milvus对象存储和消息中间件的工厂设计模式分析

需求

根据参数设置创建mq和storage
mq有kafka,pulsar
storage有local,minio,remote

配置文件

根据配置文件选择初始化mq和存储:

mq:
  type: pulsar
  
common:
  storageType: minio

对于这种类型一个是mq，一个是存储，相比工厂方法设计模式，使用抽象工厂设计模式更合理。

代码框架

工厂接口

代码路径:internal\util\dependency\factory.go

type Factory interface {
	msgstream.Factory
    // Init()给工厂传递参数。
	Init(p *paramtable.ComponentParam)
	NewPersistentStorageChunkManager(ctx context.Context) (storage.ChunkManager, error)
}

// pkg\mq\msgstream\msgstream.go
// msgstream.Factory的code
type Factory interface {
	NewMsgStream(ctx context.Context) (MsgStream, error)
	NewTtMsgStream(ctx context.Context) (MsgStream, error)
	NewMsgStreamDisposer(ctx context.Context) func([]string, string) error
}

dependency.Factory是一个工厂接口，里面包含了mq的工厂接口，和创建持久对象的方法。

这个接口创建消息中间件对象和持久存储对象。

这里为什么不这么写:

type Factory interface {
    Init(p *paramtable.ComponentParam)
	NewMsgStream(ctx context.Context) (MsgStream, error)
	NewPersistentStorageChunkManager(ctx context.Context) (storage.ChunkManager, error)
}

DefaultFactory

DefaultFactory结构体是dependency.Factory的实现。

// DefaultFactory is a factory that produces instances of storage.ChunkManager and message queue.
// internal\util\dependency\factory.go
type DefaultFactory struct {
	standAlone          bool
	chunkManagerFactory storage.Factory
	msgStreamFactory    msgstream.Factory
}

// storage.Factory
// internal\storage\factory.go
type Factory interface {
	NewPersistentStorageChunkManager(ctx context.Context) (ChunkManager, error)
}

// msgstream.Factory
// pkg\mq\msgstream\msgstream.go
type Factory interface {
	NewMsgStream(ctx context.Context) (MsgStream, error)
	NewTtMsgStream(ctx context.Context) (MsgStream, error)
	NewMsgStreamDisposer(ctx context.Context) func([]string, string) error
}

DefaultFactory实现了dependency.Factory接口的Init()函数。

在Init()函数内初始化了chunkManagerFactory、msgStreamFactory。

func (f *DefaultFactory) Init(params *paramtable.ComponentParam) {
	// skip if using default factory
	if f.msgStreamFactory != nil {
		return
	}
    // 初始化chunkManagerFactory
	f.chunkManagerFactory = storage.NewChunkManagerFactoryWithParam(params)

	// initialize mq client or embedded mq.
    // 初始化msgStreamFactory
	if err := f.initMQ(f.standAlone, params); err != nil {
		panic(err)
	}
}

f.chunkManagerFactory:

return &ChunkManagerFactory{
		persistentStorage: persistentStorage,
		config:            c,
	}

f.msgStreamFactory:

func (f *DefaultFactory) initMQ(standalone bool, params *paramtable.ComponentParam) error {
	mqType := mustSelectMQType(standalone, params.MQCfg.Type.GetValue(), mqEnable{params.RocksmqEnable(), params.NatsmqEnable(), params.PulsarEnable(), params.KafkaEnable()})
	log.Info("try to init mq", zap.Bool("standalone", standalone), zap.String("mqType", mqType))

	switch mqType {
	case mqTypeNatsmq:
		f.msgStreamFactory = msgstream.NewNatsmqFactory()
	case mqTypeRocksmq:
		f.msgStreamFactory = smsgstream.NewRocksmqFactory(params.RocksmqCfg.Path.GetValue(), &params.ServiceParam)
	case mqTypePulsar:
		f.msgStreamFactory = msgstream.NewPmsFactory(&params.ServiceParam)
	case mqTypeKafka:
		f.msgStreamFactory = msgstream.NewKmsFactory(&params.ServiceParam)
	}
	if f.msgStreamFactory == nil {
		return errors.New("failed to create MQ: check the milvus log for initialization failures")
	}
	return nil
}

持久存储

storage.Factory是创建持久存储的工厂接口。

storage.ChunkManagerFactory是storage.Factory的实现。

NewPersistentStorageChunkManager()接口的实现:

func (f *DefaultFactory) NewPersistentStorageChunkManager(ctx context.Context) (storage.ChunkManager, error) {
	return f.chunkManagerFactory.NewPersistentStorageChunkManager(ctx)
}

func (f *ChunkManagerFactory) NewPersistentStorageChunkManager(ctx context.Context) (ChunkManager, error) {
	return f.newChunkManager(ctx, f.persistentStorage)
}

func (f *ChunkManagerFactory) newChunkManager(ctx context.Context, engine string) (ChunkManager, error) {
	switch engine {
	case "local":
		return NewLocalChunkManager(RootPath(f.config.rootPath)), nil
	case "minio":
		return newMinioChunkManagerWithConfig(ctx, f.config)
	case "remote":
		return NewRemoteChunkManager(ctx, f.config)
	default:
		return nil, errors.New("no chunk manager implemented with engine: " + engine)
	}
}

根据传入的engine新建对应的持久存储对象。

LocalChunkManager、MinioChunkManager、RemoteChunkManager。

// LocalChunkManager is responsible for read and write local file.
type LocalChunkManager struct {
	localPath string
}

// MinioChunkManager is responsible for read and write data stored in minio.
type MinioChunkManager struct {
	*minio.Client
	bucketName string
	rootPath   string
}

// RemoteChunkManager is responsible for read and write data stored in minio.
type RemoteChunkManager struct {
	client ObjectStorage
	bucketName string
	rootPath   string
}

消息中间件

msgstream.Factory是创建mq的工厂接口。

工厂接口:

// pkg\mq\msgstream\msgstream.go
type Factory interface {
	NewMsgStream(ctx context.Context) (MsgStream, error)
	NewTtMsgStream(ctx context.Context) (MsgStream, error)
	NewMsgStreamDisposer(ctx context.Context) func([]string, string) error
}

实现有:

CommonFactory、KmsFactory、PmsFactory

// CommonFactory is a Factory for creating message streams with common logic.
// It contains a function field named newer, which is a function that creates
// an mqwrapper.Client when called.
// pkg\mq\msgstream\common_mq_factory.go
type CommonFactory struct {
	Newer             func(context.Context) (mqwrapper.Client, error) // client constructor
	DispatcherFactory ProtoUDFactory
	ReceiveBufSize    int64
	MQBufSize         int64
}

// pkg\mq\msgstream\mq_factory.go
// kafka工厂
type KmsFactory struct {
	dispatcherFactory ProtoUDFactory
	config            *paramtable.KafkaConfig
	ReceiveBufSize    int64
	MQBufSize         int64
}

// PmsFactory is a pulsar msgstream factory that implemented Factory interface(msgstream.go)
// pkg\mq\msgstream\mq_factory.go
// pulsar工厂
type PmsFactory struct {
	dispatcherFactory ProtoUDFactory
	// the following members must be public, so that mapstructure.Decode() can access them
	PulsarAddress    string
	PulsarWebAddress string
	ReceiveBufSize   int64
	MQBufSize        int64
	PulsarAuthPlugin string
	PulsarAuthParams string
	PulsarTenant     string
	PulsarNameSpace  string
	RequestTimeout   time.Duration
	metricRegisterer prometheus.Registerer
}

mq产品

mq的产品接口是msgstream.MsgStream

// MsgStream is an interface that can be used to produce and consume message on message queue
type MsgStream interface {
	Close()

	AsProducer(channels []string)
	Produce(*MsgPack) error
	SetRepackFunc(repackFunc RepackFunc)
	GetProduceChannels() []string
	Broadcast(*MsgPack) (map[string][]MessageID, error)

	AsConsumer(ctx context.Context, channels []string, subName string, position mqwrapper.SubscriptionInitialPosition) error
	Chan() <-chan *MsgPack
	Seek(ctx context.Context, offset []*MsgPosition) error

	GetLatestMsgID(channel string) (MessageID, error)
	CheckTopicValid(channel string) error

	EnableProduce(can bool)
}

具体产品实现有:

msgstream.mqMsgStream、msgstream.MqTtMsgStream

type mqMsgStream struct {
	ctx              context.Context
	client           mqwrapper.Client
	producers        map[string]mqwrapper.Producer
	producerChannels []string
	consumers        map[string]mqwrapper.Consumer
	consumerChannels []string

	repackFunc    RepackFunc
	unmarshal     UnmarshalDispatcher
	receiveBuf    chan *MsgPack
	closeRWMutex  *sync.RWMutex
	streamCancel  func()
	bufSize       int64
	producerLock  *sync.RWMutex
	consumerLock  *sync.Mutex
	closed        int32
	onceChan      sync.Once
	enableProduce atomic.Value
}

// MqTtMsgStream is a msgstream that contains timeticks
type MqTtMsgStream struct {
	*mqMsgStream
	chanMsgBuf         map[mqwrapper.Consumer][]TsMsg
	chanMsgPos         map[mqwrapper.Consumer]*msgpb.MsgPosition
	chanStopChan       map[mqwrapper.Consumer]chan bool
	chanTtMsgTime      map[mqwrapper.Consumer]Timestamp
	chanMsgBufMutex    *sync.Mutex
	chanTtMsgTimeMutex *sync.RWMutex
	chanWaitGroup      *sync.WaitGroup
	lastTimeStamp      Timestamp
	syncConsumer       chan int
}

存储产品

存储的产品接口是storag.ChunkManagere

// ChunkManager is to manager chunks.
// Include Read, Write, Remove chunks.
type ChunkManager interface {
	// RootPath returns current root path.
	RootPath() string
	// Path returns path of @filePath.
	Path(ctx context.Context, filePath string) (string, error)
	// Size returns path of @filePath.
	Size(ctx context.Context, filePath string) (int64, error)
	// Write writes @content to @filePath.
	Write(ctx context.Context, filePath string, content []byte) error
	// MultiWrite writes multi @content to @filePath.
	MultiWrite(ctx context.Context, contents map[string][]byte) error
	// Exist returns true if @filePath exists.
	Exist(ctx context.Context, filePath string) (bool, error)
	// Read reads @filePath and returns content.
	Read(ctx context.Context, filePath string) ([]byte, error)
	// Reader return a reader for @filePath
	Reader(ctx context.Context, filePath string) (FileReader, error)
	// MultiRead reads @filePath and returns content.
	MultiRead(ctx context.Context, filePaths []string) ([][]byte, error)
	ListWithPrefix(ctx context.Context, prefix string, recursive bool) ([]string, []time.Time, error)
	// ReadWithPrefix reads files with same @prefix and returns contents.
	ReadWithPrefix(ctx context.Context, prefix string) ([]string, [][]byte, error)
	Mmap(ctx context.Context, filePath string) (*mmap.ReaderAt, error)
	// ReadAt reads @filePath by offset @off, content stored in @p, return @n as the number of bytes read.
	// if all bytes are read, @err is io.EOF.
	// return other error if read failed.
	ReadAt(ctx context.Context, filePath string, off int64, length int64) (p []byte, err error)
	// Remove delete @filePath.
	Remove(ctx context.Context, filePath string) error
	// MultiRemove delete @filePaths.
	MultiRemove(ctx context.Context, filePaths []string) error
	// RemoveWithPrefix remove files with same @prefix.
	RemoveWithPrefix(ctx context.Context, prefix string) error
}

具体产品实现有:

LocalChunkManager、MinioChunkManager、RemoteChunkManager

// LocalChunkManager is responsible for read and write local file.
type LocalChunkManager struct {
	localPath string
}

// MinioChunkManager is responsible for read and write data stored in minio.
type MinioChunkManager struct {
	*minio.Client

	//	ctx        context.Context
	bucketName string
	rootPath   string
}

// RemoteChunkManager is responsible for read and write data stored in minio.
type RemoteChunkManager struct {
	client ObjectStorage

	//	ctx        context.Context
	bucketName string
	rootPath   string
}

总结

从代码框架可以看出每一种mq都有一个工厂，存储只有一个工厂