ -56,6 +56,15 @@ func SetLevel(lvl Level) {
level = lvl
}

// DebugEnabled returns true if debug log messages are enabled. This can be used in extremely
// hot code paths to avoid allocating the ...interface{} argument.
func DebugEnabled() bool {
mu.RLock()
lvl := level
mu.RUnlock()
return lvl == LevelDebug
}

// Debug prints the given message if the level is LevelDebug.
func Debug(fmt string, a ...interface{}) {
mu.RLock()
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NIT: Remove code duplication by calling DebugEnabled() here?

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Oops excellent suggestion; fixed

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2 changes: 2 additions & 0 deletions internal/log/log_test.go
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Expand Up @@ -60,13 +60,15 @@ func TestLog(t *testing.T) {
tp.Reset()
defer func(old Level) { level = old }(level)
SetLevel(LevelDebug)
assert.True(t, DebugEnabled())

Debug("message %d", 3)
assert.Equal(t, msg("DEBUG", "message 3"), tp.Lines()[0])
})

t.Run("off", func(t *testing.T) {
tp.Reset()
assert.False(t, DebugEnabled())
Debug("message %d", 2)
assert.Len(t, tp.Lines(), 0)
})
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