// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package protocols
import "github.com/ethereum/go-ethereum/metrics"
//define some metrics
var (
//NOTE: these metrics just define the interfaces and are currently *NOT persisted* over sessions
//All metrics are cumulative
//total amount of units credited
mBalanceCredit = metrics.NewRegisteredCounterForced("account.balance.credit", nil)
//total amount of units debited
mBalanceDebit = metrics.NewRegisteredCounterForced("account.balance.debit", nil)
//total amount of bytes credited
mBytesCredit = metrics.NewRegisteredCounterForced("account.bytes.credit", nil)
//total amount of bytes debited
mBytesDebit = metrics.NewRegisteredCounterForced("account.bytes.debit", nil)
//total amount of credited messages
mMsgCredit = metrics.NewRegisteredCounterForced("account.msg.credit", nil)
//total amount of debited messages
mMsgDebit = metrics.NewRegisteredCounterForced("account.msg.debit", nil)
//how many times local node had to drop remote peers
mPeerDrops = metrics.NewRegisteredCounterForced("account.peerdrops", nil)
//how many times local node overdrafted and dropped
mSelfDrops = metrics.NewRegisteredCounterForced("account.selfdrops", nil)
)
//Prices defines how prices are being passed on to the accounting instance
type Prices interface {
//Return the Price for a message
Price(interface{}) *Price
}
type Payer bool
const (
Sender = Payer(true)
Receiver = Payer(false)
)
//Price represents the costs of a message
type Price struct {
Value uint64 //
PerByte bool //True if the price is per byte or for unit
Payer Payer
}
//For gives back the price for a message
//A protocol provides the message price in absolute value
//This method then returns the correct signed amount,
//depending on who pays, which is identified by the `payer` argument:
//`Send` will pass a `Sender` payer, `Receive` will pass the `Receiver` argument.
//Thus: If Sending and sender pays, amount positive, otherwise negative
//If Receiving, and receiver pays, amount positive, otherwise negative
func (p *Price) For(payer Payer, size uint32) int64 {
price := p.Value
if p.PerByte {
price *= uint64(size)
}
if p.Payer == payer {
return 0 - int64(price)
}
return int64(price)
}
//Balance is the actual accounting instance
//Balance defines the operations needed for accounting
//Implementations internally maintain the balance for every peer
type Balance interface {
//Adds amount to the local balance with remote node `peer`;
//positive amount = credit local node
//negative amount = debit local node
Add(amount int64, peer *Peer) error
}
//Accounting implements the Hook interface
//It interfaces to the balances through the Balance interface,
//while interfacing with protocols and its prices through the Prices interface
type Accounting struct {
Balance //interface to accounting logic
Prices //interface to prices logic
}
func NewAccounting(balance Balance, po Prices) *Accounting {
ah := &Accounting{
Prices: po,
Balance: balance,
}
return ah
}
//Implement Hook.Send
// Send takes a peer, a size and a msg and
// - calculates the cost for the local node sending a msg of size to peer using the Prices interface
// - credits/debits local node using balance interface
func (ah *Accounting) Send(peer *Peer, size uint32, msg interface{}) error {
//get the price for a message (through the protocol spec)
price := ah.Price(msg)
//this message doesn't need accounting
if price == nil {
return nil
}
//evaluate the price for sending messages
costToLocalNode := price.For(Sender, size)
//do the accounting
err := ah.Add(costToLocalNode, peer)
//record metrics: just increase counters for user-facing metrics
ah.doMetrics(costToLocalNode, size, err)
return err
}
//Implement Hook.Receive
// Receive takes a peer, a size and a msg and
// - calculates the cost for the local node receiving a msg of size from peer using the Prices interface
// - credits/debits local node using balance interface
func (ah *Accounting) Receive(peer *Peer, size uint32, msg interface{}) error {
//get the price for a message (through the protocol spec)
price := ah.Price(msg)
//this message doesn't need accounting
if price == nil {
return nil
}
//evaluate the price for receiving messages
costToLocalNode := price.For(Receiver, size)
//do the accounting
err := ah.Add(costToLocalNode, peer)
//record metrics: just increase counters for user-facing metrics
ah.doMetrics(costToLocalNode, size, err)
return err
}
//record some metrics
//this is not an error handling. `err` is returned by both `Send` and `Receive`
//`err` will only be non-nil if a limit has been violated (overdraft), in which case the peer has been dropped.
//if the limit has been violated and `err` is thus not nil:
// * if the price is positive, local node has been credited; thus `err` implicitly signals the REMOTE has been dropped
// * if the price is negative, local node has been debited, thus `err` implicitly signals LOCAL node "overdraft"
func (ah *Accounting) doMetrics(price int64, size uint32, err error) {
if price > 0 {
mBalanceCredit.Inc(price)
mBytesCredit.Inc(int64(size))
mMsgCredit.Inc(1)
if err != nil {
//increase the number of times a remote node has been dropped due to "overdraft"
mPeerDrops.Inc(1)
}
} else {
mBalanceDebit.Inc(price)
mBytesDebit.Inc(int64(size))
mMsgDebit.Inc(1)
if err != nil {
//increase the number of times the local node has done an "overdraft" in respect to other nodes
mSelfDrops.Inc(1)
}
}
}
