les: light client protocol and API

les/flowcontrol/manager.go

@@ -0,0 +1,223 @@
+// Copyright 2015 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"
+)
+
+const rcConst = 1000000
+
+type cmNode struct {
+	node                       *ClientNode
+	lastUpdate                 int64
+	reqAccepted                int64
+	serving, recharging        bool
+	rcWeight                   uint64
+	rcValue, rcDelta           int64
+	finishRecharge, startValue int64
+}
+
+func (node *cmNode) update(time int64) {
+	dt := 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 + 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                             int64
+}
+
+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 := getTime()
+	node := &cmNode{
+		node:           cnode,
+		lastUpdate:     time,
+		finishRecharge: time,
+		rcWeight:       1,
+	}
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	self.nodes[node] = struct{}{}
+	self.update(getTime())
+	return node
+}
+
+func (self *ClientManager) removeNode(node *cmNode) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	time := getTime()
+	self.stop(node, time)
+	delete(self.nodes, node)
+	self.update(time)
+}
+
+// recalc sumWeight
+func (self *ClientManager) updateNodes(time int64) (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 int64) {
+	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(getTime())
+			cs := self.canStartReq()
+			self.lock.Unlock()
+			if cs {
+				break
+			}
+		}
+		close(rc)
+	}
+}
+
+func (self *ClientManager) accept(node *cmNode, time int64) 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 int64) {
+	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 int64) (rcValue, rcCost uint64) {
+	self.lock.Lock()
+	defer self.lock.Unlock()
+
+	self.stop(node, time)
+	return uint64(node.rcValue), uint64(node.rcValue - node.startValue)
+}