Added support for arrays (print average)

average.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"github.com/antonholmquist/jason"
+)
+
+func averageJason(array []*jason.Value) float64 {
+	var arr []float64
+	for _, v := range array {
+		val, _ := v.Float64()
+		arr = append(arr, val)
+	}
+	return average(arr)
+}
+
+// average calculates average (mean) value for int/float array
+// trimming zero values from the right.
+//
+// The whole array/average thing was added to support memstats.PauseNs
+// array, which may be filled with zeroes on very beginning.
+// Probably it would be better to use Weighted Moving Average and
+// add some advanced arrays avarages support, but it's probably wouldn't
+// be used much, but PauseNs will be for sure.
+func average(arr []float64) float64 {
+	// find rightmost non-zero and trim
+	right := len(arr)
+	for i := right; i > 0; i-- {
+		if arr[i-1] != 0.0 {
+			right = i
+			break
+		}
+	}
+	trimmed := arr[:right]
+
+	// calculate mean
+	var sum float64
+	for _, v := range trimmed {
+		sum += v
+	}
+	return sum / float64(len(trimmed))
+}

average_test.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestAverage(t *testing.T) {
+	avg := average(samplesPartial)
+	want := 621090.75
+	if avg != want {
+		t.Fatalf("Average must be %v, but got %v", want, avg)
+	}
+}
+
+var samplesPartial = []float64{507472, 433979, 610916, 931996, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

expvars_test.go

@@ -37,6 +37,14 @@ func TestExpvars(t *testing.T) {
 	if alloc == 0 {
 		t.Fatalf("Alloc should be greater than 0")
 	}
+
+	pauses, err := expvar.GetInt64Array(VarName("memstats.PauseNs").ToSlice()...)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(pauses) == 0 {
+		t.Fatalf("Pauses length should be greater than 0")
+	}
 }
 
 func TestExpvarsAdvanced(t *testing.T) {

service.go

@@ -101,6 +101,22 @@ func guessValue(value *jason.Value) interface{} {
 		return v
 	} else if v, err := value.String(); err == nil {
 		return v
+	} else if v, err := value.Array(); err == nil {
+		// if we get an array, calculate average
+
+		// empty array, treat as zero
+		if len(v) == 0 {
+			return 0
+		}
+
+		avg := averageJason(v)
+
+		// cast to int64 for Int64 values
+		if _, err := v[0].Int64(); err == nil {
+			return int64(avg)
+		}
+
+		return avg
 	}
 
 	return nil