feat: Add -monitor option

Signed-off-by: Julien Riou <julien@riou.xyz>

.gitignore

@@ -8,3 +8,4 @@ restockbot.pid
 ferret.log
 shop.fql
 *.bak
+venv

README.md

@@ -203,6 +203,7 @@ docker run -it --name restockbot --rm --link chromium:chromium -v $(pwd):/root/
 There are two modes:
 * **default**: without special argument, the bot parses websites and manage its own database
 * **API**: using the `-api` argument, the bot starts the HTTP API to expose data from the database
+* **monitor**: using the `-monitor` (optionaly with `-monitor-warning-timeout` and `-monitor-critical-timeout` arguments), the bot checks for last execution times per shop to return a Nagios compatible output
 
 ## How to contribute
 

main.go

@@ -53,6 +53,9 @@ func main() {
 	pidWaitTimeout := flag.Int("pid-wait-timeout", 0, "Seconds to wait before giving up when another instance is running")
 	retention := flag.Int("retention", 0, "Automatically remove products from the database with this number of days old (disabled by default)")
 	api := flag.Bool("api", false, "Start the HTTP API")
+	monitor := flag.Bool("monitor", false, "Perform health check with Nagios output")
+	warningTimeout := flag.Int("monitor-warning-timeout", 300, "Raise a warning alert when the last execution time has reached this number of seconds (see -monitor)")
+	criticalTimeout := flag.Int("monitor-critical-timeout", 600, "Raise a critical alert when the last execution time has reached this number of seconds (see -monitor)")
 
 	flag.Parse()
 
@@ -138,6 +141,11 @@ func main() {
 		}
 	}
 
+	// start monitoring
+	if *monitor {
+		os.Exit(Monitor(db, *warningTimeout, *criticalTimeout))
+	}
+
 	// start the api
 	if *api {
 		log.Fatal(StartAPI(db, config.APIConfig))

monitoring.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"gorm.io/gorm"
+)
+
+const (
+	// NagiosOk return the Nagios OK code (see https://nagios-plugins.org/doc/guidelines.html#AEN78)
+	NagiosOk = 0
+	// NagiosWarning return the Nagios WARNING code (see https://nagios-plugins.org/doc/guidelines.html#AEN78)
+	NagiosWarning = 1
+	// NagiosCritical return the Nagios CRITICAL code (see https://nagios-plugins.org/doc/guidelines.html#AEN78)
+	NagiosCritical = 2
+	// NagiosUnknown return the Nagios UNKNOWN code (see https://nagios-plugins.org/doc/guidelines.html#AEN78)
+	NagiosUnknown = 3
+)
+
+// MonitoringResult to store result of Nagios checks
+type MonitoringResult struct {
+	ShopName   string
+	UpdatedAt  time.Time
+	ReturnCode int
+}
+
+// String to print a MonitoringResult nicely
+func (m MonitoringResult) String() string {
+	diff := time.Now().Sub(m.UpdatedAt)
+
+	var wording string
+	if diff.Seconds() > 0 {
+		wording = "seconds"
+	} else {
+		wording = "second"
+	}
+
+	return fmt.Sprintf("%s (%d %s ago)", m.ShopName, diff, wording)
+}
+
+// FormatMonitoringResults to print a list of MonitoringResult nicely
+func FormatMonitoringResults(results []MonitoringResult) string {
+	var s []string
+	for _, result := range results {
+		s = append(s, result.String())
+	}
+	return strings.Join(s, ", ")
+}
+
+// Monitor will check for last execution time for each shop and return either
+// a warning or critical alert when the threshold has been reached
+func Monitor(db *gorm.DB, warningTimeout int, criticalTimeout int) (rc int) {
+
+	// Find date and time thresholds
+	warningTime := time.Now().Add(-time.Duration(warningTimeout) * time.Second)
+	criticalTime := time.Now().Add(-time.Duration(criticalTimeout) * time.Second)
+
+	// Map to sort monitoring result by status code
+	resultMap := make(map[int][]MonitoringResult)
+
+	// List shops
+	var shops []Shop
+	trx := db.Find(&shops)
+	if trx.Error != nil {
+		fmt.Printf("%s\n", trx.Error)
+		return NagiosUnknown
+	}
+
+	for _, shop := range shops {
+		// Fetch last execution time
+		var product Product
+		trx := db.Where(Product{ShopID: shop.ID}).Order("updated_at asc").First(&product)
+		if trx.Error == gorm.ErrRecordNotFound {
+			fmt.Printf("%s\n", fmt.Errorf("No product found for shop %s", shop.Name))
+			return NagiosCritical
+		}
+		if trx.Error != nil {
+			fmt.Printf("%s\n", trx.Error)
+			return NagiosUnknown
+		}
+
+		// Compare to thresholds and add to result map
+		result := MonitoringResult{ShopName: shop.Name, UpdatedAt: product.UpdatedAt, ReturnCode: NAGIOS_OK}
+		if product.UpdatedAt.Before(criticalTime) {
+			log.Infof("%s has been updated at %s (before time of %s) (crit)", shop.Name, product.UpdatedAt, criticalTime)
+			result.ReturnCode = NagiosCritical
+		} else if product.UpdatedAt.Before(warningTime) {
+			log.Infof("%s has been updated at %s (before time of %s) (warn)", shop.Name, product.UpdatedAt, warningTime)
+			result.ReturnCode = NagiosWarning
+		} else {
+			log.Infof("%s has been updated at %s (after %s) (ok)", shop.Name, product.UpdatedAt, warningTime)
+		}
+		resultMap[result.ReturnCode] = append(resultMap[result.ReturnCode], result)
+	}
+
+	var message, prefix string
+
+	if len(resultMap[NagiosWarning]) > 0 {
+		rc = NagiosWarning
+		prefix = "WARN"
+		message = FormatMonitoringResults(resultMap[NagiosWarning])
+	} else if len(resultMap[NagiosCritical]) > 0 {
+		rc = NagiosCritical
+		prefix = "CRIT"
+		message = FormatMonitoringResults(resultMap[NagiosCritical])
+	} else {
+		rc = NagiosOK
+		prefix = "OK"
+		message = "All shops have been updated recently"
+	}
+
+	// Print output
+	fmt.Printf("%s - %s\n", prefix, message)
+	return rc
+}