storj/satellite/metainfo/metabase/aliascache.go
Egon Elbre 61f0fb67a9 satellite/metainfo/metabase: refresh alias cache only once
When there are concurrent refreshes to the cache and the entries are
missing, it could end up causing multiple database calls, even though
only one is needed.

Change-Id: I1ae7a124bbdd1570473cf3a032d375d2f25a8426
2021-02-17 10:00:04 +00:00

260 lines
6.7 KiB
Go

// 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)
aliases := make([]NodeAlias, len(aliasPieces))
pieces := make(Pieces, len(aliasPieces))
for i, aliasPiece := range aliasPieces {
pieces[i].Number, aliases[i] = aliasPiece.Number, aliasPiece.Alias
}
nodes, err := cache.Nodes(ctx, aliases)
if err != nil {
return nil, Error.Wrap(err)
}
for i, n := range nodes {
pieces[i].StorageNode = n
}
return pieces, nil
}
// NodeAliasMap contains bidirectional mapping between node ID and a NodeAlias.
type NodeAliasMap struct {
node map[NodeAlias]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(map[NodeAlias]storj.NodeID, len(entries)),
alias: make(map[storj.NodeID]NodeAlias, len(entries)),
}
for _, e := range entries {
m.node[e.Alias] = e.ID
m.alias[e.ID] = e.Alias
}
return m
}
// Merge merges the other map into m.
func (m *NodeAliasMap) Merge(other *NodeAliasMap) {
for k, v := range other.node {
m.node[k] = v
}
for k, v := range other.alias {
m.alias[k] = v
}
}
// 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.node)
}