data.go

package meta

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"sort"
	"strings"
	"sync"
	"time"
	"unicode"

	"github.com/gogo/protobuf/proto"
	"github.com/influxdata/influxdb"
	"github.com/influxdata/influxdb/influxql"
	"github.com/influxdata/influxdb/models"
	internal "github.com/influxdata/influxdb/services/meta/internal"
)

//go:generate protoc --gogo_out=. internal/meta.proto

const (
	// DefaultRetentionPolicyReplicaN is the default value of RetentionPolicyInfo.ReplicaN.
	DefaultRetentionPolicyReplicaN = 1

	// DefaultRetentionPolicyDuration is the default value of RetentionPolicyInfo.Duration.
	DefaultRetentionPolicyDuration = time.Duration(0)

	// DefaultRetentionPolicyName is the default name for auto generated retention policies.
	DefaultRetentionPolicyName = "autogen"

	// MinRetentionPolicyDuration represents the minimum duration for a policy.
	MinRetentionPolicyDuration = time.Hour
)

// Data represents the top level collection of all metadata.
type Data struct {
	Term      uint64 // associated raft term
	Index     uint64 // associated raft index
	ClusterID uint64
	Databases []DatabaseInfo
	Users     []UserInfo

	// adminUserExists provides a constant time mechanism for determining
	// if there is at least one admin user.
	adminUserExists bool

	MaxShardGroupID uint64
	MaxShardID      uint64
}

// NewShardOwner sets the owner of the provided shard to the data node
// that currently owns the fewest number of shards. If multiple nodes
// own the same (fewest) number of shards, then one of those nodes
// becomes the new shard owner.
func NewShardOwner(s ShardInfo, ownerFreqs map[int]int) (uint64, error) {
	var (
		minId   = -1
		minFreq int
	)

	for id, freq := range ownerFreqs {
		if minId == -1 || freq < minFreq {
			minId, minFreq = int(id), freq
		}
	}

	if minId < 0 {
		return 0, fmt.Errorf("cannot reassign shard %d due to lack of data nodes", s.ID)
	}

	// Update the shard owner frequencies and set the new owner on the
	// shard.
	ownerFreqs[minId]++
	return uint64(minId), nil
}

// Database returns a DatabaseInfo by the database name.
func (data *Data) Database(name string) *DatabaseInfo {
	for i := range data.Databases {
		if data.Databases[i].Name == name {
			return &data.Databases[i]
		}
	}
	return nil
}

// CloneDatabases returns a copy of the DatabaseInfo.
func (data *Data) CloneDatabases() []DatabaseInfo {
	if data.Databases == nil {
		return nil
	}
	dbs := make([]DatabaseInfo, len(data.Databases))
	for i := range data.Databases {
		dbs[i] = data.Databases[i].clone()
	}
	return dbs
}

// CreateDatabase creates a new database.
// It returns an error if name is blank or if a database with the same name already exists.
func (data *Data) CreateDatabase(name string) error {
	if name == "" {
		return ErrDatabaseNameRequired
	} else if data.Database(name) != nil {
		return nil
	}

	// Append new node.
	data.Databases = append(data.Databases, DatabaseInfo{Name: name})

	return nil
}

// DropDatabase removes a database by name. It does not return an error
// if the database cannot be found.
func (data *Data) DropDatabase(name string) error {
	for i := range data.Databases {
		if data.Databases[i].Name == name {
			data.Databases = append(data.Databases[:i], data.Databases[i+1:]...)

			// Remove all user privileges associated with this database.
			for i := range data.Users {
				delete(data.Users[i].Privileges, name)
			}
			break
		}
	}
	return nil
}

// RetentionPolicy returns a retention policy for a database by name.
func (data *Data) RetentionPolicy(database, name string) (*RetentionPolicyInfo, error) {
	di := data.Database(database)
	if di == nil {
		return nil, influxdb.ErrDatabaseNotFound(database)
	}

	for i := range di.RetentionPolicies {
		if di.RetentionPolicies[i].Name == name {
			return &di.RetentionPolicies[i], nil
		}
	}
	return nil, nil
}

// CreateRetentionPolicy creates a new retention policy on a database.
// It returns an error if name is blank or if the database does not exist.
func (data *Data) CreateRetentionPolicy(database string, rpi *RetentionPolicyInfo, makeDefault bool) error {
	// Validate retention policy.
	if rpi == nil {
		return ErrRetentionPolicyRequired
	} else if rpi.Name == "" {
		return ErrRetentionPolicyNameRequired
	} else if rpi.ReplicaN < 1 {
		return ErrReplicationFactorTooLow
	}

	// Normalise ShardDuration before comparing to any existing
	// retention policies. The client is supposed to do this, but
	// do it again to verify input.
	rpi.ShardGroupDuration = normalisedShardDuration(rpi.ShardGroupDuration, rpi.Duration)

	if rpi.Duration > 0 && rpi.Duration < rpi.ShardGroupDuration {
		return ErrIncompatibleDurations
	}

	// Find database.
	di := data.Database(database)
	if di == nil {
		return influxdb.ErrDatabaseNotFound(database)
	} else if rp := di.RetentionPolicy(rpi.Name); rp != nil {
		// RP with that name already exists. Make sure they're the same.
		if rp.ReplicaN != rpi.ReplicaN || rp.Duration != rpi.Duration || rp.ShardGroupDuration != rpi.ShardGroupDuration {
			return ErrRetentionPolicyExists
		}
		// if they want to make it default, and it's not the default, it's not an identical command so it's an error
		if makeDefault && di.DefaultRetentionPolicy != rpi.Name {
			return ErrRetentionPolicyConflict
		}
		return nil
	}

	// Append copy of new policy.
	di.RetentionPolicies = append(di.RetentionPolicies, *rpi)

	// Set the default if needed
	if makeDefault {
		di.DefaultRetentionPolicy = rpi.Name
	}

	return nil
}

// DropRetentionPolicy removes a retention policy from a database by name.
func (data *Data) DropRetentionPolicy(database, name string) error {
	// Find database.
	di := data.Database(database)
	if di == nil {
		// no database? no problem
		return nil
	}

	// Remove from list.
	for i := range di.RetentionPolicies {
		if di.RetentionPolicies[i].Name == name {
			di.RetentionPolicies = append(di.RetentionPolicies[:i], di.RetentionPolicies[i+1:]...)
			break
		}
	}

	return nil
}

// RetentionPolicyUpdate represents retention policy fields to be updated.
type RetentionPolicyUpdate struct {
	Name               *string
	Duration           *time.Duration
	ReplicaN           *int
	ShardGroupDuration *time.Duration
}

// SetName sets the RetentionPolicyUpdate.Name.
func (rpu *RetentionPolicyUpdate) SetName(v string) { rpu.Name = &v }

// SetDuration sets the RetentionPolicyUpdate.Duration.
func (rpu *RetentionPolicyUpdate) SetDuration(v time.Duration) { rpu.Duration = &v }

// SetReplicaN sets the RetentionPolicyUpdate.ReplicaN.
func (rpu *RetentionPolicyUpdate) SetReplicaN(v int) { rpu.ReplicaN = &v }

// SetShardGroupDuration sets the RetentionPolicyUpdate.ShardGroupDuration.
func (rpu *RetentionPolicyUpdate) SetShardGroupDuration(v time.Duration) { rpu.ShardGroupDuration = &v }

// UpdateRetentionPolicy updates an existing retention policy.
func (data *Data) UpdateRetentionPolicy(database, name string, rpu *RetentionPolicyUpdate, makeDefault bool) error {
	// Find database.
	di := data.Database(database)
	if di == nil {
		return influxdb.ErrDatabaseNotFound(database)
	}

	// Find policy.
	rpi := di.RetentionPolicy(name)
	if rpi == nil {
		return influxdb.ErrRetentionPolicyNotFound(name)
	}

	// Ensure new policy doesn't match an existing policy.
	if rpu.Name != nil && *rpu.Name != name && di.RetentionPolicy(*rpu.Name) != nil {
		return ErrRetentionPolicyNameExists
	}

	// Enforce duration of at least MinRetentionPolicyDuration
	if rpu.Duration != nil && *rpu.Duration < MinRetentionPolicyDuration && *rpu.Duration != 0 {
		return ErrRetentionPolicyDurationTooLow
	}

	// Enforce duration is at least the shard duration
	if (rpu.Duration != nil && *rpu.Duration > 0 &&
		((rpu.ShardGroupDuration != nil && *rpu.Duration < *rpu.ShardGroupDuration) ||
			(rpu.ShardGroupDuration == nil && *rpu.Duration < rpi.ShardGroupDuration))) ||
		(rpu.Duration == nil && rpi.Duration > 0 &&
			rpu.ShardGroupDuration != nil && rpi.Duration < *rpu.ShardGroupDuration) {
		return ErrIncompatibleDurations
	}

	// Update fields.
	if rpu.Name != nil {
		rpi.Name = *rpu.Name
	}
	if rpu.Duration != nil {
		rpi.Duration = *rpu.Duration
	}
	if rpu.ReplicaN != nil {
		rpi.ReplicaN = *rpu.ReplicaN
	}
	if rpu.ShardGroupDuration != nil {
		rpi.ShardGroupDuration = normalisedShardDuration(*rpu.ShardGroupDuration, rpi.Duration)
	}

	if di.DefaultRetentionPolicy != rpi.Name && makeDefault {
		di.DefaultRetentionPolicy = rpi.Name
	}

	return nil
}

// DropShard removes a shard by ID.
//
// DropShard won't return an error if the shard can't be found, which
// allows the command to be re-run in the case that the meta store
// succeeds but a data node fails.
func (data *Data) DropShard(id uint64) {
	found := -1
	for dbidx, dbi := range data.Databases {
		for rpidx, rpi := range dbi.RetentionPolicies {
			for sgidx, sg := range rpi.ShardGroups {
				for sidx, s := range sg.Shards {
					if s.ID == id {
						found = sidx
						break
					}
				}

				if found > -1 {
					shards := sg.Shards
					data.Databases[dbidx].RetentionPolicies[rpidx].ShardGroups[sgidx].Shards = append(shards[:found], shards[found+1:]...)

					if len(shards) == 1 {
						// We just deleted the last shard in the shard group.
						data.Databases[dbidx].RetentionPolicies[rpidx].ShardGroups[sgidx].DeletedAt = time.Now()
					}
					return
				}
			}
		}
	}
}

// ShardGroups returns a list of all shard groups on a database and retention policy.
func (data *Data) ShardGroups(database, policy string) ([]ShardGroupInfo, error) {
	// Find retention policy.
	rpi, err := data.RetentionPolicy(database, policy)
	if err != nil {
		return nil, err
	} else if rpi == nil {
		return nil, influxdb.ErrRetentionPolicyNotFound(policy)
	}
	groups := make([]ShardGroupInfo, 0, len(rpi.ShardGroups))
	for _, g := range rpi.ShardGroups {
		if g.Deleted() {
			continue
		}
		groups = append(groups, g)
	}
	return groups, nil
}

// ShardGroupsByTimeRange returns a list of all shard groups on a database and policy that may contain data
// for the specified time range. Shard groups are sorted by start time.
func (data *Data) ShardGroupsByTimeRange(database, policy string, tmin, tmax time.Time) ([]ShardGroupInfo, error) {
	// Find retention policy.
	rpi, err := data.RetentionPolicy(database, policy)
	if err != nil {
		return nil, err
	} else if rpi == nil {
		return nil, influxdb.ErrRetentionPolicyNotFound(policy)
	}
	groups := make([]ShardGroupInfo, 0, len(rpi.ShardGroups))
	for _, g := range rpi.ShardGroups {
		if g.Deleted() || !g.Overlaps(tmin, tmax) {
			continue
		}
		groups = append(groups, g)
	}
	return groups, nil
}

// ShardGroupByTimestamp returns the shard group on a database and policy for a given timestamp.
func (data *Data) ShardGroupByTimestamp(database, policy string, timestamp time.Time) (*ShardGroupInfo, error) {
	// Find retention policy.
	rpi, err := data.RetentionPolicy(database, policy)
	if err != nil {
		return nil, err
	} else if rpi == nil {
		return nil, influxdb.ErrRetentionPolicyNotFound(policy)
	}

	return rpi.ShardGroupByTimestamp(timestamp), nil
}

// CreateShardGroup creates a shard group on a database and policy for a given timestamp.
func (data *Data) CreateShardGroup(database, policy string, timestamp time.Time) error {
	// Find retention policy.
	rpi, err := data.RetentionPolicy(database, policy)
	if err != nil {
		return err
	} else if rpi == nil {
		return influxdb.ErrRetentionPolicyNotFound(policy)
	}

	// Verify that shard group doesn't already exist for this timestamp.
	if rpi.ShardGroupByTimestamp(timestamp) != nil {
		return nil
	}

	// Create the shard group.
	data.MaxShardGroupID++
	sgi := ShardGroupInfo{}
	sgi.ID = data.MaxShardGroupID
	sgi.StartTime = timestamp.Truncate(rpi.ShardGroupDuration).UTC()
	sgi.EndTime = sgi.StartTime.Add(rpi.ShardGroupDuration).UTC()
	if sgi.EndTime.After(time.Unix(0, models.MaxNanoTime)) {
		// Shard group range is [start, end) so add one to the max time.
		sgi.EndTime = time.Unix(0, models.MaxNanoTime+1)
	}

	data.MaxShardID++
	sgi.Shards = []ShardInfo{
		{ID: data.MaxShardID},
	}

	// Retention policy has a new shard group, so update the policy. Shard
	// Groups must be stored in sorted order, as other parts of the system
	// assume this to be the case.
	rpi.ShardGroups = append(rpi.ShardGroups, sgi)
	sort.Sort(ShardGroupInfos(rpi.ShardGroups))

	return nil
}

// DeleteShardGroup removes a shard group from a database and retention policy by id.
func (data *Data) DeleteShardGroup(database, policy string, id uint64) error {
	// Find retention policy.
	rpi, err := data.RetentionPolicy(database, policy)
	if err != nil {
		return err
	} else if rpi == nil {
		return influxdb.ErrRetentionPolicyNotFound(policy)
	}

	// Find shard group by ID and set its deletion timestamp.
	for i := range rpi.ShardGroups {
		if rpi.ShardGroups[i].ID == id {
			rpi.ShardGroups[i].DeletedAt = time.Now().UTC()
			return nil
		}
	}

	return ErrShardGroupNotFound
}

// CreateContinuousQuery adds a named continuous query to a database.
func (data *Data) CreateContinuousQuery(database, name, query string) error {
	di := data.Database(database)
	if di == nil {
		return influxdb.ErrDatabaseNotFound(database)
	}

	// Ensure the name doesn't already exist.
	for _, cq := range di.ContinuousQueries {
		if cq.Name == name {
			// If the query string is the same, we'll silently return,
			// otherwise we'll assume the user might be trying to
			// overwrite an existing CQ with a different query.
			if strings.ToLower(cq.Query) == strings.ToLower(query) {
				return nil
			}
			return ErrContinuousQueryExists
		}
	}

	// Append new query.
	di.ContinuousQueries = append(di.ContinuousQueries, ContinuousQueryInfo{
		Name:  name,
		Query: query,
	})

	return nil
}

// DropContinuousQuery removes a continuous query.
func (data *Data) DropContinuousQuery(database, name string) error {
	di := data.Database(database)
	if di == nil {
		return influxdb.ErrDatabaseNotFound(database)
	}

	for i := range di.ContinuousQueries {
		if di.ContinuousQueries[i].Name == name {
			di.ContinuousQueries = append(di.ContinuousQueries[:i], di.ContinuousQueries[i+1:]...)
			return nil
		}
	}
	return ErrContinuousQueryNotFound
}

// validateURL returns an error if the URL does not have a port or uses a scheme other than UDP or HTTP.
func validateURL(input string) error {
	u, err := url.Parse(input)
	if err != nil {
		return ErrInvalidSubscriptionURL(input)
	}

	if u.Scheme != "udp" && u.Scheme != "http" && u.Scheme != "https" {
		return ErrInvalidSubscriptionURL(input)
	}

	_, port, err := net.SplitHostPort(u.Host)
	if err != nil || port == "" {
		return ErrInvalidSubscriptionURL(input)
	}

	return nil
}

// CreateSubscription adds a named subscription to a database and retention policy.
func (data *Data) CreateSubscription(database, rp, name, mode string, destinations []string) error {
	for _, d := range destinations {
		if err := validateURL(d); err != nil {
			return err
		}
	}

	rpi, err := data.RetentionPolicy(database, rp)
	if err != nil {
		return err
	} else if rpi == nil {
		return influxdb.ErrRetentionPolicyNotFound(rp)
	}

	// Ensure the name doesn't already exist.
	for i := range rpi.Subscriptions {
		if rpi.Subscriptions[i].Name == name {
			return ErrSubscriptionExists
		}
	}

	// Append new query.
	rpi.Subscriptions = append(rpi.Subscriptions, SubscriptionInfo{
		Name:         name,
		Mode:         mode,
		Destinations: destinations,
	})

	return nil
}

// DropSubscription removes a subscription.
func (data *Data) DropSubscription(database, rp, name string) error {
	rpi, err := data.RetentionPolicy(database, rp)
	if err != nil {
		return err
	} else if rpi == nil {
		return influxdb.ErrRetentionPolicyNotFound(rp)
	}

	for i := range rpi.Subscriptions {
		if rpi.Subscriptions[i].Name == name {
			rpi.Subscriptions = append(rpi.Subscriptions[:i], rpi.Subscriptions[i+1:]...)
			return nil
		}
	}
	return ErrSubscriptionNotFound
}

// User returns a user by username.
func (data *Data) User(username string) *UserInfo {
	for i := range data.Users {
		if data.Users[i].Name == username {
			return &data.Users[i]
		}
	}
	return nil
}

// CreateUser creates a new user.
func (data *Data) CreateUser(name, hash string, admin bool) error {
	// Ensure the user doesn't already exist.
	if name == "" {
		return ErrUsernameRequired
	} else if data.User(name) != nil {
		return ErrUserExists
	}

	// Append new user.
	data.Users = append(data.Users, UserInfo{
		Name:  name,
		Hash:  hash,
		Admin: admin,
	})

	// We know there is now at least one admin user.
	if admin {
		data.adminUserExists = true
	}

	return nil
}

// DropUser removes an existing user by name.
func (data *Data) DropUser(name string) error {
	for i := range data.Users {
		if data.Users[i].Name == name {
			wasAdmin := data.Users[i].Admin
			data.Users = append(data.Users[:i], data.Users[i+1:]...)

			// Maybe we dropped the only admin user?
			if wasAdmin {
				data.adminUserExists = data.hasAdminUser()
			}
			return nil
		}
	}

	return ErrUserNotFound
}

// UpdateUser updates the password hash of an existing user.
func (data *Data) UpdateUser(name, hash string) error {
	for i := range data.Users {
		if data.Users[i].Name == name {
			data.Users[i].Hash = hash
			return nil
		}
	}
	return ErrUserNotFound
}

// CloneUsers returns a copy of the user infos.
func (data *Data) CloneUsers() []UserInfo {
	if len(data.Users) == 0 {
		return []UserInfo{}
	}
	users := make([]UserInfo, len(data.Users))
	for i := range data.Users {
		users[i] = data.Users[i].clone()
	}

	return users
}

// SetPrivilege sets a privilege for a user on a database.
func (data *Data) SetPrivilege(name, database string, p influxql.Privilege) error {
	ui := data.User(name)
	if ui == nil {
		return ErrUserNotFound
	}

	if ui.Privileges == nil {
		ui.Privileges = make(map[string]influxql.Privilege)
	}
	ui.Privileges[database] = p

	return nil
}

// SetAdminPrivilege sets the admin privilege for a user.
func (data *Data) SetAdminPrivilege(name string, admin bool) error {
	ui := data.User(name)
	if ui == nil {
		return ErrUserNotFound
	}

	ui.Admin = admin

	// We could have promoted or revoked the only admin. Check if an admin
	// user exists.
	data.adminUserExists = data.hasAdminUser()
	return nil
}

// AdminUserExists returns true if an admin user exists.
func (data Data) AdminUserExists() bool {
	return data.adminUserExists
}

// UserPrivileges gets the privileges for a user.
func (data *Data) UserPrivileges(name string) (map[string]influxql.Privilege, error) {
	ui := data.User(name)
	if ui == nil {
		return nil, ErrUserNotFound
	}

	return ui.Privileges, nil
}

// UserPrivilege gets the privilege for a user on a database.
func (data *Data) UserPrivilege(name, database string) (*influxql.Privilege, error) {
	ui := data.User(name)
	if ui == nil {
		return nil, ErrUserNotFound
	}

	for db, p := range ui.Privileges {
		if db == database {
			return &p, nil
		}
	}

	return influxql.NewPrivilege(influxql.NoPrivileges), nil
}

// Clone returns a copy of data with a new version.
func (data *Data) Clone() *Data {
	other := *data

	other.Databases = data.CloneDatabases()
	other.Users = data.CloneUsers()

	return &other
}

// marshal serializes data to a protobuf representation.
func (data *Data) marshal() *internal.Data {
	pb := &internal.Data{
		Term:      proto.Uint64(data.Term),
		Index:     proto.Uint64(data.Index),
		ClusterID: proto.Uint64(data.ClusterID),

		MaxShardGroupID: proto.Uint64(data.MaxShardGroupID),
		MaxShardID:      proto.Uint64(data.MaxShardID),

		// Need this for reverse compatibility
		MaxNodeID: proto.Uint64(0),
	}

	pb.Databases = make([]*internal.DatabaseInfo, len(data.Databases))
	for i := range data.Databases {
		pb.Databases[i] = data.Databases[i].marshal()
	}

	pb.Users = make([]*internal.UserInfo, len(data.Users))
	for i := range data.Users {
		pb.Users[i] = data.Users[i].marshal()
	}

	return pb
}

// unmarshal deserializes from a protobuf representation.
func (data *Data) unmarshal(pb *internal.Data) {
	data.Term = pb.GetTerm()
	data.Index = pb.GetIndex()
	data.ClusterID = pb.GetClusterID()

	data.MaxShardGroupID = pb.GetMaxShardGroupID()
	data.MaxShardID = pb.GetMaxShardID()

	data.Databases = make([]DatabaseInfo, len(pb.GetDatabases()))
	for i, x := range pb.GetDatabases() {
		data.Databases[i].unmarshal(x)
	}

	data.Users = make([]UserInfo, len(pb.GetUsers()))
	for i, x := range pb.GetUsers() {
		data.Users[i].unmarshal(x)
	}

	// Exhaustively determine if there is an admin user. The marshalled cache
	// value may not be correct.
	data.adminUserExists = data.hasAdminUser()
}

// MarshalBinary encodes the metadata to a binary format.
func (data *Data) MarshalBinary() ([]byte, error) {
	return proto.Marshal(data.marshal())
}

// UnmarshalBinary decodes the object from a binary format.
func (data *Data) UnmarshalBinary(buf []byte) error {
	var pb internal.Data
	if err := proto.Unmarshal(buf, &pb); err != nil {
		return err
	}
	data.unmarshal(&pb)
	return nil
}

// hasAdminUser exhaustively checks for the presence of at least one admin
// user.
func (data *Data) hasAdminUser() bool {
	for _, u := range data.Users {
		if u.Admin {
			return true
		}
	}
	return false
}

// NodeInfo represents information about a single node in the cluster.
type NodeInfo struct {
	ID      uint64
	Host    string
	TCPHost string
}

// clone returns a deep copy of ni.
func (ni NodeInfo) clone() NodeInfo { return ni }

// marshal serializes to a protobuf representation.
func (ni NodeInfo) marshal() *internal.NodeInfo {
	pb := &internal.NodeInfo{}
	pb.ID = proto.Uint64(ni.ID)
	pb.Host = proto.String(ni.Host)
	pb.TCPHost = proto.String(ni.TCPHost)
	return pb
}

// unmarshal deserializes from a protobuf representation.
func (ni *NodeInfo) unmarshal(pb *internal.NodeInfo) {
	ni.ID = pb.GetID()
	ni.Host = pb.GetHost()
	ni.TCPHost = pb.GetTCPHost()
}

// NodeInfos is a slice of NodeInfo used for sorting
type NodeInfos []NodeInfo

// Len implements sort.Interface.
func (n NodeInfos) Len() int { return len(n) }

// Swap implements sort.Interface.
func (n NodeInfos) Swap(i, j int) { n[i], n[j] = n[j], n[i] }

// Less implements sort.Interface.
func (n NodeInfos) Less(i, j int) bool { return n[i].ID < n[j].ID }

// DatabaseInfo represents information about a database in the system.
type DatabaseInfo struct {
	Name                   string
	DefaultRetentionPolicy string
	RetentionPolicies      []RetentionPolicyInfo
	ContinuousQueries      []ContinuousQueryInfo
}

// RetentionPolicy returns a retention policy by name.
func (di DatabaseInfo) RetentionPolicy(name string) *RetentionPolicyInfo {
	if name == "" {
		if di.DefaultRetentionPolicy == "" {
			return nil
		}
		name = di.DefaultRetentionPolicy
	}

	for i := range di.RetentionPolicies {
		if di.RetentionPolicies[i].Name == name {
			return &di.RetentionPolicies[i]
		}
	}
	return nil
}

// ShardInfos returns a list of all shards' info for the database.
func (di DatabaseInfo) ShardInfos() []ShardInfo {
	shards := map[uint64]*ShardInfo{}
	for i := range di.RetentionPolicies {
		for j := range di.RetentionPolicies[i].ShardGroups {
			sg := di.RetentionPolicies[i].ShardGroups[j]
			// Skip deleted shard groups
			if sg.Deleted() {
				continue
			}
			for k := range sg.Shards {
				si := &di.RetentionPolicies[i].ShardGroups[j].Shards[k]
				shards[si.ID] = si
			}
		}
	}

	infos := make([]ShardInfo, 0, len(shards))
	for _, info := range shards {
		infos = append(infos, *info)
	}

	return infos
}

// clone returns a deep copy of di.
func (di DatabaseInfo) clone() DatabaseInfo {
	other := di

	if di.RetentionPolicies != nil {
		other.RetentionPolicies = make([]RetentionPolicyInfo, len(di.RetentionPolicies))
		for i := range di.RetentionPolicies {
			other.RetentionPolicies[i] = di.RetentionPolicies[i].clone()
		}
	}

	// Copy continuous queries.
	if di.ContinuousQueries != nil {
		other.ContinuousQueries = make([]ContinuousQueryInfo, len(di.ContinuousQueries))
		for i := range di.ContinuousQueries {
			other.ContinuousQueries[i] = di.ContinuousQueries[i].clone()
		}
	}

	return other
}

// marshal serializes to a protobuf representation.
func (di DatabaseInfo) marshal() *internal.DatabaseInfo {
	pb := &internal.DatabaseInfo{}
	pb.Name = proto.String(di.Name)
	pb.DefaultRetentionPolicy = proto.String(di.DefaultRetentionPolicy)

	pb.RetentionPolicies = make([]*internal.RetentionPolicyInfo, len(di.RetentionPolicies))
	for i := range di.RetentionPolicies {
		pb.RetentionPolicies[i] = di.RetentionPolicies[i].marshal()
	}

	pb.ContinuousQueries = make([]*internal.ContinuousQueryInfo, len(di.ContinuousQueries))
	for i := range di.ContinuousQueries {
		pb.ContinuousQueries[i] = di.ContinuousQueries[i].marshal()
	}
	return pb
}

// unmarshal deserializes from a protobuf representation.
func (di *DatabaseInfo) unmarshal(pb *internal.DatabaseInfo) {
	di.Name = pb.GetName()
	di.DefaultRetentionPolicy = pb.GetDefaultRetentionPolicy()

	if len(pb.GetRetentionPolicies()) > 0 {
		di.RetentionPolicies = make([]RetentionPolicyInfo, len(pb.GetRetentionPolicies()))
		for i, x := range pb.GetRetentionPolicies() {
			di.RetentionPolicies[i].unmarshal(x)
		}
	}

	if len(pb.GetContinuousQueries()) > 0 {
		di.ContinuousQueries = make([]ContinuousQueryInfo, len(pb.GetContinuousQueries()))
		for i, x := range pb.GetContinuousQueries() {
			di.ContinuousQueries[i].unmarshal(x)
		}
	}
}

// RetentionPolicySpec represents the specification for a new retention policy.
type RetentionPolicySpec struct {
	Name               string
	ReplicaN           *int
	Duration           *time.Duration
	ShardGroupDuration time.Duration
}

// NewRetentionPolicyInfo creates a new retention policy info from the specification.
func (s *RetentionPolicySpec) NewRetentionPolicyInfo() *RetentionPolicyInfo {
	return DefaultRetentionPolicyInfo().Apply(s)
}

// Matches checks if this retention policy specification matches
// an existing retention policy.
func (s *RetentionPolicySpec) Matches(rpi *RetentionPolicyInfo) bool {
	if rpi == nil {
		return false
	} else if s.Name != "" && s.Name != rpi.Name {
		return false
	} else if s.Duration != nil && *s.Duration != rpi.Duration {
		return false
	} else if s.ReplicaN != nil && *s.ReplicaN != rpi.ReplicaN {
		return false
	}

	// Normalise ShardDuration before comparing to any existing retention policies.
	// Normalize with the retention policy info's duration instead of the spec
	// since they should be the same and we're performing a comparison.
	sgDuration := normalisedShardDuration(s.ShardGroupDuration, rpi.Duration)
	return sgDuration == rpi.ShardGroupDuration
}

// marshal serializes to a protobuf representation.
func (s *RetentionPolicySpec) marshal() *internal.RetentionPolicySpec {
	pb := &internal.RetentionPolicySpec{}
	if s.Name != "" {
		pb.Name = proto.String(s.Name)
	}
	if s.Duration != nil {
		pb.Duration = proto.Int64(int64(*s.Duration))
	}
	if s.ShardGroupDuration > 0 {
		pb.ShardGroupDuration = proto.Int64(int64(s.ShardGroupDuration))
	}
	if s.ReplicaN != nil {
		pb.ReplicaN = proto.Uint32(uint32(*s.ReplicaN))
	}
	return pb
}

// unmarshal deserializes from a protobuf representation.
func (s *RetentionPolicySpec) unmarshal(pb *internal.RetentionPolicySpec) {
	if pb.Name != nil {
		s.Name = pb.GetName()
	}
	if pb.Duration != nil {
		duration := time.Duration(pb.GetDuration())
		s.Duration = &duration
	}
	if pb.ShardGroupDuration != nil {
		s.ShardGroupDuration = time.Duration(pb.GetShardGroupDuration())
	}
	if pb.ReplicaN != nil {
		replicaN := int(pb.GetReplicaN())
		s.ReplicaN = &replicaN
	}
}

// MarshalBinary encodes RetentionPolicySpec to a binary format.
func (s *RetentionPolicySpec) MarshalBinary() ([]byte, error) {
	return proto.Marshal(s.marshal())
}

// UnmarshalBinary decodes RetentionPolicySpec from a binary format.
func (s *RetentionPolicySpec) UnmarshalBinary(data []byte) error {
	var pb internal.RetentionPolicySpec
	if err := proto.Unmarshal(data, &pb); err != nil {
		return err
	}
	s.unmarshal(&pb)
	return nil
}

// RetentionPolicyInfo represents metadata about a retention policy.
type RetentionPolicyInfo struct {
	Name               string
	ReplicaN           int
	Duration           time.Duration
	ShardGroupDuration time.Duration
	ShardGroups        []ShardGroupInfo
	Subscriptions      []SubscriptionInfo
}

// NewRetentionPolicyInfo returns a new instance of RetentionPolicyInfo
// with default replication and duration.
func NewRetentionPolicyInfo(name string) *RetentionPolicyInfo {
	return &RetentionPolicyInfo{
		Name:     name,
		ReplicaN: DefaultRetentionPolicyReplicaN,
		Duration: DefaultRetentionPolicyDuration,
	}
}

// DefaultRetentionPolicyInfo returns a new instance of RetentionPolicyInfo
// with default name, replication, and duration.
func DefaultRetentionPolicyInfo() *RetentionPolicyInfo {
	return NewRetentionPolicyInfo(DefaultRetentionPolicyName)
}

// Apply applies a specification to the retention policy info.
func (rpi *RetentionPolicyInfo) Apply(spec *RetentionPolicySpec) *RetentionPolicyInfo {
	rp := &RetentionPolicyInfo{
		Name:               rpi.Name,
		ReplicaN:           rpi.ReplicaN,
		Duration:           rpi.Duration,
		ShardGroupDuration: rpi.ShardGroupDuration,
	}
	if spec.Name != "" {
		rp.Name = spec.Name
	}
	if spec.ReplicaN != nil {
		rp.ReplicaN = *spec.ReplicaN
	}
	if spec.Duration != nil {
		rp.Duration = *spec.Duration
	}
	rp.ShardGroupDuration = normalisedShardDuration(spec.ShardGroupDuration, rp.Duration)
	return rp
}

// ShardGroupByTimestamp returns the shard group in the policy that contains the timestamp,
// or nil if no shard group matches.
func (rpi *RetentionPolicyInfo) ShardGroupByTimestamp(timestamp time.Time) *ShardGroupInfo {
	for i := range rpi.ShardGroups {
		sgi := &rpi.ShardGroups[i]
		if sgi.Contains(timestamp) && !sgi.Deleted() && (!sgi.Truncated() || timestamp.Before(sgi.TruncatedAt)) {
			return &rpi.ShardGroups[i]
		}
	}

	return nil
}

// ExpiredShardGroups returns the Shard Groups which are considered expired, for the given time.
func (rpi *RetentionPolicyInfo) ExpiredShardGroups(t time.Time) []*ShardGroupInfo {
	var groups = make([]*ShardGroupInfo, 0)
	for i := range rpi.ShardGroups {
		if rpi.ShardGroups[i].Deleted() {
			continue
		}
		if rpi.Duration != 0 && rpi.ShardGroups[i].EndTime.Add(rpi.Duration).Before(t) {
			groups = append(groups, &rpi.ShardGroups[i])
		}
	}
	return groups
}

// DeletedShardGroups returns the Shard Groups which are marked as deleted.
func (rpi *RetentionPolicyInfo) DeletedShardGroups() []*ShardGroupInfo {
	var groups = make([]*ShardGroupInfo, 0)
	for i := range rpi.ShardGroups {
		if rpi.ShardGroups[i].Deleted() {
			groups = append(groups, &rpi.ShardGroups[i])
		}
	}
	return groups
}

// marshal serializes to a protobuf representation.
func (rpi *RetentionPolicyInfo) marshal() *internal.RetentionPolicyInfo {
	pb := &internal.RetentionPolicyInfo{
		Name:               proto.String(rpi.Name),
		ReplicaN:           proto.Uint32(uint32(rpi.ReplicaN)),
		Duration:           proto.Int64(int64(rpi.Duration)),
		ShardGroupDuration: proto.Int64(int64(rpi.ShardGroupDuration)),
	}

	pb.ShardGroups = make([]*internal.ShardGroupInfo, len(rpi.ShardGroups))
	for i, sgi := range rpi.ShardGroups {
		pb.ShardGroups[i] = sgi.marshal()
	}

	pb.Subscriptions = make([]*internal.SubscriptionInfo, len(rpi.Subscriptions))
	for i, sub := range rpi.Subscriptions {
		pb.Subscriptions[i] = sub.marshal()
	}

	return pb
}

// unmarshal deserializes from a protobuf representation.
func (rpi *RetentionPolicyInfo) unmarshal(pb *internal.RetentionPolicyInfo) {
	rpi.Name = pb.GetName()
	rpi.ReplicaN = int(pb.GetReplicaN())
	rpi.Duration = time.Duration(pb.GetDuration())
	rpi.ShardGroupDuration = time.Duration(pb.GetShardGroupDuration())

	if len(pb.GetShardGroups()) > 0 {
		rpi.ShardGroups = make([]ShardGroupInfo, len(pb.GetShardGroups()))
		for i, x := range pb.GetShardGroups() {
			rpi.ShardGroups[i].unmarshal(x)
		}
	}
	if len(pb.GetSubscriptions()) > 0 {
		rpi.Subscriptions = make([]SubscriptionInfo, len(pb.GetSubscriptions()))
		for i, x := range pb.GetSubscriptions() {
			rpi.Subscriptions[i].unmarshal(x)
		}
	}
}

// clone returns a deep copy of rpi.
func (rpi RetentionPolicyInfo) clone() RetentionPolicyInfo {
	other := rpi

	if rpi.ShardGroups != nil {
		other.ShardGroups = make([]ShardGroupInfo, len(rpi.ShardGroups))
		for i := range rpi.ShardGroups {
			other.ShardGroups[i] = rpi.ShardGroups[i].clone()
		}
	}

	return other
}

// MarshalBinary encodes rpi to a binary format.
func (rpi *RetentionPolicyInfo) MarshalBinary() ([]byte, error) {
	return proto.Marshal(rpi.marshal())
}

// UnmarshalBinary decodes rpi from a binary format.
func (rpi *RetentionPolicyInfo) UnmarshalBinary(data []byte) error {
	var pb internal.RetentionPolicyInfo
	if err := proto.Unmarshal(data, &pb); err != nil {
		return err
	}
	rpi.unmarshal(&pb)
	return nil
}

// shardGroupDuration returns the default duration for a shard group based on a policy duration.
func shardGroupDuration(d time.Duration) time.Duration {
	if d >= 180*24*time.Hour || d == 0 { // 6 months or 0
		return 7 * 24 * time.Hour
	} else if d >= 2*24*time.Hour { // 2 days
		return 1 * 24 * time.Hour
	}
	return 1 * time.Hour
}

// normalisedShardDuration returns normalised shard duration based on a policy duration.
func normalisedShardDuration(sgd, d time.Duration) time.Duration {
	// If it is zero, it likely wasn't specified, so we default to the shard group duration
	if sgd == 0 {
		return shardGroupDuration(d)
	}
	// If it was specified, but it's less than the MinRetentionPolicyDuration, then normalize
	// to the MinRetentionPolicyDuration
	if sgd < MinRetentionPolicyDuration {
		return shardGroupDuration(MinRetentionPolicyDuration)
	}
	return sgd
}

// ShardGroupInfo represents metadata about a shard group. The DeletedAt field is important
// because it makes it clear that a ShardGroup has been marked as deleted, and allow the system
// to be sure that a ShardGroup is not simply missing. If the DeletedAt is set, the system can
// safely delete any associated shards.
type ShardGroupInfo struct {
	ID          uint64
	StartTime   time.Time
	EndTime     time.Time
	DeletedAt   time.Time
	Shards      []ShardInfo
	TruncatedAt time.Time
}

// ShardGroupInfos implements sort.Interface on []ShardGroupInfo, based
// on the StartTime field.
type ShardGroupInfos []ShardGroupInfo

// Len implements sort.Interface.
func (a ShardGroupInfos) Len() int { return len(a) }

// Swap implements sort.Interface.
func (a ShardGroupInfos) Swap(i, j int) { a[i], a[j] = a[j], a[i] }

// Less implements sort.Interface.
func (a ShardGroupInfos) Less(i, j int) bool {
	iEnd := a[i].EndTime
	if a[i].Truncated() {
		iEnd = a[i].TruncatedAt
	}

	jEnd := a[j].EndTime
	if a[j].Truncated() {
		jEnd = a[j].TruncatedAt
	}

	if iEnd.Equal(jEnd) {
		return a[i].StartTime.Before(a[j].StartTime)
	}

	return iEnd.Before(jEnd)
}

// Contains returns true if the shard group contains data for the timestamp.
func (sgi *ShardGroupInfo) Contains(timestamp time.Time) bool {
	return !sgi.StartTime.After(timestamp) && sgi.EndTime.After(timestamp)
}

// Overlaps returns whether the shard group contains data for the time range between min and max
func (sgi *ShardGroupInfo) Overlaps(min, max time.Time) bool {
	return !sgi.StartTime.After(max) && sgi.EndTime.After(min)
}

// Deleted returns whether this ShardGroup has been deleted.
func (sgi *ShardGroupInfo) Deleted() bool {
	return !sgi.DeletedAt.IsZero()
}

// Truncated returns true if this ShardGroup has been truncated (no new writes).
func (sgi *ShardGroupInfo) Truncated() bool {
	return !sgi.TruncatedAt.IsZero()
}

// clone returns a deep copy of sgi.
func (sgi ShardGroupInfo) clone() ShardGroupInfo {
	other := sgi

	if sgi.Shards != nil {
		other.Shards = make([]ShardInfo, len(sgi.Shards))
		for i := range sgi.Shards {
			other.Shards[i] = sgi.Shards[i].clone()
		}
	}

	return other
}

// ShardFor returns the ShardInfo for a Point hash.
func (sgi *ShardGroupInfo) ShardFor(hash uint64) ShardInfo {
	return sgi.Shards[hash%uint64(len(sgi.Shards))]
}

// marshal serializes to a protobuf representation.
func (sgi *ShardGroupInfo) marshal() *internal.ShardGroupInfo {
	pb := &internal.ShardGroupInfo{
		ID:        proto.Uint64(sgi.ID),
		StartTime: proto.Int64(MarshalTime(sgi.StartTime)),
		EndTime:   proto.Int64(MarshalTime(sgi.EndTime)),
		DeletedAt: proto.Int64(MarshalTime(sgi.DeletedAt)),
	}

	if !sgi.TruncatedAt.IsZero() {
		pb.TruncatedAt = proto.Int64(MarshalTime(sgi.TruncatedAt))
	}

	pb.Shards = make([]*internal.ShardInfo, len(sgi.Shards))
	for i := range sgi.Shards {
		pb.Shards[i] = sgi.Shards[i].marshal()
	}

	return pb
}

// unmarshal deserializes from a protobuf representation.
func (sgi *ShardGroupInfo) unmarshal(pb *internal.ShardGroupInfo) {
	sgi.ID = pb.GetID()
	if i := pb.GetStartTime(); i == 0 {
		sgi.StartTime = time.Unix(0, 0).UTC()
	} else {
		sgi.StartTime = UnmarshalTime(i)
	}
	if i := pb.GetEndTime(); i == 0 {
		sgi.EndTime = time.Unix(0, 0).UTC()
	} else {
		sgi.EndTime = UnmarshalTime(i)
	}
	sgi.DeletedAt = UnmarshalTime(pb.GetDeletedAt())

	if pb != nil && pb.TruncatedAt != nil {
		sgi.TruncatedAt = UnmarshalTime(pb.GetTruncatedAt())
	}

	if len(pb.GetShards()) > 0 {
		sgi.Shards = make([]ShardInfo, len(pb.GetShards()))
		for i, x := range pb.GetShards() {
			sgi.Shards[i].unmarshal(x)
		}
	}
}

// ShardInfo represents metadata about a shard.
type ShardInfo struct {
	ID     uint64
	Owners []ShardOwner
}

// OwnedBy determines whether the shard's owner IDs includes nodeID.
func (si ShardInfo) OwnedBy(nodeID uint64) bool {
	for _, so := range si.Owners {
		if so.NodeID == nodeID {
			return true
		}
	}
	return false
}

// clone returns a deep copy of si.
func (si ShardInfo) clone() ShardInfo {
	other := si

	if si.Owners != nil {
		other.Owners = make([]ShardOwner, len(si.Owners))
		for i := range si.Owners {
			other.Owners[i] = si.Owners[i].clone()
		}
	}

	return other
}

// marshal serializes to a protobuf representation.
func (si ShardInfo) marshal() *internal.ShardInfo {
	pb := &internal.ShardInfo{
		ID: proto.Uint64(si.ID),
	}

	pb.Owners = make([]*internal.ShardOwner, len(si.Owners))
	for i := range si.Owners {
		pb.Owners[i] = si.Owners[i].marshal()
	}

	return pb
}

// UnmarshalBinary decodes the object from a binary format.
func (si *ShardInfo) UnmarshalBinary(buf []byte) error {
	var pb internal.ShardInfo
	if err := proto.Unmarshal(buf, &pb); err != nil {
		return err
	}
	si.unmarshal(&pb)
	return nil
}

// unmarshal deserializes from a protobuf representation.
func (si *ShardInfo) unmarshal(pb *internal.ShardInfo) {
	si.ID = pb.GetID()

	// If deprecated "OwnerIDs" exists then convert it to "Owners" format.
	if len(pb.GetOwnerIDs()) > 0 {
		si.Owners = make([]ShardOwner, len(pb.GetOwnerIDs()))
		for i, x := range pb.GetOwnerIDs() {
			si.Owners[i].unmarshal(&internal.ShardOwner{
				NodeID: proto.Uint64(x),
			})
		}
	} else if len(pb.GetOwners()) > 0 {
		si.Owners = make([]ShardOwner, len(pb.GetOwners()))
		for i, x := range pb.GetOwners() {
			si.Owners[i].unmarshal(x)
		}
	}
}

// SubscriptionInfo holds the subscription information.
type SubscriptionInfo struct {
	Name         string
	Mode         string
	Destinations []string
}

// marshal serializes to a protobuf representation.
func (si SubscriptionInfo) marshal() *internal.SubscriptionInfo {
	pb := &internal.SubscriptionInfo{
		Name: proto.String(si.Name),
		Mode: proto.String(si.Mode),
	}

	pb.Destinations = make([]string, len(si.Destinations))
	for i := range si.Destinations {
		pb.Destinations[i] = si.Destinations[i]
	}
	return pb
}

// unmarshal deserializes from a protobuf representation.
func (si *SubscriptionInfo) unmarshal(pb *internal.SubscriptionInfo) {
	si.Name = pb.GetName()
	si.Mode = pb.GetMode()

	if len(pb.GetDestinations()) > 0 {
		si.Destinations = make([]string, len(pb.GetDestinations()))
		for i, h := range pb.GetDestinations() {
			si.Destinations[i] = h
		}
	}
}

// ShardOwner represents a node that owns a shard.
type ShardOwner struct {
	NodeID uint64
}

// clone returns a deep copy of so.
func (so ShardOwner) clone() ShardOwner {
	return so
}

// marshal serializes to a protobuf representation.
func (so ShardOwner) marshal() *internal.ShardOwner {
	return &internal.ShardOwner{
		NodeID: proto.Uint64(so.NodeID),
	}
}

// unmarshal deserializes from a protobuf representation.
func (so *ShardOwner) unmarshal(pb *internal.ShardOwner) {
	so.NodeID = pb.GetNodeID()
}

// ContinuousQueryInfo represents metadata about a continuous query.
type ContinuousQueryInfo struct {
	Name  string
	Query string
}

// clone returns a deep copy of cqi.
func (cqi ContinuousQueryInfo) clone() ContinuousQueryInfo { return cqi }

// marshal serializes to a protobuf representation.
func (cqi ContinuousQueryInfo) marshal() *internal.ContinuousQueryInfo {
	return &internal.ContinuousQueryInfo{
		Name:  proto.String(cqi.Name),
		Query: proto.String(cqi.Query),
	}
}

// unmarshal deserializes from a protobuf representation.
func (cqi *ContinuousQueryInfo) unmarshal(pb *internal.ContinuousQueryInfo) {
	cqi.Name = pb.GetName()
	cqi.Query = pb.GetQuery()
}

// UserInfo represents metadata about a user in the system.
type UserInfo struct {
	Name       string
	Hash       string
	Admin      bool
	Privileges map[string]influxql.Privilege
}

// Authorize returns true if the user is authorized and false if not.
func (ui *UserInfo) Authorize(privilege influxql.Privilege, database string) bool {
	if ui.Admin {
		return true
	}
	p, ok := ui.Privileges[database]
	return ok && (p == privilege || p == influxql.AllPrivileges)
}

// clone returns a deep copy of si.
func (ui UserInfo) clone() UserInfo {
	other := ui

	if ui.Privileges != nil {
		other.Privileges = make(map[string]influxql.Privilege)
		for k, v := range ui.Privileges {
			other.Privileges[k] = v
		}
	}

	return other
}

// marshal serializes to a protobuf representation.
func (ui UserInfo) marshal() *internal.UserInfo {
	pb := &internal.UserInfo{
		Name:  proto.String(ui.Name),
		Hash:  proto.String(ui.Hash),
		Admin: proto.Bool(ui.Admin),
	}

	for database, privilege := range ui.Privileges {
		pb.Privileges = append(pb.Privileges, &internal.UserPrivilege{
			Database:  proto.String(database),
			Privilege: proto.Int32(int32(privilege)),
		})
	}

	return pb
}

// unmarshal deserializes from a protobuf representation.
func (ui *UserInfo) unmarshal(pb *internal.UserInfo) {
	ui.Name = pb.GetName()
	ui.Hash = pb.GetHash()
	ui.Admin = pb.GetAdmin()

	ui.Privileges = make(map[string]influxql.Privilege)
	for _, p := range pb.GetPrivileges() {
		ui.Privileges[p.GetDatabase()] = influxql.Privilege(p.GetPrivilege())
	}
}

// Lease represents a lease held on a resource.
type Lease struct {
	Name       string    `json:"name"`
	Expiration time.Time `json:"expiration"`
	Owner      uint64    `json:"owner"`
}

// Leases is a concurrency-safe collection of leases keyed by name.
type Leases struct {
	mu sync.Mutex
	m  map[string]*Lease
	d  time.Duration
}

// NewLeases returns a new instance of Leases.
func NewLeases(d time.Duration) *Leases {
	return &Leases{
		m: make(map[string]*Lease),
		d: d,
	}
}

// Acquire acquires a lease with the given name for the given nodeID.
// If the lease doesn't exist or exists but is expired, a valid lease is returned.
// If nodeID already owns the named and unexpired lease, the lease expiration is extended.
// If a different node owns the lease, an error is returned.
func (leases *Leases) Acquire(name string, nodeID uint64) (*Lease, error) {
	leases.mu.Lock()
	defer leases.mu.Unlock()

	l, ok := leases.m[name]
	if ok {
		if time.Now().After(l.Expiration) || l.Owner == nodeID {
			l.Expiration = time.Now().Add(leases.d)
			l.Owner = nodeID
			return l, nil
		}
		return l, errors.New("another node has the lease")
	}

	l = &Lease{
		Name:       name,
		Expiration: time.Now().Add(leases.d),
		Owner:      nodeID,
	}

	leases.m[name] = l

	return l, nil
}

// MarshalTime converts t to nanoseconds since epoch. A zero time returns 0.
func MarshalTime(t time.Time) int64 {
	if t.IsZero() {
		return 0
	}
	return t.UnixNano()
}

// UnmarshalTime converts nanoseconds since epoch to time.
// A zero value returns a zero time.
func UnmarshalTime(v int64) time.Time {
	if v == 0 {
		return time.Time{}
	}
	return time.Unix(0, v).UTC()
}

// ValidName checks to see if the given name can would be valid for DB/RP name
func ValidName(name string) bool {
	for _, r := range name {
		if !unicode.IsPrint(r) {
			return false
		}
	}

	return name != "" &&
		name != "." &&
		name != ".." &&
		!strings.ContainsAny(name, `/\`)
}