Add unit conversion to router

internal/metricRouter/metricRouter.go

@@ -37,6 +37,7 @@ type metricRouterConfig struct {
 	NumCacheIntervals int                                  `json:"num_cache_intervals"` // Number of intervals of cached metrics for evaluation
 	MaxForward        int                                  `json:"max_forward"`         // Number of maximal forwarded metrics at one select
 	NormalizeUnits    bool                                 `json:"normalize_units"`     // Check unit meta flag and normalize it using cc-units
+	ChangeUnitPrefix  string                               `json:"change_unit_prefix"`  // Add prefix that should be applied to all metrics where possible
 	dropMetrics       map[string]bool                      // Internal map for O(1) lookup
 }
 
@@ -263,6 +264,55 @@ func (r *metricRouter) Start() {
 				}
 			}
 		}
+		if len(r.config.ChangeUnitPrefix) > 0 {
+			prefix := units.NewPrefix(r.config.ChangeUnitPrefix)
+			if prefix != units.InvalidPrefix {
+				if in_unit, ok := point.GetMeta("unit"); ok {
+					u := units.NewUnit(in_unit)
+					if u.Valid() {
+						conv, out_unit := units.GetUnitPrefixFactor(u, prefix)
+						if conv != nil && out_unit.Valid() {
+							if val, ok := point.GetField("value"); ok {
+								newval := 0.0
+								skip := false
+								switch v := val.(type) {
+								case float64:
+									newval = v
+								case float32:
+									newval = float64(v)
+								case int64:
+									newval = float64(v)
+								case int32:
+									newval = float64(v)
+								case int:
+									newval = float64(v)
+								case string:
+									skip = true
+								}
+								if !skip {
+									newval = conv(newval)
+									var x interface{}
+									switch val.(type) {
+									case float64:
+										x = newval
+									case float32:
+										x = float32(newval)
+									case int64:
+										x = int64(newval)
+									case int32:
+										x = int32(newval)
+									case int:
+										x = int(newval)
+									}
+									point.AddField("value", x)
+									point.AddMeta("unit", out_unit.Short())
+								}
+							}
+						}
+					}
+				}
+			}
+		}
 		r.DoAddTags(point)
 		r.DoDelTags(point)