feature: add size for humanize byte size

CHANGELOG.md

@@ -6,6 +6,8 @@
 
 ### Features
 
+- [#669](https://github.com/influxdata/kapacitor/pull/669): Add size function for humanize byte size.
+
 ### Bugfixes
 
 - [#656](https://github.com/influxdata/kapacitor/pull/656): Fix issues where an expression could not be passed as a function parameter in TICKscript.

tick/stateful/functions.go

@@ -7,6 +7,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/dustin/go-humanize"
 	"github.com/influxdata/influxdb/influxql"
 )
 
@@ -83,6 +84,9 @@ func init() {
 	statelessFuncs["day"] = &day{}
 	statelessFuncs["month"] = &month{}
 	statelessFuncs["year"] = &year{}
+
+	// Humanize functions
+	statelessFuncs["size"] = &size{}
 }
 
 // Return set of built-in Funcs
@@ -598,3 +602,27 @@ func (*year) Call(args ...interface{}) (v interface{}, err error) {
 	}
 	return
 }
+
+type size struct {
+}
+
+func (*size) Reset() {
+
+}
+
+func (*size) Call(args ...interface{}) (v interface{}, err error) {
+	if len(args) != 1 {
+		return 0, errors.New("size expects exactly one argument")
+	}
+	switch a := args[0].(type) {
+	case float64:
+		v = humanize.Bytes(uint64(int64(a)))
+	case int64:
+		v = humanize.Bytes(uint64(a))
+	case uint64:
+		v = humanize.Bytes(a)
+	default:
+		err = fmt.Errorf("cannot convert %T to humanize size", a)
+	}
+	return
+}