feat(remote): Implement lazy distributed feature (#64)

THIS IS AN EXPERIMENTAL FEATURE/IMPLEMENTATION, AND IT MAY BE REMOVED IN THE FUTURE.

Note that for now, it will be an undocumented feature.

config/config.go

@@ -10,6 +10,7 @@ import (
 	"github.com/TwiN/gatus/v4/alerting/alert"
 	"github.com/TwiN/gatus/v4/alerting/provider"
 	"github.com/TwiN/gatus/v4/config/maintenance"
+	"github.com/TwiN/gatus/v4/config/remote"
 	"github.com/TwiN/gatus/v4/config/ui"
 	"github.com/TwiN/gatus/v4/config/web"
 	"github.com/TwiN/gatus/v4/core"
@@ -85,6 +86,10 @@ type Config struct {
 	// Maintenance is the configuration for creating a maintenance window in which no alerts are sent
 	Maintenance *maintenance.Config `yaml:"maintenance,omitempty"`
 
+	// Remote is the configuration for remote Gatus instances
+	// WARNING: This is in ALPHA and may change or be completely removed in the future
+	Remote *remote.Config `yaml:"remote,omitempty"`
+
 	filePath        string    // path to the file from which config was loaded from
 	lastFileModTime time.Time // last modification time
 }
@@ -185,10 +190,22 @@ func parseAndValidateConfigBytes(yamlBytes []byte) (config *Config, err error) {
 		if err := validateStorageConfig(config); err != nil {
 			return nil, err
 		}
+		if err := validateRemoteConfig(config); err != nil {
+			return nil, err
+		}
 	}
 	return
 }
 
+func validateRemoteConfig(config *Config) error {
+	if config.Remote != nil {
+		if err := config.Remote.ValidateAndSetDefaults(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func validateStorageConfig(config *Config) error {
 	if config.Storage == nil {
 		config.Storage = &storage.Config{

config/remote/remote.go

@@ -0,0 +1,38 @@
+package remote
+
+import (
+	"log"
+
+	"github.com/TwiN/gatus/v4/client"
+)
+
+// NOTICE: This is an experimental alpha feature and may be updated/removed in future versions.
+// For more information, see https://github.com/TwiN/gatus/issues/64
+
+type Config struct {
+	// Instances is a list of remote instances to retrieve endpoint statuses from.
+	Instances []Instance `yaml:"instances,omitempty"`
+
+	// ClientConfig is the configuration of the client used to communicate with the provider's target
+	ClientConfig *client.Config `yaml:"client,omitempty"`
+}
+
+type Instance struct {
+	EndpointPrefix string `yaml:"endpoint-prefix"`
+	URL            string `yaml:"url"`
+}
+
+func (c *Config) ValidateAndSetDefaults() error {
+	if c.ClientConfig == nil {
+		c.ClientConfig = client.GetDefaultConfig()
+	} else {
+		if err := c.ClientConfig.ValidateAndSetDefaults(); err != nil {
+			return err
+		}
+	}
+	if len(c.Instances) > 0 {
+		log.Println("WARNING: Your configuration is using 'remote', which is in alpha and may be updated/removed in future versions.")
+		log.Println("WARNING: See https://github.com/TwiN/gatus/issues/64 for more information")
+	}
+	return nil
+}