Add config.auto-reload switch for auto reload when the config file changed

cmd/process-exporter/main.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/fsnotify/fsnotify"
 	"github.com/ncabatoff/fakescraper"
 	common "github.com/ncabatoff/process-exporter"
 	"github.com/ncabatoff/process-exporter/config"
@@ -299,6 +300,8 @@ func main() {
 			"print manual")
 		configPath = flag.String("config.path", "",
 			"path to YAML config file")
+		autoReload = flag.Bool("config.auto-reload", false,
+			"auto reload when config file changed")
 		recheck = flag.Bool("recheck", false,
 			"recheck process names on each scrape")
 		debug = flag.Bool("debug", false,
@@ -318,61 +321,68 @@ func main() {
 		return
 	}
 
-	var matchnamer common.MatchNamer
+	var pc *NamedProcessCollector
 
-	if *configPath != "" {
-		if *nameMapping != "" || *procNames != "" {
-			log.Fatalf("-config.path cannot be used with -namemapping or -procnames")
-		}
+	RegisterController := func() {
+		var matchnamer common.MatchNamer
 
-		cfg, err := config.ReadFile(*configPath, *debug)
-		if err != nil {
-			log.Fatalf("error reading config file %q: %v", *configPath, err)
-		}
-		log.Printf("Reading metrics from %s based on %q", *procfsPath, *configPath)
-		matchnamer = cfg.MatchNamers
-		if *debug {
-			log.Printf("using config matchnamer: %v", cfg.MatchNamers)
-		}
-	} else {
-		namemapper, err := parseNameMapper(*nameMapping)
-		if err != nil {
-			log.Fatalf("Error parsing -namemapping argument '%s': %v", *nameMapping, err)
-		}
+		if *configPath != "" {
+			if *nameMapping != "" || *procNames != "" {
+				log.Fatalf("-config.path cannot be used with -namemapping or -procnames")
+			}
 
-		var names []string
-		for _, s := range strings.Split(*procNames, ",") {
-			if s != "" {
-				if _, ok := namemapper.mapping[s]; !ok {
-					namemapper.mapping[s] = nil
+			cfg, err := config.ReadFile(*configPath, *debug)
+			if err != nil {
+				log.Fatalf("error reading config file %q: %v", *configPath, err)
+			}
+			log.Printf("Reading metrics from %s based on %q", *procfsPath, *configPath)
+			matchnamer = cfg.MatchNamers
+			if *debug {
+				log.Printf("using config matchnamer: %v", cfg.MatchNamers)
+			}
+		} else {
+			namemapper, err := parseNameMapper(*nameMapping)
+			if err != nil {
+				log.Fatalf("Error parsing -namemapping argument '%s': %v", *nameMapping, err)
+			}
+
+			var names []string
+			for _, s := range strings.Split(*procNames, ",") {
+				if s != "" {
+					if _, ok := namemapper.mapping[s]; !ok {
+						namemapper.mapping[s] = nil
+					}
+					names = append(names, s)
 				}
-				names = append(names, s)
 			}
+
+			log.Printf("Reading metrics from %s for procnames: %v", *procfsPath, names)
+			if *debug {
+				log.Printf("using cmdline matchnamer: %v", namemapper)
+			}
+			matchnamer = namemapper
 		}
 
-		log.Printf("Reading metrics from %s for procnames: %v", *procfsPath, names)
-		if *debug {
-			log.Printf("using cmdline matchnamer: %v", namemapper)
+		var err error
+		pc, err = NewProcessCollector(
+			ProcessCollectorOption{
+				ProcFSPath:  *procfsPath,
+				Children:    *children,
+				Threads:     *threads,
+				GatherSMaps: *smaps,
+				Namer:       matchnamer,
+				Recheck:     *recheck,
+				Debug:       *debug,
+			},
+		)
+		if err != nil {
+			log.Fatalf("Error initializing: %v", err)
 		}
-		matchnamer = namemapper
-	}
 
-	pc, err := NewProcessCollector(
-		ProcessCollectorOption{
-			ProcFSPath:  *procfsPath,
-			Children:    *children,
-			Threads:     *threads,
-			GatherSMaps: *smaps,
-			Namer:       matchnamer,
-			Recheck:     *recheck,
-			Debug:       *debug,
-		},
-	)
-	if err != nil {
-		log.Fatalf("Error initializing: %v", err)
+		prometheus.MustRegister(pc)
 	}
 
-	prometheus.MustRegister(pc)
+	RegisterController()
 
 	if *onceToStdoutDelay != 0 {
 		// We throw away the first result because that first collection primes the pump, and
@@ -385,6 +395,56 @@ func main() {
 		return
 	}
 
+	if *autoReload {
+		watcher, err := fsnotify.NewWatcher()
+		if err != nil {
+			log.Fatalf("Start watcher failed, %v", err)
+		}
+		defer watcher.Close()
+
+		err = watcher.Add(*configPath)
+		if err != nil {
+			log.Fatalf("Add watcher for %s failed, %v", *configPath, err)
+		}
+
+		log.Printf("Starting file system watcher for %s", *configPath)
+
+		go func() {
+			for {
+				select {
+				case e := <-watcher.Events:
+					if e.Op&(fsnotify.Write|fsnotify.Remove|fsnotify.Rename) != 0 {
+						err = watcher.Remove(*configPath)
+						if err != nil {
+							log.Fatalf("Remove old watcher for %s failed, %v", *configPath, err)
+						}
+
+						for {
+							if stat, err := os.Stat(*configPath); (err != nil && !os.IsExist(err)) || stat.Size() == 0 {
+								log.Printf("Config file removed or renamed, waiting")
+								time.Sleep(5 * time.Second)
+							} else {
+								log.Printf("Config file changed, reloading")
+
+								err = watcher.Add(*configPath)
+								if err != nil {
+									log.Fatalf("Add watcher for %s failed, %v", *configPath, err)
+								}
+
+								prometheus.Unregister(pc)
+								RegisterController()
+
+								break
+							}
+						}
+					}
+				case err := <-watcher.Errors:
+					log.Printf("Config watcher failed, %v", err)
+				}
+			}
+		}()
+	}
+
 	http.Handle(*metricsPath, prometheus.Handler())
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {

go.mod

@@ -4,6 +4,7 @@ go 1.12
 
 require (
 	github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973 // indirect
+	github.com/fsnotify/fsnotify v1.4.9
 	github.com/golang/protobuf v1.1.0 // indirect
 	github.com/google/go-cmp v0.3.1
 	github.com/kr/pretty v0.1.0 // indirect

go.sum

@@ -1,13 +1,12 @@
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973 h1:xJ4a3vCFaGF/jqvzLMYoU8P317H5OQ+Via4RmuPwCS0=
 github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
+github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
+github.com/fsnotify/fsnotify v1.4.9/go.mod h1:znqG4EE+3YCdAaPaxE2ZRY/06pZUdp0tY4IgpuI1SZQ=
 github.com/golang/protobuf v1.1.0 h1:0iH4Ffd/meGoXqF2lSAhZHt8X+cPgkfn/cb6Cce5Vpc=
 github.com/golang/protobuf v1.1.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
-github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
-github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/matttproud/golang_protobuf_extensions v1.0.1 h1:4hp9jkHxhMHkqkrB3Ix0jegS5sx/RkqARlsWZ6pIwiU=
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
@@ -21,20 +20,14 @@ github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910 h1:idejC8f
 github.com/prometheus/client_model v0.0.0-20180712105110-5c3871d89910/go.mod h1:MbSGuTsp3dbXC40dX6PRTWyKYBIrTGTE9sqQNg2J8bo=
 github.com/prometheus/common v0.0.0-20180801064454-c7de2306084e h1:n/3MEhJQjQxrOUCzh1Y3Re6aJUUWRp2M9+Oc3eVn/54=
 github.com/prometheus/common v0.0.0-20180801064454-c7de2306084e/go.mod h1:daVV7qP5qjZbuso7PdcryaAu0sAZbrN9i7WWcTMWvro=
-github.com/prometheus/procfs v0.0.12-0.20200505152635-9654394ca94a h1:zTuAihdFbve/GW/PAf5sLu2vEO5kRYKLxasyYn53o8c=
-github.com/prometheus/procfs v0.0.12-0.20200505152635-9654394ca94a/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
-github.com/prometheus/procfs v0.0.12-0.20200513160535-c6ff04bafc38 h1:KXSM0/EjZ5wAEa5nUl/1Ec5cG7fB/SbgSELkCevjsF8=
-github.com/prometheus/procfs v0.0.12-0.20200513160535-c6ff04bafc38/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
 github.com/prometheus/procfs v0.1.3 h1:F0+tqvhOksq22sc6iCHF5WGlWjdwj92p0udFh1VFBS8=
 github.com/prometheus/procfs v0.1.3/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
-golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e h1:vcxGaoTs7kV8m5Np9uUNQin4BrLOthgV7252N8V+FwY=
 golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20200106162015-b016eb3dc98e h1:LwyF2AFISC9nVbS6MgzsaQNSUsRXI49GS+YQ5KX/QH0=
+golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200106162015-b016eb3dc98e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200803210538-64077c9b5642 h1:B6caxRw+hozq68X2MY7jEpZh/cr4/aHLv9xU8Kkadrw=
 golang.org/x/sys v0.0.0-20200803210538-64077c9b5642/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.1 h1:mUhvW9EsL+naU5Q3cakzfE91YhliOondGd6ZrsDBHQE=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=