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fetcher.go
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fetcher.go
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package fetcher
import (
"sync"
"time"
"code.cloudfoundry.org/lager"
aiven "github.com/aiven/aiven-go-client"
)
func init() {
initMetrics()
}
const (
defaultInterval = 120 * time.Second
userAgent = "govuk-paas-aiven-service-discovery-fetcher"
)
type Fetcher interface {
Services() []aiven.Service
Start()
Stop()
SetInterval(time.Duration)
}
type fetcher struct {
aivenProject string
aivenClient aiven.Client
logger lager.Logger
stop chan struct{}
wg sync.WaitGroup
interval time.Duration
servicesMutex sync.RWMutex
services []aiven.Service
}
func NewFetcher(
aivenProject string,
aivenAPIToken string,
logger lager.Logger,
) (Fetcher, error) {
lsession := logger.Session("fetcher", lager.Data{"project": aivenProject})
aivenClient, err := aiven.NewTokenClient(aivenAPIToken, userAgent)
if err != nil {
lsession.Error("err-aiven-new-token-client", err)
return nil, err
}
f := fetcher{
aivenProject: aivenProject,
aivenClient: *aivenClient,
logger: lsession,
stop: make(chan struct{}),
interval: defaultInterval,
}
return &f, nil
}
func (f *fetcher) Services() []aiven.Service {
f.servicesMutex.RLock()
defer f.servicesMutex.RUnlock()
return f.services
}
func (f *fetcher) fetch() {
lsession := f.logger.Session("fetch")
lsession.Info("begin")
defer lsession.Info("end")
FetcherFetchesTotal.Inc()
aivenServices, err := f.aivenClient.Services.List(f.aivenProject)
if err != nil {
lsession.Error("err-aiven-services-list", err)
FetcherAivenListServicesErrorsTotal.Inc()
return
}
f.servicesMutex.Lock()
defer f.servicesMutex.Unlock()
services := make([]aiven.Service, 0)
for _, service := range aivenServices {
if service == nil {
lsession.Info("skip-nil-service")
} else {
services = append(services, *service)
}
}
f.services = services
}
func (f *fetcher) loop() {
lsession := f.logger.Session("loop")
lsession.Info("begin")
defer lsession.Info("end")
f.wg.Add(1)
for {
select {
case <-time.After(f.interval):
f.fetch()
case <-f.stop:
f.wg.Done()
return
}
}
}
func (f *fetcher) Start() {
lsession := f.logger.Session("start")
lsession.Info("begin")
defer lsession.Info("end")
go f.loop()
}
func (f *fetcher) Stop() {
lsession := f.logger.Session("stop")
lsession.Info("begin")
defer lsession.Info("end")
close(f.stop)
f.wg.Wait()
}
func (f *fetcher) SetInterval(interval time.Duration) {
f.interval = interval
}