feat(alerting): Make email alert provider e-mail customizable

alerting/provider/email/email.go

@@ -29,6 +29,17 @@ type Config struct {
 	Port     int    `yaml:"port"`
 	To       string `yaml:"to"`
 
+	// Strings used in the email body and subject
+	// These fields are optional and will be replaced with default values if not set
+	TextEmailSubjectTriggered   string `yaml:"text-email-subject-triggered,omitempty"`
+	TextEmailSubjectResolved    string `yaml:"text-email-subject-resolved,omitempty"`
+	TextEmailBodyTriggered      string `yaml:"text-email-body-triggered,omitempty"`
+	TextEmailBodyResolved       string `yaml:"text-email-body-resolved,omitempty"`
+	TextEmailHeader             string `yaml:"text-email-header,omitempty"`
+	TextEmailFooter             string `yaml:"text-email-footer,omitempty"`
+	TextEmailDescription        string `yaml:"text-email-description,omitempty"`
+	TextIncludeConditionResults *bool  `yaml:"text-include-condition-results,omitempty"`
+
 	// ClientConfig is the configuration of the client used to communicate with the provider's target
 	ClientConfig *client.Config `yaml:"client,omitempty"`
 }
@@ -68,6 +79,30 @@ func (cfg *Config) Merge(override *Config) {
 	if len(override.To) > 0 {
 		cfg.To = override.To
 	}
+	if len(override.TextEmailSubjectTriggered) > 0 {
+		cfg.TextEmailSubjectTriggered = override.TextEmailSubjectTriggered
+	}
+	if len(override.TextEmailSubjectResolved) > 0 {
+		cfg.TextEmailSubjectResolved = override.TextEmailSubjectResolved
+	}
+	if len(override.TextEmailBodyTriggered) > 0 {
+		cfg.TextEmailBodyTriggered = override.TextEmailBodyTriggered
+	}
+	if len(override.TextEmailBodyResolved) > 0 {
+		cfg.TextEmailBodyResolved = override.TextEmailBodyResolved
+	}
+	if len(override.TextEmailHeader) > 0 {
+		cfg.TextEmailHeader = override.TextEmailHeader
+	}
+	if len(override.TextEmailFooter) > 0 {
+		cfg.TextEmailFooter = override.TextEmailFooter
+	}
+	if len(override.TextEmailDescription) > 0 {
+		cfg.TextEmailDescription = override.TextEmailDescription
+	}
+	if override.TextIncludeConditionResults != nil {
+		cfg.TextIncludeConditionResults = override.TextIncludeConditionResults
+	}
 }
 
 // AlertProvider is the configuration necessary for sending an alert using SMTP
@@ -113,7 +148,7 @@ func (provider *AlertProvider) Send(ep *endpoint.Endpoint, alert *alert.Alert, r
 	} else {
 		username = cfg.From
 	}
-	subject, body := provider.buildMessageSubjectAndBody(ep, alert, result, resolved)
+	subject, body := provider.buildMessageSubjectAndBody(cfg, ep, alert, result, resolved)
 	m := gomail.NewMessage()
 	m.SetHeader("From", cfg.From)
 	m.SetHeader("To", strings.Split(cfg.To, ",")...)
@@ -140,17 +175,40 @@ func (provider *AlertProvider) Send(ep *endpoint.Endpoint, alert *alert.Alert, r
 }
 
 // buildMessageSubjectAndBody builds the message subject and body
-func (provider *AlertProvider) buildMessageSubjectAndBody(ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) (string, string) {
-	var subject, message string
+func (provider *AlertProvider) buildMessageSubjectAndBody(cfg *Config, ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) (string, string) {
+	var header, footer, subject, message string
+	if len(cfg.TextEmailHeader) > 0 {
+		header = cfg.TextEmailHeader + "\n\n"
+	}
+	if len(cfg.TextEmailFooter) > 0 {
+		footer = "\n\n" + cfg.TextEmailFooter
+	}
 	if resolved {
-		subject = fmt.Sprintf("[%s] Alert resolved", ep.DisplayName())
-		message = fmt.Sprintf("An alert for %s has been resolved after passing successfully %d time(s) in a row", ep.DisplayName(), alert.SuccessThreshold)
+		if len(cfg.TextEmailSubjectResolved) > 0 {
+			subject = strings.Replace(cfg.TextEmailSubjectResolved, "{endpoint}", ep.DisplayName(), 1)
+		} else {
+			subject = fmt.Sprintf("[%s] Alert resolved", ep.DisplayName())
+		}
+		if len(cfg.TextEmailBodyResolved) > 0 {
+			message = strings.Replace(strings.Replace(cfg.TextEmailBodyResolved, "{endpoint}", ep.DisplayName(), 1), "{threshold}", string(rune(alert.SuccessThreshold)), 1)
+		} else {
+			message = fmt.Sprintf("An alert for %s has been resolved after passing successfully %d time(s) in a row", ep.DisplayName(), alert.SuccessThreshold)
+		}
 	} else {
-		subject = fmt.Sprintf("[%s] Alert triggered", ep.DisplayName())
-		message = fmt.Sprintf("An alert for %s has been triggered due to having failed %d time(s) in a row", ep.DisplayName(), alert.FailureThreshold)
+		if len(cfg.TextEmailSubjectTriggered) > 0 {
+			subject = strings.Replace(cfg.TextEmailSubjectTriggered, "{endpoint}", ep.DisplayName(), 1)
+		} else {
+			subject = fmt.Sprintf("[%s] Alert triggered", ep.DisplayName())
+		}
+		if len(cfg.TextEmailBodyTriggered) > 0 {
+			message = strings.Replace(strings.Replace(cfg.TextEmailBodyTriggered, "{endpoint}", ep.DisplayName(), 1), "{threshold}", string(rune(alert.FailureThreshold)), 1)
+		} else {
+			message = fmt.Sprintf("An alert for %s has been triggered due to having failed %d time(s) in a row", ep.DisplayName(), alert.FailureThreshold)
+		}
 	}
 	var formattedConditionResults string
-	if len(result.ConditionResults) > 0 {
+	if len(result.ConditionResults) > 0 && (cfg.TextIncludeConditionResults == nil || *cfg.TextIncludeConditionResults) {
+		// If the condition results are included, format them
 		formattedConditionResults = "\n\nCondition results:\n"
 		for _, conditionResult := range result.ConditionResults {
 			var prefix string
@@ -164,9 +222,14 @@ func (provider *AlertProvider) buildMessageSubjectAndBody(ep *endpoint.Endpoint,
 	}
 	var description string
 	if alertDescription := alert.GetDescription(); len(alertDescription) > 0 {
-		description = "\n\nAlert description: " + alertDescription
+		if len(cfg.TextEmailDescription) > 0 {
+			description = "\n\n" + strings.Replace(cfg.TextEmailDescription, "{description}", alertDescription, 1)
+		} else {
+			// If no description is provided, use the alert's description}
+			description = "\n\nAlert description: " + alertDescription
+		}
 	}
-	return subject, message + description + formattedConditionResults
+	return subject, header + message + description + formattedConditionResults + footer
 }
 
 // GetDefaultAlert returns the provider's default alert configuration

alerting/provider/email/email_test.go

@@ -99,6 +99,7 @@ func TestAlertProvider_buildRequestBody(t *testing.T) {
 	for _, scenario := range scenarios {
 		t.Run(scenario.Name, func(t *testing.T) {
 			subject, body := scenario.Provider.buildMessageSubjectAndBody(
+				&Config{},
 				&endpoint.Endpoint{Name: "endpoint-name"},
 				&scenario.Alert,
 				&endpoint.Result{