Expressions: Move GEL into core as expressions (#29072)

* comes from grafana/gel-app * remove transform plugin code * move __expr__ and -100 constants to expr pkg * set OrgID on request plugin context * use gtime for resample duration * in resample, rename "rule" to "window", use gtime for duration, parse duration before exec * remove gel entry from plugins-bundled/external.json which creates an empty array for plugins
2020-11-19 07:17:00 -05:00
parent f01c3f35e1
commit 0cb29d337a
44 changed files with 5770 additions and 401 deletions
@@ -0,0 +1,83 @@
+package mathexp
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/data"
+)
+
+// Resample turns the Series into a Number based on the given reduction function
+func (s Series) Resample(interval time.Duration, downsampler string, upsampler string, tr backend.TimeRange) (Series, error) {
+	newSeriesLength := int(float64(tr.To.Sub(tr.From).Nanoseconds()) / float64(interval.Nanoseconds()))
+	if newSeriesLength <= 0 {
+		return s, fmt.Errorf("the series cannot be sampled further; the time range is shorter than the interval")
+	}
+	resampled := NewSeries(s.GetName(), s.GetLabels(), s.TimeIdx, s.TimeIsNullable, s.ValueIdx, s.ValueIsNullabe, newSeriesLength+1)
+	bookmark := 0
+	var lastSeen *float64
+	idx := 0
+	t := tr.From
+	for !t.After(tr.To) && idx <= newSeriesLength {
+		vals := make([]*float64, 0)
+		sIdx := bookmark
+		for {
+			if sIdx == s.Len() {
+				break
+			}
+			st, v := s.GetPoint(sIdx)
+			if st.After(t) {
+				break
+			}
+			bookmark++
+			sIdx++
+			lastSeen = v
+			vals = append(vals, v)
+		}
+		var value *float64
+		if len(vals) == 0 { // upsampling
+			switch upsampler {
+			case "pad":
+				if lastSeen != nil {
+					value = lastSeen
+				} else {
+					value = nil
+				}
+			case "backfilling":
+				if sIdx == s.Len() { // no vals left
+					value = nil
+				} else {
+					_, value = s.GetPoint(sIdx)
+				}
+			case "fillna":
+				value = nil
+			default:
+				return s, fmt.Errorf("upsampling %v not implemented", upsampler)
+			}
+		} else { // downsampling
+			fVec := data.NewField("", s.GetLabels(), vals)
+			var tmp *float64
+			switch downsampler {
+			case "sum":
+				tmp = Sum(fVec)
+			case "mean":
+				tmp = Avg(fVec)
+			case "min":
+				tmp = Min(fVec)
+			case "max":
+				tmp = Max(fVec)
+			default:
+				return s, fmt.Errorf("downsampling %v not implemented", downsampler)
+			}
+			value = tmp
+		}
+		tv := t // his is required otherwise all points keep the latest timestamp; anything better?
+		if err := resampled.SetPoint(idx, &tv, value); err != nil {
+			return resampled, err
+		}
+		t = t.Add(interval)
+		idx++
+	}
+	return resampled, nil
+}