Implement graceful shutdown

- Shutdown the HTTP server before exiting
- Persist data to store before exiting, if applicable

storage/storage.go

@@ -42,7 +42,19 @@ func Initialize(cfg *Config) error {
 		if err != nil {
 			return err
 		}
-		go provider.(*memory.Store).AutoSave(7 * time.Minute)
+		go autoSave(7 * time.Minute)
 	}
 	return nil
 }
+
+// autoSave automatically calls the Save function of the provider at every interval
+func autoSave(interval time.Duration) {
+	for {
+		time.Sleep(interval)
+		log.Printf("[storage][autoSave] Saving")
+		err := provider.Save()
+		if err != nil {
+			log.Println("[storage][autoSave] Save failed:", err.Error())
+		}
+	}
+}

storage/store/memory/memory.go

@@ -3,8 +3,6 @@ package memory
 import (
 	"encoding/gob"
 	"encoding/json"
-	"log"
-	"time"
 
 	"github.com/TwinProduction/gatus/core"
 	"github.com/TwinProduction/gatus/util"
@@ -94,17 +92,8 @@ func (s *Store) Clear() {
 
 // Save persists the cache to the store file
 func (s *Store) Save() error {
-	return s.cache.SaveToFile(s.file)
-}
-
-// AutoSave automatically calls the Save function at every interval
-func (s *Store) AutoSave(interval time.Duration) {
-	for {
-		time.Sleep(interval)
-		log.Printf("[memory][AutoSave] Persisting data to file")
-		err := s.Save()
-		if err != nil {
-			log.Printf("[memory][AutoSave] failed to save to file=%s: %s", s.file, err.Error())
-		}
+	if len(s.file) > 0 {
+		return s.cache.SaveToFile(s.file)
 	}
+	return nil
 }

storage/store/memory/memory_test.go

@@ -250,3 +250,22 @@ func TestStore_DeleteAllServiceStatusesNotInKeys(t *testing.T) {
 		t.Error("firstService should still exist")
 	}
 }
+
+func TestStore_Save(t *testing.T) {
+	files := []string{
+		"",
+		t.TempDir() + "/test.db",
+	}
+	for _, file := range files {
+		t.Run(file, func(t *testing.T) {
+			store, err := NewStore(file)
+			if err != nil {
+				t.Fatal("expected no error, got", err.Error())
+			}
+			err = store.Save()
+			if err != nil {
+				t.Fatal("expected no error, got", err.Error())
+			}
+		})
+	}
+}

storage/store/store.go

@@ -26,6 +26,9 @@ type Store interface {
 
 	// Clear deletes everything from the store
 	Clear()
+
+	// Save persists the data if and where it needs to be persisted
+	Save() error
 }
 
 var (