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aliascache.go
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aliascache.go
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// Copyright (C) 2021 Storj Labs, Inc.
// See LICENSE for copying information.
package metabase
import (
"context"
"sync"
"sync/atomic"
"storj.io/common/storj"
)
// NodeAliasDB is an interface for looking up node alises.
type NodeAliasDB interface {
EnsureNodeAliases(ctx context.Context, opts EnsureNodeAliases) error
ListNodeAliases(ctx context.Context) (_ []NodeAliasEntry, err error)
}
// NodeAliasCache is a write-through cache for looking up node ID and alias mapping.
type NodeAliasCache struct {
db NodeAliasDB
refreshing sync.Mutex
latest atomic.Value // *NodeAliasMap
}
// NewNodeAliasCache creates a new cache using the specified database.
func NewNodeAliasCache(db NodeAliasDB) *NodeAliasCache {
cache := &NodeAliasCache{
db: db,
}
cache.latest.Store(NewNodeAliasMap(nil))
return cache
}
func (cache *NodeAliasCache) getLatest() *NodeAliasMap {
return cache.latest.Load().(*NodeAliasMap)
}
// Nodes returns node ID-s corresponding to the aliases,
// refreshing the cache once when an alias is missing.
// This results in an error when the alias is not in the database.
func (cache *NodeAliasCache) Nodes(ctx context.Context, aliases []NodeAlias) ([]storj.NodeID, error) {
latest := cache.getLatest()
nodes, missing := latest.Nodes(aliases)
if len(missing) == 0 {
return nodes, nil
}
if len(missing) > 0 {
var err error
latest, err = cache.refresh(ctx, nil, missing)
if err != nil {
return nil, Error.New("failed to refresh node alias db: %w", err)
}
}
nodes, missing = latest.Nodes(aliases)
if len(missing) == 0 {
return nodes, nil
}
return nil, Error.New("aliases missing in database: %v", missing)
}
// Aliases returns node aliases corresponding to the node ID-s,
// adding missing node ID-s to the database when needed.
func (cache *NodeAliasCache) Aliases(ctx context.Context, nodes []storj.NodeID) ([]NodeAlias, error) {
latest := cache.getLatest()
aliases, missing := latest.Aliases(nodes)
if len(missing) == 0 {
return aliases, nil
}
if len(missing) > 0 {
var err error
latest, err = cache.ensure(ctx, missing...)
if err != nil {
return nil, Error.Wrap(err)
}
}
aliases, missing = latest.Aliases(nodes)
if len(missing) == 0 {
return aliases, nil
}
return nil, Error.New("nodes still missing after ensuring: %v", missing)
}
// ensure tries to ensure that the specified missing node ID-s are assigned a alias.
func (cache *NodeAliasCache) ensure(ctx context.Context, missing ...storj.NodeID) (_ *NodeAliasMap, err error) {
defer mon.Task()(&ctx)(&err)
if err := cache.db.EnsureNodeAliases(ctx, EnsureNodeAliases{
Nodes: missing,
}); err != nil {
return nil, Error.New("failed to update node alias db: %w", err)
}
return cache.refresh(ctx, missing, nil)
}
// refresh refreshses the state of the cache.
func (cache *NodeAliasCache) refresh(ctx context.Context, missingNodes []storj.NodeID, missingAliases []NodeAlias) (_ *NodeAliasMap, err error) {
defer mon.Task()(&ctx)(&err)
cache.refreshing.Lock()
defer cache.refreshing.Unlock()
latest := cache.getLatest()
// Maybe some other goroutine already refreshed the list, double-check.
if latest.ContainsAll(missingNodes, missingAliases) {
return latest, nil
}
entries, err := cache.db.ListNodeAliases(ctx)
if err != nil {
return nil, err
}
// Since we never remove node aliases we can assume that the alias map that contains more
// entries is the latest one.
//
// Note: we merge the maps here rather than directly replacing.
// This is not ideal from performance side, however it should reduce possible consistency issues.
xs := NewNodeAliasMap(entries)
xs.Merge(latest)
cache.latest.Store(xs)
return xs, nil
}
// ConvertPiecesToAliases converts pieces to alias pieces.
func (cache *NodeAliasCache) ConvertPiecesToAliases(ctx context.Context, pieces Pieces) (_ AliasPieces, err error) {
defer mon.Task()(&ctx)(&err)
nodes := make([]storj.NodeID, len(pieces))
for i, p := range pieces {
nodes[i] = p.StorageNode
}
aliases, err := cache.Aliases(ctx, nodes)
if err != nil {
return nil, Error.Wrap(err)
}
aliasPieces := make(AliasPieces, len(aliases))
for i, alias := range aliases {
aliasPieces[i] = AliasPiece{
Number: pieces[i].Number,
Alias: alias,
}
}
return aliasPieces, nil
}
// ConvertAliasesToPieces converts alias pieces to pieces.
func (cache *NodeAliasCache) ConvertAliasesToPieces(ctx context.Context, aliasPieces AliasPieces) (_ Pieces, err error) {
defer mon.Task()(&ctx)(&err)
latest := cache.getLatest()
pieces := make(Pieces, len(aliasPieces))
var missing []NodeAlias
for i, aliasPiece := range aliasPieces {
node, ok := latest.Node(aliasPiece.Alias)
if !ok {
missing = append(missing, aliasPiece.Alias)
continue
}
pieces[i].Number = aliasPiece.Number
pieces[i].StorageNode = node
}
if len(missing) > 0 {
var err error
latest, err = cache.refresh(ctx, nil, missing)
if err != nil {
return nil, Error.New("failed to refresh node alias db: %w", err)
}
for i, aliasPiece := range aliasPieces {
node, ok := latest.Node(aliasPiece.Alias)
if !ok {
return nil, Error.New("aliases missing in database: %v", missing)
}
pieces[i].Number = aliasPiece.Number
pieces[i].StorageNode = node
}
}
return pieces, nil
}
// NodeAliasMap contains bidirectional mapping between node ID and a NodeAlias.
type NodeAliasMap struct {
node []storj.NodeID
alias map[storj.NodeID]NodeAlias
}
// NewNodeAliasMap creates a new alias map from the given entries.
func NewNodeAliasMap(entries []NodeAliasEntry) *NodeAliasMap {
m := &NodeAliasMap{
node: make([]storj.NodeID, len(entries)),
alias: make(map[storj.NodeID]NodeAlias, len(entries)),
}
for _, e := range entries {
m.setNode(e.Alias, e.ID)
m.alias[e.ID] = e.Alias
}
return m
}
// setNode sets a value in `m.node` and increases the size when necessary.
func (m *NodeAliasMap) setNode(alias NodeAlias, value storj.NodeID) {
if int(alias) >= len(m.node) {
m.node = append(m.node, make([]storj.NodeID, int(alias)-len(m.node)+1)...)
}
m.node[alias] = value
}
// Merge merges the other map into m.
func (m *NodeAliasMap) Merge(other *NodeAliasMap) {
for k, v := range other.node {
if !v.IsZero() {
m.setNode(NodeAlias(k), v)
}
}
for k, v := range other.alias {
m.alias[k] = v
}
}
// Node returns NodeID for the given alias.
func (m *NodeAliasMap) Node(alias NodeAlias) (x storj.NodeID, ok bool) {
if int(alias) >= len(m.node) {
return storj.NodeID{}, false
}
v := m.node[alias]
return v, !v.IsZero()
}
// Nodes returns NodeID-s for the given aliases and aliases that are not in this map.
func (m *NodeAliasMap) Nodes(aliases []NodeAlias) (xs []storj.NodeID, missing []NodeAlias) {
xs = make([]storj.NodeID, 0, len(aliases))
for _, p := range aliases {
if x, ok := m.Node(p); ok {
xs = append(xs, x)
} else {
missing = append(missing, p)
}
}
return xs, missing
}
// Aliases returns alises-s for the given node ID-s and node ID-s that are not in this map.
func (m *NodeAliasMap) Aliases(nodes []storj.NodeID) (xs []NodeAlias, missing []storj.NodeID) {
xs = make([]NodeAlias, 0, len(nodes))
for _, n := range nodes {
if x, ok := m.alias[n]; ok {
xs = append(xs, x)
} else {
missing = append(missing, n)
}
}
return xs, missing
}
// ContainsAll returns true when the table contains all entries.
func (m *NodeAliasMap) ContainsAll(nodeIDs []storj.NodeID, nodeAliases []NodeAlias) bool {
for _, id := range nodeIDs {
if _, ok := m.alias[id]; !ok {
return false
}
}
for _, alias := range nodeAliases {
if _, ok := m.Node(alias); !ok {
return false
}
}
return true
}
// Size returns the number of entries in this map.
func (m *NodeAliasMap) Size() int {
if m == nil {
return 0
}
return len(m.alias)
}