feat(alerting): Add support for n8n alerts (#1309)

alerting/provider/n8n/n8n.go

@@ -0,0 +1,179 @@
+package n8n
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/TwiN/gatus/v5/alerting/alert"
+	"github.com/TwiN/gatus/v5/client"
+	"github.com/TwiN/gatus/v5/config/endpoint"
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	ErrWebhookURLNotSet       = errors.New("webhook-url not set")
+	ErrDuplicateGroupOverride = errors.New("duplicate group override")
+)
+
+type Config struct {
+	WebhookURL string `yaml:"webhook-url"`
+	Title      string `yaml:"title,omitempty"` // Title of the message that will be sent
+}
+
+func (cfg *Config) Validate() error {
+	if len(cfg.WebhookURL) == 0 {
+		return ErrWebhookURLNotSet
+	}
+	return nil
+}
+
+func (cfg *Config) Merge(override *Config) {
+	if len(override.WebhookURL) > 0 {
+		cfg.WebhookURL = override.WebhookURL
+	}
+	if len(override.Title) > 0 {
+		cfg.Title = override.Title
+	}
+}
+
+// AlertProvider is the configuration necessary for sending an alert using n8n
+type AlertProvider struct {
+	DefaultConfig Config `yaml:",inline"`
+	// DefaultAlert is the default alert configuration to use for endpoints with an alert of the appropriate type
+	DefaultAlert *alert.Alert `yaml:"default-alert,omitempty"`
+	// Overrides is a list of Override that may be prioritized over the default configuration
+	Overrides []Override `yaml:"overrides,omitempty"`
+}
+
+// Override is a case under which the default integration is overridden
+type Override struct {
+	Group  string `yaml:"group"`
+	Config `yaml:",inline"`
+}
+
+// Validate the provider's configuration
+func (provider *AlertProvider) Validate() error {
+	registeredGroups := make(map[string]bool)
+	if provider.Overrides != nil {
+		for _, override := range provider.Overrides {
+			if isAlreadyRegistered := registeredGroups[override.Group]; isAlreadyRegistered || override.Group == "" {
+				return ErrDuplicateGroupOverride
+			}
+			registeredGroups[override.Group] = true
+		}
+	}
+	return provider.DefaultConfig.Validate()
+}
+
+// Send an alert using the provider
+func (provider *AlertProvider) Send(ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) error {
+	cfg, err := provider.GetConfig(ep.Group, alert)
+	if err != nil {
+		return err
+	}
+	buffer := bytes.NewBuffer(provider.buildRequestBody(cfg, ep, alert, result, resolved))
+	request, err := http.NewRequest(http.MethodPost, cfg.WebhookURL, buffer)
+	if err != nil {
+		return err
+	}
+	request.Header.Set("Content-Type", "application/json")
+	response, err := client.GetHTTPClient(nil).Do(request)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	if response.StatusCode > 399 {
+		body, _ := io.ReadAll(response.Body)
+		return fmt.Errorf("call to provider alert returned status code %d: %s", response.StatusCode, string(body))
+	}
+	return err
+}
+
+type Body struct {
+	Title            string            `json:"title"`
+	EndpointName     string            `json:"endpoint_name"`
+	EndpointGroup    string            `json:"endpoint_group,omitempty"`
+	EndpointURL      string            `json:"endpoint_url"`
+	AlertDescription string            `json:"alert_description,omitempty"`
+	Resolved         bool              `json:"resolved"`
+	Message          string            `json:"message"`
+	ConditionResults []ConditionResult `json:"condition_results,omitempty"`
+}
+
+type ConditionResult struct {
+	Condition string `json:"condition"`
+	Success   bool   `json:"success"`
+}
+
+// buildRequestBody builds the request body for the provider
+func (provider *AlertProvider) buildRequestBody(cfg *Config, ep *endpoint.Endpoint, alert *alert.Alert, result *endpoint.Result, resolved bool) []byte {
+	var message string
+	if resolved {
+		message = fmt.Sprintf("An alert for %s has been resolved after passing successfully %d time(s) in a row", ep.DisplayName(), alert.SuccessThreshold)
+	} 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)
+	}
+	title := "Gatus"
+	if cfg.Title != "" {
+		title = cfg.Title
+	}
+	var conditionResults []ConditionResult
+	for _, conditionResult := range result.ConditionResults {
+		conditionResults = append(conditionResults, ConditionResult{
+			Condition: conditionResult.Condition,
+			Success:   conditionResult.Success,
+		})
+	}
+	body := Body{
+		Title:            title,
+		EndpointName:     ep.Name,
+		EndpointGroup:    ep.Group,
+		EndpointURL:      ep.URL,
+		AlertDescription: alert.GetDescription(),
+		Resolved:         resolved,
+		Message:          message,
+		ConditionResults: conditionResults,
+	}
+	bodyAsJSON, _ := json.Marshal(body)
+	return bodyAsJSON
+}
+
+// GetDefaultAlert returns the provider's default alert configuration
+func (provider *AlertProvider) GetDefaultAlert() *alert.Alert {
+	return provider.DefaultAlert
+}
+
+// GetConfig returns the configuration for the provider with the overrides applied
+func (provider *AlertProvider) GetConfig(group string, alert *alert.Alert) (*Config, error) {
+	cfg := provider.DefaultConfig
+	// Handle group overrides
+	if provider.Overrides != nil {
+		for _, override := range provider.Overrides {
+			if group == override.Group {
+				cfg.Merge(&override.Config)
+				break
+			}
+		}
+	}
+	// Handle alert overrides
+	if len(alert.ProviderOverride) != 0 {
+		overrideConfig := Config{}
+		if err := yaml.Unmarshal(alert.ProviderOverrideAsBytes(), &overrideConfig); err != nil {
+			return nil, err
+		}
+		cfg.Merge(&overrideConfig)
+	}
+	// Validate the configuration
+	err := cfg.Validate()
+	return &cfg, err
+}
+
+// ValidateOverrides validates the alert's provider override and, if present, the group override
+func (provider *AlertProvider) ValidateOverrides(group string, alert *alert.Alert) error {
+	_, err := provider.GetConfig(group, alert)
+	return err
+}