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eventmetrics.go
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eventmetrics.go
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// Copyright 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package metrics
import (
"errors"
"fmt"
"strconv"
"strings"
"sync"
"time"
)
// Kind represents EventMetrics type. There are currently only two kinds
// of EventMetrics supported: CUMULATIVE and GAUGE
type Kind int
const (
// CUMULATIVE metrics accumulate with time and are usually used to
// represent counters, e.g. number of requests.
CUMULATIVE = iota
// GAUGE metrics are used to represent values at a certain point of
// time, e.g. pending queries.
GAUGE
)
// EventMetrics respresents metrics associated with a particular time event.
type EventMetrics struct {
mu sync.RWMutex
Timestamp time.Time
Kind Kind
// Keys are metrics names
metrics map[string]Value
metricsKeys []string
// Labels are the labels associated with a particular set of metrics,
// e.g. ptype=ping, dst=google.com, etc.
labels map[string]string
labelsKeys []string
LatencyUnit time.Duration
}
// NewEventMetrics return a new EventMetrics object with internals maps initialized.
func NewEventMetrics(ts time.Time) *EventMetrics {
return &EventMetrics{
Timestamp: ts,
metrics: make(map[string]Value),
labels: make(map[string]string),
}
}
// AddMetric adds a metric (name & value) into the receiver EventMetric. If a
// metric with the same name exists already, new metric is ignored. AddMetric
// returns the receiver EventMetrics to allow for the chaining of these calls,
// for example:
// em := metrics.NewEventMetrics(time.Now()).
// AddMetric("sent", &prr.sent).
// AddMetric("rcvd", &prr.rcvd).
// AddMetric("rtt", &prr.rtt)
func (em *EventMetrics) AddMetric(name string, val Value) *EventMetrics {
em.mu.Lock()
defer em.mu.Unlock()
if _, ok := em.metrics[name]; ok {
// TODO(manugarg): We should probably log such cases. We'll have to
// plumb logger for that.
return em
}
em.metrics[name] = val
em.metricsKeys = append(em.metricsKeys, name)
return em
}
// Metric returns an EventMetrics metric value by name. Metric will return nil
// for a non-existent metric.
func (em *EventMetrics) Metric(name string) Value {
em.mu.RLock()
defer em.mu.RUnlock()
return em.metrics[name]
}
// MetricsKeys returns the list of all metric keys.
func (em *EventMetrics) MetricsKeys() []string {
em.mu.RLock()
defer em.mu.RUnlock()
return append([]string{}, em.metricsKeys...)
}
// AddLabel adds a label (name & value) into the receiver EventMetrics. If a
// label with the same name exists already, new label is ignored. AddLabel
// returns the receiver EventMetrics to allow for the chaining of these calls,
// for example:
// em := metrics.NewEventMetrics(time.Now()).
// AddMetric("sent", &prr.sent).
// AddLabel("ptype", "http").
// AddLabel("dst", target)
func (em *EventMetrics) AddLabel(name string, val string) *EventMetrics {
em.mu.Lock()
defer em.mu.Unlock()
if _, ok := em.labels[name]; ok {
// TODO(manugarg): We should probably log such cases. We'll have to
// plumb logger for that.
return em
}
em.labels[name] = val
em.labelsKeys = append(em.labelsKeys, name)
return em
}
// Label returns an EventMetrics label value by name. Label will return a
// zero-string ("") for a non-existent label.
func (em *EventMetrics) Label(name string) string {
em.mu.RLock()
defer em.mu.RUnlock()
return em.labels[name]
}
// LabelsKeys returns the list of all label keys.
func (em *EventMetrics) LabelsKeys() []string {
em.mu.RLock()
defer em.mu.RUnlock()
return append([]string{}, em.labelsKeys...)
}
// Clone clones the underlying fields. This is useful for creating copies of the EventMetrics objects.
func (em *EventMetrics) Clone() *EventMetrics {
em.mu.RLock()
defer em.mu.RUnlock()
newEM := &EventMetrics{
Timestamp: em.Timestamp,
Kind: em.Kind,
metrics: make(map[string]Value),
labels: make(map[string]string),
}
for _, lk := range em.labelsKeys {
newEM.labels[lk] = em.labels[lk]
newEM.labelsKeys = append(newEM.labelsKeys, lk)
}
for _, mk := range em.metricsKeys {
newEM.metrics[mk] = em.metrics[mk].Clone()
newEM.metricsKeys = append(newEM.metricsKeys, mk)
}
return newEM
}
// Update updates the receiver EventMetrics with the incoming one.
func (em *EventMetrics) Update(in *EventMetrics) error {
if em.Kind != in.Kind {
return fmt.Errorf("EventMetrics of different kind cannot be merged. Receiver's kind: %d, incoming: %d", em.Kind, in.Kind)
}
switch em.Kind {
case GAUGE:
for name, newVal := range in.metrics {
_, ok := em.metrics[name]
if !ok {
return fmt.Errorf("receiver EventMetrics doesn't have %s metric", name)
}
em.metrics[name] = newVal.Clone()
}
return nil
case CUMULATIVE:
for name, newVal := range in.metrics {
val, ok := em.metrics[name]
if !ok {
return fmt.Errorf("receiver EventMetrics doesn't have %s metric", name)
}
val.Add(newVal)
}
return nil
default:
return errors.New("Unknown metrics kind")
}
}
// String returns the string representation of the EventMetrics.
// Note that this is compatible with what vmwatcher understands.
// Example output string:
// 1519084040 labels=ptype=http sent=62 rcvd=52 resp-code=map:code,200:44,204:8
func (em *EventMetrics) String() string {
em.mu.RLock()
defer em.mu.RUnlock()
var b strings.Builder
b.Grow(128)
b.WriteString(strconv.FormatInt(em.Timestamp.Unix(), 10))
// Labels section: labels=ptype=http,probe=homepage
b.WriteString(" labels=")
for i, key := range em.labelsKeys {
if i != 0 {
b.WriteByte(',')
}
b.WriteString(key)
b.WriteByte('=')
b.WriteString(em.labels[key])
}
// Values section: " sent=62 rcvd=52 resp-code=map:code,200:44,204:8"
for _, name := range em.metricsKeys {
b.WriteByte(' ')
b.WriteString(name)
b.WriteByte('=')
b.WriteString(em.metrics[name].String())
}
return b.String()
}