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// Copyright 2016 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 flowcontrol implements a client side flow control mechanism
package flowcontrol
import (
"sync"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
)
const rcConst = 1000000
type cmNode struct {
node *ClientNode
lastUpdate mclock.AbsTime
serving, recharging bool
rcWeight uint64
rcValue, rcDelta, startValue int64
finishRecharge mclock.AbsTime
}
func (node *cmNode) update(time mclock.AbsTime) {
dt := int64(time - node.lastUpdate)
node.rcValue += node.rcDelta * dt / rcConst
node.lastUpdate = time
if node.recharging && time >= node.finishRecharge {
node.recharging = false
node.rcDelta = 0
node.rcValue = 0
}
}
func (node *cmNode) set(serving bool, simReqCnt, sumWeight uint64) {
if node.serving && !serving {
node.recharging = true
sumWeight += node.rcWeight
}
node.serving = serving
if node.recharging && serving {
node.recharging = false
sumWeight -= node.rcWeight
}
node.rcDelta = 0
if serving {
node.rcDelta = int64(rcConst / simReqCnt)
}
if node.recharging {
node.rcDelta = -int64(node.node.cm.rcRecharge * node.rcWeight / sumWeight)
node.finishRecharge = node.lastUpdate + mclock.AbsTime(node.rcValue*rcConst/(-node.rcDelta))
}
}
type ClientManager struct {
lock sync.Mutex
nodes map[*cmNode]struct{}
simReqCnt, sumWeight, rcSumValue uint64
maxSimReq, maxRcSum uint64
rcRecharge uint64
resumeQueue chan chan bool
time mclock.AbsTime
}
func NewClientManager(rcTarget, maxSimReq, maxRcSum uint64) *ClientManager {
cm := &ClientManager{
nodes: make(map[*cmNode]struct{}),
resumeQueue: make(chan chan bool),
rcRecharge: rcConst * rcConst / (100*rcConst/rcTarget - rcConst),
maxSimReq: maxSimReq,
maxRcSum: maxRcSum,
}
go cm.queueProc()
return cm
}
func (self *ClientManager) Stop() {
self.lock.Lock()
defer self.lock.Unlock()
// signal any waiting accept routines to return false
self.nodes = make(map[*cmNode]struct{})
close(self.resumeQueue)
}
func (self *ClientManager) addNode(cnode *ClientNode) *cmNode {
time := mclock.Now()
node := &cmNode{
node: cnode,
lastUpdate: time,
finishRecharge: time,
rcWeight: 1,
}
self.lock.Lock()
defer self.lock.Unlock()
self.nodes[node] = struct{}{}
self.update(mclock.Now())
return node
}
func (self *ClientManager) removeNode(node *cmNode) {
self.lock.Lock()
defer self.lock.Unlock()
time := mclock.Now()
self.stop(node, time)
delete(self.nodes, node)
self.update(time)
}
// recalc sumWeight
func (self *ClientManager) updateNodes(time mclock.AbsTime) (rce bool) {
var sumWeight, rcSum uint64
for node := range self.nodes {
rc := node.recharging
node.update(time)
if rc && !node.recharging {
rce = true
}
if node.recharging {
sumWeight += node.rcWeight
}
rcSum += uint64(node.rcValue)
}
self.sumWeight = sumWeight
self.rcSumValue = rcSum
return
}
func (self *ClientManager) update(time mclock.AbsTime) {
for {
firstTime := time
for node := range self.nodes {
if node.recharging && node.finishRecharge < firstTime {
firstTime = node.finishRecharge
}
}
if self.updateNodes(firstTime) {
for node := range self.nodes {
if node.recharging {
node.set(node.serving, self.simReqCnt, self.sumWeight)
}
}
} else {
self.time = time
return
}
}
}
func (self *ClientManager) canStartReq() bool {
return self.simReqCnt < self.maxSimReq && self.rcSumValue < self.maxRcSum
}
func (self *ClientManager) queueProc() {
for rc := range self.resumeQueue {
for {
time.Sleep(time.Millisecond * 10)
self.lock.Lock()
self.update(mclock.Now())
cs := self.canStartReq()
self.lock.Unlock()
if cs {
break
}
}
close(rc)
}
}
func (self *ClientManager) accept(node *cmNode, time mclock.AbsTime) bool {
self.lock.Lock()
defer self.lock.Unlock()
self.update(time)
if !self.canStartReq() {
resume := make(chan bool)
self.lock.Unlock()
self.resumeQueue <- resume
<-resume
self.lock.Lock()
if _, ok := self.nodes[node]; !ok {
return false // reject if node has been removed or manager has been stopped
}
}
self.simReqCnt++
node.set(true, self.simReqCnt, self.sumWeight)
node.startValue = node.rcValue
self.update(self.time)
return true
}
func (self *ClientManager) stop(node *cmNode, time mclock.AbsTime) {
if node.serving {
self.update(time)
self.simReqCnt--
node.set(false, self.simReqCnt, self.sumWeight)
self.update(time)
}
}
func (self *ClientManager) processed(node *cmNode, time mclock.AbsTime) (rcValue, rcCost uint64) {
self.lock.Lock()
defer self.lock.Unlock()
self.stop(node, time)
return uint64(node.rcValue), uint64(node.rcValue - node.startValue)
}
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