Fix memory leak by updating go-ole and adding wbem initialization (#82)

README.md

@@ -18,10 +18,13 @@ net | [Win32_PerfRawData_Tcpip_NetworkInterface](https://technet.microsoft.com/e
 os | [Win32_OperatingSystem](https://msdn.microsoft.com/en-us/library/aa394239) metrics (memory, processes, users) | ✓
 service | [Win32_Service](https://msdn.microsoft.com/en-us/library/aa394418(v=vs.85).aspx) metrics (service states) | ✓
 system | Win32_PerfRawData_PerfOS_System metrics (system calls) | ✓
+vmware | Performance counters installed by the Vmware Guest agent |
 
 The HELP texts shows the WMI data source, please see MSDN documentation for details.
 
 ## Installation
+The latest release can be downloaded from the [releases page](https://github.com/martinlindhe/wmi_exporter/releases).
+
 Each release provides a .msi installer. The installer will setup the WMI Exporter as a Windows service, as well as create an exception in the Windows Firewall.
 
 If the installer is run without any parameters, the exporter will run with default settings for enabled collectors, ports, etc. The following parameters are available:

collector/vmware.go

@@ -0,0 +1,335 @@
+// returns data points from Win32_PerfRawData_vmGuestLib_VMem and Win32_PerfRawData_vmGuestLib_VCPU
+package collector
+
+import (
+	"log"
+
+	"github.com/StackExchange/wmi"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func init() {
+	Factories["vmware"] = NewVmwareCollector
+}
+
+// A VmwareCollector is a Prometheus collector for WMI Win32_PerfRawData_vmGuestLib_VMem/Win32_PerfRawData_vmGuestLib_VCPU metrics
+type VmwareCollector struct {
+	MemActive      *prometheus.Desc
+	MemBallooned   *prometheus.Desc
+	MemLimit       *prometheus.Desc
+	MemMapped      *prometheus.Desc
+	MemOverhead    *prometheus.Desc
+	MemReservation *prometheus.Desc
+	MemShared      *prometheus.Desc
+	MemSharedSaved *prometheus.Desc
+	MemShares      *prometheus.Desc
+	MemSwapped     *prometheus.Desc
+	MemTargetSize  *prometheus.Desc
+	MemUsed        *prometheus.Desc
+
+	CpuLimitMHz           *prometheus.Desc
+	CpuReservationMHz     *prometheus.Desc
+	CpuShares             *prometheus.Desc
+	CpuStolenTotal        *prometheus.Desc
+	CpuTimeTotal          *prometheus.Desc
+	EffectiveVMSpeedMHz   *prometheus.Desc
+	HostProcessorSpeedMHz *prometheus.Desc
+}
+
+func NewVmwareCollector() (Collector, error) {
+	const subsystem = "vmware"
+	return &VmwareCollector{
+		MemActive: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_active_bytes"),
+			"(MemActiveMB)",
+			nil,
+			nil,
+		),
+		MemBallooned: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_ballooned_bytes"),
+			"(MemBalloonedMB)",
+			nil,
+			nil,
+		),
+		MemLimit: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_limit_bytes"),
+			"(MemLimitMB)",
+			nil,
+			nil,
+		),
+		MemMapped: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_mapped_bytes"),
+			"(MemMappedMB)",
+			nil,
+			nil,
+		),
+		MemOverhead: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_overhead_bytes"),
+			"(MemOverheadMB)",
+			nil,
+			nil,
+		),
+		MemReservation: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_reservation_bytes"),
+			"(MemReservationMB)",
+			nil,
+			nil,
+		),
+		MemShared: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_shared_bytes"),
+			"(MemSharedMB)",
+			nil,
+			nil,
+		),
+		MemSharedSaved: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_shared_saved_bytes"),
+			"(MemSharedSavedMB)",
+			nil,
+			nil,
+		),
+		MemShares: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_shares"),
+			"(MemShares)",
+			nil,
+			nil,
+		),
+		MemSwapped: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_swapped_bytes"),
+			"(MemSwappedMB)",
+			nil,
+			nil,
+		),
+		MemTargetSize: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_target_size_bytes"),
+			"(MemTargetSizeMB)",
+			nil,
+			nil,
+		),
+		MemUsed: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "mem_used_bytes"),
+			"(MemUsedMB)",
+			nil,
+			nil,
+		),
+
+		CpuLimitMHz: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "cpu_limit_mhz"),
+			"(CpuLimitMHz)",
+			nil,
+			nil,
+		),
+		CpuReservationMHz: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "cpu_reservation_mhz"),
+			"(CpuReservationMHz)",
+			nil,
+			nil,
+		),
+		CpuShares: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "cpu_shares"),
+			"(CpuShares)",
+			nil,
+			nil,
+		),
+		CpuStolenTotal: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "cpu_stolen_seconds_total"),
+			"(CpuStolenMs)",
+			nil,
+			nil,
+		),
+		CpuTimeTotal: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "cpu_time_seconds_total"),
+			"(CpuTimePercents)",
+			nil,
+			nil,
+		),
+		EffectiveVMSpeedMHz: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "effective_vm_speed_mhz"),
+			"(EffectiveVMSpeedMHz)",
+			nil,
+			nil,
+		),
+		HostProcessorSpeedMHz: prometheus.NewDesc(
+			prometheus.BuildFQName(Namespace, subsystem, "host_processor_speed_mhz"),
+			"(HostProcessorSpeedMHz)",
+			nil,
+			nil,
+		),
+	}, nil
+}
+
+// Collect sends the metric values for each metric
+// to the provided prometheus Metric channel.
+func (c *VmwareCollector) Collect(ch chan<- prometheus.Metric) error {
+	if desc, err := c.collectMem(ch); err != nil {
+		log.Println("[ERROR] failed collecting vmware memory metrics:", desc, err)
+		return err
+	}
+	if desc, err := c.collectCpu(ch); err != nil {
+		log.Println("[ERROR] failed collecting vmware cpu metrics:", desc, err)
+		return err
+	}
+	return nil
+}
+
+type Win32_PerfRawData_vmGuestLib_VMem struct {
+	MemActiveMB      uint64
+	MemBalloonedMB   uint64
+	MemLimitMB       uint64
+	MemMappedMB      uint64
+	MemOverheadMB    uint64
+	MemReservationMB uint64
+	MemSharedMB      uint64
+	MemSharedSavedMB uint64
+	MemShares        uint64
+	MemSwappedMB     uint64
+	MemTargetSizeMB  uint64
+	MemUsedMB        uint64
+}
+
+type Win32_PerfRawData_vmGuestLib_VCPU struct {
+	CpuLimitMHz           uint64
+	CpuReservationMHz     uint64
+	CpuShares             uint64
+	CpuStolenMs           uint64
+	CpuTimePercents       uint64
+	EffectiveVMSpeedMHz   uint64
+	HostProcessorSpeedMHz uint64
+}
+
+func (c *VmwareCollector) collectMem(ch chan<- prometheus.Metric) (*prometheus.Desc, error) {
+	var dst []Win32_PerfRawData_vmGuestLib_VMem
+	q := wmi.CreateQuery(&dst, "")
+	if err := wmi.Query(q, &dst); err != nil {
+		return nil, err
+	}
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemActive,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemActiveMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemBallooned,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemBalloonedMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemLimit,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemLimitMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemMapped,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemMappedMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemOverhead,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemOverheadMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemReservation,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemReservationMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemShared,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemSharedMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemSharedSaved,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemSharedSavedMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemShares,
+		prometheus.GaugeValue,
+		float64(dst[0].MemShares),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemSwapped,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemSwappedMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemTargetSize,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemTargetSizeMB),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.MemUsed,
+		prometheus.GaugeValue,
+		mbToBytes(dst[0].MemUsedMB),
+	)
+
+	return nil, nil
+}
+
+func mbToBytes(mb uint64) float64 {
+	return float64(mb * 1024 * 1024)
+}
+
+func (c *VmwareCollector) collectCpu(ch chan<- prometheus.Metric) (*prometheus.Desc, error) {
+	var dst []Win32_PerfRawData_vmGuestLib_VCPU
+	q := wmi.CreateQuery(&dst, "")
+	if err := wmi.Query(q, &dst); err != nil {
+		return nil, err
+	}
+
+	ch <- prometheus.MustNewConstMetric(
+		c.CpuLimitMHz,
+		prometheus.GaugeValue,
+		float64(dst[0].CpuLimitMHz),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.CpuReservationMHz,
+		prometheus.GaugeValue,
+		float64(dst[0].CpuReservationMHz),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.CpuShares,
+		prometheus.GaugeValue,
+		float64(dst[0].CpuShares),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.CpuStolenTotal,
+		prometheus.CounterValue,
+		float64(dst[0].CpuStolenMs)*ticksToSecondsScaleFactor,
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.CpuTimeTotal,
+		prometheus.CounterValue,
+		float64(dst[0].CpuTimePercents)*ticksToSecondsScaleFactor,
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.EffectiveVMSpeedMHz,
+		prometheus.GaugeValue,
+		float64(dst[0].EffectiveVMSpeedMHz),
+	)
+
+	ch <- prometheus.MustNewConstMetric(
+		c.HostProcessorSpeedMHz,
+		prometheus.GaugeValue,
+		float64(dst[0].HostProcessorSpeedMHz),
+	)
+
+	return nil, nil
+}

exporter.go

@@ -13,6 +13,7 @@ import (
 
 	"golang.org/x/sys/windows/svc"
 
+	"github.com/StackExchange/wmi"
 	"github.com/martinlindhe/wmi_exporter/collector"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
@@ -130,6 +131,18 @@ func init() {
 	prometheus.MustRegister(version.NewCollector("wmi_exporter"))
 }
 
+func initWbem() {
+	// This initialization prevents a memory leak on WMF 5+. See
+	// https://github.com/martinlindhe/wmi_exporter/issues/77 and linked issues
+	// for details.
+	log.Debugf("Initializing SWbemServices")
+	s, err := wmi.InitializeSWbemServices(wmi.DefaultClient)
+	if err != nil {
+		log.Fatal(err)
+	}
+	wmi.DefaultClient.SWbemServicesClient = s
+}
+
 func main() {
 	var (
 		showVersion       = flag.Bool("version", false, "Print version information.")
@@ -158,6 +171,8 @@ func main() {
 		return
 	}
 
+	initWbem()
+
 	isInteractive, err := svc.IsAnInteractiveSession()
 	if err != nil {
 		log.Fatal(err)

vendor/github.com/StackExchange/wmi/README.md

@@ -1,4 +1,6 @@
 wmi
 ===
 
-Package wmi provides a WQL interface for WMI on Windows.
+Package wmi provides a WQL interface to Windows WMI.
+
+Note: It interfaces with WMI on the local machine, therefore it only runs on Windows.

vendor/github.com/StackExchange/wmi/swbemservices.go

@@ -0,0 +1,260 @@
+// +build windows
+
+package wmi
+
+import (
+	"fmt"
+	"reflect"
+	"runtime"
+	"sync"
+
+	"github.com/go-ole/go-ole"
+	"github.com/go-ole/go-ole/oleutil"
+)
+
+// SWbemServices is used to access wmi. See https://msdn.microsoft.com/en-us/library/aa393719(v=vs.85).aspx
+type SWbemServices struct {
+	//TODO: track namespace. Not sure if we can re connect to a different namespace using the same instance
+	cWMIClient            *Client //This could also be an embedded struct, but then we would need to branch on Client vs SWbemServices in the Query method
+	sWbemLocatorIUnknown  *ole.IUnknown
+	sWbemLocatorIDispatch *ole.IDispatch
+	queries               chan *queryRequest
+	closeError            chan error
+	lQueryorClose         sync.Mutex
+}
+
+type queryRequest struct {
+	query    string
+	dst      interface{}
+	args     []interface{}
+	finished chan error
+}
+
+// InitializeSWbemServices will return a new SWbemServices object that can be used to query WMI
+func InitializeSWbemServices(c *Client, connectServerArgs ...interface{}) (*SWbemServices, error) {
+	//fmt.Println("InitializeSWbemServices: Starting")
+	//TODO: implement connectServerArgs as optional argument for init with connectServer call
+	s := new(SWbemServices)
+	s.cWMIClient = c
+	s.queries = make(chan *queryRequest)
+	initError := make(chan error)
+	go s.process(initError)
+
+	err, ok := <-initError
+	if ok {
+		return nil, err //Send error to caller
+	}
+	//fmt.Println("InitializeSWbemServices: Finished")
+	return s, nil
+}
+
+// Close will clear and release all of the SWbemServices resources
+func (s *SWbemServices) Close() error {
+	s.lQueryorClose.Lock()
+	if s == nil || s.sWbemLocatorIDispatch == nil {
+		s.lQueryorClose.Unlock()
+		return fmt.Errorf("SWbemServices is not Initialized")
+	}
+	if s.queries == nil {
+		s.lQueryorClose.Unlock()
+		return fmt.Errorf("SWbemServices has been closed")
+	}
+	//fmt.Println("Close: sending close request")
+	var result error
+	ce := make(chan error)
+	s.closeError = ce //Race condition if multiple callers to close. May need to lock here
+	close(s.queries)  //Tell background to shut things down
+	s.lQueryorClose.Unlock()
+	err, ok := <-ce
+	if ok {
+		result = err
+	}
+	//fmt.Println("Close: finished")
+	return result
+}
+
+func (s *SWbemServices) process(initError chan error) {
+	//fmt.Println("process: starting background thread initialization")
+	//All OLE/WMI calls must happen on the same initialized thead, so lock this goroutine
+	runtime.LockOSThread()
+	defer runtime.LockOSThread()
+
+	err := ole.CoInitializeEx(0, ole.COINIT_MULTITHREADED)
+	if err != nil {
+		oleCode := err.(*ole.OleError).Code()
+		if oleCode != ole.S_OK && oleCode != S_FALSE {
+			initError <- fmt.Errorf("ole.CoInitializeEx error: %v", err)
+			return
+		}
+	}
+	defer ole.CoUninitialize()
+
+	unknown, err := oleutil.CreateObject("WbemScripting.SWbemLocator")
+	if err != nil {
+		initError <- fmt.Errorf("CreateObject SWbemLocator error: %v", err)
+		return
+	} else if unknown == nil {
+		initError <- ErrNilCreateObject
+		return
+	}
+	defer unknown.Release()
+	s.sWbemLocatorIUnknown = unknown
+
+	dispatch, err := s.sWbemLocatorIUnknown.QueryInterface(ole.IID_IDispatch)
+	if err != nil {
+		initError <- fmt.Errorf("SWbemLocator QueryInterface error: %v", err)
+		return
+	}
+	defer dispatch.Release()
+	s.sWbemLocatorIDispatch = dispatch
+
+	// we can't do the ConnectServer call outside the loop unless we find a way to track and re-init the connectServerArgs
+	//fmt.Println("process: initialized. closing initError")
+	close(initError)
+	//fmt.Println("process: waiting for queries")
+	for q := range s.queries {
+		//fmt.Printf("process: new query: len(query)=%d\n", len(q.query))
+		errQuery := s.queryBackground(q)
+		//fmt.Println("process: s.queryBackground finished")
+		if errQuery != nil {
+			q.finished <- errQuery
+		}
+		close(q.finished)
+	}
+	//fmt.Println("process: queries channel closed")
+	s.queries = nil //set channel to nil so we know it is closed
+	//TODO: I think the Release/Clear calls can panic if things are in a bad state.
+	//TODO: May need to recover from panics and send error to method caller instead.
+	close(s.closeError)
+}
+
+// Query runs the WQL query using a SWbemServices instance and appends the values to dst.
+//
+// dst must have type *[]S or *[]*S, for some struct type S. Fields selected in
+// the query must have the same name in dst. Supported types are all signed and
+// unsigned integers, time.Time, string, bool, or a pointer to one of those.
+// Array types are not supported.
+//
+// By default, the local machine and default namespace are used. These can be
+// changed using connectServerArgs. See
+// http://msdn.microsoft.com/en-us/library/aa393720.aspx for details.
+func (s *SWbemServices) Query(query string, dst interface{}, connectServerArgs ...interface{}) error {
+	s.lQueryorClose.Lock()
+	if s == nil || s.sWbemLocatorIDispatch == nil {
+		s.lQueryorClose.Unlock()
+		return fmt.Errorf("SWbemServices is not Initialized")
+	}
+	if s.queries == nil {
+		s.lQueryorClose.Unlock()
+		return fmt.Errorf("SWbemServices has been closed")
+	}
+
+	//fmt.Println("Query: Sending query request")
+	qr := queryRequest{
+		query:    query,
+		dst:      dst,
+		args:     connectServerArgs,
+		finished: make(chan error),
+	}
+	s.queries <- &qr
+	s.lQueryorClose.Unlock()
+	err, ok := <-qr.finished
+	if ok {
+		//fmt.Println("Query: Finished with error")
+		return err //Send error to caller
+	}
+	//fmt.Println("Query: Finished")
+	return nil
+}
+
+func (s *SWbemServices) queryBackground(q *queryRequest) error {
+	if s == nil || s.sWbemLocatorIDispatch == nil {
+		return fmt.Errorf("SWbemServices is not Initialized")
+	}
+	wmi := s.sWbemLocatorIDispatch //Should just rename in the code, but this will help as we break things apart
+	//fmt.Println("queryBackground: Starting")
+
+	dv := reflect.ValueOf(q.dst)
+	if dv.Kind() != reflect.Ptr || dv.IsNil() {
+		return ErrInvalidEntityType
+	}
+	dv = dv.Elem()
+	mat, elemType := checkMultiArg(dv)
+	if mat == multiArgTypeInvalid {
+		return ErrInvalidEntityType
+	}
+
+	// service is a SWbemServices
+	serviceRaw, err := oleutil.CallMethod(wmi, "ConnectServer", q.args...)
+	if err != nil {
+		return err
+	}
+	service := serviceRaw.ToIDispatch()
+	defer serviceRaw.Clear()
+
+	// result is a SWBemObjectSet
+	resultRaw, err := oleutil.CallMethod(service, "ExecQuery", q.query)
+	if err != nil {
+		return err
+	}
+	result := resultRaw.ToIDispatch()
+	defer resultRaw.Clear()
+
+	count, err := oleInt64(result, "Count")
+	if err != nil {
+		return err
+	}
+
+	enumProperty, err := result.GetProperty("_NewEnum")
+	if err != nil {
+		return err
+	}
+	defer enumProperty.Clear()
+
+	enum, err := enumProperty.ToIUnknown().IEnumVARIANT(ole.IID_IEnumVariant)
+	if err != nil {
+		return err
+	}
+	if enum == nil {
+		return fmt.Errorf("can't get IEnumVARIANT, enum is nil")
+	}
+	defer enum.Release()
+
+	// Initialize a slice with Count capacity
+	dv.Set(reflect.MakeSlice(dv.Type(), 0, int(count)))
+
+	var errFieldMismatch error
+	for itemRaw, length, err := enum.Next(1); length > 0; itemRaw, length, err = enum.Next(1) {
+		if err != nil {
+			return err
+		}
+
+		err := func() error {
+			// item is a SWbemObject, but really a Win32_Process
+			item := itemRaw.ToIDispatch()
+			defer item.Release()
+
+			ev := reflect.New(elemType)
+			if err = s.cWMIClient.loadEntity(ev.Interface(), item); err != nil {
+				if _, ok := err.(*ErrFieldMismatch); ok {
+					// We continue loading entities even in the face of field mismatch errors.
+					// If we encounter any other error, that other error is returned. Otherwise,
+					// an ErrFieldMismatch is returned.
+					errFieldMismatch = err
+				} else {
+					return err
+				}
+			}
+			if mat != multiArgTypeStructPtr {
+				ev = ev.Elem()
+			}
+			dv.Set(reflect.Append(dv, ev))
+			return nil
+		}()
+		if err != nil {
+			return err
+		}
+	}
+	//fmt.Println("queryBackground: Finished")
+	return errFieldMismatch
+}

vendor/github.com/StackExchange/wmi/wmi.go

@@ -72,7 +72,10 @@ func QueryNamespace(query string, dst interface{}, namespace string) error {
 //
 // Query is a wrapper around DefaultClient.Query.
 func Query(query string, dst interface{}, connectServerArgs ...interface{}) error {
-	return DefaultClient.Query(query, dst, connectServerArgs...)
+	if DefaultClient.SWbemServicesClient == nil {
+		return DefaultClient.Query(query, dst, connectServerArgs...)
+	}
+	return DefaultClient.SWbemServicesClient.Query(query, dst, connectServerArgs...)
 }
 
 // A Client is an WMI query client.
@@ -99,6 +102,11 @@ type Client struct {
 	// Setting this to true allows custom queries to be used with full
 	// struct definitions instead of having to define multiple structs.
 	AllowMissingFields bool
+
+	// SWbemServiceClient is an optional SWbemServices object that can be
+	// initialized and then reused across multiple queries. If it is null
+	// then the method will initialize a new temporary client each time.
+	SWbemServicesClient *SWbemServices
 }
 
 // DefaultClient is the default Client and is used by Query, QueryNamespace
@@ -362,6 +370,21 @@ func (c *Client) loadEntity(dst interface{}, src *ole.IDispatch) (errFieldMismat
 				}
 			}
 		default:
+			// Only support []string slices for now
+			if f.Kind() == reflect.Slice && f.Type().Elem().Kind() == reflect.String {
+				safeArray := prop.ToArray()
+				if safeArray != nil {
+					arr := safeArray.ToValueArray()
+					fArr := reflect.MakeSlice(f.Type(), len(arr), len(arr))
+					for i, v := range arr {
+						s := fArr.Index(i)
+						s.SetString(v.(string))
+					}
+					f.Set(fArr)
+					break
+				}
+			}
+
 			typeof := reflect.TypeOf(val)
 			if typeof == nil && (isPtr || c.NonePtrZero) {
 				if (isPtr && c.PtrNil) || (!isPtr && c.NonePtrZero) {

vendor/github.com/go-ole/go-ole/variant_s390x.go

@@ -0,0 +1,12 @@
+// +build s390x
+
+package ole
+
+type VARIANT struct {
+	VT         VT      //  2
+	wReserved1 uint16  //  4
+	wReserved2 uint16  //  6
+	wReserved3 uint16  //  8
+	Val        int64   // 16
+	_          [8]byte // 24
+}

vendor/vendor.json

@@ -9,10 +9,10 @@
 			"revisionTime": "2016-08-29T20:23:21Z"
 		},
 		{
-			"checksumSHA1": "9NR0rrcAT5J76C5xMS4AVksS9o0=",
+			"checksumSHA1": "qtjd74+bErubh+qyv3s+lWmn9wc=",
 			"path": "github.com/StackExchange/wmi",
-			"revision": "e54cbda6595d7293a7a468ccf9525f6bc8887f99",
-			"revisionTime": "2016-08-11T21:45:55Z"
+			"revision": "ea383cf3ba6ec950874b8486cd72356d007c768f",
+			"revisionTime": "2017-04-10T19:29:09Z"
 		},
 		{
 			"checksumSHA1": "spyv5/YFBjYyZLZa1U2LBfDR8PM=",
@@ -21,10 +21,10 @@
 			"revisionTime": "2016-08-04T10:47:26Z"
 		},
 		{
-			"checksumSHA1": "wDZdTaY9JiqqqnF4c3pHP71nWmk=",
+			"checksumSHA1": "oyULO1B/l2OLy2xereo+2w3hYk4=",
 			"path": "github.com/go-ole/go-ole",
-			"revision": "7dfdcf409020452e29b4babcbb22f984d2aa308a",
-			"revisionTime": "2016-07-29T03:38:29Z"
+			"revision": "02d3668a0cf01f58411cc85cd37c174c257ec7c2",
+			"revisionTime": "2017-06-01T13:56:11Z"
 		},
 		{
 			"checksumSHA1": "qLYVTQDhgrVIeZ2KI9eZV51mmug=",