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datapoint.go
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datapoint.go
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package datapoint
import (
"bytes"
"encoding/json"
"fmt"
"strings"
"time"
"github.com/signalfx/golib/errors"
)
// Documentation taken from http://metrics20.org/spec/
// MetricType define how to display the Value. It's more metadata of the series than data about the
// series itself. See target_type of http://metrics20.org/spec/
type MetricType int
const (
// Gauge is values at each point in time
Gauge MetricType = iota
// Count is a number per a given interval (such as a statsd flushInterval); not very useful
Count
// Enum is an added type: Values aren't important relative to each other but are just important as distinct
// items in a set. Usually used when Value is type "string"
Enum
// Counter is a number that keeps increasing over time (but might wrap/reset at some points)
// (no statsd counterpart), i.e. a gauge with the added notion of "i usually want to derive this"
Counter
// Rate is a number per second
Rate
// Timestamp value represents a unix timestamp
Timestamp
)
func (mt MetricType) String() string {
switch mt {
case Count:
return "counter"
case Counter:
return "cumulative counter"
case Gauge:
return "gauge"
case Enum:
return "enum"
case Rate:
return "rate"
case Timestamp:
return "timestamp"
default:
return fmt.Sprintf("MetricType(%d)", int(mt))
}
}
// UnmarshalText decodes text as a MetricType in a case-insensitive way
func (mt *MetricType) UnmarshalText(text []byte) error {
switch strings.ToLower(string(text)) {
case "counter":
*mt = Count
case "cumulative counter":
*mt = Counter
case "gauge":
*mt = Gauge
case "enum":
*mt = Enum
case "rate":
*mt = Rate
case "timestamp":
*mt = Timestamp
default:
return fmt.Errorf("unrecognized metric type: %q", text)
}
return nil
}
// UnmarshalJSON decodes JSON number as a MetricType
func (mt *MetricType) UnmarshalJSON(b []byte) error {
var n int
if err := json.Unmarshal(b, &n); err != nil {
return err
}
*mt = MetricType(n)
return nil
}
// A Datapoint is the metric that is saved. Designed around http://metrics20.org/spec/
type Datapoint struct {
// What is being measured. We think metric, rather than "unit" of metrics20, should be the
// required identity of a datapoint and the "unit" should be a property of the Value itself
Metric string `json:"metric"`
// Dimensions of what is being measured. They are intrinsic. Contributes to the identity of
// the metric. If this changes, we get a new metric identifier
Dimensions map[string]string `json:"dimensions"`
// Meta is information that's not particularly important to the datapoint, but may be important
// to the pipeline that uses the datapoint. They are extrinsic. It provides additional
// information about the metric. changes in this set doesn't change the metric identity
Meta map[interface{}]interface{} `json:"-"`
// Value of the datapoint
Value Value `json:"value"`
// The type of the datapoint series
MetricType MetricType `json:"metric_type"`
// The unix time of the datapoint
Timestamp time.Time `json:"timestamp"`
}
type jsonDatapoint struct {
Metric string `json:"metric"`
Dimensions map[string]string `json:"dimensions"`
Value interface{} `json:"value"`
MetricType MetricType `json:"metric_type"`
Timestamp time.Time `json:"timestamp"`
}
// UnmarshalJSON decodes JSON into a datapoint, creating the correct Value interface types for the
// type of JSON value that was encoded
func (dp *Datapoint) UnmarshalJSON(b []byte) error {
var m jsonDatapoint
dec := json.NewDecoder(bytes.NewBuffer(b))
dec.UseNumber()
if err := dec.Decode(&m); err != nil {
return errors.Annotatef(err, "JSON decoding of byte array %v failed", b)
}
switch t := m.Value.(type) {
case string:
dp.Value = NewStringValue(t)
case json.Number:
if num, e := t.Int64(); e == nil {
dp.Value = NewIntValue(num)
} else if num, e := t.Float64(); e == nil {
dp.Value = NewFloatValue(num)
}
}
dp.Metric = m.Metric
dp.Dimensions = m.Dimensions
dp.MetricType = m.MetricType
dp.Timestamp = m.Timestamp
return nil
}
func (dp *Datapoint) String() string {
return fmt.Sprintf("DP[%s\t%s\t%s\t%d\t%s]", dp.Metric, dp.Dimensions, dp.Value, dp.MetricType, dp.Timestamp.String())
}
type metadata int
const (
tsProperty metadata = iota
)
// SetProperty sets a property to be used when the time series associated with the datapoint is created
func (dp *Datapoint) SetProperty(key string, value interface{}) {
if dp.Meta[tsProperty] == nil {
dp.Meta[tsProperty] = make(map[string]interface{}, 1)
}
dp.GetProperties()[key] = value
}
// RemoveProperty removes a property from the map of properties to be used when the time series associated with the datapoint is created
func (dp *Datapoint) RemoveProperty(key string) {
if dp.Meta[tsProperty] != nil {
delete(dp.GetProperties(), key)
if len(dp.GetProperties()) == 0 {
delete(dp.Meta, tsProperty)
}
}
}
// GetProperties gets the map of properties to set when creating the time series associated with the datapoint. nil if no properties are set.
func (dp *Datapoint) GetProperties() map[string]interface{} {
m, ok := dp.Meta[tsProperty].(map[string]interface{})
if !ok {
return nil
}
return m
}
// New creates a new datapoint with empty meta data
func New(metric string, dimensions map[string]string, value Value, metricType MetricType, timestamp time.Time) *Datapoint {
return NewWithMeta(metric, dimensions, map[interface{}]interface{}{}, value, metricType, timestamp)
}
// NewWithMeta creates a new datapoint with passed metadata
func NewWithMeta(metric string, dimensions map[string]string, meta map[interface{}]interface{}, value Value, metricType MetricType, timestamp time.Time) *Datapoint {
return &Datapoint{
Metric: metric,
Dimensions: dimensions,
Meta: meta,
Value: value,
MetricType: metricType,
Timestamp: timestamp,
}
}
// AddMaps adds two maps of dimensions and returns a new map of dimensions that is a + b. Note that
// b takes precedent. Works with nil or empty a/b maps. Does not modify either map, but may return
// a or b if the other is empty.
func AddMaps(a, b map[string]string) map[string]string {
if len(a) == 0 {
if len(b) == 0 {
return map[string]string{}
}
return b
}
if len(b) == 0 {
return a
}
r := make(map[string]string, len(a)+len(b))
for k, v := range a {
r[k] = v
}
for k, v := range b {
r[k] = v
}
return r
}