milvus/docs/developer_guides/chap05_proxy.md
Xiangyu Wang b6e1713044 Change int to MessageID
Signed-off-by: Xiangyu Wang <xiangyu.wang@zilliz.com>
2021-01-12 10:52:57 +08:00

8.3 KiB

6. Proxy

6.0 Proxy Service API

type Client interface {
  RegisterLink() (ProxyInfo, error)
  RegisterNode(req NodeInfo) (InitParams, error)
  GetTimeTickChannel() (string, error)
  GetStatsChannel() (string, error)
}
  • RegisterLink
type ProxyInfo struct {
  Address string
  Port int32
}
  • RegisterNode
type NodeInfo struct {}

type InitParams struct {}

6.0 ProxyNode

type ProxyNode interface {
  Start() error
  Close() error
  
  SetTimeTickChannel(channelID string) error
  SetStatsChannel(channelID string) error
  
	CreateCollection(req CreateCollectionRequest) error
  DropCollection(req DropCollectionRequest) error
  HasCollection(req HasCollectionRequest) (bool, error)
  DescribeCollection(req DescribeCollectionRequest) (CollectionDescription, error)
  ShowCollections(req ShowCollectionRequest) ([]string, error)
  CreatePartition(req CreatePartitionRequest) error
  DropPartition(req DropPartitionRequest) error
  HasPartition(req HasPartitionRequest) (bool, error)
  DescribePartition(req DescribePartitionRequest) (PartitionDescription, error)
  ShowPartitions(req ShowPartitionRequest) ([]string, error)
  CreateIndex(req CreateIndexRequest) error
  DescribeIndex(DescribeIndexRequest) (DescribeIndexResponse, error)
  
  Insert(req RowBatch) (InsertResponse, error)
  Search(req SearchRequest) (SearchResults, error)
}

6.1 Proxy Instance

type Proxy struct {
  servicepb.UnimplementedMilvusServiceServer
  masterClient mpb.MasterClient
  
  timeTick *timeTick
  ttStream *MessageStream
  scheduler *taskScheduler
  tsAllocator *TimestampAllocator
  ReqIdAllocator *IdAllocator
  RowIdAllocator *IdAllocator
  SegIdAssigner *segIdAssigner
}

func (proxy *Proxy) Start() error
func NewProxy(ctx context.Context) *Proxy

Global Parameter Table

type GlobalParamsTable struct {
}
func (*paramTable GlobalParamsTable) ProxyId() int64
func (*paramTable GlobalParamsTable) ProxyAddress() string
func (*paramTable GlobalParamsTable) MasterAddress() string
func (*paramTable GlobalParamsTable) PulsarAddress() string
func (*paramTable GlobalParamsTable) TimeTickTopic() string
func (*paramTable GlobalParamsTable) InsertTopics() []string
func (*paramTable GlobalParamsTable) QueryTopic() string
func (*paramTable GlobalParamsTable) QueryResultTopics() []string
func (*paramTable GlobalParamsTable) Init() error

var ProxyParamTable GlobalParamsTable

6.2 Task

type task interface {
  Id() int64	// return ReqId
  PreExecute() error
  Execute() error
  PostExecute() error
  WaitToFinish() error
  Notify() error
}
  • Base Task
type baseTask struct {
  Type ReqType
  ReqId int64
  Ts Timestamp
  ProxyId int64
}

func (task *baseTask) PreExecute() error
func (task *baseTask) Execute() error
func (task *baseTask) PostExecute() error
func (task *baseTask) WaitToFinish() error
func (task *baseTask) Notify() error
  • Insert Task

    Take insertTask as an example:

type insertTask struct {
  baseTask
  SegIdAssigner *segIdAssigner
  RowIdAllocator *IdAllocator
  rowBatch *RowBatch
}

func (task *InsertTask) Execute() error
func (task *InsertTask) WaitToFinish() error
func (task *InsertTask) Notify() error

6.2 Task Scheduler

  • Base Task Queue
type baseTaskQueue struct {
  unissuedTasks *List
  activeTasks map[int64]*task
  utLock sync.Mutex	// lock for UnissuedTasks
  atLock sync.Mutex	// lock for ActiveTasks
}
func (queue *baseTaskQueue) AddUnissuedTask(task *task)
func (queue *baseTaskQueue) FrontUnissuedTask() *task
func (queue *baseTaskQueue) PopUnissuedTask(id int64) *task
func (queue *baseTaskQueue) AddActiveTask(task *task)
func (queue *baseTaskQueue) PopActiveTask(id int64) *task
func (queue *baseTaskQueue) TaskDoneTest(ts Timestamp) bool

AddUnissuedTask(task *task) will put a new task into unissuedTasks, while maintaining the list by timestamp order.

TaskDoneTest(ts Timestamp) will check both unissuedTasks and unissuedTasks. If no task found before ts, then the function returns true, indicates that all the tasks before ts are completed.

  • Data Definition Task Queue
type ddTaskQueue struct {
  baseTaskQueue
  lock sync.Mutex
}
func (queue *ddTaskQueue) Enqueue(task *task) error

func newDdTaskQueue() *ddTaskQueue

Data definition tasks (i.e. CreateCollectionTask) will be put into DdTaskQueue. If a task is enqueued, Enqueue(task *task) will set Ts, ReqId, ProxyId, then push it into queue. The timestamps of the enqueued tasks should be strictly monotonically increasing. As Enqueue(task *task) will be called in parallel, setting timestamp and queue insertion need to be done atomically.

  • Data Manipulation Task Queue
type dmTaskQueue struct {
  baseTaskQueue
}
func (queue *dmTaskQueue) Enqueue(task *task) error

func newDmTaskQueue() *dmTaskQueue

Insert tasks and delete tasks will be put into DmTaskQueue.

If a insertTask is enqueued, Enqueue(task *task) will set Ts, ReqId, ProxyId, SegIdAssigner, RowIdAllocator, then push it into queue. The SegIdAssigner and RowIdAllocator will later be used in the task's execution phase.

  • Data Query Task Queue
type dqTaskQueue struct {
  baseTaskQueue
}
func (queue *dqTaskQueue) Enqueue(task *task) error

func newDqTaskQueue() *dqTaskQueue

Queries will be put into DqTaskQueue.

  • Task Scheduler
type taskScheduler struct {
  DdQueue *ddTaskQueue
  DmQueue *dmTaskQueue
  DqQueue *dqTaskQueue
  
  tsAllocator *TimestampAllocator
  ReqIdAllocator *IdAllocator
}

func (sched *taskScheduler) scheduleDdTask() *task
func (sched *taskScheduler) scheduleDmTask() *task
func (sched *taskScheduler) scheduleDqTask() *task

func (sched *taskScheduler) Start() error
func (sched *taskScheduler) TaskDoneTest(ts Timestamp) bool

func newTaskScheduler(ctx context.Context, tsAllocator *TimestampAllocator, ReqIdAllocator *IdAllocator) *taskScheduler

scheduleDdTask() selects tasks in a FIFO manner, thus time order is garanteed.

The policy of scheduleDmTask() should target on throughput, not tasks' time order. Note that the time order of the tasks' execution will later be garanteed by the timestamp & time tick mechanism.

The policy of scheduleDqTask() should target on throughput. It should also take visibility into consideration. For example, if an insert task and a query arrive in a same time tick and the query comes after insert, the query should be scheduled in the next tick thus the query can see the insert.

TaskDoneTest(ts Timestamp) will check all the three task queues. If no task found before ts, then the function returns true, indicates that all the tasks before ts are completed.

  • Statistics
// ActiveComponent interfaces
func (sched *taskScheduler) Id() String
func (sched *taskScheduler) Status() Status
func (sched *taskScheduler) Clean() Status
func (sched *taskScheduler) Restart() Status
func (sched *taskScheduler) heartbeat()

// protobuf
message taskSchedulerHeartbeat {
  string id
  uint64 dd_queue_length
  uint64 dm_queue_length
  uint64 dq_queue_length
  uint64 num_dd_done
  uint64 num_dm_done
  uint64 num_dq_done
}

6.3 Time Tick

  • Time Tick
type timeTick struct {
  lastTick Timestamp
  currentTick Timestamp
  wallTick Timestamp
  tickStep Timestamp
  syncInterval Timestamp
  
  tsAllocator *TimestampAllocator
  scheduler *taskScheduler
  ttStream *MessageStream
  
  ctx context.Context
}

func (tt *timeTick) Start() error
func (tt *timeTick) synchronize() error

func newTimeTick(ctx context.Context, tickStep Timestamp, syncInterval Timestamp, tsAllocator *TimestampAllocator, scheduler *taskScheduler, ttStream *MessageStream) *timeTick

Start() will enter a loop. On each tickStep, it tries to send a TIME_TICK typed TsMsg into ttStream. After each syncInterval, it sychronizes its wallTick with tsAllocator by calling synchronize(). When currentTick + tickStep < wallTick holds, it will update currentTick with wallTick on next tick. Otherwise, it will update currentTick with currentTick + tickStep.

  • Statistics
// ActiveComponent interfaces
func (tt *timeTick) ID() String
func (tt *timeTick) Status() Status
func (tt *timeTick) Clean() Status
func (tt *timeTick) Restart() Status
func (tt *timeTick) heartbeat()

// protobuf
message TimeTickHeartbeat {
  string id
  uint64 last_tick
}