Fix more golint warnings in the zero package. (#3562)

dgraph/cmd/zero/oracle.go

@@ -37,6 +37,7 @@ type syncMark struct {
 	ts    uint64
 }
 
+// Oracle stores and manages the transaction state and conflict detection.
 type Oracle struct {
 	x.SafeMutex
 	commits map[uint64]uint64 // startTs -> commitTs
@@ -54,6 +55,7 @@ type Oracle struct {
 	syncMarks   []syncMark
 }
 
+// Init initializes the oracle.
 func (o *Oracle) Init() {
 	o.commits = make(map[uint64]uint64)
 	o.keyCommit = make(map[string]uint64)
@@ -274,6 +276,7 @@ func (o *Oracle) storePending(ids *pb.AssignedIds) {
 	o.maxAssigned = x.Max(o.maxAssigned, max)
 }
 
+// MaxPending returns the maximum assigned timestamp.
 func (o *Oracle) MaxPending() uint64 {
 	o.RLock()
 	defer o.RUnlock()
@@ -397,6 +400,10 @@ func (s *Server) commit(ctx context.Context, src *api.TxnContext) error {
 	return s.proposeTxn(ctx, src)
 }
 
+// CommitOrAbort either commits a transaction or aborts it.
+// The abortion can happen under the following conditions
+// 1) the api.TxnContext.Aborted flag is set in the src argument
+// 2) if there's an error (e.g server is not the leader or there's a conflicting transaction)
 func (s *Server) CommitOrAbort(ctx context.Context, src *api.TxnContext) (*api.TxnContext, error) {
 	if ctx.Err() != nil {
 		return nil, ctx.Err()
@@ -417,7 +424,11 @@ func (s *Server) CommitOrAbort(ctx context.Context, src *api.TxnContext) (*api.T
 var errClosed = errors.New("Streaming closed by oracle")
 var errNotLeader = errors.New("Node is no longer leader")
 
-func (s *Server) Oracle(unused *api.Payload, server pb.Zero_OracleServer) error {
+// Oracle streams the oracle state to the alphas.
+// The first entry sent by Zero contains the entire state of transactions. Zero periodically
+// confirms receipt from the group, and truncates its state. This 2-way acknowledgement is a
+// safe way to get the status of all the transactions.
+func (s *Server) Oracle(_ *api.Payload, server pb.Zero_OracleServer) error {
 	if !s.Node.AmLeader() {
 		return errNotLeader
 	}
@@ -448,6 +459,7 @@ func (s *Server) Oracle(unused *api.Payload, server pb.Zero_OracleServer) error
 	}
 }
 
+// SyncedUntil returns the timestamp up to which all the nodes have synced.
 func (s *Server) SyncedUntil() uint64 {
 	s.orc.Lock()
 	defer s.orc.Unlock()
@@ -467,6 +479,7 @@ func (s *Server) SyncedUntil() uint64 {
 	return syncUntil
 }
 
+// TryAbort attempts to abort the given transactions which are not already committed..
 func (s *Server) TryAbort(ctx context.Context,
 	txns *pb.TxnTimestamps) (*pb.OracleDelta, error) {
 	delta := &pb.OracleDelta{}

dgraph/cmd/zero/run.go

@@ -56,6 +56,7 @@ type options struct {
 
 var opts options
 
+// Zero is the sub-command used to start Zero servers.
 var Zero x.SubCommand
 
 func init() {

dgraph/cmd/zero/telemetry.go

@@ -28,6 +28,7 @@ import (
 	"github.com/golang/glog"
 )
 
+// Telemetry holds information about the state of the zero server.
 type Telemetry struct {
 	Arch        string
 	Cid         string

dgraph/cmd/zero/zero.go

@@ -39,6 +39,7 @@ var (
 	errServerShutDown    = errors.New("Server is being shut down")
 )
 
+// Server implements the zero server.
 type Server struct {
 	x.SafeMutex
 	Node *node
@@ -62,6 +63,7 @@ type Server struct {
 	blockCommitsOn *sync.Map
 }
 
+// Init initializes the zero server.
 func (s *Server) Init() {
 	s.Lock()
 	defer s.Unlock()
@@ -143,6 +145,7 @@ func (s *Server) member(addr string) *pb.Member {
 	return nil
 }
 
+// Leader returns a connection pool to the zero leader.
 func (s *Server) Leader(gid uint32) *conn.Pool {
 	s.RLock()
 	defer s.RUnlock()
@@ -171,6 +174,7 @@ func (s *Server) Leader(gid uint32) *conn.Pool {
 	return healthyPool
 }
 
+// KnownGroups returns a list of the known groups.
 func (s *Server) KnownGroups() []uint32 {
 	var groups []uint32
 	s.RLock()
@@ -198,6 +202,7 @@ func (s *Server) hasLeader(gid uint32) bool {
 	return false
 }
 
+// SetMembershipState updates the membership state to the given one.
 func (s *Server) SetMembershipState(state *pb.MembershipState) {
 	s.Lock()
 	defer s.Unlock()
@@ -220,6 +225,7 @@ func (s *Server) SetMembershipState(state *pb.MembershipState) {
 	s.nextGroup = uint32(len(state.Groups) + 1)
 }
 
+// MarshalMembershipState returns the marshaled membership state.
 func (s *Server) MarshalMembershipState() ([]byte, error) {
 	s.Lock()
 	defer s.Unlock()
@@ -369,7 +375,9 @@ func (s *Server) createProposals(dst *pb.Group) ([]*pb.ZeroProposal, error) {
 	return res, nil
 }
 
-// Its users responsibility to ensure that node doesn't come back again before calling the api.
+// removeNode removes the given node from the given group.
+// It's the user's responsibility to ensure that node doesn't come back again
+// before calling the api.
 func (s *Server) removeNode(ctx context.Context, nodeId uint64, groupId uint32) error {
 	if groupId == 0 {
 		return s.Node.ProposePeerRemoval(ctx, nodeId)
@@ -525,6 +533,7 @@ func (s *Server) Connect(ctx context.Context,
 	return resp, nil
 }
 
+// ShouldServe returns the tablet serving the predicate passed in the request.
 func (s *Server) ShouldServe(
 	ctx context.Context, tablet *pb.Tablet) (resp *pb.Tablet, err error) {
 	ctx, span := otrace.StartSpan(ctx, "Zero.ShouldServe")
@@ -577,6 +586,7 @@ func (s *Server) ShouldServe(
 	return tab, nil
 }
 
+// UpdateMembership updates the membership of the given group.
 func (s *Server) UpdateMembership(ctx context.Context, group *pb.Group) (*api.Payload, error) {
 	proposals, err := s.createProposals(group)
 	if err != nil {
@@ -670,6 +680,7 @@ func (s *Server) deletePredicates(ctx context.Context, group *pb.Group) error {
 	return nil
 }
 
+// StreamMembership periodically streams the membership state to the given stream.
 func (s *Server) StreamMembership(_ *api.Payload, stream pb.Zero_StreamMembershipServer) error {
 	// Send MembershipState right away. So, the connection is correctly established.
 	ctx := stream.Context()

worker/draft.go

@@ -537,8 +537,7 @@ func (n *node) leaderBlocking() (*conn.Pool, error) {
 	if pool == nil {
 		// Functions like retrieveSnapshot and joinPeers are blocking at initial start and
 		// leader election for a group might not have happened when it is called. If we can't
-		// find a leader, get latest state from
-		// Zero.
+		// find a leader, get latest state from Zero.
 		if err := UpdateMembershipState(context.Background()); err != nil {
 			return nil, fmt.Errorf("Error while trying to update membership state: %+v", err)
 		}

worker/groups.go

@@ -808,9 +808,6 @@ func (g *groupi) processOracleDeltaStream() {
 		ctx, cancel := context.WithCancel(context.Background())
 		defer cancel()
 		c := pb.NewZeroClient(pl.Get())
-		// The first entry send by Zero contains the entire state of transactions. Zero periodically
-		// confirms receipt from the group, and truncates its state. This 2-way acknowledgement is a
-		// safe way to get the status of all the transactions.
 		stream, err := c.Oracle(ctx, &api.Payload{})
 		if err != nil {
 			glog.Errorf("Error while calling Oracle %v\n", err)