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json.go
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json.go
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package api
import (
"encoding/json"
"fmt"
"collectd.org/cdtime"
)
// jsonValueList represents the format used by collectd's JSON export.
type jsonValueList struct {
Values []json.Number `json:"values"`
DSTypes []string `json:"dstypes"`
DSNames []string `json:"dsnames,omitempty"`
Time cdtime.Time `json:"time"`
Interval cdtime.Time `json:"interval"`
Host string `json:"host"`
Plugin string `json:"plugin"`
PluginInstance string `json:"plugin_instance,omitempty"`
Type string `json:"type"`
TypeInstance string `json:"type_instance,omitempty"`
}
// MarshalJSON implements the "encoding/json".Marshaler interface for
// ValueList.
func (vl *ValueList) MarshalJSON() ([]byte, error) {
jvl := jsonValueList{
Values: make([]json.Number, len(vl.Values)),
DSTypes: make([]string, len(vl.Values)),
DSNames: make([]string, len(vl.Values)),
Time: cdtime.New(vl.Time),
Interval: cdtime.NewDuration(vl.Interval),
Host: vl.Host,
Plugin: vl.Plugin,
PluginInstance: vl.PluginInstance,
Type: vl.Type,
TypeInstance: vl.TypeInstance,
}
for i, v := range vl.Values {
switch v := v.(type) {
case Gauge:
jvl.Values[i] = json.Number(fmt.Sprintf("%.15g", v))
case Derive:
jvl.Values[i] = json.Number(fmt.Sprintf("%d", v))
case Counter:
jvl.Values[i] = json.Number(fmt.Sprintf("%d", v))
default:
return nil, fmt.Errorf("unexpected data source type: %T", v)
}
jvl.DSTypes[i] = v.Type()
jvl.DSNames[i] = vl.DSName(i)
}
return json.Marshal(jvl)
}
// UnmarshalJSON implements the "encoding/json".Unmarshaler interface for
// ValueList.
//
// Please note that this function is currently not compatible with write_http's
// "StoreRates" setting: if enabled, write_http converts derives and counters
// to a rate (a floating point number), but still puts "derive" or "counter" in
// the "dstypes" array. UnmarshalJSON will try to parse such values as
// integers, which will fail in many cases.
func (vl *ValueList) UnmarshalJSON(data []byte) error {
var jvl jsonValueList
if err := json.Unmarshal(data, &jvl); err != nil {
return err
}
vl.Host = jvl.Host
vl.Plugin = jvl.Plugin
vl.PluginInstance = jvl.PluginInstance
vl.Type = jvl.Type
vl.TypeInstance = jvl.TypeInstance
vl.Time = jvl.Time.Time()
vl.Interval = jvl.Interval.Duration()
vl.Values = make([]Value, len(jvl.Values))
if len(jvl.Values) != len(jvl.DSTypes) {
return fmt.Errorf("invalid data: %d value(s), %d data source type(s)",
len(jvl.Values), len(jvl.DSTypes))
}
for i, n := range jvl.Values {
switch jvl.DSTypes[i] {
case "gauge":
v, err := n.Float64()
if err != nil {
return err
}
vl.Values[i] = Gauge(v)
case "derive":
v, err := n.Int64()
if err != nil {
return err
}
vl.Values[i] = Derive(v)
case "counter":
v, err := n.Int64()
if err != nil {
return err
}
vl.Values[i] = Counter(v)
default:
return fmt.Errorf("unexpected data source type: %q", jvl.DSTypes[i])
}
}
if len(jvl.DSNames) >= len(vl.Values) {
vl.DSNames = make([]string, len(vl.Values))
copy(vl.DSNames, jvl.DSNames)
}
return nil
}