From 7e4dc2428d14b0ca6418801e4a3e6114cd5f3a5c Mon Sep 17 00:00:00 2001
From: Chris Schinnerl <chris@sia.tech>
Date: Thu, 27 Apr 2023 11:34:23 +0200
Subject: [PATCH] stores: cache settings in memory

---
 internal/stores/settingsdb.go      | 30 ++++++++++++++++++++++++++++--
 internal/stores/settingsdb_test.go | 14 ++++++++++++++
 internal/stores/sql.go             |  5 +++++
 3 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/internal/stores/settingsdb.go b/internal/stores/settingsdb.go
index a7995f439..3b1eafc31 100644
--- a/internal/stores/settingsdb.go
+++ b/internal/stores/settingsdb.go
@@ -24,11 +24,26 @@ func (dbSetting) TableName() string { return "settings" }
 
 // DeleteSetting implements the bus.SettingStore interface.
 func (s *SQLStore) DeleteSetting(ctx context.Context, key string) error {
+	// Delete from cache.
+	s.settingsMu.Lock()
+	delete(s.settings, key)
+	s.settingsMu.Unlock()
+
+	// Delete from database.
 	return s.db.Where(&dbSetting{Key: key}).Delete(&dbSetting{}).Error
 }
 
 // Setting implements the bus.SettingStore interface.
 func (s *SQLStore) Setting(ctx context.Context, key string) (string, error) {
+	// Check cache first.
+	s.settingsMu.Lock()
+	defer s.settingsMu.Unlock()
+	value, ok := s.settings[key]
+	if ok {
+		return value, nil
+	}
+
+	// Check database.
 	var entry dbSetting
 	err := s.db.Where(&dbSetting{Key: key}).
 		Take(&entry).Error
@@ -37,7 +52,7 @@ func (s *SQLStore) Setting(ctx context.Context, key string) (string, error) {
 	} else if err != nil {
 		return "", err
 	}
-
+	s.settings[key] = entry.Value
 	return entry.Value, nil
 }
 
@@ -50,11 +65,22 @@ func (s *SQLStore) Settings(ctx context.Context) ([]string, error) {
 
 // UpdateSetting implements the bus.SettingStore interface.
 func (s *SQLStore) UpdateSetting(ctx context.Context, key, value string) error {
-	return s.db.Clauses(clause.OnConflict{
+	// Update db first.
+	s.settingsMu.Lock()
+	defer s.settingsMu.Unlock()
+
+	err := s.db.Clauses(clause.OnConflict{
 		Columns:   []clause.Column{{Name: "key"}},
 		DoUpdates: clause.AssignmentColumns([]string{"value"}),
 	}).Create(&dbSetting{
 		Key:   key,
 		Value: value,
 	}).Error
+	if err != nil {
+		return err
+	}
+
+	// Update cache second.
+	s.settings[key] = value
+	return nil
 }
diff --git a/internal/stores/settingsdb_test.go b/internal/stores/settingsdb_test.go
index 228e433c2..e420e7b1c 100644
--- a/internal/stores/settingsdb_test.go
+++ b/internal/stores/settingsdb_test.go
@@ -2,7 +2,10 @@ package stores
 
 import (
 	"context"
+	"errors"
 	"testing"
+
+	"go.sia.tech/renterd/api"
 )
 
 // TestSQLSettingStore tests the bus.SettingStore methods on the SQLSettingStore.
@@ -49,4 +52,15 @@ func TestSQLSettingStore(t *testing.T) {
 	} else if value != "barbaz" {
 		t.Fatalf("unexpected value, %s != 'barbaz'", value)
 	}
+
+	// delete the setting
+	if err := ss.DeleteSetting(ctx, "foo"); err != nil {
+		t.Fatal(err)
+	} else if _, err := ss.Setting(ctx, "foo"); !errors.Is(err, api.ErrSettingNotFound) {
+		t.Fatal("should fail with gorm.ErrRecordNotFound", err)
+	} else if keys, err := ss.Settings(ctx); err != nil {
+		t.Fatal(err)
+	} else if len(keys) != 0 {
+		t.Fatalf("unexpected number of settings, %v != 0", len(keys))
+	}
 }
diff --git a/internal/stores/sql.go b/internal/stores/sql.go
index 1f4f352c8..515cc04ea 100644
--- a/internal/stores/sql.go
+++ b/internal/stores/sql.go
@@ -40,6 +40,10 @@ type (
 		unappliedRevisions     map[types.FileContractID]revisionUpdate
 		unappliedProofs        map[types.FileContractID]uint64
 
+		// SettingsDB related fields.
+		settingsMu sync.Mutex
+		settings   map[string]string
+
 		mu           sync.Mutex
 		hasAllowlist bool
 		hasBlocklist bool
@@ -207,6 +211,7 @@ func NewSQLStore(conn gorm.Dialector, migrate bool, persistInterval time.Duratio
 		persistInterval:      persistInterval,
 		hasAllowlist:         allowlistCnt > 0,
 		hasBlocklist:         blocklistCnt > 0,
+		settings:             make(map[string]string),
 		unappliedHostKeys:    make(map[types.PublicKey]struct{}),
 		unappliedRevisions:   make(map[types.FileContractID]revisionUpdate),
 		unappliedProofs:      make(map[types.FileContractID]uint64),