Add configurable memory limits and LRU eviction for runtime cache

internal/config/config_test.go

@@ -46,6 +46,9 @@ func TestLoadDefaults(t *testing.T) {
 	if cfg.Cache.MediaTTLSeconds != 90 {
 		t.Fatalf("expected default media cache ttl 90, got %d", cfg.Cache.MediaTTLSeconds)
 	}
+	if cfg.Cache.MemoryMaxSizeMB != DefaultCacheMemoryMaxSizeMB {
+		t.Fatalf("expected default runtime cache memory limit %d, got %d", DefaultCacheMemoryMaxSizeMB, cfg.Cache.MemoryMaxSizeMB)
+	}
 	if cfg.Search.Index != "mebox_media" {
 		t.Fatalf("expected default search index, got %q", cfg.Search.Index)
 	}
@@ -88,6 +91,7 @@ func TestEnvOverride(t *testing.T) {
 	t.Setenv("MEBOX_DATABASE_DSN", "postgres://mebox:secret@postgres:5432/mebox?sslmode=disable")
 	t.Setenv("MEBOX_CACHE_REDIS_URL", "redis://redis:6379/0")
 	t.Setenv("MEBOX_CACHE_MEDIA_TTL_SECONDS", "30")
+	t.Setenv("MEBOX_CACHE_MEMORY_MAX_SIZE_MB", "48")
 	t.Setenv("MEBOX_SEARCH_BACKEND", "opensearch")
 	t.Setenv("MEBOX_SEARCH_OPENSEARCH_URL", "http://opensearch:9200")
 	t.Setenv("MEBOX_LICENSE_SERVER_URL", "https://license.example.com")
@@ -103,8 +107,8 @@ func TestEnvOverride(t *testing.T) {
 	if cfg.Database.Type != "postgres" || cfg.Database.DSN == "" {
 		t.Fatalf("expected postgres database config from env, got type=%q dsn=%q", cfg.Database.Type, cfg.Database.DSN)
 	}
-	if cfg.Cache.RedisURL != "redis://redis:6379/0" || cfg.Cache.MediaTTLSeconds != 30 {
-		t.Fatalf("expected redis cache config from env, got url=%q ttl=%d", cfg.Cache.RedisURL, cfg.Cache.MediaTTLSeconds)
+	if cfg.Cache.RedisURL != "redis://redis:6379/0" || cfg.Cache.MediaTTLSeconds != 30 || cfg.Cache.MemoryMaxSizeMB != 48 {
+		t.Fatalf("expected redis cache config from env, got url=%q ttl=%d memory=%d", cfg.Cache.RedisURL, cfg.Cache.MediaTTLSeconds, cfg.Cache.MemoryMaxSizeMB)
 	}
 	if cfg.Search.Backend != "opensearch" || cfg.Search.OpenSearchURL != "http://opensearch:9200" {
 		t.Fatalf("expected opensearch config from env, got backend=%q url=%q", cfg.Search.Backend, cfg.Search.OpenSearchURL)

internal/config/defaults.go

@@ -7,6 +7,7 @@ const (
 	defaultDatabaseMaxIdleConns = 4
 	defaultLicenseServerURL     = "https://mgosever.3jzs.com"
 	defaultLicensePublicKey     = "MCowBQYDK2VwAyEABRXnXy+urjrbKit6Yu/HiezWgP0NdsZW3tsegJWRrtI="
+	DefaultCacheMemoryMaxSizeMB = 128
 )
 
 func setDefaults(v *viper.Viper) {
@@ -44,6 +45,7 @@ func setDefaults(v *viper.Viper) {
 
 	v.SetDefault("cache.cache_dir", "./cache")
 	v.SetDefault("cache.images_max_size_mb", 500)
+	v.SetDefault("cache.memory_max_size_mb", DefaultCacheMemoryMaxSizeMB)
 	v.SetDefault("cache.cleanup_interval_min", 60)
 	v.SetDefault("cache.redis_url", "")
 	v.SetDefault("cache.redis_prefix", "mebox")

internal/config/normalize.go

@@ -47,6 +47,9 @@ func (c *Config) normalize() error {
 	if c.Cache.ImagesMaxSizeMB < 0 {
 		c.Cache.ImagesMaxSizeMB = 0
 	}
+	if c.Cache.MemoryMaxSizeMB <= 0 {
+		c.Cache.MemoryMaxSizeMB = DefaultCacheMemoryMaxSizeMB
+	}
 	if c.Cache.RedisPrefix == "" {
 		c.Cache.RedisPrefix = "mebox"
 	}

internal/config/types.go

@@ -113,10 +113,12 @@ type LoggingConfig struct {
 	MaxBackups     int    `mapstructure:"max_backups"`
 }
 
-// CacheConfig 控制磁盘转码/刮削缓存。
+// CacheConfig 控制磁盘转写缓存和进程内热缓存。
 type CacheConfig struct {
-	CacheDir           string `mapstructure:"cache_dir"`
-	ImagesMaxSizeMB    int    `mapstructure:"images_max_size_mb"`
+	CacheDir        string `mapstructure:"cache_dir"`
+	ImagesMaxSizeMB int    `mapstructure:"images_max_size_mb"`
+	// MemoryMaxSizeMB 限制进程内 L1 缓存总字节数，JSON/对象缓存共用该预算。
+	MemoryMaxSizeMB    int    `mapstructure:"memory_max_size_mb"`
 	MaxDiskUsageMB     int    `mapstructure:"max_disk_usage_mb"`
 	TTLHours           int    `mapstructure:"ttl_hours"`
 	AutoCleanup        bool   `mapstructure:"auto_cleanup"`