Replace the CS collector with native WinAPI calls to sysinfoapi

Signed-off-by: Ben Ridley <benridley29@gmail.com>

collector/cs.go

@@ -3,10 +3,8 @@
 package collector
 
 import (
-	"errors"
-
-	"github.com/StackExchange/wmi"
 	"github.com/prometheus-community/windows_exporter/log"
+	"github.com/prometheus-community/windows_exporter/sysinfoapi"
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -60,51 +58,45 @@ func (c *CSCollector) Collect(ctx *ScrapeContext, ch chan<- prometheus.Metric) e
 	return nil
 }
 
-// Win32_ComputerSystem docs:
-// - https://msdn.microsoft.com/en-us/library/aa394102
-type Win32_ComputerSystem struct {
-	NumberOfLogicalProcessors uint32
-	TotalPhysicalMemory       uint64
-	DNSHostname               string
-	Domain                    string
-	Workgroup                 *string
-}
-
 func (c *CSCollector) collect(ch chan<- prometheus.Metric) (*prometheus.Desc, error) {
-	var dst []Win32_ComputerSystem
-	q := queryAll(&dst)
-	if err := wmi.Query(q, &dst); err != nil {
+	cs := sysinfoapi.GetNumLogicalProcessors()
+
+	pm, err := sysinfoapi.GetPhysicalMemory()
+	if err != nil {
 		return nil, err
 	}
-	if len(dst) == 0 {
-		return nil, errors.New("WMI query returned empty result set")
-	}
 
 	ch <- prometheus.MustNewConstMetric(
 		c.LogicalProcessors,
 		prometheus.GaugeValue,
-		float64(dst[0].NumberOfLogicalProcessors),
+		float64(cs),
 	)
 
 	ch <- prometheus.MustNewConstMetric(
 		c.PhysicalMemoryBytes,
 		prometheus.GaugeValue,
-		float64(dst[0].TotalPhysicalMemory),
+		float64(pm),
 	)
 
-	var fqdn string
-	if dst[0].Workgroup == nil || dst[0].Domain != *dst[0].Workgroup {
-		fqdn = dst[0].DNSHostname + "." + dst[0].Domain
-	} else {
-		fqdn = dst[0].DNSHostname
+	hostname, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSHostname)
+	if err != nil {
+		return nil, err
+	}
+	domain, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSDomain)
+	if err != nil {
+		return nil, err
+	}
+	fqdn, err := sysinfoapi.GetComputerName(sysinfoapi.ComputerNameDNSFullyQualified)
+	if err != nil {
+		return nil, err
 	}
 
 	ch <- prometheus.MustNewConstMetric(
 		c.Hostname,
 		prometheus.GaugeValue,
 		1.0,
-		dst[0].DNSHostname,
-		dst[0].Domain,
+		hostname,
+		domain,
 		fqdn,
 	)
 

collector/cs_test.go

@@ -0,0 +1,23 @@
+package collector
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func BenchmarkCsCollect(b *testing.B) {
+	c, err := NewCSCollector()
+	if err != nil {
+		b.Error(err)
+	}
+	metrics := make(chan prometheus.Metric)
+	go func() {
+		for {
+			<-metrics
+		}
+	}()
+	for i := 0; i < b.N; i++ {
+		c.Collect(&ScrapeContext{}, metrics)
+	}
+}

sysinfoapi/sysinfoapi.go

@@ -0,0 +1,112 @@
+// Copyright 2020 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package sysinfoapi wraps some WinAPI sysinfoapi functions used by the exporter to produce metrics.
+// It is fairly opinionated for the exporter's internal use, and is not intended to be a
+// generic wrapper for the WinAPI's sysinfoapi.
+package sysinfoapi
+
+import (
+	"unicode/utf16"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// WinProcInfo is a wrapper for
+type WinProcInfo struct {
+	WReserved              uint16
+	WProcessorArchitecture uint16
+}
+
+// WinSystemInfo is a wrapper for LPSYSTEM_INFO
+type WinSystemInfo struct {
+	Arch                        WinProcInfo
+	DwPageSize                  uint32
+	LpMinimumApplicationAddress *byte
+	LpMaximumApplicationAddress *byte
+	DwActiveProcessorMask       *uint32
+	DwNumberOfProcessors        uint32
+	DwProcessorType             uint32
+	DwAllocationGranularity     uint32
+	WProcessorLevel             uint16
+	WProcessorRevision          uint16
+}
+
+// WinComputerNameFormat is a wrapper for COMPUTER_NAME_FORMAT
+type WinComputerNameFormat int
+
+// Definitions for WinComputerNameFormat constants
+const (
+	ComputerNameNetBIOS WinComputerNameFormat = iota
+	ComputerNameDNSHostname
+	ComputerNameDNSDomain
+	ComputerNameDNSFullyQualified
+	ComputerNamePhysicalNetBIOS
+	ComputerNamePhysicalDNSHostname
+	ComputerNamePhysicalDNSDomain
+	ComputerNamePhysicalDNSFullyQualified
+	ComputerNameMax
+)
+
+// WinMemoryStatus is a wrapper for LPMEMORYSTATUSEX
+type WinMemoryStatus struct {
+	dwLength                uint32
+	dwMemoryLoad            uint32
+	ullTotalPhys            uint64
+	ullAvailPhys            uint64
+	ullTotalPageFile        uint64
+	ullAvailPageFile        uint64
+	ullTotalVirtual         uint64
+	ullAvailVirtual         uint64
+	ullAvailExtendedVirtual uint64
+}
+
+var (
+	kernel32                 = windows.NewLazySystemDLL("kernel32.dll")
+	procGetSystemInfo        = kernel32.NewProc("GetSystemInfo")
+	procGlobalMemoryStatusEx = kernel32.NewProc("GlobalMemoryStatusEx")
+	procGetComputerNameExW   = kernel32.NewProc("GetComputerNameExW")
+)
+
+// GetNumLogicalProcessors returns the number of logical processes provided by sysinfoapi's GetSystemInfo function.
+func GetNumLogicalProcessors() int {
+	var sysInfo WinSystemInfo
+	pInfo := uintptr(unsafe.Pointer(&sysInfo))
+	procGetSystemInfo.Call(pInfo)
+	return int(sysInfo.DwNumberOfProcessors)
+}
+
+// GetPhysicalMemory returns the system's installed physical memory provided by sysinfoapi's GlobalMemoryStatusEx function.
+func GetPhysicalMemory() (int, error) {
+	var wm WinMemoryStatus
+	wm.dwLength = (uint32)(unsafe.Sizeof(wm))
+	r1, _, err := procGlobalMemoryStatusEx.Call(uintptr(unsafe.Pointer(&wm)))
+	if r1 != 1 {
+		return 0, err
+	}
+	return int(wm.ullTotalPhys), nil
+}
+
+// GetComputerName provides the requested computer name provided by sysinfoapi's GetComputerNameEx function.
+func GetComputerName(f WinComputerNameFormat) (string, error) {
+	size := 4096
+	var buffer [4096]uint16
+	r1, _, err := procGetComputerNameExW.Call(uintptr(f), uintptr(unsafe.Pointer(&buffer)), uintptr(unsafe.Pointer(&size)))
+	if r1 == 0 {
+		return "", err
+	}
+	bytes := buffer[0:size]
+	out := utf16.Decode(bytes)
+	return string(out), nil
+}