Implement Slack alerting (#2)

alerting/slack.go

@@ -13,8 +13,8 @@ type requestBody struct {
 }
 
 // SendSlackMessage sends a message to the given Slack webhook
-func SendSlackMessage(webhookUrl, msg string) error {
+func SendSlackMessage(webhookUrl, service, description string) error {
-	body, _ := json.Marshal(requestBody{Text: msg})
+	body, _ := json.Marshal(requestBody{Text: fmt.Sprintf("*[Gatus]*\n*service:* %s\n*description:* %s", service, description)})
 	response, err := client.GetHttpClient().Post(webhookUrl, "application/json", bytes.NewBuffer(body))
 	if err != nil {
 		return err

core/service.go

@@ -26,6 +26,9 @@ type Service struct {
 	Headers    map[string]string `yaml:"headers,omitempty"`
 	Interval   time.Duration     `yaml:"interval,omitempty"`
 	Conditions []*Condition      `yaml:"conditions"`
+	Alerts     []*Alert          `yaml:"alerts"`
+
+	numberOfFailuresInARow int
 }
 
 func (service *Service) Validate() {
@@ -68,9 +71,28 @@ func (service *Service) EvaluateConditions() *Result {
 		}
 	}
 	result.Timestamp = time.Now()
+	if result.Success {
+		service.numberOfFailuresInARow = 0
+	} else {
+		service.numberOfFailuresInARow++
+	}
 	return result
 }
 
+func (service *Service) GetAlertsTriggered() []Alert {
+	var alerts []Alert
+	if service.numberOfFailuresInARow == 0 {
+		return alerts
+	}
+	for _, alert := range service.Alerts {
+		if alert.Enabled && alert.Threshold == service.numberOfFailuresInARow {
+			alerts = append(alerts, *alert)
+			continue
+		}
+	}
+	return alerts
+}
+
 func (service *Service) getIp(result *Result) {
 	urlObject, err := url.Parse(service.Url)
 	if err != nil {

watchdog/watchdog.go

@@ -2,6 +2,7 @@ package watchdog
 
 import (
 	"fmt"
+	"github.com/TwinProduction/gatus/alerting"
 	"github.com/TwinProduction/gatus/config"
 	"github.com/TwinProduction/gatus/core"
 	"github.com/TwinProduction/gatus/metric"
@@ -54,6 +55,21 @@ func monitor(service *core.Service) {
 			result.Duration.Round(time.Millisecond),
 			extra,
 		)
+
+		cfg := config.Get()
+		if cfg.Alerting != nil {
+			for _, alertTriggered := range service.GetAlertsTriggered() {
+				if alertTriggered.Type == core.SlackAlert {
+					if len(cfg.Alerting.Slack) > 0 {
+						log.Printf("[watchdog][monitor] Sending Slack alert because alert with description=%s has been triggered", alertTriggered.Description)
+						alerting.SendSlackMessage(cfg.Alerting.Slack, service.Name, alertTriggered.Description)
+					} else {
+						log.Printf("[watchdog][monitor] Not sending Slack alert despite being triggered, because there is no Slack webhook configured")
+					}
+				}
+			}
+		}
+
 		log.Printf("[watchdog][monitor] Waiting for interval=%s before monitoring serviceName=%s", service.Interval, service.Name)
 		time.Sleep(service.Interval)
 	}