Fix metric SetAggregate didn't work

[stitchcula]

Fixes the bug that metric SetAggregate didn't work, when using sync.Pool to reserve metrics from outputs.

Required for all PRs:

• Signed CLA.
• Has appropriate unit tests.

[reimda]

SetAggregate is a deprecated interface. See

telegraf/metric.go

Line 128 in 57cd20a

// This method may be removed in the future and its use is discouraged.

It's not used in telegraf any more. Can you share more detail why you need it to work?

[stitchcula]

SetAggregate is a deprecated interface. See

telegraf/metric.go

Line 128 in 57cd20a

// This method may be removed in the future and its use is discouraged.

It's not used in telegraf any more. Can you share more detail why you need it to work?

In my fork, I use sync.Pool to reuse metrics, just like:

type reservable struct {
	telegraf.Metric
}

var pool = &sync.Pool{New: func() interface{} {
	m, _ := metric.New("", nil, nil, time.Time{})
	return &reservable{Metric: m}
}

// call it to get blank Metric in parser plugin
func NewMetric() telegraf.Metric {
	return pool.Get().(*reservable)
}

func reserve(m *reservable) {
	m.SetName("")
	m.SetTime(zeroTime)
	m.SetAggregate(false) // it always set aggregate true

	//...

	pool.Put(m)
}

//...

func (m *metric) Accept() {
	reserve(m)
}

func (m *metric) Drop() {
	reserve(m)
}

In function reserve, m.SetAggregate(false) always set aggregate true, because of an obvious mistake in metric.go:

telegraf/metric/metric.go

Line 255 in 57cd20a

m.aggregate = true

As well, reusing metric can significantly improve the pressure of GC. Maybe I can start a new pull request?

[reimda]

Since SetAggregate() is deprecated and not used anywhere I would rather remove it along with IsAggregate() and metric.aggregate rather than fix it and add tests for it.

[srebhan]

@stitchcula any progress on this?

[sspaink]

Closing due to no response, feel free to re-open if you are still interested in completing this pr. Thanks!