💾Key Value Storage

Key Value Storage package allows our full-node to store and lookup data with several engines.

Interface and implementation

DatabaseEngine is the common interface which will be shared among its implementations, this approach will allow us to support new storage engine in the future without sacrifice the consistency.

• LevelDbEngine: A implementation of DatabaseEngine for LevelDB

• MemoryEngine: A implementation of DatabaseEngine for Memory

• KeyValueStorage: A implementation of DatabaseEngine, It's also a wrapper of LevelDbEngine and MemoryEngine

type EngineType int

const (
	MemoryEngine EngineType = iota
	LevelDbEngine
)

type SupportedFeature struct {
	Atomic      bool
	Synchronous bool
	Persistent  bool
}

type EngineOption struct {
	Url  string
	Type EngineType
}

type EngineCallOption struct {
	Expired int
}

type DatabaseEngine interface {
	Open(options ...func())
	Get(key []byte) ([]byte, error)
	Put(key []byte, value []byte) bool
	Del(key []byte) error
	BatchPut(keys [][]byte, values [][]byte) []bool
	BatchGet(keys [][]byte) ([][]byte, error)
	BatchDel(keys [][]byte) error
	Option(callOptions EngineCallOption) DatabaseEngine
	Feature() SupportedFeature
	EngineType() EngineType
	Close() error
}

KeyValueStorage will wrap the engine and provide the same interface.

Option modifier

This mechanism allows us to modify the options much more flexible

type LevelDbEngine struct {
}

func (l LevelDbEngine) Open(options ...func()) {
	for _, opt := range options {
		opt()
	}
}

func LevelDbDefaultOption(option *EngineOption, url string) func() {
	return func() {
		option.Type = LEVEL_DB_ENGINE
		option.Url = url
	}
}

func LevelDbChangeDb(option *EngineOption, url string) func() {
	return func() {
		option.Url = url
	}
}

// Usage
levelDb := LevelDbEngine{}
levelDbOption := &EngineOption{}
levelDb.Open(
  LevelDbDefaultOption(levelDbOption, "/data/test.ldb"),
  LevelDbChangeDb(levelDbOption, "/data/another.ldb")
)

Call Option

We allow user to set the option for the next call

Option(callOptions EngineCallOption) DatabaseEngine

// Usage
levelDb.Option(EngineCallOption{Expired: 30000}).set([]byte("testGo"), []byte("AAA"))