frostfs-api-go-pogpp/netmap/attributes.go

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package netmap
import (
"errors"
"fmt"
"strings"
"github.com/nspcc-dev/neofs-api-go/v2/refs"
)
// prefix of keys to subnet attributes.
const attrSubnetPrefix = "__NEOFS__SUBNET_"
const (
// subnet attribute's value denoting subnet entry
attrSubnetValEntry = "True"
// subnet attribute's value denoting subnet exit
attrSubnetValExit = "False"
)
// NodeSubnetInfo groups information about subnet which can be written to NodeInfo.
//
// Zero value represents entry to zero subnet.
type NodeSubnetInfo struct {
exit bool
id *refs.SubnetID
}
// Enabled returns true iff subnet membership is enabled for the node.
func (x NodeSubnetInfo) Enabled() bool {
return !x.exit
}
// SetEntryFlag sets the subnet entry flag.
func (x *NodeSubnetInfo) SetEntryFlag(enters bool) {
x.exit = !enters
}
// ID returns identifier of the subnet.
func (x NodeSubnetInfo) ID() *refs.SubnetID {
return x.id
}
// SetID sets identifier of the subnet.
func (x *NodeSubnetInfo) SetID(id *refs.SubnetID) {
x.id = id
}
func subnetAttributeKey(id *refs.SubnetID) string {
txt, _ := id.MarshalText() // never returns an error
return attrSubnetPrefix + string(txt)
}
// WriteSubnetInfo writes NodeSubnetInfo to NodeInfo via attributes. NodeInfo must not be nil.
//
// Existing subnet attributes are expected to be key-unique, otherwise undefined behavior.
//
// Does not add (removes existing) attribute if node:
// * disables non-zero subnet;
// * enables zero subnet.
//
// Attribute key is calculated from ID using format `__NEOFS__SUBNET_%s`.
// Attribute Value is:
// * `True` if node enters the subnet;
// * `False`, otherwise.
func WriteSubnetInfo(node *NodeInfo, info NodeSubnetInfo) {
attrs := node.GetAttributes()
id := info.ID()
enters := info.Enabled()
// calculate attribute key
key := subnetAttributeKey(id)
if refs.IsZeroSubnet(id) == enters {
for i := range attrs {
if attrs[i].GetKey() == key {
attrs = append(attrs[:i], attrs[i+1:]...)
break // attributes are expected to be key-unique
}
}
} else {
var val string
if enters {
val = attrSubnetValEntry
} else {
val = attrSubnetValExit
}
presented := false
for i := range attrs {
if attrs[i].GetKey() == key {
attrs[i].SetValue(val)
presented = true
}
}
if !presented {
index := len(attrs)
attrs = append(attrs, Attribute{})
attrs[index].SetKey(key)
attrs[index].SetValue(val)
}
}
node.SetAttributes(attrs)
}
// ErrRemoveSubnet is returned when a node needs to leave the subnet.
var ErrRemoveSubnet = errors.New("remove subnet")
var errNoSubnets = errors.New("no subnets")
// IterateSubnets iterates over all subnets the node belongs to and passes the IDs to f.
// Handler must not be nil.
//
// Subnet attributes are expected to be key-unique, otherwise undefined behavior.
//
// If f returns ErrRemoveSubnet, then removes subnet entry. Note that this leads to an instant mutation of NodeInfo.
// Breaks on any other non-nil error and returns it.
//
// Returns an error if any subnet attribute has wrong format.
// Returns an error if the node is not included in any subnet by the end of the loop.
func IterateSubnets(node *NodeInfo, f func(refs.SubnetID) error) error {
attrs := node.GetAttributes()
var (
err error
id refs.SubnetID
entries uint
zeroEntry = true
)
for i := 0; i < len(attrs); i++ { // range must not be used because of attrs mutation in body
key := attrs[i].GetKey()
// cut subnet ID string
idTxt := strings.TrimPrefix(key, attrSubnetPrefix)
if len(idTxt) == len(key) {
// not a subnet attribute
continue
}
// check value
val := attrs[i].GetValue()
if val != attrSubnetValExit && val != attrSubnetValEntry {
return fmt.Errorf("invalid attribute value: %s", val)
}
// decode subnet ID
if err = id.UnmarshalText([]byte(idTxt)); err != nil {
return fmt.Errorf("invalid ID text: %w", err)
}
// update status of zero subnet
isZero := refs.IsZeroSubnet(&id)
if isZero {
zeroEntry = val == attrSubnetValEntry
}
// continue to process only the subnets to which the node belongs
if val == attrSubnetValExit {
continue
}
// pass ID to the handler
err = f(id)
isRemoveErr := errors.Is(err, ErrRemoveSubnet)
if err != nil && !isRemoveErr {
return err
}
if isRemoveErr {
if isZero {
// we can't remove attribute of zero subnet because it means entry
attrs[i].SetValue(attrSubnetValExit)
} else {
// we can set False or remove attribute, latter is more memory/network efficient.
attrs = append(attrs[:i], attrs[i+1:]...)
i--
}
continue
}
entries++
}
if zeroEntry {
// missing attribute of zero subnet equivalent to entry
refs.MakeZeroSubnet(&id)
err = f(id)
if err != nil {
if !errors.Is(err, ErrRemoveSubnet) {
return err
}
// zero subnet should be clearly removed with False value
index := len(attrs)
attrs = append(attrs, Attribute{})
attrs[index].SetKey(subnetAttributeKey(&id))
attrs[index].SetValue(attrSubnetValExit)
} else {
entries++
}
}
if entries <= 0 {
return errNoSubnets
}
node.SetAttributes(attrs)
return nil
}