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emit.go
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emit.go
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package metric
import (
"fmt"
"strings"
"time"
"code.cloudfoundry.org/lager"
flags "github.com/jessevdk/go-flags"
)
type Event struct {
Name string
Value float64
Attributes map[string]string
Host string
Time time.Time
}
//go:generate counterfeiter . Emitter
type Emitter interface {
Emit(lager.Logger, Event)
}
//go:generate counterfeiter . EmitterFactory
type EmitterFactory interface {
Description() string
IsConfigured() bool
NewEmitter() (Emitter, error)
}
var emitterFactories []EmitterFactory
func RegisterEmitter(factory EmitterFactory) {
emitterFactories = append(emitterFactories, factory)
}
func WireEmitters(group *flags.Group) {
for _, factory := range emitterFactories {
_, err := group.AddGroup(fmt.Sprintf("Metric Emitter (%s)", factory.Description()), "", factory)
if err != nil {
panic(err)
}
}
}
type eventEmission struct {
event Event
logger lager.Logger
}
var (
emitter Emitter
eventHost string
eventAttributes map[string]string
emissions chan eventEmission
)
func Initialize(logger lager.Logger, host string, attributes map[string]string, bufferSize uint32) error {
logger.Debug("metric-initialize", lager.Data{
"host": host,
"attributes": attributes,
"buffer-size": bufferSize,
})
var (
emitterDescriptions []string
err error
)
for _, factory := range emitterFactories {
if factory.IsConfigured() {
emitterDescriptions = append(emitterDescriptions, factory.Description())
}
}
if len(emitterDescriptions) > 1 {
return fmt.Errorf("Multiple emitters configured: %s", strings.Join(emitterDescriptions, ", "))
}
for _, factory := range emitterFactories {
if factory.IsConfigured() {
emitter, err = factory.NewEmitter()
if err != nil {
return err
}
}
}
if emitter == nil {
return nil
}
eventHost = host
eventAttributes = attributes
emissions = make(chan eventEmission, int(bufferSize))
go emitLoop()
return nil
}
func Deinitialize(logger lager.Logger) {
close(emissions)
emitterFactories = nil
}
func emit(logger lager.Logger, event Event) {
if emitter == nil {
return
}
event.Host = eventHost
event.Time = time.Now()
mergedAttributes := map[string]string{}
for k, v := range eventAttributes {
mergedAttributes[k] = v
}
if event.Attributes != nil {
for k, v := range event.Attributes {
mergedAttributes[k] = v
}
}
event.Attributes = mergedAttributes
select {
case emissions <- eventEmission{logger: logger, event: event}:
default:
logger.Error("queue-full", nil)
}
}
func emitLoop() {
for emission := range emissions {
emitter.Emit(emission.logger.Session("emit"), emission.event)
}
}