chore: refactor http handler

Signed-off-by: Jan-Otto Kröpke <[email protected]>
Signed-off-by: Jan-Otto Kröpke <[email protected]>

Author: jkroepke

exporter.go

@@ -28,6 +28,7 @@ import (
 	"github.com/alecthomas/kingpin/v2"
 	"github.com/prometheus-community/windows_exporter/pkg/collector"
 	"github.com/prometheus-community/windows_exporter/pkg/config"
+	"github.com/prometheus-community/windows_exporter/pkg/httphandler"
 	winlog "github.com/prometheus-community/windows_exporter/pkg/log"
 	"github.com/prometheus-community/windows_exporter/pkg/log/flag"
 	"github.com/prometheus-community/windows_exporter/pkg/types"
@@ -251,7 +252,12 @@ func main() {
 	logger.Info("Enabled collectors: " + strings.Join(enabledCollectorList, ", "))
 
 	mux := http.NewServeMux()
-	mux.HandleFunc("GET "+*metricsPath, withConcurrencyLimit(*maxRequests, collectors.BuildServeHTTP(logger, *disableExporterMetrics, *timeoutMargin)))
+	mux.Handle("GET "+*metricsPath, httphandler.New(logger, collectors, &httphandler.Options{
+		DisableExporterMetrics: *disableExporterMetrics,
+		TimeoutMargin:          *timeoutMargin,
+		MaxRequests:            *maxRequests,
+	}))
+
 	mux.HandleFunc("GET /health", func(w http.ResponseWriter, _ *http.Request) {
 		w.Header().Set("Content-Type", "application/json")
 		if _, err := fmt.Fprintln(w, `{"status":"ok"}`); err != nil {
@@ -260,6 +266,7 @@ func main() {
 			)
 		}
 	})
+
 	mux.HandleFunc("GET /version", func(w http.ResponseWriter, _ *http.Request) {
 		// we can't use "version" directly as it is a package, and not an object that
 		// can be serialized.
@@ -292,7 +299,7 @@ func main() {
 		ReadHeaderTimeout: 5 * time.Second,
 		IdleTimeout:       60 * time.Second,
 		ReadTimeout:       5 * time.Second,
-		WriteTimeout:      10 * time.Minute,
+		WriteTimeout:      5 * time.Minute,
 		Handler:           mux,
 	}
 
@@ -322,22 +329,3 @@ func main() {
 
 	logger.Info("windows_exporter has shut down")
 }
-
-func withConcurrencyLimit(n int, next http.HandlerFunc) http.HandlerFunc {
-	if n <= 0 {
-		return next
-	}
-
-	sem := make(chan struct{}, n)
-	return func(w http.ResponseWriter, r *http.Request) {
-		select {
-		case sem <- struct{}{}:
-			defer func() { <-sem }()
-		default:
-			w.WriteHeader(http.StatusServiceUnavailable)
-			_, _ = w.Write([]byte("Too many concurrent requests"))
-			return
-		}
-		next(w, r)
-	}
-}

go.mod

@@ -15,6 +15,7 @@ require (
 	github.com/prometheus/exporter-toolkit v0.12.0
 	github.com/stretchr/testify v1.9.0
 	github.com/yusufpapurcu/wmi v1.2.4
+	golang.org/x/exp v0.0.0-20231006140011-7918f672742d
 	golang.org/x/sys v0.25.0
 	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -118,6 +118,8 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.27.0 h1:GXm2NjJrPaiv/h1tb2UH8QfgC/hOf/+z0p6PT8o1w7A=
 golang.org/x/crypto v0.27.0/go.mod h1:1Xngt8kV6Dvbssa53Ziq6Eqn0HqbZi5Z6R0ZpwQzt70=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
 golang.org/x/lint v0.0.0-20181026193005-c67002cb31c3/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
 golang.org/x/lint v0.0.0-20190227174305-5b3e6a55c961/go.mod h1:wehouNa3lNwaWXcvxsM5YxQ5yQlVC4a0KAMCusXpPoU=
 golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=

pkg/collector/collector.go

@@ -69,7 +69,7 @@ import (
 )
 
 // NewWithFlags To be called by the exporter for collector initialization before running kingpin.Parse.
-func NewWithFlags(app *kingpin.Application) *Collectors {
+func NewWithFlags(app *kingpin.Application) *MetricCollectors {
 	collectors := map[string]Collector{}
 
 	for name, builder := range BuildersWithFlags {
@@ -82,8 +82,8 @@ func NewWithFlags(app *kingpin.Application) *Collectors {
 // NewWithConfig To be called by the external libraries for collector initialization without running kingpin.Parse
 //
 //goland:noinspection GoUnusedExportedFunction
-func NewWithConfig(config Config) *Collectors {
-	collectors := map[string]Collector{}
+func NewWithConfig(config Config) *MetricCollectors {
+	collectors := Map{}
 	collectors[ad.Name] = ad.New(&config.AD)
 	collectors[adcs.Name] = adcs.New(&config.ADCS)
 	collectors[adfs.Name] = adfs.New(&config.ADFS)
@@ -142,26 +142,26 @@ func NewWithConfig(config Config) *Collectors {
 }
 
 // New To be called by the external libraries for collector initialization.
-func New(collectors Map) *Collectors {
-	return &Collectors{
-		collectors: collectors,
-		wmiClient: &wmi.Client{
+func New(collectors Map) *MetricCollectors {
+	return &MetricCollectors{
+		Collectors: collectors,
+		WMIClient: &wmi.Client{
 			AllowMissingFields: true,
 		},
 	}
 }
 
-func (c *Collectors) SetPerfCounterQuery(logger *slog.Logger) error {
+func (c *MetricCollectors) SetPerfCounterQuery(logger *slog.Logger) error {
 	var (
 		err error
 
 		perfCounterNames []string
 		perfIndicies     []string
 	)
 
-	perfCounterDependencies := make([]string, 0, len(c.collectors))
+	perfCounterDependencies := make([]string, 0, len(c.Collectors))
 
-	for _, collector := range c.collectors {
+	for _, collector := range c.Collectors {
 		perfCounterNames, err = collector.GetPerfCounter(logger)
 		if err != nil {
 			return err
@@ -175,31 +175,31 @@ func (c *Collectors) SetPerfCounterQuery(logger *slog.Logger) error {
 		perfCounterDependencies = append(perfCounterDependencies, strings.Join(perfIndicies, " "))
 	}
 
-	c.perfCounterQuery = strings.Join(perfCounterDependencies, " ")
+	c.PerfCounterQuery = strings.Join(perfCounterDependencies, " ")
 
 	return nil
 }
 
 // Enable removes all collectors that not enabledCollectors.
-func (c *Collectors) Enable(enabledCollectors []string) {
-	for name := range c.collectors {
+func (c *MetricCollectors) Enable(enabledCollectors []string) {
+	for name := range c.Collectors {
 		if !slices.Contains(enabledCollectors, name) {
-			delete(c.collectors, name)
+			delete(c.Collectors, name)
 		}
 	}
 }
 
 // Build To be called by the exporter for collector initialization.
-func (c *Collectors) Build(logger *slog.Logger) error {
+func (c *MetricCollectors) Build(logger *slog.Logger) error {
 	var err error
 
-	c.wmiClient.SWbemServicesClient, err = wmi.InitializeSWbemServices(c.wmiClient)
+	c.WMIClient.SWbemServicesClient, err = wmi.InitializeSWbemServices(c.WMIClient)
 	if err != nil {
 		return fmt.Errorf("initialize SWbemServices: %w", err)
 	}
 
-	for _, collector := range c.collectors {
-		if err = collector.Build(logger, c.wmiClient); err != nil {
+	for _, collector := range c.Collectors {
+		if err = collector.Build(logger, c.WMIClient); err != nil {
 			return fmt.Errorf("error build collector %s: %w", collector.GetName(), err)
 		}
 	}
@@ -208,12 +208,12 @@ func (c *Collectors) Build(logger *slog.Logger) error {
 }
 
 // PrepareScrapeContext creates a ScrapeContext to be used during a single scrape.
-func (c *Collectors) PrepareScrapeContext() (*types.ScrapeContext, error) {
-	if c.perfCounterQuery == "" { // if perfCounterQuery is empty, no perf counters are needed.
+func (c *MetricCollectors) PrepareScrapeContext() (*types.ScrapeContext, error) {
+	if c.PerfCounterQuery == "" { // if perfCounterQuery is empty, no perf counters are needed.
 		return &types.ScrapeContext{}, nil
 	}
 
-	objs, err := perflib.GetPerflibSnapshot(c.perfCounterQuery)
+	objs, err := perflib.GetPerflibSnapshot(c.PerfCounterQuery)
 	if err != nil {
 		return nil, err
 	}
@@ -222,17 +222,17 @@ func (c *Collectors) PrepareScrapeContext() (*types.ScrapeContext, error) {
 }
 
 // Close To be called by the exporter for collector cleanup.
-func (c *Collectors) Close(logger *slog.Logger) error {
-	errs := make([]error, 0, len(c.collectors))
+func (c *MetricCollectors) Close(logger *slog.Logger) error {
+	errs := make([]error, 0, len(c.Collectors))
 
-	for _, collector := range c.collectors {
+	for _, collector := range c.Collectors {
 		if err := collector.Close(logger); err != nil {
 			errs = append(errs, err)
 		}
 	}
 
-	if c.wmiClient != nil && c.wmiClient.SWbemServicesClient != nil {
-		if err := c.wmiClient.SWbemServicesClient.Close(); err != nil {
+	if c.WMIClient != nil && c.WMIClient.SWbemServicesClient != nil {
+		if err := c.WMIClient.SWbemServicesClient.Close(); err != nil {
 			errs = append(errs, err)
 		}
 	}