runtimes/google/vsync/vsyncd.go - release.go.x.ref - Git at Google

 package vsync

 // Package vsync provides veyron sync daemon utility functions. Sync
 // daemon serves incoming GetDeltas requests and contacts other peers
 // to get deltas from them. When it receives a GetDeltas request, the
 // incoming generation vector is diffed with the local generation
 // vector, and missing generations are sent back. When it receives
 // log records in response to a GetDeltas request, it replays those
 // log records to get in sync with the sender.
 import (
 	"sync"
 	"time"

 	"veyron/services/store/raw"

 	"veyron2/ipc"
 	"veyron2/naming"
 	"veyron2/storage"
 	"veyron2/vlog"
 	"veyron2/vom"

 	_ "veyron/services/store/typeregistryhack"
 )

 // syncd contains the metadata for the sync daemon.
 type syncd struct {
 	// Pointers to metadata structures.
 	log    *iLog
 	devtab *devTable
 	dag    *dag

 	// Local device id.
 	id DeviceID

 	// RWlock to concurrently access log and device table data structures.
 	lock sync.RWMutex
 	// State to coordinate shutting down all spawned goroutines.
 	pending sync.WaitGroup
 	closed  chan struct{}

 	// Local Veyron store.
 	storeEndpoint string
 	store         raw.Store

 	// Handlers for goroutine procedures.
 	hdlGC        *syncGC
 	hdlWatcher   *syncWatcher
 	hdlInitiator *syncInitiator
 }

 // NewSyncd creates a new syncd instance.
 //
 // Syncd concurrency: syncd initializes three goroutines at
 // startup. The "watcher" thread is responsible for watching the store
 // for changes to its objects. The "initiator" thread is responsible
 // for periodically checking the neighborhood and contacting a peer to
 // obtain changes from that peer. The "gc" thread is responsible for
 // periodically checking if any log records and dag state can be
 // pruned. All these 3 threads perform write operations to the data
 // structures, and synchronize by acquiring a write lock on s.lock. In
 // addition, when syncd receives an incoming RPC, it responds to the
 // request by acquiring a read lock on s.lock. Thus, at any instant in
 // time, either one of the watcher, initiator or gc threads is active,
 // or any number of responders can be active, serving incoming
 // requests. Fairness between these threads follows from
 // sync.RWMutex. The spec says that the writers cannot be starved by
 // the readers but it does not guarantee FIFO. We may have to revisit
 // this in the future.
 func NewSyncd(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint string, syncTick time.Duration) *syncd {
 	// Connect to the local Veyron store.
 	// At present this is optional to allow testing (from the command-line) w/o Veyron store running.
 	// TODO: connecting to Veyron store should be mandatory.
 	var store raw.Store
 	if storeEndpoint != "" {
 		var err error
 		store, err = raw.BindStore(naming.JoinAddressName(storeEndpoint, raw.RawStoreSuffix))
 		if err != nil {
 			vlog.Fatalf("NewSyncd: cannot connect to Veyron store endpoint (%s): %s", storeEndpoint, err)
 		}
 	}

 	return newSyncdCore(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint, store, syncTick)
 }

 // newSyncdCore is the internal function that creates the Syncd
 // structure and initilizes its thread (goroutines).  It takes a
 // Veyron Store parameter to separate the core of Syncd setup from the
 // external dependency on Veyron Store.
 func newSyncdCore(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint string,
 	store raw.Store, syncTick time.Duration) *syncd {
 	s := &syncd{}

 	// Bootstrap my own DeviceID.
 	s.id = DeviceID(devid)

 	var err error
 	// Log init.
 	if s.log, err = openILog(storePath+"/ilog", s); err != nil {
 		vlog.Fatalf("newSyncd: ILogInit failed: err %v", err)
 	}

 	// DevTable init.
 	if s.devtab, err = openDevTable(storePath+"/dtab", s); err != nil {
 		vlog.Fatalf("newSyncd: DevTableInit failed: err %v", err)
 	}

 	// Dag Init.
 	if s.dag, err = openDAG(storePath + "/dag"); err != nil {
 		vlog.Fatalf("newSyncd: OpenDag failed: err %v", err)
 	}

 	// Veyron Store.
 	s.storeEndpoint = storeEndpoint
 	s.store = store
 	vlog.VI(1).Infof("newSyncd: Local Veyron store: %s", s.storeEndpoint)

 	// Register these Watch data types with VOM.
 	// TODO(tilaks): why aren't they auto-retrieved from the IDL?
 	vom.Register(&raw.Mutation{})
 	vom.Register(&storage.DEntry{})

 	// Channel to propagate close event to all threads.
 	s.closed = make(chan struct{})

 	s.pending.Add(3)

 	// Get deltas every peerSyncInterval.
 	s.hdlInitiator = newInitiator(s, peerEndpoints, peerDeviceIDs, syncTick)
 	go s.hdlInitiator.contactPeers()

 	// Garbage collect every garbageCollectInterval.
 	s.hdlGC = newGC(s)
 	go s.hdlGC.garbageCollect()

 	// Start a watcher thread that will get updates from local store.
 	s.hdlWatcher = newWatcher(s)
 	go s.hdlWatcher.watchStore()

 	return s
 }

 // Close cleans up syncd state.
 func (s *syncd) Close() {
 	close(s.closed)
 	s.pending.Wait()

 	// TODO(hpucha): close without flushing.
 }

 // isSyncClosing returns true if Close() was called i.e. the "closed" channel is closed.
 func (s *syncd) isSyncClosing() bool {
 	select {
 	case <-s.closed:
 		return true
 	default:
 		return false
 	}
 }

 // GetDeltas responds to the incoming request from a client by sending missing generations to the client.
 func (s *syncd) GetDeltas(_ ipc.ServerContext, In GenVector, ClientID DeviceID, Stream SyncServiceGetDeltasStream) (GenVector, error) {
 	vlog.VI(1).Infof("GetDeltas:: Received vector %v from client %s", In, ClientID)

 	if err := s.updateDeviceInfo(ClientID, In); err != nil {
 		vlog.Fatalf("GetDeltas:: updateDeviceInfo failed with err %v", err)
 	}

 	// TODO(hpucha): Hack, fills fake log and dag state for testing.
 	//s.log.fillFakeWatchRecords()
 	out, gens, gensInfo, err := s.prepareGensToReply(In)
 	if err != nil {
 		vlog.Fatalf("GetDeltas:: prepareGensToReply failed with err %v", err)
 	}

 	for pos, v := range gens {
 		gen := gensInfo[pos]
 		var count uint64
 		for i := LSN(0); i <= gen.MaxLSN; i++ {
 			count++
 			rec, err := s.getLogRec(v.devID, v.genID, i)
 			if err != nil {
 				vlog.Fatalf("GetDeltas:: Couldn't get log record %s %d %d, err %v",
 					v.devID, v.genID, i, err)
 			}
 			vlog.VI(1).Infof("Sending log record %v", rec)
 			if err := Stream.Send(*rec); err != nil {
 				vlog.Errorf("GetDeltas:: Couldn't send stream err: %v", err)
 				return GenVector{}, err
 			}
 		}
 		if count != gen.Count {
 			vlog.Fatalf("GetDeltas:: GenMetadata has incorrect log records for generation %s %d %v",
 				v.devID, v.genID, gen)
 		}
 	}
 	return out, nil
 }

 // updateDeviceInfo updates the remote device's information based on
 // the incoming GetDeltas request.
 func (s *syncd) updateDeviceInfo(ClientID DeviceID, In GenVector) error {
 	s.lock.Lock()
 	defer s.lock.Unlock()

 	// Note that the incoming client generation vector cannot be
 	// used for garbage collection. We can only garbage collect
 	// based on the generations we receive from other
 	// devices. Receiving a set of generations assures that all
 	// updates branching from those generations are also received
 	// and hence generations present on all devices can be
 	// GC'ed. This function sends generations to other devices and
 	// hence does not use the generation vector for GC.
 	//
 	// TODO(hpucha): Cache the client's incoming generation vector
 	// to assist in tracking missing generations and hence next
 	// peer to contact.
 	if !s.devtab.hasDevInfo(ClientID) {
 		if err := s.devtab.addDevice(ClientID); err != nil {
 			return err
 		}
 	}
 	return nil
 }

 // prepareGensToReply processes the incoming generation vector and
 // returns the metadata of all the missing generations between the
 // incoming and the local generation vector.
 func (s *syncd) prepareGensToReply(In GenVector) (GenVector, []*genOrder, []*genMetadata, error) {
 	s.lock.RLock()
 	defer s.lock.RUnlock()

 	// Get local generation vector.
 	out, err := s.devtab.getGenVec(s.id)
 	if err != nil {
 		return GenVector{}, nil, nil, err
 	}

 	// Diff the two generation vectors.
 	gens, err := s.devtab.diffGenVectors(out, In)
 	if err != nil {
 		return GenVector{}, nil, nil, err
 	}

 	// Get the metadata for all the generations in the reply.
 	gensInfo := make([]*genMetadata, len(gens))
 	for pos, v := range gens {
 		gen, err := s.log.getGenMetadata(v.devID, v.genID)
 		if err != nil || gen.Count <= 0 {
 			return GenVector{}, nil, nil, err
 		}
 		gensInfo[pos] = gen
 	}

 	return out, gens, gensInfo, nil
 }

 // getLogRec gets the log record for a given generation and lsn.
 func (s *syncd) getLogRec(dev DeviceID, gen GenID, lsn LSN) (*LogRec, error) {
 	s.lock.RLock()
 	defer s.lock.RUnlock()
 	return s.log.getLogRec(dev, gen, lsn)
 }
	package vsync

	// Package vsync provides veyron sync daemon utility functions. Sync
	// daemon serves incoming GetDeltas requests and contacts other peers
	// to get deltas from them. When it receives a GetDeltas request, the
	// incoming generation vector is diffed with the local generation
	// vector, and missing generations are sent back. When it receives
	// log records in response to a GetDeltas request, it replays those
	// log records to get in sync with the sender.
	import (
	"sync"
	"time"

	"veyron/services/store/raw"

	"veyron2/ipc"
	"veyron2/naming"
	"veyron2/storage"
	"veyron2/vlog"
	"veyron2/vom"

	_ "veyron/services/store/typeregistryhack"
	)

	// syncd contains the metadata for the sync daemon.
	type syncd struct {
	// Pointers to metadata structures.
	log *iLog
	devtab *devTable
	dag *dag

	// Local device id.
	id DeviceID

	// RWlock to concurrently access log and device table data structures.
	lock sync.RWMutex
	// State to coordinate shutting down all spawned goroutines.
	pending sync.WaitGroup
	closed chan struct{}

	// Local Veyron store.
	storeEndpoint string
	store raw.Store

	// Handlers for goroutine procedures.
	hdlGC *syncGC
	hdlWatcher *syncWatcher
	hdlInitiator *syncInitiator
	}

	// NewSyncd creates a new syncd instance.
	//
	// Syncd concurrency: syncd initializes three goroutines at
	// startup. The "watcher" thread is responsible for watching the store
	// for changes to its objects. The "initiator" thread is responsible
	// for periodically checking the neighborhood and contacting a peer to
	// obtain changes from that peer. The "gc" thread is responsible for
	// periodically checking if any log records and dag state can be
	// pruned. All these 3 threads perform write operations to the data
	// structures, and synchronize by acquiring a write lock on s.lock. In
	// addition, when syncd receives an incoming RPC, it responds to the
	// request by acquiring a read lock on s.lock. Thus, at any instant in
	// time, either one of the watcher, initiator or gc threads is active,
	// or any number of responders can be active, serving incoming
	// requests. Fairness between these threads follows from
	// sync.RWMutex. The spec says that the writers cannot be starved by
	// the readers but it does not guarantee FIFO. We may have to revisit
	// this in the future.
	func NewSyncd(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint string, syncTick time.Duration) *syncd {
	// Connect to the local Veyron store.
	// At present this is optional to allow testing (from the command-line) w/o Veyron store running.
	// TODO: connecting to Veyron store should be mandatory.
	var store raw.Store
	if storeEndpoint != "" {
	var err error
	store, err = raw.BindStore(naming.JoinAddressName(storeEndpoint, raw.RawStoreSuffix))
	if err != nil {
	vlog.Fatalf("NewSyncd: cannot connect to Veyron store endpoint (%s): %s", storeEndpoint, err)
	}
	}

	return newSyncdCore(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint, store, syncTick)
	}

	// newSyncdCore is the internal function that creates the Syncd
	// structure and initilizes its thread (goroutines). It takes a
	// Veyron Store parameter to separate the core of Syncd setup from the
	// external dependency on Veyron Store.
	func newSyncdCore(peerEndpoints, peerDeviceIDs, devid, storePath, storeEndpoint string,
	store raw.Store, syncTick time.Duration) *syncd {
	s := &syncd{}

	// Bootstrap my own DeviceID.
	s.id = DeviceID(devid)

	var err error
	// Log init.
	if s.log, err = openILog(storePath+"/ilog", s); err != nil {
	vlog.Fatalf("newSyncd: ILogInit failed: err %v", err)
	}

	// DevTable init.
	if s.devtab, err = openDevTable(storePath+"/dtab", s); err != nil {
	vlog.Fatalf("newSyncd: DevTableInit failed: err %v", err)
	}

	// Dag Init.
	if s.dag, err = openDAG(storePath + "/dag"); err != nil {
	vlog.Fatalf("newSyncd: OpenDag failed: err %v", err)
	}

	// Veyron Store.
	s.storeEndpoint = storeEndpoint
	s.store = store
	vlog.VI(1).Infof("newSyncd: Local Veyron store: %s", s.storeEndpoint)

	// Register these Watch data types with VOM.
	// TODO(tilaks): why aren't they auto-retrieved from the IDL?
	vom.Register(&raw.Mutation{})
	vom.Register(&storage.DEntry{})

	// Channel to propagate close event to all threads.
	s.closed = make(chan struct{})

	s.pending.Add(3)

	// Get deltas every peerSyncInterval.
	s.hdlInitiator = newInitiator(s, peerEndpoints, peerDeviceIDs, syncTick)
	go s.hdlInitiator.contactPeers()

	// Garbage collect every garbageCollectInterval.
	s.hdlGC = newGC(s)
	go s.hdlGC.garbageCollect()

	// Start a watcher thread that will get updates from local store.
	s.hdlWatcher = newWatcher(s)
	go s.hdlWatcher.watchStore()

	return s
	}

	// Close cleans up syncd state.
	func (s *syncd) Close() {
	close(s.closed)
	s.pending.Wait()

	// TODO(hpucha): close without flushing.
	}

	// isSyncClosing returns true if Close() was called i.e. the "closed" channel is closed.
	func (s *syncd) isSyncClosing() bool {
	select {
	case <-s.closed:
	return true
	default:
	return false
	}
	}

	// GetDeltas responds to the incoming request from a client by sending missing generations to the client.
	func (s *syncd) GetDeltas(_ ipc.ServerContext, In GenVector, ClientID DeviceID, Stream SyncServiceGetDeltasStream) (GenVector, error) {
	vlog.VI(1).Infof("GetDeltas:: Received vector %v from client %s", In, ClientID)

	if err := s.updateDeviceInfo(ClientID, In); err != nil {
	vlog.Fatalf("GetDeltas:: updateDeviceInfo failed with err %v", err)
	}

	// TODO(hpucha): Hack, fills fake log and dag state for testing.
	//s.log.fillFakeWatchRecords()
	out, gens, gensInfo, err := s.prepareGensToReply(In)
	if err != nil {
	vlog.Fatalf("GetDeltas:: prepareGensToReply failed with err %v", err)
	}

	for pos, v := range gens {
	gen := gensInfo[pos]
	var count uint64
	for i := LSN(0); i <= gen.MaxLSN; i++ {
	count++
	rec, err := s.getLogRec(v.devID, v.genID, i)
	if err != nil {
	vlog.Fatalf("GetDeltas:: Couldn't get log record %s %d %d, err %v",
	v.devID, v.genID, i, err)
	}
	vlog.VI(1).Infof("Sending log record %v", rec)
	if err := Stream.Send(*rec); err != nil {
	vlog.Errorf("GetDeltas:: Couldn't send stream err: %v", err)
	return GenVector{}, err
	}
	}
	if count != gen.Count {
	vlog.Fatalf("GetDeltas:: GenMetadata has incorrect log records for generation %s %d %v",
	v.devID, v.genID, gen)
	}
	}
	return out, nil
	}

	// updateDeviceInfo updates the remote device's information based on
	// the incoming GetDeltas request.
	func (s *syncd) updateDeviceInfo(ClientID DeviceID, In GenVector) error {
	s.lock.Lock()
	defer s.lock.Unlock()

	// Note that the incoming client generation vector cannot be
	// used for garbage collection. We can only garbage collect
	// based on the generations we receive from other
	// devices. Receiving a set of generations assures that all
	// updates branching from those generations are also received
	// and hence generations present on all devices can be
	// GC'ed. This function sends generations to other devices and
	// hence does not use the generation vector for GC.
	//
	// TODO(hpucha): Cache the client's incoming generation vector
	// to assist in tracking missing generations and hence next
	// peer to contact.
	if !s.devtab.hasDevInfo(ClientID) {
	if err := s.devtab.addDevice(ClientID); err != nil {
	return err
	}
	}
	return nil
	}

	// prepareGensToReply processes the incoming generation vector and
	// returns the metadata of all the missing generations between the
	// incoming and the local generation vector.
	func (s syncd) prepareGensToReply(In GenVector) (GenVector, []genOrder, []*genMetadata, error) {
	s.lock.RLock()
	defer s.lock.RUnlock()

	// Get local generation vector.
	out, err := s.devtab.getGenVec(s.id)
	if err != nil {
	return GenVector{}, nil, nil, err
	}

	// Diff the two generation vectors.
	gens, err := s.devtab.diffGenVectors(out, In)
	if err != nil {
	return GenVector{}, nil, nil, err
	}

	// Get the metadata for all the generations in the reply.
	gensInfo := make([]*genMetadata, len(gens))
	for pos, v := range gens {
	gen, err := s.log.getGenMetadata(v.devID, v.genID)
	if err != nil \|\| gen.Count <= 0 {
	return GenVector{}, nil, nil, err
	}
	gensInfo[pos] = gen
	}

	return out, gens, gensInfo, nil
	}

	// getLogRec gets the log record for a given generation and lsn.
	func (s syncd) getLogRec(dev DeviceID, gen GenID, lsn LSN) (LogRec, error) {
	s.lock.RLock()
	defer s.lock.RUnlock()
	return s.log.getLogRec(dev, gen, lsn)
	}