Add prometheus metrics exporter

This should add metrics parity to the Python version

Makefile

@@ -1,6 +1,7 @@
+.PHONY: all
 DOCKER_TAG ?= minitor-go-${USER}
 
-.PHONY: test
+.PHONY: default
 default: test
 
 .PHONY: build
@@ -12,7 +13,7 @@ minitor-go:
 
 .PHONY: run
 run: minitor-go build
-	./minitor-go -debug
+	./minitor-go -debug -metrics
 
 .PHONY: test
 test:
@@ -24,7 +25,6 @@ test:
 	@go tool cover -func=coverage.out | awk -v target=80.0% \
 		'/^total:/ { print "Total coverage: " $$3 " Minimum coverage: " target; if ($$3+0.0 >= target+0.0) print "ok"; else { print "fail"; exit 1; } }'
 
-
 .PHONY: clean
 clean:
 	rm -f ./minitor-go

config.go

@@ -84,7 +84,9 @@ func LoadConfig(filePath string) (config Config, err error) {
 		return
 	}
 
-	log.Printf("config:\n%v\n", config)
+	if LogDebug {
+		log.Printf("DEBUG: Config values:\n%v\n", config)
+	}
 
 	if !config.IsValid() {
 		err = errors.New("Invalid configuration")

go.mod

@@ -2,4 +2,7 @@ module git.iamthefij.com/iamthefij/minitor-go
 
 go 1.12
 
-require gopkg.in/yaml.v2 v2.2.4
+require (
+	github.com/prometheus/client_golang v1.2.1
+	gopkg.in/yaml.v2 v2.2.4
+)

go.sum

@@ -1,3 +1,78 @@
+github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
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+github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
+github.com/alecthomas/units v0.0.0-20190717042225-c3de453c63f4/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=
+github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24TaqPxmxbtue+5NUziq4I4S80YR8gNf3Q=
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+gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

main.go

@@ -11,6 +11,13 @@ var (
 	// LogDebug will control whether debug messsages should be logged
 	LogDebug = false
 
+	// ExportMetrics will track whether or not we want to export metrics to prometheus
+	ExportMetrics = false
+	// MetricsPort is the port to expose metrics on
+	MetricsPort = 8080
+	// Metrics contains all active metrics
+	Metrics = NewMetrics()
+
 	// version of minitor being run
 	version = "dev"
 )
@@ -18,7 +25,13 @@ var (
 func checkMonitors(config *Config) error {
 	for _, monitor := range config.Monitors {
 		if monitor.ShouldCheck() {
-			_, alertNotice := monitor.Check()
+			success, alertNotice := monitor.Check()
+
+			hasAlert := alertNotice != nil
+
+			// Track status metrics
+			Metrics.SetMonitorStatus(monitor.Name, success)
+			Metrics.CountCheck(monitor.Name, success, hasAlert)
 
 			// Should probably consider refactoring everything below here
 			if alertNotice != nil {
@@ -50,6 +63,9 @@ func checkMonitors(config *Config) error {
 								err,
 							)
 						}
+
+						// Count alert metrics
+						Metrics.CountAlert(monitor.Name, alert.Name)
 					} else {
 						// This case should never actually happen since we validate against it
 						log.Printf("ERROR: Unknown alert for monitor %s: %s", alertNotice.MonitorName, alertName)
@@ -66,12 +82,13 @@ func checkMonitors(config *Config) error {
 func main() {
 	// Get debug flag
 	flag.BoolVar(&LogDebug, "debug", false, "Enables debug logs (default: false)")
+	flag.BoolVar(&ExportMetrics, "metrics", false, "Enables prometheus metrics exporting (default: false)")
 	var showVersion = flag.Bool("version", false, "Display the version of minitor and exit")
 	flag.Parse()
 
 	// Print version if flag is provided
 	if *showVersion {
-		fmt.Println("Minitor version:", version)
+		log.Println("Minitor version:", version)
 		return
 	}
 
@@ -81,6 +98,12 @@ func main() {
 		log.Fatalf("Error loading config: %v", err)
 	}
 
+	// Serve metrics exporter, if specified
+	if ExportMetrics {
+		log.Println("INFO: Exporting metrics to Prometheus")
+		go ServeMetrics()
+	}
+
 	// Start main loop
 	for {
 		err = checkMonitors(&config)

metrics.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"fmt"
+	"github.com/prometheus/client_golang/prometheus"
+	// "github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"net/http"
+)
+
+// TODO: Not sure if this is the best way to handle. A global instance for
+// metrics isn't bad, but it might be nice to curry versions of the metrics
+// for each monitor. Especially since every monitor has it's own. Perhaps
+// another new function that essentially curries each metric for a given
+// monitor name would do. This could be run when validating monitors and
+// initializing alert templates.
+
+// MinitorMetrics contains all counters and metrics that Minitor will need to access
+type MinitorMetrics struct {
+	alertCount    *prometheus.CounterVec
+	checkCount    *prometheus.CounterVec
+	monitorStatus *prometheus.GaugeVec
+}
+
+// NewMetrics creates and initializes all metrics
+func NewMetrics() *MinitorMetrics {
+	// Initialize all metrics
+	metrics := &MinitorMetrics{
+		alertCount: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "minitor_alert_total",
+				Help: "Number of Minitor alerts",
+			},
+			[]string{"alert", "monitor"},
+		),
+		checkCount: prometheus.NewCounterVec(
+			prometheus.CounterOpts{
+				Name: "minitor_check_total",
+				Help: "Number of Minitor checks",
+			},
+			[]string{"monitor", "status", "is_alert"},
+		),
+		monitorStatus: prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "minitor_monitor_up_count",
+				Help: "Status of currently responsive monitors",
+			},
+			[]string{"monitor"},
+		),
+	}
+
+	// Register newly created metrics
+	prometheus.MustRegister(metrics.alertCount)
+	prometheus.MustRegister(metrics.checkCount)
+	prometheus.MustRegister(metrics.monitorStatus)
+
+	return metrics
+}
+
+// SetMonitorStatus sets the current status of Monitor
+func (metrics *MinitorMetrics) SetMonitorStatus(monitor string, isUp bool) {
+	val := 0.0
+	if isUp {
+		val = 1.0
+	}
+	metrics.monitorStatus.With(prometheus.Labels{"monitor": monitor}).Set(val)
+}
+
+// CountCheck counts the result of a particular Monitor check
+func (metrics *MinitorMetrics) CountCheck(monitor string, isSuccess bool, isAlert bool) {
+	status := "failure"
+	if isSuccess {
+		status = "success"
+	}
+
+	alertVal := "false"
+	if isAlert {
+		alertVal = "true"
+	}
+
+	metrics.checkCount.With(
+		prometheus.Labels{"monitor": monitor, "status": status, "is_alert": alertVal},
+	).Inc()
+}
+
+// CountAlert counts an alert
+func (metrics *MinitorMetrics) CountAlert(monitor string, alert string) {
+	metrics.alertCount.With(
+		prometheus.Labels{
+			"alert":   alert,
+			"monitor": monitor,
+		},
+	).Inc()
+}
+
+// ServeMetrics starts an http server with a Prometheus metrics handler
+func ServeMetrics() {
+	http.Handle("/metrics", promhttp.Handler())
+	host := fmt.Sprintf(":%d", MetricsPort)
+	_ = http.ListenAndServe(host, nil)
+}