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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package ledger
import (
"container/list"
"github.com/algorand/go-algorand/data/basics"
"github.com/algorand/go-algorand/ledger/store/trackerdb"
)
// Worst case memory usage = 2500 * 320 * 150B = 120MB
const onlineAccountsCacheMaxSize = 2500
type onlineAccountsCache struct {
// each List stores online account data with newest
// at the front, and oldest at the back.
accounts map[basics.Address]*list.List
maxCacheSize int
}
// init initializes the onlineAccountsCache for use.
// thread locking semantics : write lock
func (o *onlineAccountsCache) init(accts []trackerdb.PersistedOnlineAccountData, maxCacheSize int) {
o.accounts = make(map[basics.Address]*list.List)
o.maxCacheSize = maxCacheSize
for _, acct := range accts {
// if cache full, stop writing
cachedAcct := cachedOnlineAccount{
BaseOnlineAccountData: acct.AccountData,
updRound: acct.UpdRound,
}
if !o.writeFront(acct.Addr, cachedAcct) {
break
}
}
}
func (o *onlineAccountsCache) full() bool {
return len(o.accounts) >= o.maxCacheSize
}
// read the cachedOnlineAccount object that the cache has for the given address.
// thread locking semantics : read lock
func (o *onlineAccountsCache) read(addr basics.Address, rnd basics.Round) (cachedOnlineAccount, bool) {
if list := o.accounts[addr]; list != nil {
node := list.Back()
prevValue := node.Value.(*cachedOnlineAccount)
if prevValue.updRound > rnd {
return cachedOnlineAccount{}, false
}
for node.Prev() != nil {
node = node.Prev()
// only need one entry that is targetRound or older
currentValue := node.Value.(*cachedOnlineAccount)
if currentValue.updRound > rnd {
return *prevValue, true
}
prevValue = currentValue
}
return *prevValue, true
}
return cachedOnlineAccount{}, false
}
// write a single cachedOnlineAccount to the cache
// thread locking semantics : write lock
func (o *onlineAccountsCache) writeFront(addr basics.Address, acctData cachedOnlineAccount) bool {
var l *list.List
var ok bool
if l, ok = o.accounts[addr]; !ok {
if o.full() {
return false
}
l = list.New()
}
// do not insert if acctData would not be the newest entry in the cache
if l.Front() != nil && acctData.updRound <= l.Front().Value.(*cachedOnlineAccount).updRound {
return false
}
l.PushFront(&acctData)
o.accounts[addr] = l
return true
}
// write a single cachedOnlineAccount to the cache only if there are some history entries
// thread locking semantics : write lock
func (o *onlineAccountsCache) writeFrontIfExist(addr basics.Address, acctData cachedOnlineAccount) {
var l *list.List
var ok bool
if l, ok = o.accounts[addr]; !ok {
return
}
if l.Len() == 0 {
return
}
// do not insert if acctData would not be the newest entry in the cache
if l.Front() != nil && acctData.updRound <= l.Front().Value.(*cachedOnlineAccount).updRound {
return
}
l.PushFront(&acctData)
o.accounts[addr] = l
}
// prune trims the onlineAccountsCache by only keeping entries that would give account state
// of rounds targetRound and later, repeating the deletion logic from the history DB
// thread locking semantics : write lock
func (o *onlineAccountsCache) prune(targetRound basics.Round) {
for addr, list := range o.accounts {
node := list.Back()
for node.Prev() != nil {
node = node.Prev()
// keep only one entry that is targetRound or older
// discard all entries older than targetRound other than the current entry
if node.Value.(*cachedOnlineAccount).updRound < targetRound {
list.Remove(node.Next())
} else {
break
}
}
// only one item left in cache
if node.Prev() == nil && node.Next() == nil {
if node.Value.(*cachedOnlineAccount).IsVotingEmpty() {
delete(o.accounts, addr)
}
}
}
}
// delete cache for a particular address
func (o *onlineAccountsCache) clear(addr basics.Address) {
delete(o.accounts, addr)
}
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