feat(BRIDGE-363): Observability metrics for IMAP connections; minor unleash service refactor;

internal/services/imapsmtpserver/imap.go

@@ -24,6 +24,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"time"
 
 	"github.com/Masterminds/semver/v3"
 	"github.com/ProtonMail/gluon"
@@ -40,6 +41,12 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
+const (
+	rollingCounterNewConnectionThreshold = 300
+	rollingCounterNumberOfBuckets        = 6
+	rollingCounterBucketRotationInterval = time.Second * 10
+)
+
 var logIMAP = logrus.WithField("pkg", "server/imap") //nolint:gochecknoglobals
 
 type IMAPSettingsProvider interface {
@@ -126,6 +133,7 @@ func newIMAPServer(
 		gluon.WithUIDValidityGenerator(uidValidityGenerator),
 		gluon.WithPanicHandler(panicHandler),
 		gluon.WithObservabilitySender(observability.NewAdapter(observabilitySender), int(observability.GluonImapError), int(observability.GluonMessageError), int(observability.GluonOtherError)),
+		gluon.WithConnectionRollingCounter(rollingCounterNewConnectionThreshold, rollingCounterNumberOfBuckets, rollingCounterBucketRotationInterval),
 	}
 
 	if disableIMAPAuthenticate {

internal/services/imapsmtpserver/service.go

@@ -200,6 +200,14 @@ func (sm *Service) RemoveSMTPAccount(ctx context.Context, service *bridgesmtp.Se
 	return err
 }
 
+func (sm *Service) GetOpenIMAPSessionCount() int {
+	return sm.imapServer.GetOpenSessionCount()
+}
+
+func (sm *Service) GetRollingIMAPConnectionCount() int {
+	return sm.imapServer.GetRollingIMAPConnectionCount()
+}
+
 func (sm *Service) run(ctx context.Context, subscription events.Subscription) {
 	eventSub := subscription.Add()
 	defer subscription.Remove(eventSub)