Add service middleware for Connect service to record last_checkin each time a device contacts the MDM

Add method UpdateDeviceCheckinByUDID to device.Datastore which updates the current checkin timestamp for a given device.
Middleware set up in main.go

connect/middleware.go

@@ -0,0 +1,28 @@
+package connect
+
+import (
+	"github.com/micromdm/micromdm/device"
+	"golang.org/x/net/context"
+)
+
+type lastCheckinMiddleware struct {
+	devices device.Datastore
+	next    Service
+}
+
+func NewMiddleware(datastore device.Datastore, next Service) (*lastCheckinMiddleware) {
+	return &lastCheckinMiddleware{
+		datastore,
+		next,
+	}
+}
+
+func (mw lastCheckinMiddleware) Acknowledge(ctx context.Context, req mdmConnectRequest) (int, error) {
+	mw.devices.UpdateDeviceCheckinByUDID(req.UDID)
+	return mw.next.Acknowledge(ctx, req)
+}
+
+func (mw lastCheckinMiddleware) NextCommand(ctx context.Context, req mdmConnectRequest) ([]byte, int, error) {
+	mw.devices.UpdateDeviceCheckinByUDID(req.UDID)
+	return mw.next.NextCommand(ctx, req)
+}

device/datastore.go

@@ -81,6 +81,7 @@ type Datastore interface {
 	GetDeviceByUDID(udid string, fields ...string) (*Device, error)
 	GetDeviceByUUID(uuid string, fields ...string) (*Device, error)
 	UpdateDeviceQueryResponseByUDID(udid string, responses mdm.QueryResponses) (error)
+	UpdateDeviceCheckinByUDID(udid string) (error)
 	Devices(params ...interface{}) ([]Device, error)
 	Save(msg string, dev *Device) error
 }
@@ -160,6 +161,14 @@ func (store pgStore) UpdateDeviceQueryResponseByUDID(udid string, responses mdm.
 	return err
 }
 
+// Bump the last_checkin timestamp
+func (store pgStore) UpdateDeviceCheckinByUDID(udid string) (error) {
+	stmt := `UPDATE devices SET last_checkin = NOW() WHERE udid = $1`
+	_, err := store.Exec(stmt, udid)
+
+	return err
+}
+
 func (store pgStore) New(src string, d *Device) (string, error) {
 	switch src {
 	case "fetch":

main.go

@@ -187,6 +187,7 @@ func main() {
 	commandSvc := command.NewService(commandDB)
 	checkinSvc := checkin.NewService(deviceDB, mgmtSvc, commandSvc, enrollmentProfile)
 	connectSvc := connect.NewService(deviceDB, commandSvc)
+	connectSvc = connect.NewMiddleware(deviceDB, connectSvc)
 
 	httpLogger := log.NewContext(logger).With("component", "http")
 	managementHandler := management.ServiceHandler(ctx, mgmtSvc, httpLogger)