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fix: descheduler_loop_duration_seconds has wrong value #1215

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merged 1 commit into from
Aug 10, 2023
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fix: descheduler_loop_duration_seconds has wrong value #1215

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5 changes: 3 additions & 2 deletions pkg/descheduler/descheduler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -112,8 +112,9 @@ func (d *descheduler) runDeschedulerLoop(ctx context.Context, nodes []*v1.Node)
var span trace.Span
ctx, span = tracing.Tracer().Start(ctx, "runDeschedulerLoop")
defer span.End()
loopStartDuration := time.Now()
defer metrics.DeschedulerLoopDuration.With(map[string]string{}).Observe(time.Since(loopStartDuration).Seconds())
defer func(loopStartDuration time.Time) {
metrics.DeschedulerLoopDuration.With(map[string]string{}).Observe(time.Since(loopStartDuration).Seconds())
}(time.Now())
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@ingvagabund ingvagabund Aug 10, 2023 •
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Should not this be more like:

loopStartDuration := time.Now()
defer func(loopStartDuration time.Time) {
	metrics.DeschedulerLoopDuration.With(map[string]string{}).Observe(time.Since(loopStartDuration).Seconds())
}(loopStartDuration)

?
Or just:

loopStartDuration := time.Now()
defer func() {
	metrics.DeschedulerLoopDuration.With(map[string]string{}).Observe(time.Since(loopStartDuration).Seconds())
}()

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I think both of these changes work.

It's straightforward to use defer func(...) {...} (time.Now()) because that's the only place the loopStartDuration variable is used, and it doesn't seem like it needs an extra variable defined.

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time.Now() will have different value for loopStartDuration := time.Now() and when defer is invoked. Unless I incorrectly understand how the defer statement invokes the function/code. My assumption is anything after defer gets invoke right before a function/method exits.

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https://go.dev/tour/flowcontrol/12 says:

The deferred call's arguments are evaluated immediately, but the function call is not executed until the surrounding function returns.

Interesting.


// if len is still <= 1 error out
if len(nodes) <= 1 {
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