Added Prometheus metrics.

Makefile

@@ -5,16 +5,16 @@ BUILD   := $(shell date '+%FT%T%z')
 COMMIT  := $(shell git describe --always --long)
 
 build:
-	go build -ldflags="-X main.version=$(VERSION) -X main.build=$(BUILD) -X main.commit=$(COMMIT)"
+	@go build -ldflags="-X main.version=$(VERSION) -X main.build=$(BUILD) -X main.commit=$(COMMIT)"
 
 static_build:
-	CGO_ENABLED=0 go build -ldflags="-X main.version=$(VERSION) -X main.build=$(BUILD) -X main.commit=$(COMMIT)"
+	@CGO_ENABLED=0 go build -ldflags="-X main.version=$(VERSION) -X main.build=$(BUILD) -X main.commit=$(COMMIT)"
 
 .PHONY: docker
 docker:
 	docker build . -t $(IMAGE)
 
-.PHONY: publish 
+.PHONY: publish
 publish:
 	@docker buildx create --use --name=crossplat --node=crossplat && \
 	docker buildx build \

README.md

@@ -21,6 +21,7 @@ Additionally, Janitor has a web interface where you can see the current status a
 Finally, Janitor includes a simple JSON api with the following endpoints:
 * `/api/data` provides a snapshot of all monitoring related data.
 * `/api/stats` provides the count of monitoring targets in functional/dysfunctional state.
+* `/api/metrics` provides target statistics in Prometheus metrics format.
 
 ## Screenshot
 ![Screenshot](https://raw.githubusercontent.com/a-bali/janitor/master/docs/screenshot.png)
@@ -58,7 +59,7 @@ Once you created a configuration file, Janitor can be launched as follows:
 
     $ janitor path/to/your/configfile.yml
 
-Janitor will log to standard output. The log is viewable on the web interface as well, where you can delete monitored targets and reload the configuration file (e.g. in case you added new targets or changed any of the settings). 
+Janitor will log to standard output. The log is viewable on the web interface as well, where you can delete monitored targets and reload the configuration file (e.g. in case you added new targets or changed any of the settings).
 
 Janitor will not daemonize itself. It is recommended to create a systemd service for janitor in case you want it running continuously.
 

config.yml

@@ -9,6 +9,9 @@ debug: true
 # Maximum size of log history to maintain (default: 1000)
 logsize: 1000
 
+# hostname (default: obtained from OS or "janitor"), used for Prometheus metrics
+hostname: "janitor"
+
 # Configuration of built in web server:
 # - Host name (default: '' meaning all interfaces will be bound)
 # - Port number (default: 8080)

main.go

@@ -6,7 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"hash/fnv"
-	"io/ioutil"
+	"io"
 	"math"
 	"net/http"
 	"net/url"
@@ -26,9 +26,10 @@ import (
 
 // Config stores the variables for runtime configuration.
 type Config struct {
-	Debug   bool
-	LogSize int
-	Web     struct {
+	Debug    bool
+	LogSize  int
+	HostName string
+	Web      struct {
 		Host string
 		Port int
 	}
@@ -172,11 +173,11 @@ type ExecMonitorData struct {
 
 // MonitorData stores the actual status data of the monitoring process.
 type MonitorData struct {
-	MQTT map[string]*MQTTMonitorData
-	Ping map[string]*PingMonitorData
-	HTTP map[string]*HTTPMonitorData
-	Exec map[string]*ExecMonitorData
-	sync.RWMutex
+	MQTT         map[string]*MQTTMonitorData
+	Ping         map[string]*PingMonitorData
+	HTTP         map[string]*HTTPMonitorData
+	Exec         map[string]*ExecMonitorData
+	sync.RWMutex `json:"-"`
 }
 
 // Data struct for serving main web page.
@@ -238,6 +239,8 @@ var (
 const (
 	// MAXLOGSIZE defines the maximum lenght of the log history maintained (can be overridden in config)
 	MAXLOGSIZE = 1000
+	// Default hostname
+	HOSTNAME = "janitor"
 	// Status flags for monitoring.
 	STATUS_OK    = 0
 	STATUS_WARN  = 1
@@ -264,11 +267,19 @@ func main() {
 	http.HandleFunc("/config", configWebItem)
 	http.HandleFunc("/api/stats", serveAPIStats)
 	http.HandleFunc("/api/data", serveAPIData)
+	http.HandleFunc("/api/metrics", serveAPIMetrics)
 	panic(http.ListenAndServe(fmt.Sprintf("%s:%d", getConfig().Web.Host, getConfig().Web.Port), nil))
 }
 
 // Set defaults for configuration values.
 func setDefaults(c *Config) {
+	if c.HostName == "" {
+		hostname, err := os.Hostname()
+		if err != nil {
+			hostname = HOSTNAME
+		}
+		c.HostName = hostname
+	}
 	if c.LogSize == 0 {
 		c.LogSize = MAXLOGSIZE
 	}
@@ -325,7 +336,7 @@ func loadConfig() {
 	log("Starting " + fullversion)
 
 	// (re)populate config struct from file
-	yamlFile, err := ioutil.ReadFile(configFile)
+	yamlFile, err := os.ReadFile(configFile)
 	if err != nil {
 		log("Unable to load config: " + err.Error())
 		return
@@ -921,7 +932,7 @@ func performHTTPCheck(url string, pattern string, timeout int) (bool, string, st
 		errValue = fmt.Sprintf("status code %d", resp.StatusCode)
 	} else {
 		defer resp.Body.Close()
-		bodyBytes, bodyErr := ioutil.ReadAll(resp.Body)
+		bodyBytes, bodyErr := io.ReadAll(resp.Body)
 		if bodyErr != nil {
 			errValue = bodyErr.Error()
 		} else {
@@ -1022,48 +1033,86 @@ func serveIndex(w http.ResponseWriter, r *http.Request) {
 	logLock.RUnlock()
 }
 
-// Serves the api/stats page.
-func serveAPIStats(w http.ResponseWriter, r *http.Request) {
-	debug("Web request " + r.RequestURI + " from " + r.RemoteAddr)
-	o := 0
-	e := 0
+// Counts targets per type and status
+func calcStats() (map[string]int, map[string]int) {
+	up := make(map[string]int)
+	down := make(map[string]int)
+
 	monitorData.RLock()
+
+	up["mqtt"] = 0
+	down["mqtt"] = 0
 	for k := range monitorData.MQTT {
 		if !monitorData.MQTT[k].Deleted {
 			if monitorData.MQTT[k].Status == STATUS_ERROR {
-				e++
+				down["mqtt"]++
 			} else {
-				o++
+				up["mqtt"]++
 			}
 		}
 	}
+	up["ping"] = 0
+	down["ping"] = 0
 	for k := range monitorData.Ping {
 		if monitorData.Ping[k].Status == STATUS_ERROR {
-			e++
+			down["ping"]++
 		} else {
-			o++
+			up["ping"]++
 		}
 	}
+	up["http"] = 0
+	down["http"] = 0
 	for k := range monitorData.HTTP {
 		if monitorData.HTTP[k].Status == STATUS_ERROR {
-			e++
+			down["http"]++
 		} else {
-			o++
+			up["http"]++
 		}
 	}
+	up["exec"] = 0
+	down["exec"] = 0
 	for k := range monitorData.Exec {
 		if monitorData.Exec[k].Status == STATUS_ERROR {
-			e++
+			down["exec"]++
 		} else {
-			o++
+			up["exec"]++
 		}
 	}
 
 	monitorData.RUnlock()
+	return up, down
+
+}
+
+// Serves the api/stats page.
+func serveAPIStats(w http.ResponseWriter, r *http.Request) {
+	debug("Web request " + r.RequestURI + " from " + r.RemoteAddr)
+	o := 0
+	e := 0
+	up, down := calcStats()
+	for k, c := range up {
+		o += c
+		e += down[k]
+	}
 	w.Header().Set("Content-Type", "application/json")
 	json.NewEncoder(w).Encode(StatsData{o, e})
 }
 
+// Serves the api/metrics page.
+func serveAPIMetrics(w http.ResponseWriter, r *http.Request) {
+	debug("Web request " + r.RequestURI + " from " + r.RemoteAddr)
+	w.Header().Set("Content-Type", "text/plain")
+	fmt.Fprintln(w, "HELP janitor_targets Number of Janitor targets")
+	fmt.Fprintln(w, "TYPE janitor_targets gauge")
+	up, down := calcStats()
+	for t, c := range up {
+		fmt.Fprintf(w, "janitor_targets{state=\"%s\", type=\"%s\", host=\"%s\"} %d\n", "up", t, config.HostName, c)
+	}
+	for t, c := range down {
+		fmt.Fprintf(w, "janitor_targets{state=\"%s\", type=\"%s\", host=\"%s\"} %d\n", "down", t, config.HostName, c)
+	}
+}
+
 // Serves the api/data page.
 func serveAPIData(w http.ResponseWriter, r *http.Request) {
 	debug("Web request " + r.RequestURI + " from " + r.RemoteAddr)